Photonics Maintaining Competitiveness in the Information Era (1988) / Chapter Skim
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Appendix D: Technology Status of Optical Telecommunications
Appendix D: Technology Status of Optical Telecommunications
Pages 84-94
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From page 84... ...
External cavity lasers that have been extensively investigated include the cleaved-coupled cavity laser (C3 laser) ; graded-index, external cavity laser; fiber external cavity laser; the silicon chip Bragg reflector (SCBR)
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From page 85... ...
Even though tuning features have been demonstrated in the laboratory, we do not to date have a stable, compact, widely tunable, single-frequency semiconductor laser suitable for practical commercial use. Further research in this area is warranted.
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From page 86... ...
86 APPENDIX D research effort that should proceed simultaneously with other activities to facilitate alternative system designs. Beyond attenuation and bandwidth are a number of environmental requirements defining fiber degradation in use.
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From page 87... ...
There is a lack of sufficiently precise, threedimensional forming techniques for manufacture of optical fiber system components. The two-dimensional solution, photolithography, has been used to some advantage when the third dimension is small; but it is generally inadequate.
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From page 88... ...
Connectors with low reflection coefficients are increasingly important in high-data-rate and coherent communications systems because reflections returned to the lasers used in those applications can cause instabilities in the laser output that are harmful to system performance. Reflections at connectors placed in series along a fiber can also cause fluctuations in the output power at the end of the fiber due to interference effects.
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From page 89... ...
The possibility of using the mature silicon materials and processing technology for fabrication of low-loss waveguides and gratings on a silicon chip is particularly attractive. Fiber Backplane and Other Optical Interconnects As data rates increase, interconnections inside equipment become increasingly difficult to implement with conventional copper traces on circuit boards and backplanes, twisted pairs, and coaxial cables.
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From page 90... ...
PHOTONIC SWITCHES A number of technologies have been demonstrated for switching an optical signal between two or more outgoing paths. These include mechanical devices that physically move fibers or that physically move lenses or mirrors directing an optical beam; optoelectronic devices where an applied voltage across two or more electrodes causes a field within an electro-optic material, which in turn changes the coupling of waveguides within the material or otherwise modifies the optical characteristics of an optical circuit within the material; electrically, acoustically, or optically controlled gratings created within a material to cause diffraction of an optical beam; and electrically or optically controlled non-linear optical devices.
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From page 91... ...
, and in optical switching to compensate for losses in the switches. Over the last few years, there has been considerable worldwide activity in developing amplifiers with large available gain, low insertion loss, low noise, large bandwidth, and saturation output power.
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From page 92... ...
Compound semiconductor-based transistors are intrinsically faster than Si ones, and the monolithic approach provides significant additional improvements through reduction of undesirable parasitics associated with packaging discrete devices. A key stumbling block in the exploitation of optoelectronic integrated devices has been the materials and processing technology.
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From page 93... ...
as well as high bandwidth requires careful circuit design and the use of advanced electronic integrated-circuit technology. The United States is well positioned in terms of both detector technology and low-noise mnplif~er technology, although recently the Japanese have been more aggressive in the development of InGaAsP APDs (which were fast demonstrated in U.S.
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From page 94... ...
The sensitivity of a receiver employing an APD is determined by the relative impact ionization rates of electrons and holes and by dark current. Recently, several advanced APDs have been proposed that rely on superlattice bandstructure engineering to modi~the relative impact ionization rates.
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