Chapter 14. Optical Networks and WDM Systems

Optical communication systems have been developed to meet two main objectives: reaching higher data transmission bandwidths and reducing the overall cost of communication networks. Optical communication technology uses principles of light emission in a glass medium, which can carry more information over longer distances than electrical signals can carry in a copper or coaxial medium. This chapter focuses on principles of optical communications, optical multiplexing, and switching used in optical computer networks. Following are the major topics covered:

• Overview of optical networks

• Basic optical networking devices

• Large-scale optical switches

• Optical routers

• Wavelength allocation in networks

• Case study of SSN, an all-optical switch

Some basic optical devices are optical filters , wavelength-division multiplexers (WDM), optical switches , and optical buffers and delay lines . Optical switches are given special attention, as they are core engine of all-optical networks. Contention-resolution methods for optical switches are explained and types of switch elements identified.

In optical networks, a number of optical routing devices are interconnected by optical links. The routing devices have optical multiplexing, switching, and routing components , and links are optical fibers. An important issue in optical networks is wavelength reuse and allocation . To keep lightpaths separated on a link, they should be allocated different wavelengths . The case study at the end of the chapter describes an optical switching network with a spherical switching network (SSN) topology.