1. Introduction
With the invention of the laser in 1960’s, a great interest in
optical systems for data communications began. The
invention of laser, motivated researchers to study the
potential of fiber optics for data communications, sensing,
and other applications. Laser systems could send a much
larger amount of data than microwave, and other electrical
systems. The first experiment with the laser involved the
free transmission of the laser beam in the air. Researchers
also conducted experiments by transmitting the laser beam
through different types of waveguides. Glass fibers soon
became the preferred medium for transmission of light.
Initially, the existence of large losses in optical fibers
prevented coaxial cables from being replaced by optical
fibers. Early fibers had losses around 1000 dB/km making
them impractical for communications use [1].