Evolutionary Trends in Lightwave Communications

The optical fiber as the transmission medium for lightwave communication is now well established. Optical fibers provide enormous and unsurpassed transmission bandwidth, and are now the transmission medium of choice for long distance and high data rate transmission. Networks which operate at the 1300 nm window are now in state of art situation. Advanced fiber designs for operation at lowest loss 1550 nm window are reaching to state of art situation for long haul routes. These systems are based on dispersion shifted fibers and erbium-doped fiber amplifiers. The erbium-doped fiber amplifiers (EDFAs) provide large and broad band optical gains. Large number of wavelength division multiplexed information channels can be transmitted and simultaneously provided gain by EDFAs. The use of erbium-doped fiber amplifier increases the power confinement inside optical fibers. Therefore in such systems effects of optical nonlinearities may become important. The aim of this paper is to trace the evolutionary trends in fiber optic communications seen since the first low loss fiber. Some nonlinear optical effects that are important for designing of fiber optic communication systems will also be discussed.