R&D is conducted in industry, which—for competitive reasons—keeps these subjects quite proprietary; very little work is done in this area in university or government laboratories.

The field of information technology provides many examples of the enabling role of optical technology. Often these enablers are small in size or cost but have an impact on a grand scale in large systems and applications. A tiny semiconductor laser, for example, enables the building of an optical transmitter, which enables a transmission system, which enables the construction of a telecommunications network, which enables the delivery of information age services such as multimedia or the Internet. Another example is the optical fiber, which enables the construction of an optical cable, which enables the construction of a network, and so on. A third example is the liquid crystal, which enables the flat-panel display, without which the laptop computer could not exist. These chains of enablers make it difficult to place firm dollar values on individual component technologies; components such as lasers or fibers are relatively inexpensive, but the service revenues of telecommunications networks are in the hundreds of billions of dollars. Box 1.2 gives a more detailed illustration of the enabling devices for long-haul information transport systems.

As for optics in general, optical materials play an important enabling role. Chapter 6 gives further details of this topic (see Box 6.2, "Photonic Materials").

A few rather obvious but critical points about high-tech mass markets and low-cost manufacturing should be more widely understood and appreciated. They clearly apply to the mass markets for optical information technologies:

BOX 1.2 ENABLING PHOTONIC DEVICES FOR PRESENT AND FUTURE LIGHTWAVE LONG-HAUL SYSTEMS

Semiconductor lasers

  • High-power pumps for fiber optical amplifiers

  • Integrated laser-modulator transmitters

  • Multiwavelength transmitters

  • Tunable transmitters

  • Soliton sources

Semiconductor optical amplifiers

  • Power amplifiers in integrated transmitters

  • 1. 3-µm optical amplifiers

  • Optical switches and switch arrays

  • Wavelength converters and other nonlinear functions

Photodetectors and OEIC receivers

  • High-speed (>10 gigabit-per-second [Gb/s]) and high-sensitivity OEIC receivers

  • High-speed (>10 Gb/s) avalanche photodiodes

Planar integrated waveguide components

  • Couplers

  • Filters (fixed and tunable)

  • Wavelength multiplexers and routers

  • Modulators and switches

  • Doped-waveguide devices

  • Dispersion compensators

Fiber-type components

  • Doped-fiber devices (amplifiers and lasers)

  • Couplers

  • Grating filters

  • Wavelength multiplexers

  • Dispersion compensators

  • Switches (mechanical)

  • High-power lasers and brightness converters

  • Isolators and circulators

  • Nonlinear devices

(Source: T. Li, AT&T Laboratories.)



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