Introduction

Abstract

In recent years a great deal of interest has centered on using optical frequencies as carriers of information. This interest has been motivated by improved optical sources, notably the laser. The advantages with respect to optical frequencies lie in the large potential bandwidth available, as a percentage of the carrier frequency, and the extremely short wavelengths with the attendant small component size. Although there was an initial flurry of activity in optical communications after the advent of the laser, scientists and engineers were soon faced with the realities of providing reliable communications under adverse conditions. Clouds, rain, and turbulence dispelled much of the initial enthusiasm, and it was not until the development of virtually lossless glass fibers that optical communications became a commercial reality. Nevertheless, just as there are still obstacles in the deployment of fiber optic communications systems, so too have strides been taken in the understanding and utilization of other means of optical communications. Other books have focused either on the theory of optical communications or on the device technology that either exists or is being developed. In this book we will focus on the physical channels over which optical transmissions might pass and try to develop a common framework by which they can all be considered. We will consider component characterization only insofar as it aids our understanding of optical transmission.