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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 68
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 69
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 71
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 72
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 73
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 74
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 76
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 81
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 82
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 84
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 85
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 86
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 87
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 88
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 89
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 90
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 91
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 92
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 93
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 94
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 95
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 96
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 97
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 98
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 99
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 100
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 101
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 102
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 103
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 104
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 105
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 112
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Page 113
Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
×
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Suggested Citation:"A.1.2 Fiber Mediums and Terminals." Transportation Research Board. 1996. Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/6338.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Generic Requirements for the Digital Data System (DDS) Network Ounce Channel Unit. BeRcore Technical Advisory TA-TSY-000083, April 1986. Available from BeUcore Documents Resists. Generic Requirements for the Subrate Multiplexer. BeDcore Technical Advisoty TA-TSY 000189, April 1986. Available from Be~core Documents Registrar. Digital Data System (DDSJ Multipoint Junction Unit (M]UJ Requirements. BeRcore Technical Advisory TA-TSY-000192, Apn! 1986. Available from Be~core Documents Register. A readily available reference on engineering of T! carrier repeatered lines is: Cravis, H., Crater, T. "Engineenng of T1 Camer System Repeatered Lines," Bell System Technical Journal Vol. XLE, March 1963, p. 431. A.~.2 Fiber Mediums and Terminals A.~.2.1 Fiber Cable Plants by Siecor Corporation-Raleigh, Norm Carolina Since the invention of practical optical fiber in the early 1970s, Be demand for optical fiber has grown tremendously. Today the uses of optical fiber are numerous. The applications of optical fiber are widespread from global networks to optical fiber extending aU the way to a subscnber's home or desktop computer. Applications for optical fiber include cable television, medicine, weapons guidance systems, aircraft control and instrumentation (fly-by-light), shipboard co~nrnunications, optical fiber gyroscopes, and remote lighting in automobiles, to name a few. Optical fiber provides many advantages for Be telecommunications system designer. It has extremely high information carrying capabilities and very low loss when compared to copper or coaxial telecommunications cables. This means Nat the distance between repeaters and regenerators can be very long (70 - 80 lan). This long distance between repeaters is best exploited when Be cables can be manufactured in lengths in excess of 10 km. Long lengths, light weight, and small diameters make optical fiber cable instaDabons much easier and less expensive Can copper. Optical fiber cables can be instaBed wad Be same ~:\NCHRPPhase:~pr NCHRP 3-51 ~ Phase 2 Final Report A1-55

equipment that is used to install copper and coaxial cables, with some modifications due to Weir small size and limited pull tensions. Optical cables can be instated in duct systems of 4000m or more depending on the condition, layout of the duct system, and installation technique. The remaining cable would be coiled and pulled further into the duct system. These long lengths of cable reduce the number of splice points making the total installation more efficient and reliable. The small size also saves on valuable conduit space. Aenal and direct buried installations also exploit the advantage of having long cable lengths with Me length limited only by the installation equipment. Another advantage is the dielectric nature of optical fiber cables. Since optical fiber is made of glass, it does not conduct electncity, nor is it affected by electromagnetic interference or radio frequency interference. This makes it the ultimate in electromagnetic transmission mediums and eliminates such issues as: unwanted, dangerous ground loops; requirement for separate electrical conduit; voltage spikes from the cycling of heavy electrical equipment; and isolation of control rooms. All dielectric optical fiber cable does not require grounding and bonding at building entrances. Since optical fiber cames a light signal instead of an electrical signal, Me cable does not emit electromagnetic signals that can affect nearby equipment and over cables. A.~.2.~.! Fiber Performance 1) Fiber Theory - Principles of Operation Every optical fiber used for telecommunications comprises three areas: core, cladding, and protective coating. The core consists of silica glass and a dopant to control the index of refraction of the glass. A typical dopant is germane. The cladding is concentric around Me core and composed of pure silica glass. The core and the cladding are manufactured as a single piece of glass and cannot be separated one from the other. The refractive index characteristics of Me core and the cladding are designed to contain the light in the core as it travels down Me fiber. Standard core diameters in use today are 8.3 ,um (single-mode), 50 ,um, and 62.5 Am (multimode). The cladding surrounding each of these cores is 125 I. Core sizes of 85 ~ "d 100 Am have been used in some applications but, they are not common today. L:~h~t NCHRP 3-51 · Phase 2 Few Ream A1-56

The Bird section of an optical fiber is Me outer protective coating. The typical diameter of a coated fiber is 245 ,um. The protective coating is typically an ultra violet (UV) cured acrylate coating applied during We manufacturing process. The coating provides mechanical and environmental protection for the fiber. a. Apex of Refraction In order to understand how light travels down a fiber, one must have a basic understanding of Be principles of how light behaves when traveling Trough a medium. In a vacuum, light travels at approximately 3.0 X 108 m/s. In any over medium (air, water, glass, etc.) light travels more slowly. The ratio of the speed of lift In a vacuum to He speed of light in a medium is caned the Index of refraction. It is typically represented by Be letter "n" and its value is always greater than one (~) unless the medium is a vacuum, Den Be index of refraction would be equal to one. The slower light travels in a medium, the larger Be index of refraction. b. Total Internal Reflection When light passes from one medium to another, and the second medium has a different index of refraction, Be light is either reflected back into Be first medium at the interface or refracted (bent) as it passes Into the second medium. This pnnciple is caned SneR's Law.) The effect is similar to placing a stick in water, i.e., it appears bent. Whether the light reflects or refiacts depends on the angle of incidence and the index of refraction of the two materials. There is an angle at which the lift is refracted along Be interface of the two materials. This angle is called the cntical angle. When light approaches the intersection of two materials win different indices of refraction, at an angle less than the critical angle, the light is refracted. For angles of incidence greater than the critical angle, Be light is reflected back into the medium. The angle of reflection is equal to Be angle of incidence. This property is caned total internal reflection. This can be visualized by the following example: When standing on the shore of a smooth lake with a mountain range in the backdrop, at a certain distance Be mountain range is reflected off Be water's surface; however, Were is a point at which the mountain is no longer reflected and Be bottom of the lake is visible. This is similar to light traveling down an optical fiber. L:;wCHRP`Phasc2.rpt NCHRP 3-51 · Pie 2 Fly Rein A1-57

c. Numerical Aperture To ensure that the light reflects and stays in the core, He light must enter the core through an imaginary acceptance cone. The size of the acceptance cone is a function of Be refractive index difference of the core and the cladding. The acceptance cone is not specified for a typical optical fiber, it is expressed as the numencal aperture. The numencal aperture of an optical fiber is a measure of Be maximum angle of light entering the end of Be fiber Cat watt propagate in the core of Be fiber. The numencal aperture in mathematical terms is the sine of the cntical angle. d. Modes After light is coupled into an optical fiber, it travels down the fiber in propagation states calved modes. There can be from one to hundreds of modes, depending on the type of fiber. (See single-mode and multimode fiber). Each mode Cannes a percentage of the launched light. A separate signal cannot be transmitted down He different modes. The approximate number of modes is based on the core diameter; He lower the wavelength of operation, He larger He number of modes In an optical fiber. This gives a simplified reason for the different data rate capacities of different multimode fibers. The greater He number of modes, He greater He modal dispersion among those modes and subsequently He lower the data rate capacity; however, He larger fiber cores (in multimode fibers) have a larger numerical aperture which makes it easier to couple light into those fibers. 2) System Parameters a. Wavelength Multimode fibers generally operate at two primary wavelengths: 850 nm and 1300 nm. The wavelength of operation can affect the data rate capacity so higher data rate systems generally operate at He longer wavelength. Single-mode fibers generally operate at two primary wavelengths: 1310 nm and 1550 nm. For single-mode fibers aD of He optical power is contained in only one mode. (Data rate capacities in single-mode fiber will be discussed later.) As a note, ah four of these wavelengths (850 nm, 1300 nm, 1310 nm, and 1550 nm) are invisible to He naked eye and in He near infrared region of He electromagnetic spectrum. L:`NCHRP\Phase:.rp ~NCH~P 3-51 · Phase 2 final Report A1-58

b. Attenuation One of the most important optical parameters is attenuation. Attenuation is the loss of optical power as the light pulse travels down the optical fiber. The power coupled into the fiber at the transmitter loses some energy as it transmits down He fiber. There are two main types of attenuation, intrinsic and extrinsic. Intrinsic attenuation is We result of inherent effects within the optical fiber that either absorb or scatter the light pulse. Absorption occurs when nature impurities in He fiber absorb energy from the transmitted light. This effect is minimized during manufactunng of the optical fiber. Scattering of light occurs when light traveling in the fiber collides wad small imperfections in the glass, scattering light In all directions. This form of attenuation is He source of more than 90% of optical fiber attenuation. Again, this effect is minimized by the optical fiber manufacturer. There are two types of extrinsic attenuation: macrobending and m~crobending. Macrobending consists of large scale bends induced on the optical fiber. This bending effects He light guiding properties of He fiber, and a portion of He light traveling in the fiber's core is lost into He cladding. This loss is due to localized change in the critical angle. The percentage of loss depends on the severity of the bend. The energy loss associated with macrobends is reversible with removal of He bend. Microbends are small scale distortions of the fiber Hat alter He index of refraction at He point of stress. This altered index changes the light guiding properties of He fiber at Hat point, and causes light to escape into He cladding due to He change in index of refraction. These bends are typically caused by temperature, or by tensile- or crush-related effects on the optical fiber cable or the unprotected optical fiber. Optical fiber attenuation is typically stated in terms of decibels (dB) and normalized to decibels per kilometer (dBA`m). The end-to-end attenuation of a fiber link will typically be stated in dB, while the cabled fiber attenuation will be specified in dB/km. Specifying attenuation is usually done in He windows of operation for He optical fiber. A multimode fiber will have He attenuation specified at 850 rim and 1300 nm, while a single-mode fiber will have attenuation specified at 1310 nm and 1550 nm. Typical values for multimode optical fibers are 3.5 dB/km .~.= NCH"3-51 · P~2F - ~n A1-59

at 850 nm and I.5 dB/km at 1300 nm. For single-mode optical fiber, typical values are 0.4 dBA`m at 1310 nm and 0.3 dB/km at 1550 nm. An optical fiber system can be limited by the attenuation and/or the dispersion. The attenuation limit comes from loss in optical power. If the system is too long, Me signal wait not have enough energy to be detectable when it reaches We receiver. It should be noted that this can be a function of the end equipment as well as the optical fiber. The transmitter may not have enough power, the receiver threshold may be too high, or the optical fiber link may have too much attenuation. One must consider splice and connector loss as weB as the fiber loss with distance. (Dispersion limits are discussed in Me next section.) c. Dispersion Data rates are limited by dispersion which causes the input pulse to spread in time as it travels through a fiber. This spreading increases the potential for interference between sequential pulses. Pulses launched closely together High data rates) that spread too much High dispersion) result in bit errors at the receiver. For example: if He input pulse is 5 ns long, the output pulse may be 6 ns long after 5 km. There are three types of dispersion; modal and chromatic are He two most common and have the most impact on typical telecommunications systems. The Bird Thorpe is polarization mode dispersion. Modal dispersion occurs only In multimode fiber while chromatic dispersion occurs in bow single-mode and multimode fiber. Modal Dispersion: Each mode of light in a multimode fiber follows a different path through the core of the fiber. These individual paths have different associated lengths relative to the fiber length. The modes following the shortest paths will arrive at He end of the fiber before the modes following the longer paths. A pulse of light consisting of hundreds of modes in a multimode fiber will, therefore, broaden In time as it travels through He fiber. Chromatic Dispersion: Chromatic dispersion is determined by He fiber's composition, structure, and design, and by He operating wavelength and spectral width of the light source. Chromatic dispersion is measured in units of (ps/nm x km): picoseconds of light pulse spread L:~h~.~t N~P3-51 e P~2F~Re"n A1-60

per nanometer of spectral width and per kilometer of fiber length. Chromatic dispersion occurs because different wavelengths of light experience a change In index of refraction and, therefore, transmit at different speeds. There are two components of chromatic dispersion: material and wavegu~de. The amount of material dispersion vanes web the composition of He glass and is a function of the wavelength of the light source. No transmitter produces a pure light source of only one wavelength. Instead, sources produce a range of wavelengths, resulting In pulse spreading that increases with distance. Wavegaide dispersion results from a portion of the light traveling In Me cladding as weR as He core of the fiber. Since He mode field diameter is a function of wavelength and each pulse consists of more than one wavelength, the pulse spreads out. This also increases with distance. Both material and wavegu~de dispersion can be decreased by using a better light source (smalder spectral we. Modal dispersion is the dominant factor in multimode fiber but does not occur in single-mode fiber because there is only one mode. Chromatic dispersion is present in both fiber types. A maximum dispersion value is specified for single-mode fiber in most industry standards to aid in calculating He data rate capacity for the fiber. This must be used in conjunction with transmitter and receiver specifications. Industry standards for multimode fiber, however, specify bandwidth instead of dispersion. Polarization mode dispersion: (PMD) is an optical effect which can spread or disperse an optical signal, occulting in commonly used single-mode fibers. It originates web the source, typically a narrow-linewidth laser diode. Light which is restricted to a narrow spectral width is polarized when it is emitted. The light is then coupled into He single-mode fiber where it is resolved into two orthogonaNy-polanzed components which make up the fundamental mode. PI occurs when He two components which comprise the fundamental mode beg n to propagate at different speeds. The result is a distortion of the originally transmitted signal. This difference in propagation velocity represents a difference in the index of refraction for the two components, referred to as He fiber's birefringence. Since both of the polarized components carry a portion of the transmitted power, any offset in the arnval time of He components acts to distort the lingual signal. In digital commun~cabon systems, the result is dual imaging of the signal at the receiver. This dual imaging is destructive to the signal integrity, liming operational transmission capacity. Additionally, it is important to note that PMr) increases at the square root of the length, while chromatic dispersion increases linearly win length. Therefore, c;WCHRmPhasc:.rpr NCHRP 3-51 · Phase 2 final Report A1-61

Be impact of PI diminishes wig longer length systems which is not the case with chromatic dispersion. PMO may be an issue with long haul applications. Test methods and specifications are still under development. d. Bandwidth Bandwidth is a measure of Be data rate capacity for multimode fiber. It is typically measured by Be fiber manufacturer on the bare fiber and repotted in units of MHz-km. Due to the fact that bandwidth is not linear, special care must be taken when estimating the data rate capacity for an installed system since a number of fibers may be concatenated together to comprise the system. Bandwidths of fibers Cat are concatenated together forming a long span cannot be simply added together then divided by the length to get the band of Be system. The formulas for calculating system bandwidth are beyond the scope of this article but can be obtained from the fiber or cable manufacturer. Suffice it to say, Be end equipment manufacturer should state the fiber bandwidth necessary for proper operation of a system over a given length. 3) Fiber Types There are two major classifications of fiber. In general, multimode fiber is Lest suited for local network use, where links are short (less Man 2000 m) and there are many connectors. The higher numencal aperture of multimode fiber allows the use of relatively inexpensive Light Emitting Diode (LED) transmitters and lower cost connectors. Single-mode fiber is best suited for long distance applications or applications requiting extremely high data rates. Given these two optical fiber types and typical trar~sm~tter and receiver specifications, which fiber type is best suited for Be applications listed above for a given distance? The following tables summarize all of these parameters. utNC~Phasc2~pt NClIRP3-51a Phase2FmalReport A1-62

Table A.~.2.~.~-1 Applications Summary for 62.5/125 Am Multimode Optical Fiber Application/ Maximum Data Rate (MBiVs} Bandwiclth Attenuation Wavelength (nary) Specification Distance (m) (MHz-km) (dBllcm) 568-A 2000/90 _ ~ 60/500 3.75/1 .5 e50/'300 Ethernet 2000 10 160 3.75 850 10Base F Ethernet 2000 100 500 2 5 Note 2 1300 100Base F Ethernet ~Note 3 ~ GO ~Note 3 ~50/' 300 VGAnvLAN . _ _ ._ Token Ring 2000 4 160 3.75 850 Token Ring 2000 16 160 3 75 850 FDDI-PMD 2000 100 500 2 5 Note 2 1300 . . . FDDI-LCF 500 100 500 N= ~1300 FDDi-850 1 Note 3 1 00 1 Note 3 1 Note 3 1 8~50 __ Fiber Channel 1500 133 160/500 1.0 1300 _ Fiber Channel 1500 266 160/500 1.0 1300 ATM l Nots 3 ~52 ~Note 3 ~Note 3 ~ 300 ATM 2000 155 500 1 .5 1300 ATM | 300 622 | Note 3 Note 3 | Note 3 ] Siecor 1 _ 1 200/500 1 3.5/1 .0 1 850/1300 Note 1: Backbone~onzontal distances Note 2: Typical (end-to-end attenuation is specified at 11 dB) Note 3: Standard is son under development Note 4: End-to-end attenuation is specified at 7 dB; typical normalized attenuation is not specified. Table A.~.2.~.~-2 Applications Summary for Single-Mode Optical Fiber Application/ Maximum Data Rate Attenuation Wavelength (nary) Specification Distance (m) (MBiVs) {dB/km} 568-A 60,000 ~1. 0/1.0 13 10/1530 FDDI-SMF ~60,000 ~100 ~0 5 Note 3 ~t 300 Fiber Channel 10,000 531 0.5 1300 . Fiber Channel 10,000 1063 0.5 1300 Siecor _ 0.5/0.4 1 310/1 550 Note 1: Beyond Me scope of ~A/ElA-568-A. L:~h~.~t NCH~3-51 a P0e2F~Re"n A1-63

Note 2: Maximum attenuation for inside optical fiber cable; maximum attenuation of outside optical fiber cable is 0.5/0.5 dBAcn at 1310/1550 nm. Note 3: Typical (end-to-end attenuation is specified up to 32 dB) a. Multimode Optical Fiber Wavelength of operation is another important parameter that must be considered in Me design of this system. Multimode fiber usually operates in two different windows: 850 nm and 1300 nm. The Milt signal will behave differently at each wavelength. The attenuation at 850 nm will tend to be higher than at 1300 nm. In addition, the bandwidth at 850 nm tends to be lower than at 1300 nm. Quite simply, multimode fiber performance is better at 1300 rim than at 850 nm, making longer system lengths possible at 1300 nm; however, the cost of the end equipment (primarily LEDs) may be less at 850 nm, lowering Me overall system cost. b. S=gle-mode Optical Fiber Standard single-mode fiber is designed to operate at 1310 rim and 1550 nm; however, Mere are tradeoffs at bow wavelengths. The attenuation at 1550 rim is generally lower Man at 1310 nm. The dispersion, however, is much higher at 1550 nm than at 1310 nm, since the zero dispersion wavelength is closer to 1310 nm. If the system designer desires bow low dispersion and low attenuation at 1550 nm, dispersion- shifted (DS) single-mode fiber is available. DS s~ngle-mode fiber is generally used for long distance and high data rate applications where the lowest possible loss is desired without A · · - sacr~nc~ng low dispersion. Regardless of Me fiber type chosen, the designer should specify Me attenuation and bandwidth (dispersion for single-mode fiber) at bow performance windows: 850 rim and 1300 nm for multimode fiber, and 1310 nm and 1550 nm for single-mode fiber. Specifying these values gives Me design more flexibility to accommodate future upgrades. L;WCHRP\Phase2.rpt NCHRP 3-51 · Phase 2 Final Report A1-64

As data rates increase and the system designer considers new applications, certain key end equipment (transmitter and receiver) parameters can be changed to improve system performance on the instaHed optical fiber. While optical fiber has the necessary bandwidth to handle applications wed into the future, the end equipment may have to be replaced to achieve higher system performance. As discussed above, changing the center wavelength may improve attenuation and/or bandwidth. Another key factor is spectral width. Tightening He spectral width will reduce chromatic dispersion and thus allow for a higher banded. Rise and fall tunes of the transmitter and receiver can also be lowered to achieve a higher bandwidth. Cable manufacturers and/or end equipment manufacturers can assist in evaluating a system with different light source characteristics (center wavelength and spectral width). 4) Comparison Between Fiber, Copper, ant Coax A number of considerations justify the transition from copper to fiber at such an accelerated pace. Fiber-based communication networks provide gigahertz bandwidth as compared win megahertz bandwidth available win copper twisted pair communications. Single-mode fiber supports link distances up to 80 kilometers without degrading its bandwidth capacity, while maintaining a lower noise floor or larger signal-to-noise ratio Han copper cable. In addidon, advanced multimedia commun~cadons services such as real-time interactive video-require the significant banded Hat optical fiber can deliver. Optical fiber systems support much greater distances between electronics without the necessity of line amplifiers and repeaters, simplifying He network, due to lower attenuation. Compared with copper twisted pair, optical communication systems exhibit a much lower bit error rate (BER) while operating at much higher data or bit rates. As a result, communication of Intelligent Transportation Systems FITS) data is both faster and more reliable over optical fiber systems. At high data rates (typically in the Gbps range) copper twisted pair communications can exhibit a bit error rate of lo-6. At 2.5 Gbps fiber optic networks typically exhibit a bit error rate of lO~9 and are tested at 10~~. Networks carrying critical data, particularly Hose involving safety and finance, demand He reliability that is possible with optical fiber. c:`NCHR~Phasc2.'p' NCHRP 3-51 · Phase 2 Final Report A1-65

Finally, it is important to note Hat optical fiber systems are user friendly. Optical fiber connection and termination procedures are weB defined; Be smaller size and lighter weight of optical cable make it easier to work wig; and optical cable has superior bend performance and flexibility as compared with copper cable. b. Environmental Factors ~ J EMI and RE] interference Copper cables can act as antennae, receiving electromagnetic or radio frequency interference signals (EME/RF[), from sources like electric motors, high-voltage transmission lines, vehicle engines, public radio, TV broadcast equipment, and other machinery. These signals, when superimposed on a data stream, may sometimes make it difficult for Be receiver to differentiate between valid data and EMYRFI-induced noise. This is especially true for long runs Mat comprise mixed components from multiple vendors. Due to their dielectric nature, optical fibers are immune to such interference. 2} Crosstalk CrosstaLk occurs when unwanted signals are coupled between transmitting and receiving copper pairs. This is especially troublesome near He transmit source (near-end crosstalk or NEXT). The result is an increased possibility of corrupted data due to receiver difficulty in differentiating between normal and coupled signals. This phenomena is common u id copper twisted pair cables but rarely occurs with fiber. 3J Temperature Elects The manufacturing process of optical fiber cable plays a major role in He effect Hat temperature will have on its performance. Polymers used in He manufacture of the cables expand and contract at a rate different from that of silica glass fiber. Loose tube cable is designed for operation in outside plant environments. The temperature range for these cables is 40° C to 70° C. Tight buffered cable designs are trpicaDy installed in controlled environments. The temperature range for these cables is O or -20° C to +70° C. The water blocking capability of cable designs also helps determine the environment in which the cable can be used. ~ is undesirable to have water In a cable core because, where temperatures drop below freezing, the water expanding as it freezes will exert crush forces on the optical fibers. :`NCHRP`Phase2 rp' NIP 3-51 · Phase 2 Final Report A1-66

A.~.2.~.2 Cable Plan f 1) Cable Types andFAppl~cations Optical fiber cables are designed to provide optimum performance based on He environment Key experience over Heir service life. Over factors, including ease of installation and terminator, must be evaluated when selecting an optical fiber cable. Outside Plant Environment Outside plant cables must be capable of withstanding a variety of environmental and mechanical extremes. The cable must offer excellent attenuation performance over a wide range of temperatures. Waterblocking capabilities must be provided to ensure water cannot migrate into He cable and subsequently freeze. The cable must be sufficiently strong to endure the rigors of instalIabon and must provide protection against ultraviolet (UV) radiation, gnawing rodents, and mechanical disturbances. Fur~ennore, He cable should allow high packing density to maximize the use of available installation space. Inside Plant Environment Unlike outside cables, in side plant cables generally experience a controlled stable environment. Therefore, He performance requirements are based on other factors. Cables must meet He requirements of He National Electncal Code (NEC) and local building codes based on Heir installed location Riser, plenum, general putpose). Cables should be easy to terminate and must be available in the high fiber counts required by the network's architecture. There are two distinct optical fiber cable designs that meet the specific demands of the cable environment: loose tube cable and tight buffered cable. a. Cable Design Options Loose Tube Cables [See Figure A.~.2.~.2-~(a and b)] Typical loose tube cable construction incorporates one to twelve fibers placed in gel-~Bed buffer tubes to isolate Hem from external forces. After optical fibers have been buffered, the buffer tubes are sided around an anti-buckling central member using He reverse-oscillation, or t:`NCH~Whasez rest NCHRP 3-51 · Phase 2 final Report A 1-67

~ ·e c' ~ - l 4 · - en Cal c a.) ._ = LL. c' ·L ~ ~ .o ~ an c) ~ ~ -c ~ o c' 0 HI r CL U) i. ~//~ ^ V//A- ' ~ 7 \~( 1 ~ l ~ _C In ~5 o 1 / ~ C) Q ._ to 0 U) ·- At) c' n ·O o~ ) ~ Q) m a' Q) C' a' C) U] a' n · _ ) a) \ \ r . . J m lo: fir a o I 0 ~ m U) lo lo a fir an 1 Cut Cal . at: 0 al .

"S-Z," standing memos. This stranding method enhances He tensile performance of the cable and allows easy m-span access to Be optical fibers. Dielectric strength members, such as fiberglass and framed yarns, are applied to provide tensile strength. The use of high strength yarns ensures cable flexibility and craft friendliness dunng installation and cable entry. A water blocking material is placed in the interstitial areas of Me cable to block the ingress and migration of water in the cable. Such cable is typically suitable for installation in up to ten feet of standing water without special precautions. The entire cable core is jacketed by a polyethylene (PE) outer sheath which provides excellent strength and a low coefficient of friction for easy instalIabon. Additionally, He polyethylene sheath contains carbon black to provide W resistance. Tight Buffered Cables [see Figure A.~.2.~.2-2 (a and b) ~ Tilt buffered cables are designed for use in intrabuilding backbones, horizontal applications, and interconnection/cross-connection applications. Tight buffered cables contain optical fibers that have been coated wig a thermoplastic buffer to a diameter of 900 Em (micrometers). Tight buffered cables are desirable for intrabuilding applications because of their ability to meet building fire code requirements as well as their increased physical flexibility, smaller bend radius, ease of connectorization, and easier handling characteristics in low fiber counts. These cables, however, are typically more sensitive to temperature extremes and mechanical disturbances than loose tube cables. As a result, tight buffered cables are generally not recommended for outside plant (interbuilding) applications. b. Available Reel Lengths Typical reel lengths are limited by several parameters ranging from fiber lengths (multimode only), to reel capacities, to installer's equipment limitations. The most common limitation in multimode systems is the fact that the maximum distance typical data rates cart be transmitted is only 2 kilometers. Similar performance limitations inhibit the lengths of copper Hat can be L:~h~.~t NIP 3-51 · PI 2 Few Ream A1-69

/ a' A) a) o ) o Q . _ Or a' _ ._ ~ a) D a) £ .a) a' ~, ~ ~ ~ ~ -it ~ .o I _=i~ ~ ~n ,~ Am . ::: :~- Cal in Q) o ) 0 D O (a . _ ) ~ a) A D ~ ._ a) m J · _ ~ a' 0 D .a) LO ) a' E ~ _ ~C 3 ~ · a' er lo lo z c m em - lo m n ~ I m ~L N N C~ ~: 0 CD ._

instaUed. Single-mode optical fiber can be used for distances up to 70 kilometers without regeneration; however, reed sizes, cable weight, and manufacturing and installation equipment constraints limit Me lengths of single-mode optical fiber cables. The lengths can be up to 12 kilometers (40,000 feet) for outside plant cables and up to 6 kilometers for indoor cables. c. Installations There are Free main types of installations: aerial, direct buried, and duct. All three of these nstaRation methods are widely used. Installation techniques are similar to those employed with copper Installation. The installer needs to be aware of We cable's minimum bend radius and tensile ratings under load (short term) and installed (Ion" term). In addidon, the cable planner needs to be conscious of the duct utilization, cable protection, and who National Electrical Safety Code (NEC) and /local codes. ]. Aerial Appropriate planning for aerial cable installations includes taking into account proper clearances and allowable cable and messenger stress loading. Planning for proper clearances requires knowing the "sag" characteristics of the (planned) installation. A clear understanding of We expected tensile loads placed on an aenal plant is necessary to ensure that legal safety requirements are met and We plant's expected lifeline is not unnecessarily shortened due to exceeding the cable's design limits. When considering an aenal installation, the cable's construction, span distance, allowable sag, type of messenger, and environmental loading conditions, as defined by the National Electncal Safety Code (NEC), must be considered. The optical fiber cable manufacturer can help in determining We proper installation parameter for each specific application. 2. Direct Buriec] When planning to direct bury an optical fiber cable, the soil condition and local environment are important considerations. If Were is a possibility of rodents gnawing through the cable, the use of armored cable is required; however, placement of a cable encoded in a conduchng medium underground increases We probability of lightning strikes. The metallic component will also require grounding and bonding at all building entrances. An armored cable also provides extra L:W~h~.~t New 3-51 · Phase 2 PI Rent A1-71

mechanical protection from rocky soil. The optical fiber cable must be instaBed at least 30 inches deep according to the National Electrical Code (NEC). A final concern deals with locating the cable once it is buried. If He choice has been made to install an aB-dielectric cable, Were is no way to tone the cable. This is usually overcome by burying a drop wire or metallic locating tape above the cable. 3. Duct The major concern when insuring cable in inner duct is the tensile rating of the cable. If the tensile load exceeds the rating of the cable, long term reliability of the optical fiber can be compromised. This may not be evident in the final system testing; however, it may show up in the next year or two. Duct installations can be accomplished a number of ways. The cable can be puDed in by attaching a pulling grip and having a pun rope In the inner duct. The cable can be hand pulled, using hand holes, or the cable can be jetted in. The cable jetting process uses high volumes of air blowing through He duct to assist the cable Trough the duct. In all of these modes the limiting factor is *fiction. There are many puBing lubncants available to reduce He amount of friction and Hereby allow greater lengths of cable to be instaHed. If He cable is longer Man what can be instaBed in one pun or jet, then He cable must be 'Y]gure-eighted" at He assist point or another cable jetting machine must be placed at He m~d-assist point. This allows longer lengths of cable to be instaBed without unwanted splice points. A second concern is the minimum bend radius of He optical fiber cable. Installations in manholes require that cable be brought out of He manhole to He installation equipment. In this case, routing should be designed to maintain He minimum bend radius ensuring no damage to He cable. d. National Electrical Code Restrictions of He NEC and local building codes must be adhered to when installing optical fiber cable. An understanding of the limitations imposed by He NEC will aid in cable selection and design of He network. Please note Hat He NEC is advisory in nature. Local building codes should be consulted to verify compliance web regulations in each area. L:~h~.~t NCH"3-51e P~2F~Re~n A1-72

Overview of UL listings The NEC identifies three intrabuilding regions wig regard to cable placement: plenums, risers, and general purpose. Plenum area: A compartment or chamber Hat forms part of the air distnbudon system and to which one or more air ducts are connected is a plenum. A room with a primary function of air handling is also considered a plenum space (Type OFNP). Riser: An opening or shaft through which cable may pass vertically from floor to floor in a building is a riser (Type OFNR). General Purpose: All over indoor areas Mat are not plenums or risers are categorized as general purpose (Type OWN). Different cables are specifically listed for use in each of these applications. The NEC does allow a cable wig a more stringent UL lisdng to be used in an application requiring a lesser UL listing. For example, a Type OFNP cable can be used in a riser application. A Type OFNR cable cannot be used in a plenum environment, however, unless other conditions are met. Substitutions may be an important consideration if an indoor run will travel through both plenum and riser areas. Plenum cable can be run on the entire route to avoid an additional splice point. This may not always be cost-effecEve, since plenum-rated cables may be more expensive than cables wig less stringent UL listings. Consult Be cable manufacturer for more information on these specific conditions. Use of Unlisted Cables Indoors The National Electrical Code allows He use of unlisted cable in inside plant applications, wig some restrictions. Unlisted cables are allowed to enter a building from the outside and extend up to 50 feet from the point of entry. If He cable is terminated within the first 50 feet, no special precautions are necessary. If the cable termination point is farther than 50 feet from He building entrance, special precautions must be observed. Non-conductive cables must be installed in conduit that is installed in accordance with Chapter 3 of the NEC. A conductive cable, containing some type of metallic component must be installed in rigid metallic conduit. ~:\NCHR~Phase:.rp' NCHRP3-51e Phase2F~nalReport A1-73

When a cable will be exposed to both indoor and outdoor environments in the same run (such as between two buildings), Mere is a choice between using loose tube cable for the entire run or transitioning to inside plant cable 50 feet or less from the point of entry into a building. A transition splice win slightly increase We fiber link loss and may add some cost to the installation. These considerations have to be weighed against the cost of nod metallic conduit or an alternate conduit installation that would be required to install unlisted cable to the desired ternunabon point; however, because Were is a cost difference between loose tube cable and tight buffered cable, the options should be compared. A combination of loose tube cable spliced to tight buffered cable might be more cost-effective. Grounding of Armored Cables The NEC requires that metallic components be grounded as close as possible to the point of building entry. The coated steel tape alienor of armored cables, steel central members, or steed messengers of figure-eight cables must all be grounded in this manner. e. Fiber Telmination Alternatives ]. Options In the traffic control environment, the designer/instaNer can often avoid the requirement of fiber to-fiber splicing by installing a continuous cable; however, because of the cable plant layout, length, duct congestion, transition between indoor and outdoor cable, or a drop and insert situation, splices cannot always be avoided. Typical field splicing can be grouped into two categones: fusion and mechanical. There are advantages and disadvantages for bow methods, but the choice primanly depends upon the application, customer preference, and volume of splices, as wed as He ~nstaBer's equipment preference and level of training. Both methods are field-proven and have excellent long term reliability. 2. Fusion Splicing Fusion splicing consists of aligning the cores of two clean (stripped of coating) cleaved fibers and fusing the ends together with an electric arc. The fiber ends are positioned and aligned using various methods. Alignment can be Axed or three-dimensional, manual or automatic, and is normally accomplished with the aid of a viewing scope, video camera, or specialized optical power meter, such as a unit for local injection and detection (LID) of light. Him voltage L::\NC~Phase2.rp ~NCHRP 3-51 · Phase 2 Fmal Report A1-74

electrodes, contained in the splicer, arc across the fiber ends as the fibers are moved together, fusing the fibers together. Maximum core alignment can be verified prior to splicing and splice loss measured after He fusion process by Be use of local detection devices and profile alignment devices. Currently, fusion splicers are available in a wide range of prices and features. The highest precision machines come USA a fiber cleaver, an LCD display, a high resolution video monitor, bu~It-in batteries for field use, and automated functions that align the fibers (using LID devices or a profile alignment system, or both). Not only do these fission splicers automatically align fibers, determine cleave quality, and fuse Be fibers, they also offer splice optimization and verification systems and provide the operator with accurate splice loss measurements. In addition, these fusion splicers provide high productivity after a short Gaining period. Typical splice loss under field conditions is less Can .05 dB. Medium range splicers sacrifice splice optimization inherent with Be LID, but offer automatic operation and splice loss estimation critical for low splice loss. They cost thousands less, yet they are still capable of basically the same low splice loss results as Be high precision machines. These splicers actively align the fibers in three dimensions using fixed V-groove technology with completely automatic operation, and splice loss calculation. Bow are extremely easy to use and provide a good combination of features for bow multimode and single-mode splicing. Typical splice loss for bow machines is less than 0.10 dB. Low cost machines offer Be low reflection characteristics inherent in fusion splicing win good splice loss and productivity. They do, however, sacrifice splice optimization and automation. Typical splice loss is O.IS dB. Meckanicat Splicing A mechanical splice, by comparison, is a junction where two or more optical fibers are aligned and held in place by a self-contained assembly approximately two inches in length. Single-fiber mechanical splices rely upon Be alignment of the outer diameter of Be fibers, making the accuracy of core/cIadding concentricity critical to achieving low splice losses. This method aligns Be two fiber ends to a common centerline, Hereby aligning the cores. The cleaned (stripped of coating) fiber ends are cleaved and inserted into an alignment tube, then L.WCH~h~c2.~t NCHRP 3-51 · PI 2 Few Ream A1-75

butted together. The tube has factory-instaDed index matching gel to reduce Fresnel reflections and loss at Me splice point. Usually, the fibers are held together by compression or friction, although some older mesons rely on epoxy to permanently secure the fibers. Win tuning, the Cam-type splices can consistently achieve excellent loss results (0.10 to 0.15 dB) on s~ngle- mode fibers. Mass Splicing For high fiber count applications, an increasingly popular method is mass splicing. The term mass indicates Mat multiple fibers are being spliced at once. Most common today are 12-fiber splices (2-, 4-, and 6-fiber splice chucks are also available). Mass splicing can be accomplished via fusion or mechanically and is faster than single-fiber splicing. 3. Protection Fusion and mechanical splicing are reliable and suitable for both indoor and outdoor use when Me splices are completed in accordance win Me manufacturer's instructions and are adequately protected. When splicing outdoors, typically the splices and stripped cable should be protected by a splice closure. When the cable is installed in a splice closure, there are venous methods of providing strain relief and protection of Me shipped fiber splice. All fiber splices are housed in splice trays or organizers inside a closure. The proper splice tray should be selected based on Me type of protection required by Me splice. For example, mechanucal splices have a form of strain relief and fiber protection built in which is then secured in a splice tray or organizer. Fusion splices, however, require additional protection and strain relief which can be provided by heat shrink tubing, crimp protectors' or silicone sealant (commonly referred to as RTV). For single fiber fusion splicing, the use of splice trays win organizers designed for use win RTV is recommended. Once the fibers are set inside small channels in Me organizer, Me RTV is added to Me channels, providing effective strain relief and protection to Me bare fibers. c.:\NCHRP\Phase:.'p ~NCHRP 3-51 · Phase 2 Fine Report A1-76

When splicing inside a building, a splice center can be used, provided rack or wall space is available. Additionally, most termination patch panels have built-in or accompanying splice centers which allow fiber termination and through splicing when required. 4. General Considerations While fiber splicing has been performed for a number of years, He technology is dynamic, with continual introduction of faster, simpler, and less expensive splicing equipment and consumables. The chosen splicing method affects both equipment (fusion splicer, mechanical splice fixtures, etc.) and hardware requirements (splice trays, splice closures and centers for storage and protection of Be splices). The primary considerations for an installer when determining the most appropriate method are: · Capital or rental expense versus consumable expense, · Volume of splices per crew (annually), Number of crews being deployed simultaneously, Labor costs, Customer preference, Training, and Reliability. Presently, an installer faces a capital investment or rental charge for fusion splicers, depending on the type of machine desired. Mechanical splicing requires a nominal charge ~tiaNy; however, mechanical methods have a per splice consumables cost. Fusion splicing has essentially no per-splice cost. For an installer already owning a fission splicer, fusion splicing is He most economical method. The economics of each type of splice are extremely dependent upon He number of crews, volume of splicing per crew, and labor rate. In addidon, the time required to perform each type of splice is dependent on the experience of the splicer. Fusion splicing generally ranges from 2 to 3 minutes per splice after set-up and preparation are complete. The installer must also consider how the fiber will be terminated and whether field connectorizadon or pigtail splicing will be required. It usually makes sense to use the same L;\NCHRP\Phase~rpt NCHRP3-51e Phase2~malReport A1-77

splicing technology, if possible, for both through splicing and pigtail termination splicing. Training must also be considered. Fusion splicing is a technical sew Mat must be acquired through an initial training penod. Mechanical splicing, however, requires little training and many crews can be trained and equipped~quickly. Splice loss values are comparable between single-fiber fusion and mechanical means, while mass splicing losses are slightly higher. When designing a system, a designer should allow sufficient loss margins for the splice loss. Though the ElA=A-568 Commercial Building Wiling Standard allows for a maximum individual splice loss of 0.30 dB for multimode fibers, today's technology makes possible average losses of 0.10 dB or belter. Lastly, Me installer must consider the preference of his customer. For example, many customers, including long distance camers and cable TV companies, specify fusion splicing because of the low reflectance needed for transmitting analog video signals. For the majority of local area networks and digital applications, reflections are insignificant. In those cases, it is generally preferable that Me end user specify end-to-end system attenuation and splice loss and let the installation contractor decide on the splice method. 5. Connector and Terminator One of the last steps in the installation of optical fiber cable is termination This section will discuss three methods of termination, with focus on field installation. In the field installation section, generic requirements for malting quality connections are discussed, as well as recommendations for which connector technology to use in which location. Fan-out options are also discussed. Lastly, a discussion of connector types is included (ST compatible versus SC) wig recommendations. There are three basic ways to terminate optical fibers. They are: pigtail splicing, preconnectonzed cable assemblies, and field connector~zation. These options apply to Me termination of both backbone and honzontal distribution fiber optic cables. Each option has advantages and disadvantages that depend on the application, installer expenence, and preference. L;U<CHR~Phasc2.rp' NCHRP 3-51 · Phase 2 Final Report A1-78

First, it is important to define the terminology used in connector technology since certain parts win be referred to often. While He style of connector may change, generically, the parts win be the same. 1. Boot 2. Stra~n-relief 3. Spring 4. Fe~Tule and ferrule holder 5. Latching mechanism 6. Dust cap Pigtail SpUc~g endface. Protects cable interface to fiber and maintains the fiber's minimum bend radius. Captures aramid yarn, typically used on patch cords and jumpers for pull-out resistance. Maintains positive force to keep endfaces touching. Houses He fiber once it is bonded into it and He endface is polished. Attaches connector to adapter. Keeps contamination to a minimum and protects polished A fiber optic pigtail is typically a one- or two-fiber cable Hat has been terminated on one end who a fiber connector. The other end remains untenn~nated. This unterminated end is spliced to He cable that requires termination. This splice can be either a fusion or mechanical splice. After splicing, He splice point is protected by a splice tray and placed into term~nadng hardware. Pigtail splicing has some advantages in He form of savings on consumables and elimination of spares; however, He disadvantages of hardware protection and material costs typically outweigh these advantages, specifically in premises applications. L:~.NCHRP\Phase2.rp ~NCHRP3-51 a Phase2FinalReport A1-79

Preconnector~zed Assemblies The use of factory connectonzed cable assemblies is recommended for use as cross-connecl equipment jumpers, work area jumpers, and patch cords because the installation (cable placement) of these jumpers is rarely difficult and Me short lengths are readily available. In addition, their use canonizes the labor and time involved in any ~nstaDation, and generally guarantees more consistent quality of workmanship. t, Preconnectorized assemblies are available in aB lengths and wad all connector types. Hybrid jumpers are also available with the equipment interface connector style on one end, and the cross-connect or outlet connector style on the over end. When equipment connectors do not match the connecting hardware interface, We use of hybrid jumpers, with different types of connectors on each end is recommended instead of hybrid adapters. Field Connector~zation General Connectorization Technology With the advent of easy-to-install field connectors and new methods of fanning out loose-tube cables, field connectonzation has become the most common method for tenn~nadng fiber optic cables in the ITS market. Use of field connectonzation throughout We network, is recommended TV He exception of patch cords, equipment cords, or cross-connect jumpers. Advancements now make field connectorization He best means of term~nahng optical fiber cables regardless of whether He fiber is single-mode or 62.5 An fiber, and regardless of whether it is of loose tube or tight-buffered construction. There are numerous types of connectors on He market, each requiring slightly different installation procedures; however, all connectors require two Important installation steps. First, the fiber must be secured in He connector who epoxy. This process is important to He long-tenn reliability of the connector. The epoxy keeps fiber movement due to temperature at a minimum, allows polishing without fear of fracturing He fiber, and seals He fiber from the effects of environment. In addition, it allows He fiber to be aggressively cleaned on the endface. Therefore, it is very important that the epoxy be present around He entire length of the bare L:\NCHRP\Phase2erpt NCHRP3-51e Phase2F~nalReport A1-80

fiber, around Me buffer where We fiber enters the connector, and as a bead surrounding the fiber on the endface of the connector. Secondly, He connector endface must be polished. A physical contact (PC) finish is recommended and specified by TIA/ElA-56SA. This means the fibers win be physically touching inside tile connector adapter as they are held under compression. Lack of a PC finish results in an air gap between the fibers and increases attenuation. There are several polishing methods recommended, which are typically dependent on He ferrule material used. In general, if the ferrule matenal is very hard, like ceramic, it is common for the ferrule to be radiused on the endface, and is referred to as preradiused. Softer ferrule materials such as composite thermoplastic or glass-in-ceramic may be polished flat. These materials wear away at approximately the same rate as He fiber and can therefore be polished aggressively and still maintain a PC finish. A/ElA-568 specifies PC finish connectors for both 62.5 ,um and single-mode connectors. The standard specifies a reflectance of < -20 dB for 62.5 ,um and ~ -26 dB for single-mode. A PC polish should ensure these return loss values in the field. Typical specifications include a PC polish for 62.5 En and a Super PC finish for single-mode with a reflectance of ~ 40 dB. In lieu of field testing for reflectance values, use of connectors and polishing techniques that ensure these reflectance values is recommended. Connector Instaliation Options Even Cough aR fibers must be epoxied into the connector and then polished, there are many alternatives for installation in the field. This section offers some explanation of ST and SC connectors with recommendations as to which connector should be used in each part of He network; however, installer preference based on expenence, labor rates, and tools often determines which technology is selected. Heat-cured Connectors Advantages: Batch tenn~nabon, available in single-mode and multimode, and low connector material cost. u~NCH~Whas~.'p ~NCHRP3-51e Phase2PinalReport A1-81

Heat-cured connectors are a cost-effective way to make cable assemblies at an assembly house, or to install in a location where a large number of fibers are terminated at one time. The connector piece part cost is generally low, and several ferrule materials are available for heat- cunng; however, consumables cost can become excessive due to limited epoxy life. Additionally, heat-cured connectors typically require more time and skill to install. They provide an acceptable termination method for Main or Intermediate Cross-Connects where term~nadng large numbers of fibers produces econom~zation. Uv-cure] Connectors Advantages: Very low consumables cost (< $0.30 per part), no heat generation, very robust polish for 99+% yield, and faster installation. The increase in field installation has become the focus for connector development in recent years. Decreases in epoxy and polish hme have created connectors termed! "quick mount," aimed at reducing Be labor required for insuring connectors. Recent advances in He W-curable connector have allowed manufacturers to offer a pre-assembled, reduced-piece-part connector, and a multicuring W Milt to increase productivity. The UV-curable connector product line can be tenned glass-insert connectors. The ferrule features a glass insert surrounded by ceramic matenal. The glass insert allows the installer to do two things. First, the glass insert propagates light; therefore, a W-curable adhesive can be used to bond the fiber into the female in a mere 45 seconds. Secondly, He glass insert protrudes beyond He ceramic outer sleeve so He glass insert is polished Long with He fiber. We glass is roughly the same hardness as the fiber and polishes at He same rate.) This results in a flat PC polish that routinely gives 99~% yield in the field. The glass-insert connector product line offers the installer an easy-to-use and cost-effective alternative to heat-cured connectors. The UV-curable connector saves labor, consumables, and scrap, making it one of the most cost-effective connectors on He market. Manufacturers recommend use of the W-curable connector in high fiber count locations such as Mam, Intermediate, and Horizontal Cross-Connects (MC, IC, and HC). Additionally, the W-cured connector could be used at multi-user outlets where typically 12 to 24 fibers are terminated at one location. ~:\NCHRP\Phase2.rpr NCHRP3-51e Phase2FmalReport A1-82

No-Cure, No-Polish Connectors Advantages: No epoxy, no polish in the field, no consumables, few tools needed, and minimal set-up required. This connector incorporates a fiber stub already bonded into the ferrule in the factory, where He endface of Be ferrule is polished to a PC finish. The over end of the fiber is cleaved and resides inside the connector. The field fiber is cleaved and inserted into Be connector until it '`butts up" against the fiber stub. A simple cam actuation process completes the connector web no epoxy or polishing required. The advantage of the cam-type connector design over other no-cure connectors is Mat the fiber is fully protected from the environment. Since the epoxy process and polishing process are performed in the factory, it is virtually certain the connector will last the entire life of Be network. The most significant advantages of the cam-type connector are clear when using it for installation at the outlet. The only tools required are a stripper, a cleaver, the workstation installation tool, and an alcohol pad. As a result, assembly space can be kept to a minimum, set- up is quacks and assembly is relatively fast and easy with no consumables. At the Work Area Telecommunications Outlet, where few fibers are terminated, Be cam-type connector is the connector of choice. Evaluation of Connector Choices Evaluation of connector technology can be difficult. Ultimately, connector users must base Weir buying decisions on cost. The Total Cost Connector Equation consists of: Materials (unterminated bag-of-parts, tool kit) Consumables (adhesive/epoxy and polishing paper) Labor (curing, polishing, set-up, and tear-dou n) + Scrap (as a % of above subtotal) Total Installed Connector Cost. u\NC~Phas~.rp ~NCHRP3-51e Phase2F~nalReport A1-83

Fan-out Kits When certain cable types, bow loose tube and fight buffered, are to be field connectonzed, fan- out kits may be required. It is recommended Mat with loose tube, 245 ,um coated fibers, a fan- out kit be used to maintain We flexibility and ease of handling of We fibers. Not recommended is We use of fan-out kits for tight-buffered cables when terminated in patch panels or outlets, because We 900 Am buffered fibers provide excellent reliability when protected by the patch panel. There are severe alternatives for fanning out cables; the decision depends on We type of cable used and We application. SC and ST Connectors If a substantial backbone network has been instaDed with ST compatible connectors, and Me current need is merely to add to an existing system, staying wad the ST compatible connector is recommended. If 1 here is no installed base, or it is limited compared to future capacity, Me 56SSC Interface should be given strong consideration. When planning a fiber-to-desk network, the 568SC interface should be considered because of the benefits of duplex connection at the user workstation. Siecor does not recommend Me use of hybrid adapters (ST-compatible to SC) or the use of duplex ST-compatible connectors. A.~.2.~.3 Fiber Costs ]) Instai~ion Costs staBation costs vary from state to state and union to union. Each individual system win have different requirements Mat wiR either raise or lower Me cost of installation. a. Duct Duct installation costs win vary widely depending on the condition of the inner duct and the layout of the plant. If there are multiple 90 degree turns in Me duct bank, it is difficult to install long lengths of cable in a single pull. The turns create sidewall pressure on the cable, depending on Me incoming tension on Me turn. If there is significant tension prior to Me turn, it is likely that the pun will not continue a long distance after the turn. If a specific pun has multiple turns in a short distance, it is best to place Me turns at Me beginning of Me pull segment. This gready L;\NCHR~Phasc2.rp ~NCHRP3-51 · Phase2FinalReport A1-84

reduces sidewall pressure in Me turns. Cable manufacturers can assist in We development of a pull plan for a specific duct layout. Typical inner duct installation costs range from $0.75 to $~.50 per sheaf foot. b. Aerial Aerial installations are generally less expensive Man direct buried and duct pulls. The main concerns are the relative sag and tensions of the plant to be instaDed. The cost win very depending on span distances, and whether the installation requires overIashing to more than one cable, or insuring a figure--type cable versus overIashing to a messenger. Typical installation costs we be about $0.50 per sheath foot. c. Direct Buried This memos has Me greatest vanability in cost. There are many concerns centered around the type of soil in which the cable watt be placed. If the soil is rocky and may require blasting to complete installation, Me cost win be greater. If the cable is instaRed using trenching, Me cost may be greater Man if a vibratory plow is used. Another concern is the number of roadway crossings that may have to be directionally Aided. Typical costs range from $~.00 to $3.00 per sheath foot. 2) Measurement and Installation Equipment ~- There are two choices for obtaining optical measurement and instaDation equipment. The equipment can be rented on a per day/week/mon~ basis or it can be purchased. If Me proposed job is going to be a one-time installation of optical fiber, Me equipment should probably be rented. If Mere are plans to install a large quantity of optical fiber, Men Me equipment should probably be purchased. Some general purchase cost estimates, depending on Me features, are: fusion splicers, $10k to $40k; outdoors, $10k to $50k; and connector tools kits, $800 to $1500. The expenditure of capital funds may force the use of outside contractors to complete Me installations. ~\NCHRP\Phase:.rp ~NCHRP 3-51 · Phase 2 Fmal Report A1-85

3) Personnel - Training and Contract There are two basic personnel options when planning to install optical fiber cables. The work can be contracted to an outside vendor or internal personnel can be trained- to complete the work. The work is typically contracted on either a complete job basis or a per fiber splice basis. To have internal personnel trained typically takes 3 to 5 days and approximately $700 to $1500 per student, depending on the type and length of class. In addition, students win require several hands-on field assignments to get completely up to speed on Me ins and outs of optical fiber . . sp. 1cmg. A.~.2.~.4 Fiber System /nsfa//ation Procedures - Testing an`Documenfafion Testing of the optical fiber system is one of the most crucial steps in instaUing a fiber basis network. Testing We instaRed system ensures He end-user that the network has been instaRed correctly and that there win be no problems related to the cable plant when He system is turned on. Testing also verifies system performance in relation to the specifications and establishes reliability with He vendor and contractors. One of the most important considerations, and often He one given the least thought, is the fact that adequate testing and documentation allow for minimal downtime and efficient system reconfiguration. A wed documented system allows a maintenance technician to look at the down link with an OTDR and Pus locate a fault site by comparison to He instaBed traces. He wed documented system creates a map of He instaded cable plant and summarizes He locations wad patch panels, both of which create an easy plan for upgrading or reconfiguring He instaBed network. There are Free types of testing that should be completed after He cable has been installed, spliced, and connectorized. These are end-to-end attenuation testing, OTDR testing, and transm~tter/receiver testing. The end-to-end testing is completed to verify that the total link loss meets the link loss budget. It measures He total optical power loss from connector tip to connector rip. This measurement includes fission and mechanical splices as well as connector pairs. This measurement should be completed for bow wavelengths of operation for the type of fiber that is instaRed (850 rim and ~wCHRP\Phase:.rp: NCHRP 3-51 · Phase 2 final Report A1-86

1300 nm for multimode and 1310 nm and 1550 nm for single-mode). This measurement gives a number as the total optical power loss on the link, independent of direction. The second measurement Mat should be completed is end-to end OTDR ~cesdng. This gives the end user a 'picture' of the attenuation associated with We fiber, each connector, and each fusion splice. This allows for easy efficient network trouble shoodng. Traces should be created for each operational wavelength for the type of fiber in the system. The OTDR can also be used for individual splice loss measurements. The principle that the OTDR works on allows for the distance to be calculated as wed as the attenuation. This feature allows the operator to determine the actual distance between the splice and the location where He measurement is taking place. trouble shooting, this determines He distance to He fault. The final testing that should be completed is the transmitter and receiver level testing. This test ensures Hat the transmitter is launching the specified amount of optical energy and verifies that He received power is great enough to be detected by He receiver. Once all of the testing is completed on He instaBed cable plant, it must be documented. Typical documentation includes the end-to-end attenuation testing, splice loss measurements, the OTDR traces, He transmitter and receiver level testing, and route diagrams. The route diagrams are included to give a physical layout of He cable plant. Documentation should include He cable part numbers, manufacturer, cable length markings, cable routing map, location of splice points, and He hardware at each splice location. These drawings allow any future system upgrade or trouble shooting effort to be fast, efficient, and accurate. A.~.2.2 Low~end Fiber Optic Transmission Systems for ITS Applications by Irwin Maw, Technical Director, Maw Associates, Inc. Aniityville, New York /ntroaluction There are a significant number of applications for so-called "Low-end Fiber Optic Transmission Systems" in He emerging [rs market. These systems transmit the common data and video signals used by this marketplace via interference-free, ground-Ioop-free fiber optic cable, and are ~:\NCHRP\Phasc:.~p' NCHRP 3-51 · Phase 2 Final Report A1-87

intended for use in localized signal distribution and monitoring installations or as supplementary signal paths to and from central data collection points. This section will attempt to provide an introduction and guide to understanding He nature and operation of these systems. Advantages of Fiber Optic Transmission To fully appreciate Be benefits of fiber optic transmission systems, it is necessary to remember two basic facts: optical fiber is made of glass or plastic, and the signal it carries is light. There is absolutely no electncal or metallic connection between the two ends of the system. The primary advantages of these properties are: . . . No interference: Since the carrier of signal information is light, at a frequency thousands of times higher than normal electrical signals, fiber optic cable is simply not affected by conventional electrical Interference. It will not pick up stray RF or electro-magnetic energy. It can be run inside a conduit win a high voltage power feeder without concern and even lightning win not effect it. Wide Bandwidth: The attenuation of fiber optic cable is uniform as a function of distance, not frequency dependent as is the case wad coaxial cable. As a result, high data rates or high frequency signals can be conveyed over long distances without repeaters or special equalizing equipment. Signal fidelity is perfect even over thousands of meters. Total Isolation: As there is no electrical connection between Be two ends of the fiber optic transmission system, there is no possibility of ground loops or pickup of signals other than Pose specifically desired. · Safety: Since glass is unaffected by most chemicals or solvents, the fiber optic cable can be used in all sorts of hazardous environments. A broken fiber win not cause a spark leading to an explosion nor win it create a dangers to personnel. ~ addition, since there is no electrical current, Be effects of water are non-ex~stent. Short circuits are a thing of Be past. c:`NCHRP`Phase:.'p ~NCHRP 3-51 · Phase 2 Final Report A1-88

The fiber optic sYstem's ability to carry interference-tree si Pl.RlR R~v~.~1 miles through all ~ - r-- -J ~ J ~ d ~ ^^-~-^^-- ^' ---~ ~-~-~ lA~O Ill ~1 ~1~ of hostile environments without amplification or regeneration make it the ideal transmission medium for most ITS applications. Low-end vs. High-end Fiber Optic Transmission Systems Low-end fiber optic transmission systems primarily consist of point-to-point links, carrying data wad bit rates of 50 to 100 Kb/s or less compared to high-end systems which usually operate at multi-megabit data rates. SONET, ATM, and FDDI, for example, constitute high-end systems while RS-232 and RS~22 links, operating at data rates of 9600 Baud, for example, constitute low-end systems. High-end systems may also consist of multi-channel broadband bi-d~rectional networks cawing multiple RF-encoded video signals. Low-end systems are usually limited to one or two baseband video signals although bi-directional systems do exist. In addition, tow-end systems often operate over relatively short distances (up to 2 or 3 miles) while high-end systems operate over distances of 20 to 30 miles or more. In cost comparison, low-end systems usually cost from $500 to $1000 per link while highland systems can cost tens of thousands of dollars per system. SdN Were is clearly a Beet! for bow types in the emerging ITS marketplace. Theory and Concepts of Fiber Optic Transmission The Fiber Optic [ink The basic point-to-point fiber optic transmission scheme, as used in most low-end products, is shown in Figure A.~.2.2-! and consists of three elements: c:\NC~Phase:.`pr NCHRP3-51e Phase2F'nalRepon A1-89

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Optical transmitter, which converts an electrical analog or digital signal into a corresponding optical signal. The source of the optical signal can be either a light emitting diode, or a solid state laser diode. Most operation is at a wavelengths of 850, 1300, or 1500 nanometers. 2. Fiber optic cable, consisting of one or more glass fibers which act as waveguides for We optical signal. This cable is usually constructed along Me lines of similar electrical cable, but with special protective means for Me optical fiber within. For systems requiring transmission over distances of a few kilometers, or where two or more fiber optic cables must be joined, an optical splice is commonly used. Optical receiver, which converts the optical signal back into a replica of the original electrical signal. The detector of the optical signal is either a PIN-type photodiode or an avalanche-type photodiode. Optical Transmitters The basic optical transmitter converts input electncal signals to modulated light for transmission over an optical fiber. Depending on the nature of dais signal, the resulting modulated light may be turned on and off or may be linearly modulated between two predetermined levels. Figure A.~.2.2-2 is a graphic representation of these two basic schemes. Light Sources The most common devices used as the light source in optical transmitters are Me light emitting diode ~ED), and the laser diode ~D). In a fiber optic system, these devices are mounted in a package that enables an optical fiber to be placed very close to the Milt emitting region In order to couple as much light as possible into the fiber. In some cases, the emitter is fitted with a tiny spherical lens to collect and focus light onto the fiber. In other cases, a fiber is "pigtailed" directly to the actual surface of Me emitter. Obviously, Me main goal is to couple as much light to the tiny optical fiber as possible. OEDs have relatively large emitting areas and as a result are not as for good light sources as LDS. They are much more economical, however, and also much easier to interface wig. LDs on the t:\NCHRP`Phase2.rp: NCHRP 3-51 · Phase 2 Final Report A1-91

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over hand have very small light emoting surfaces and can couple many times more power to Me fiber than L`EDs. They usually require more elaborate circuitry to operate properly. Operating Wavelengths LEDs and LDs operate in We infra-red portion of the spectrum so Mat their light output is usually invisible to Me human eye. The exact operating wavelengths are chosen to be compatible web the optimum transmission wavelengths of glass fibers and sensitivity ranges of photo diodes. The most common wavelengths in use today are: 820 to 850 nanometers, 1300 nanometers, and 1550 nanometers. Modulation Methods LEOs and LDs, as previously stated, are modulated in one of two ways: on and off, or linearly. Figure A.~.2.2-3 shows simplified circuitry to achieve either method wad an LED. As can be seen from the figure, a transistor is used to switch the LED on and off in step with an input digital signal. This signal can be converted from almost any digital format, by He appropriate circuitry, into the base drive for the transistor. Overall speed is then determined by the circuitry and speed of the LED. Used in this manner, speeds of several hundred megahertz are readily achieved for LEDs and thousands of megahertz, for LDs. Linear modulation can be accomplished by an operational amplifier circuit. The inverting input is used to supply the modulating drive to the LED while the non-~nverdug input supplies a DC bias reference. This reference is usualEy chosen to be at half the maximum desired output of the LED. As in the case of the on/off circuit, maximum speed is determined by the LED and the circuitry. Digital on/off modulation of an LED or LD can take a number of fonns. The simplest, as we have already seen, is "on" for a logic 1, and "off' for a logic 0. Two other common forms are pulse width modulation, and pulse rate modulation. ~ the former, a constant rate of pulses is produced win one urban signifying a logic "1" and another wide, a logic "0." In Me latter, Be pulses are all of He same width but He rate changes between logics "I" and "0." ~:\NCHRP\Ph~.rp' NCHRP 3-51 · Phase 2 Final Report A1-93

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Analog modulation can also take a number of forms. The simplest is intensity modulation where He brightness of an LED is varied in direct step win Be variations of Me signal to be tr~srn~tted. In over methods, a camer is frequency modulated win another signal or, in some cases, several camers are separately modulated with separate signals. All are Den combined and transmitted as one complex waveform. Figure A.~.2.2-4 shows ad of the above modulation melons as a function of light output. The equivalent operating frequency of todays LEDs and LDs is extremely high, on We order of 1,000,000 GHz. The operating bandwidth of these devices is also quite high, about 1,000 GHz for an LD and 10,000 GHz for an LED. Unfortunately, today's technology does not allow this bandwidth to be selectively used in the way that conventional RF transmissions are used. Rather, the entire optical bandwidth is turned on and off similar to the way early "spark transmitters" in He infancy of radio, turned wide portions of the RF spectrum on and off. Research being done, however, to attempt to fine tune these devices so that, in the future, coherent transmissions as they are caned, may wed be the way the fiber optic field progresses. The Optical Fiber Once the transmitter has converted He input signal to whatever form of modulated light is desired, the light must be "launched" into the optical fiber. To understand He venous factors Hat must be considered in this operation, as weB as what happens to the lift during its journey Trough the fiber, there are certain parameters that should be understood about fibers and light. As previously mentioned, there are two methods whereby light is coupled into a fiber. One is by pigtailing, and the other by simple proximity to an LED or LD. When proximity coupling is employed, He amount of light that win enter the fiber is a function of one of four factors: the intensity of He LED or LD, the area of He light emoting surface, the acceptance angle of He fiber, and the losses due to reflections and scattering. ~:`NCHR~Phas~p: NCHRP 3-51 · Phase 2 Final Report A1-95

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Intensity The intensity of an LED or LD is a function of its design and is usually specified in terms of total power output at a particular drive current. Sometimes this figure is given as actual power Hat is delivered into a particular type of fiber. AD over factors being equal, Be more power an LED or LD can provide, the more power "launched" into a fiber. Area The amount of light "launched" into a fiber is a function of Me area of We light emoting surface and He area of He light accepting core of He fiber. The smaller the difference in this ratio, He more light "launched" into He fiber. Acceptance Angle The acceptance angle of a fiber is determined by He numencal aperture (NA) of He fiber. The numencal aperture is defined as He sine of half of He acceptance angle of He fiber. Typical NA values are 0. ~ to 0.4, which correspond to ~ ~ to 46 degrees. Other Losses Other than opaque obstructions on the surface of a fiber, Here is always a loss due to reflection from He surface of He fiber. This loss is caned the FresneB Loss and is about 4% for each transition between air and glass. There are special coupling gels Hat can be applied between glass surfaces to reduce this loss when necessary. Fiber Characteristics There are three types of fibers in use today: Step Index, Graded Index, and Single Mode. The first two are also referred to as multi-mode fibers. Figure A.~.2.2-5 is a drawing of He details of each and how light tends to propagate through them. L:WCH~h=~t NCH~3-51~ Ph~e2F~Re~n A1-97

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As can be seen from the drawing, step index fiber consists of a core of low-Ioss glass surrounded by a cladding of lower refractive index glass. This causes light to continually "bounce" between Me core/cIadding interface along the entire length of We fiber. In graded index fiber, only one type of glass is used; however, Me index of refraction gradually decreases as Me distance from the core increases. The result of this is that lift continuously bends toward the center of the fiber. In single mode fiber, Me core is so small that only one mode of propagation can exist. (apical fiber is commonly characterized in teens of Me core/cladding dimensions, which are given in microns. Currently, there are two popular sizes in general use although larger and smaller sizes do exist for special applications. The popular sizes are 62.5/125 multimode and 8- 10/125 single mode. Multimode fibers are In common use for short and medium length point-to- point transmission systems, while single mode fiber is commonly used for long distance purposes. Multimode fiber is usually convex by L`EDs while single mode fiber is almost always Given by a laser diode. Other Man the losses exhibited when coupling LEDs or LDs into a fiber, Mere are two other areas where losses can occur. One is as the light travels through the actual fiber and Me other is when Me light leaves the fiber. The core of an optical fiber is made of ultra-Iow-loss glass. Considering Mat light has to pass Trough thousands of feet or more, the purity of the glass used must be extremely high. As a comparison of Me purity of this glass, consider a piece of broken window glass. The edges appear green because light passing edgewise Trough the glass must travel several inches. Windows appear clear because the light paw is only I/16 to I/4 inch long. Imagine Me loss in a thousand feet! Most genera purpose optical fiber exhibits losses of 4 to 6 dB per Km at a wavelength of 820- 850 nm. When Me wavelength is changed to l 300nm, Me loss drops to about 3 to 4 dB per Km, while at 1550 nm it is even lower. Premium fibers are available with loss figures of 3 dB per Km at 820-850 nm and 1 dB per Km at 1300. These losses are the result of random scauenng of light and actual ~mpunties within Me glass. t.:\.NCHRP\Phase:.'p: NCHRP 3-51 · Please 2 Final Report Al-99

Another source of loss within a fiber is due to excessive bending. If a fiber is bent around a comer or edge such Hat its bend radius is less than about ~/z inch, light bouncing or being refracted through He fiber win leave He core area resulting in loss. The smaller He bend radius, the greater the loss. It is always advisable, therefore, to limit any bend in a fiber optic cable to about one inch. All of the above attenuation factors result In simple attenuation that is independent of bandwidth. In other words a 3 dB loss means Hat 50% of He light urn be lost whether it is being modulated at 10 Hz, or 100 MHz. There is an actual bar~dw~d~ limutahon of optical fiber, however, and this is measured in MHz or Km. The easiest way to understand why this loss occurs is to refer to Figure A.~.2.2-6. It should be noted that light entering at a small angle has a shorter paw through He fiber than light entering at an angle close to He maximum acceptance angle. As a result, different "rays" of light reach He end of He fiber at different times, even Cough the original source is the same LEO or LD. This produces a "smearing" effect or uncertainty where the start and end of the pulse occur, and it limits He maximum frequency that can be smutted. Typical bandwidths for common fibers range from a few hundred MA per Km for multimode fiber, to thousands of MHi per Km for single mode fiber. A fact to consider when designing high speed systems is that the fiber bandwidth win reduce in direct proportion to the length of the fiber. A 400 MA per Km fiber, for example, win only support a 400 MHz signal if He length is ~ Km. Likewise a 200 MHz signal will only support a 200 MHz signal at 2 Km. Figure A.~.2.2-7 shows typical degradation of band for a typical fiber. Fiber optic cable comes In aB sizes and shapes. Like electrical cable, He actual construction of He cable itself is a function of He final application. The basic optical fiber is provided wig a buffer coating which is used mainly for protection during manufacture. The fiber is Hen enclosed in a loose tube which allows the fiber to flex and bend, particularly when going around corners or when being pulled Trough conduits. Around He loose tube is a braided Kevlar strength member which absorbs most of He strain put on He fiber during instalIabon. Finally, a PVC outer jacket seals He cable and prevents moisture from entering. This type of cable construction is ideal for most inter-building applications where ~:\NC~Phase:.rp ~NCHRP3-51e Phase2F~nalReport A1-100

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extreme ruggedness is not required. Coincidentally, fiber optic cable looks and handles much like common coaxial cable. Cables are available for just about any application from direct buned, armored rodent resistant cable with steed outer jackets, to UL approved plenum grade cable. Multi-fiber cable in all of We above constructions is also available. There is another range of fibers Mat should be briefly mentioned for informational purposes that are normally not employed for series data transmission. These are the very large core silica fibers, and the types made of plastics. Silica fibers are usually available with core sizes that range from lOO microns to 1000 microns (l mm). These couple very large amounts of light but have very low bandwidths and are therefore primarily used for sensors and applications that involve high power laser transmission. Fiber optic cables used for medical laser survey employ these types of fibers. Plastic fibers are occasionally mentioned for use in short-hau} data transmission systems, but these fibers exhibit very high attenuation levels on Me order of 100 to 200 dB per Km . The usable distance that can be covered is therefore quite short. The large core diameter (1 mm typically) does initially couple a large amount of light so these fibers are sometimes used for very short data links within equipment. An isolation system for use as part of a high voltage power supply would be a typical example. Optical Connectors Fiber optic cable is usually connected to peripheral equipment and to other fibers by means of optical connectors. These connectors are similar to Weir electrical counterparts in function and outward appearance but are actually high precision devices. In operation, Me connector centers Me small fiber so Mat it lies directly over and in line wig Me light source (or over fiber) to tolerances of a few tenths of a thousands of an inch. Since Me core size of common 62.5 micron fiber is only about 0.003 inches, it is easy to see why such extreme tolerances are necessary. :`NC}~Phase2.'pr NCHRP3-51 · Phase2FmalReport A1-103

The ST Connector There are many different types of optical connectors but the so-called ST style is the most popular type in use today for multimode fibers. Primarily developed by AT&T for telecommunications purposes, this connector is a spring-Ioaded tw~st-Iock type of design with a locating keyway to prevent rotation. A typical mated pair of ST connectors win exhibit less than ~ dB of loss. ST connectors are also available for use wad single-mode fibers. ST connectors are installed by securing the fiber into a tiny, close-fitting hole within the barrel using epoxy. Then the fiber is ground and polished to a smooth clear finish, flush and parallel with the end of the barrel. Finally, the cable jacket is secured to the rear of the connector with epoxy or by crimping. Once an installer is trained in Me procedure (which takes about 30 minutes to an hours, ST connectors can be installed In about 10 to 15 minutes per connector, much of this tune is waiting time for epoxy to set. Recently, a no-epoxy version of Me ST connector has been developed which significantly reduces installation time. The SMA Connector An older optical connector, Me SMA connector, is still found in some systems. The SMA usually has a step-down front barrel and is recommended for connecting fibers to each other or to fiber optic transmission equipment. Two plastic sleeves are supplied with each type connector. A half sleeve is supplied for connecting to transmission equipment and a full sleeve, for connecting two plugs to each over to produce a splice. Either sleeve provides the unnost in tolerances and Be lowest losses for an SMA connector. A mated pair of SMA connectors will usually exhibit a loss of less than I.5 dB. Another version of the SMA connector does not have a step-down front. It tends to be less accurate and is commonly used in short distance applications. Stainless steel is Be most widely used material for ST or SMA connectors because it is durable, maintains high tolerances and is the least corrosive of the popular alloys. Aluminum' zinc, and brass are lower-cost alternatives, but these should only be chosen for indoor environments as Hey exhibit limited corrosion resistance. c:`NCHRP`Phasc:.rp ~NCHRP 3-51 · Phase 2 final Report A1-104

The FCPC Connector The FCPC connector is Me most popular choice for use with single mode fiber. Borrowing the locating key~vay from Me ST and the hard screw lock from the SMA, Me FCPC provides the best of both connectors. Rotational errors are eliminated by the keyway while the screw lock prevents changes in attenuation from cable pulling. A mated pair of FCPC connectors will usually exhibit a loss of less Man 1.0 dB. Other types of optical connectors available are too numerous to mention. Although there is no real standard, when in doubt, the ST (for multimode use) and the FCPC (for single-mode use) are usually good choices. Optical Splices While optical connectors can be used to connect fiber optic cables together, there are over methods that result In much lower losses. Two of the most common and popular are Be elastomenc splice, and the fission splice. Both are capable of losses of less Man 0.5 dB. A carefi~By performed fusion splice can exhibit a loss of only 0.1 dB. The elastomeric splice consists of a precisely formed "Vet' groove inside a precision glass sleeve. The fibers are cleaved and then pushed into the sleeve where Hey come in contact wad each over. An optical coupling gel is also injected at the fiber junction to eliminate reflective losses. When everything is in position, a W curing epoxy is added to lock everything into place and complete the procedure. Elastomeric splices are available for all fiber sizes including single mode fibers. The fusion splice is Be lowest loss splice. In a fusion splice, one fiber is carefully aligned win Be over fiber. Then the glass of Be two fibers is actually melted together win an electric arc. The result is a continuous fiber without a break. Fusion splices unfortunately require special expensive splicing equipment but Key reduce splicing time to about ~ minute per splice. If many splices are necessary, Be value of time saved may outweigh Be cost. Since a fission splice is fragile, mechanical devices are employed to protect Be finished splice. A diagram of a completed fusion splice is shown in Figure A.~.2.2-~. u\NCHRP`Phase2.rp' NCHRP 3-51 · Phase 2 Fmal Report A1-105

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Optical Receivers The basic optical receiver converts the modulated light coming from He optical fiber back into a replica of the original signal applied to the transmitter. The detector of this modulated light is usually a PIN or Avalanche-type photodiode. This detector is mounted in a connector similar to the one used for the LED or LD. Photo diodes often have large sensitive detecting areas compared to Be size of Me fiber. This diminishes We need for special precautions in centering the fiber win the result that optical receivers are usually much less sensitive to alignment than transmitters. Since the amount of lift Hat exits a fiber is quite small, optical receivers usually have high gain first stages. This makes them prone to overloading. Undike transmitters, optical receivers must be used only wad the fiber size for which Hey were designed. A s~ngle-mode receiver for example, designed to accept He tiny amount of light coming from an 8/10 micron fiber, would overload if connected to He output of a 62.5 micron fiber. By He same token, a 62.5 micron transmitter would only launch a tiny amount of light into an 8/10 micron single mode fiber. As in He case of transmitters, optical receivers are available in analog or digital versions. Either type usually employs an analog pre-amplifier stage followed by an al og or digital output stage depending on He type of receiver. Figure A.~.2.2~9 is a functional diagram of a simple al og optical receiver. The first state is an operational amplifier connected as a current to voltage converter. This stage takes He thy current from He photodiode and converts it into a voltage in the millivolt range. The next stage is a simple operational voltage amplifier. Here He signal is raised to He desired output level. Figure A.~.2.2~10 is a functional diagram of a simple digital optical receiver. As in the case of the analog receiver, the first stage is a current to voltage converter. The output of this stage, however, is fed to a voltage comparator, which produces a clean digital output signal with a fast rise time. L;~CHRP`Phase2 rip NCHRP 3-51 · Phase 2 Final Report A1-107

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These two basic optical receivers form Me heart of many over elaborate systems. Demodulators, various digital protocol converters, etc., can be added to Hem to configure almost any type of optical transmission system desired. Designing a Fiber Optic System The design of a fiber optic system requires that several primary factors be considered. While not complicated, these determinations are necessary to assure that enough light Will be present at We receiver for proper operation and Rat Be final overall system will operate as desired. Step-by-step, the procedure is as follows: I. Determine the correct transmitter and receiver based upon the signal to be transmitted (analog, digital, audio, video, RS-232, RS422, etc.) 2. Determine the operating power available (AC, DC, etc.) 3. Detelmine Be special modifications necessary (impedances, bandwidths, special connectors, special fiber size, etc.) 4. Calculate We total optical loss (in dB) in We system by adding the cable loss, splice loss, and connector losses. Some of these parameters should be available from the manufacturers of Be components. Others may have to be measured in Be actual system. 5. Compare the loss figure obtained in step 4 win the allowable optical loss budget of Be receiver. A safety factor of at least 3 dB in the entire system is necessary. 6. Check that Be fiber bandwidth is adequate to pass Be signal desired. 7. If any of Be above factors are not adequate, select either a different transmitter/receiver combination, or a lower loss fiber. The sample specification guide in Figure A.~.2.2-~1 provides an organized procedure for obtaining Be necessary intonation when actually designing a system. c:\NCHRP`Phascz.rpr NCHRP3-51· Phase2F~nalRepon Al-110

Figure A.~.2.2~1~ Sample Fiber Optic Transmission System Specification Guide 1. Application: Brief description of intended use. Anticipated yearly quantity 2. Electrical Parameters: Analog Digital Over kaput Voltage Output Voltage Input Impedance Output Impedance Signal/Noise Ratio Bit Error Rate DC or AC Coupled System Gain (hi) Compatibility (RS-232, TTE, etc.) BandwidWData Rate Signal Connectors Temperature Range Power Availability Power Connectors Other Details 3. Fiber Optic Parameters: Optical Wavelength Optical Connectors Fiber Core Diameter Cladding Diameter Fiber Cable Length Attenuation (dB/Km) Ambient Requirements Environmental (Underground Conduit) Temperature Range Other Details 4. Mechanical Parameters: Housing Size (Case, P/C Board) Environmental (Outdoors, Hazardous) Mounting Method Over Details _ S. Additional Comments: L;WCHRP\Phase2.rpt NCHRP 3-51 · Phase 2 Final Report Al-111

A.162.3 SONET SONET (Synchronous Optical Network) technology was conceived in 1985 and a standardization process initiated in an ANSI-accredited T! Committee to standardize commercial camer-to-ca~ner optical interfaces. Single Mode Fiber Optic (SMFO) cable was emerging as Me medium of choice for high-speed digital transmission systems and associated multiplexing equipment. It should be noted that Me T! digital hierarchy (see Section A.~.~.4) does not define Me physical media standards for fiber, so Mat many fiber-based DS-n implementations do not always facilitate off-the-shelf mul~vendor interoperability. The fundamental motivations for SONET emphasized the need to procure fiber-based equipment for multiple-owner systems from multiple manufacturers that win intemperate. These standards provide bow a usable standard for ITS and a recent example of a successful standards process. The SONET bit rates are presented in Table A.1.2.3-1. It should be noted Mat SONET was originally motivated as a "mid-fiber meet" for Be emerging mid-80s competitive Long Distance carriers (e.g., MCI' Sprint) to Be diverted Regional Bell Operating Companies (RBOCs) (e.g., SBC, NYNEX, Bell South U.S. West, etc.). ~stoncally, this was predominantly accomplished using DS-3 TDM equipment. Thus, Be fundamental OC-1 bit rate was selected at 51.84 Mbps which provides DS-3 payload capabilities and approximately 15% overhead pnmary for enhancements to provide additional capabilities identified Trough years of T1 deployment expenence. Table A.~.2.3-1 SONET Multiplexing Hierarchy . Number of Number of Number of ~ Oplical/ElectricalLeve' ~B'lRate ~DS ~DS-1 ~DS-0 | OC-1/STS-1 ~51.84 Mbps ~1 ~28 ~672 OC-3/STS-3 155.52 Mbps 3 84 2,016 . OC-9/STS-9 466.56 Mbps 9 252 6,048 OC-12/STS-12 622.09 Mbps 12 336 8,064 OC-18/STS-18 1 933.12 Mbps 1 18 1 504 1 12,096 OC-241STS-24 1244.16 Mbps 24 672 16,128 OC-36/STS-36 1866.24 Mbps 36 1,008 24,192 OC-481STS-48 2488.32 Mbps 48 1,344 32,256 OC-961STS-96 4876.64 Mbps 96 2,688 64,512 OC-192/STS-192 1 9953.28 Mbps 1 192 1 5,376 1 129,024 1 L:\NCHRP\Phase2.rpt NCHRP 3-51 · Phase 2 Final Report Al-1 12

AddidonaBy, SONET offers advantages over Me T! digital hierarchy Eat include: SONET is synchronous and can support add/drop capabilities of lower rate signals to the DS-O 64 kbps level. Thus, expensive multiplexing equipment is not required to insert/extract lower rate signals at intermediate network locations. Figures A.~.2.3-la and b iBus~ate the concept. Thus, networks can be more cost-effectively implemented (40 50%). The SONET standard provides nearly 5% of the bit rate for support of advanced network management, operations, administration, maintenance, and provising functions. This is in addition to We fundamental payload. These capabilities are not consistently defined (mostly not available) in He T! hierarchy. SONET was conceived as a fiber standard, OC-ns. Although STS-n defines electrical standards, electrical physical level transmission is not deployed. In contrast, the DS-n, T1 digital hierarchy evolved to support wire and radio and does not define optical physical transmission standards. SONET is an international standard [called Synchronous Digital Hierarchy (SDH) internationally] . N SONET can transport the legacy' widely deployed, DS-n, T1 hierarchy signals but has the flexibility to transport emerging signal types such as LAN/WAN data, videos etc. Ability to implement/integrate fault tolerant architectures/topologies in an integrated network design. The standards and equipment have integrated support for this capability. The elements of a SONET network are similar to elements of a T} network (Section A.~.2.3) and generally consist of: Network controllers (e.g., network management); Digital cross-connect systems; Digital multiplexing equipment/terminals; and c:WCHRP\Phase:.rpr NCHRP 3-51 · Phase 2 Final Report A1-1 13

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· Transport systems. The significant new capability is Me Add-drop Multiplexer (ADM) Mat permits cost-effective adding/dropping of lower level DS-N/SONET signals to DS-0, 64 kbps signals. The SONET signal format consists of payload (application data) and multiple levels of overhead for flexible implementation of network management, provising, monitonng, and control. These overhead functions, if implemented, were accomplished USA non-standard methods in T1 networks. SONET standards define these capabilities, or win define Hem (not aD standards are complete). The SONET OC-! signal format consists of 49.536 Mbps payload and 2.304 Mbps Overhead as depicted in Figure A.~.2.3-2. Based on years of %1 experience, Be SONET standard developers placed a great deal of emphasis on operations, administration, maintenance, and provising (OAM&P) requirements Mat win become more essential in multivendor system implementations. Thus, the overhead assignments presented in Figure A.~.2.3-2 are generally assigned for implementation as presented in Figure A.~.2.3-3 A path represents repeaterIess links; a line represents node to node links; and a path represents end-to-end application/user links. Spare communications capacity available for these functions is allocated independent of Me payload. The fundamental OC-! payload was conceived for transporting a DS-3, 44.736 Mbps, signal consisting of 28 DS-Is or 672 DS-0s (see Section A.~.2.3~. The 49.54 Mbps OC-1 payload includes extra byte allocations for synchronizing aBocations and paw overhead avocations. The SONET data actually framed is a 125 M sec (U sec = 10~9) frame which is Me standard T} 8000 frames/second rate. Pointers are employed in the line overhead bytes to allow floating payload frames. To avoid traditional T! buffering requirements and resulting slippage. The above SONET features allow simple synchronous bit-interleaving multiplexing techniques Mat permit cost-effective equipment development and simple interconnect of network elements of varying functionality. The SONET standards define: . Optical interface Specifications :`NCHRP`Phase2.rp: NCHRP 3-51 · Phase 2 Fmal Report Al-1 15

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Rate and Fonnat Specifications Operational Specifications SONET Standards Relevant U.S. standards dealing with SONET include: ANS! T].101 Synchronization Interface Standards for Digital Networks. ANS T].106, Digital Hierarchy-Optical Interface Specifications (Single-modeJ. ANS T].102, Digital Hierarchy Electrical Interfaces. SONETA~-drop Multiplex Equipment (SONETADMJ Generic Criteria TR-TSY-000496, Issue 2 (Be~core, September 19891. Integrated Digital Loop Carrier System Generic Requirements, Objectives, and Interface. TR-TSY-000303, Issue ~ (Bet/core, September 1986) plus Revisions and Supplements. Digital Synchronization Network Plan. TA-NPL-000436, Issue l (Bet/core, November 19861. Synchronous Optical Network (SONETJ Transport Systems: Common Generic Criteria. TR TSY-000253, Issue ~ (Bellcore, September 1989~. (A module of TSGR, FR-NWT 000440,. Transport Systems Generic Requirements (TSGRJ: Common Requirements. TR-TSY-000499, Issue 3 (BeNcore, December 1989~. (A module of TSGR, FR-NW1-000440~. Synchronous Optical Network (SONET) Transport Systems: Common Generic Criteria TA NWT-000253, Issue 6 (BelIcore, September 1990), plus Bullets No. I, August 1991. Generic Reliability Assurance Requirements for Fiber Optic Transport Systems. TA-NWT 00418, Issue (Be~core, to be issued). Relevant, ITU-T international recommendations swim essentially the effect of a standard) on SONET/SDH include: G.702 Digital hierarchy bit rates G.703 Physical/elec~ical characteristics of hierarchical digital interfaces G.707 Synchronous digital hierarchy bit rates G.708 Network node interface for the synchronous digital hierarchy G.709 Synchronous multiplexing structure G.773 Protocol suites for Q interfaces for management of transmission systems c:\NCHRP\Phase2~p ~NCHRP3-51· Phase2FmalReport A1-118

G.781 Structure of recommendations on multiplexing equipment for the synchronous digital hierarchy G.782 Types and general characteristics of synchronous digital hierarchy multiplexing equipment G.783 Charactenstics of synchronous digital hierarchy multiplexing equipment G.784 Synchronous digital hierarchy management G.955 Digital line systems based on Me I.544-Mbps hierarchy on optical-fiber cables G.956 Digital line systems based on Me 2.048-Mbps hierarchy on optical-fiber cables G.957 Optical interfaces for equnpment and systems relating to Me synchronous digital hierarchy G.958 Digital line systems based on Me synchronous digital hierarchy for use on op~cal-fiber cables G.652 Character~shcs of a single-mode optical-fiber cable G.653 Charactenshcs of a dispersion-shifted, s~ngle-mode, optical-fiber cable G.654 Charactenstics of a I,500-nm wavelength, loss-m~zed s~ngle-mode, optical-fiber cable M.30 Telecommunications management network A.~.2.4 Asynchronous Transfer Mode (ATM) As discussed in Section A.2.4 voice and video require constant delay traditionally served by c~rcuit-svv~tched communication technology. conversely, random arrival, bursty, data has been traditionally served by packet data communication technology. In reality, video has been served by analog technology and has not histonca}Ry represented a digital network load. The emerging "video-on~emand" and very popular Internet are creating demand for broadband services. LANs can provide local broadband data services; however, w~de-area broadband services have not been cost-effectively available except to large bulb users. Fur~elmore, LANs have not served video and voice well, due to random delays and out-of-order packet amvals.. ATM is Me industry solution to provide Integrated multimedia communication services on a common public network infrastructure. ATM is the switching technology and SONET is the generally preferred transmission technology. The concept Is depicted in Figure A.~.2.4-~. ~:\NCHRP`Phasc2.rpr NCHRP3-51 · Phase2FmalReport Al-1 19

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Table A.~.2.4-! presents an overview of the role SONET and ATM in emerging multimedia networks. Table A.~.2.4~1 Role of SONET and ATM in Multimedia Network SONET ATM · Transmission/Multiplexing Services · Services · Operations, Administration, and · User network interfaces Maintenance (OAM) functions · Switching operations between SONET links In many private networks, switching is not required. Thus, ATM may not be needed in many ITS-related communication infrastructures, particularly ATMS systems that have limited switching requirements. ATM technology is based on fast packet technology Mat is intended for operation over low BER circuits (i.e., SONET). It employs a 53-byte cell structure consisting of 48 bytes of user data and 5 bytes of protocol overhead. In terms of the OSI protocol model, ATM defines physical (~) layer and link (2) layer protocols, although the physical layer definition generally references over standards such as SONET. The short fixed (53) packet cell structure and low overhead is a well conceived compromise to accommodate isochronous voice and video traffic as wed as packet data ATM is a connection-oriented technology Hat pemlits every ATM cell to travel over the same route that is defined during cad setup on switched services or by provisioning in private line services. ATM supports virtual networking in that Be route is fixed during a connection, but may be changed based on time-of-day, failure, reconfiguration, or over requirements. Virtual networks should allow public services providers to offer lower cost, more reliable, alternatives to dedicated leased lines as redundant facilities can be shared/reaBocated among many users. The ATM connection exists as sets of routing tables in each switch, based on the address contained in Be cell headers. ATM we define Public and Private User Network Interfaces ~s). ATM and SONET are generally Be technologies of the Broadband ISDN (BISDN) services Cat are being defined by :\NCHRP\Phasez.rp ~NCHRP3-51e Phase2F~nalReport A1-121

ITU-T for fixture public multimedia telecommunication services. ATM defines bow ~ infrastructure and end user interfaces and services. ATM standards (e.g., ATM 25) are defined for desktop interfaces that could eventually replace LANs in corporate networks and have weD- conceived MAN/WAN strategies. These wiN undoubtedly have ITS-related applications as Hey become established in the marketplace. The fundamental goal of ATM is to provide common communication infrastructure and interfaces for multimedia networks of video, graphics, voice, and data. BISDN, ATM, and SONET wig integrate the many disjointed LAN/MAN/WAN and T! services now available. ATM standards are still In development, but He key ATM current standards are presented in Table A.~.2.4-2. L.:`NC~Phase2.rp ~NCHRP 3-51 · Phase 2 Fmal Report A1-122

Table 1.2.4~2 ATM Standards and Specifications [1] | ATM Forum, "ATM User-Network Interface Specification, Version 3.0, 1993, Prentice Hall [2] ATM Forum, ``Network Compatible ATM for Local Network Applications," Phase 1, Version 1.0, 1992 [3] ATM Forum, ATM UNI Specification. V.22, July 1993 [4] Bellcore, SR-NWT-002076 Report on the Broadband ISDN Protocols for Providing SMDS and Exchange Access SMDS," Issue 1, September 1991 _ [5] ITU-T Recommendation 1.1 13, "Vocabulary Terms for Broadband Aspects of ISDN,n 1992 (Rev.) _ . [6] ITU-T Recommendation 1.121, Broadband Aspects of ISDN," 1990 [7] ITU-T Recommendation 1.150, UBISDb1 ATM Functional Characteristics," 1992 (Rev.) [8] ITU-T Recommendation 1.21 1, BISON Service Aspects," 1992 (Rev.) [9] ITU-T Recommendation 1.31 1, UBISDN General Network Aspects," 1992 (Rev.) [10] ITU-T Recommendation 1.321, "BISDN Protocol Reference Model and its Application," 1990 [1 1] ITU-T Recommendation 1.327' aBISDN Functional Architecture Aspects," 1992 [12] ITU-T Recommendation 1.35B, "BISDN ATM Cell Transfer Performance," 1992 (Draft) [13] ITU-T Recommendation 1.361, "BISDN ATM Layer Specification, 1992 [14] ITU-T Recommendation 1.362, BISON ATM Adaptation Layer (ML) Functional Description," 1992 .. [15] ITU-T Recommendation 1.363, MISDO ATM Adaptation Layer (ML) Specification," 1992 L;~.NCHRP\P~.rpr NCHRP3-51a Phase2FmalReport A1-123

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