OPTICAL COMMUNICATIONS: COMPONENTS AND SYSTEMS
Optical communications make use of light waves, very high frequency (100 terahertz) electromagnetic waves, for information transmission. Modern optical communications were begun in the 1960s, when lasers were invented as a coherent light source. Since then, the rapid development of photonic technologies has made possible optical communication links with a capacity of terabits per second and a transmission distance of many thousands of kilometers. The explosive growth of optical communication technology in the past decades has revolutionized the telecom industry and created a global communication infrastructure with optical networks.
A typical fiber optic communication system consists of an optical transmitter, optical fiber, and an optical receiver. The optical transmitter converts the information-carrying electronic signal to an optical signal, which are then sent through a long length of optical fiber. At the receiver end, an optical detector converts the optical signal back to an electronic signal so that the information is recovered and delivered to the destination. In this chapter we focus on the fundamentals of optical communication technologies. The emphasis is on the enabling technologies and physical-layer design for passive optical networks. First, key components of optical communication systems are discussed, including the main characteristics and performance features of optical fibers, transmitters, receivers, ...