As we move toward the final years of this century, the demand for sophisticated information processing grows even rapidly.
Information is transmitted from one place to another via a communication system.
The distances can be within a single room, or can be separated by transoceanic distances. Information is often carried by an electro-magnetic carrier wave whose frequency can vary from a few megahertz to hundred terahertz. Optical fibers are used along with Fiber communication system for information transmission. During the 1980s, many lightwave systems were developed worldwide and have revolutionized the field of communications. In order to better understand its importance, we need to know its historical perspective, its physical appearance, its theoretical bases, as well as its usages.