Optical networking adds another dimension to the concepts of system design you
learned in Chapter 21 for the simple case of a single optical channel per fiber. This
chapter covers systems that transmit two or more optical channels per fiber, where signals are managed by wavelength or optical channel. The extra optical channels increase the complexity of system design, and the number of factors that must be considered.
This chapter opens with a review of optical networking concepts. It then explains how optical channels are packed together, contrasting wavelength-division and time-division multiplexing, and dense and coarse channel spacing. Then it covers the properties of optical fibers and optical amplifiers that affect optical networking design. Finally it covers optical switching and channel management, including the importance of wavelength conversion. Optical network design is still a young field, so we will not cover it in as much detail as we did single-channel design in Chapter 21.
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