Optical fiber communication technology has been deployed widely all over the world and has become an integral part of telecommunications. This is due to the fact that, compared to copper cables, optical fibers offer a much higher capacity, are smaller, weigh less, and are immune to electromagnetic interference effects. Initially the term optical networks referred to collections of optical cable routes that were used for high-capacity point-to-point transmission links. In these networks much of the telecommunication network infrastructure still relied on using electronic signals, particularly in critical functions such as routing and switching of signals. Currently the next generation of optical networks is transitioning some of the routing, switching, and network intelligence into the optical domain.

This chapter first presents some general network concepts in Sec. 17.1, to show what networks consist of and what the related terminology is. Section 17.2 then describes the characteristics and implementations of SONET/SDH networks, which are used for transmission and multiplexing of high-speed signals within the global telecommunications infrastructure. Following this, Sec. 17.3 gives an overview of the meaning and applications of optical Ethernet. A variety of fiber applications to the so-called access networks are the topic of Sec. 17.4. These networks represent the cable segments running from the service provider facility to the business or home user. Finally Sec. 17.5 describes the evolution of optical networks to include concepts such as using all-optical methodologies to reduce the electronic overhead in packet transmissions and the idea of delivering optical services directly to the...