The Fiber-Optic Channel

Abstract

Perhaps the most important optical communication channel is the optical fiber. The fiber is a thin “pipe” of glass through which one can shine an optical beam to transmit optical energy from one point to another. The fiber is the optical equivalent of a coaxial cable or waveguide commonly used for microwave transmission. Decades ago attempts to communicate by fiber over long distances were hampered by the severe attenuation of this channel. However, in the early 1970s the demonstration of a fiber with 20 dB/km of loss indicated the potential of this link, coupling the high data rates of the optical carriers with the small spatial occupancy of the fiber. Fiber losses have now been reduced to about 0.1 dB/km, and the technological development of solid-state sources and detectors has further advanced the fiber communication channel. In this chapter we attempt to outline the basic communication characteristics of this type of channel.