Fiber Optic Communications: Fundamentals and Applications

Chapter 2Optical Fiber Transmission

2.1 Introduction

Until the mid-1970s, communication systems transmitted information over copper cables or free space. In 1966, Charles Kao and George Hockham working at Standard Telecommunications in the UK proposed that an optical fiber might be used as a means of communication provided the signal loss could be much less than 20 dB/km [1]. They also illustrated that the attenuation in fibers available at that time was caused by impurities which could be removed. At Corning Glass Works, Robert Maurer, Douald Keck, and Peter Schultz worked with fused silica, a material that can be made extremely pure. In 1970, they developed a single-mode fiber with attenuation below 20 dB/km [2]. In 1977, the first optical telecommunication system was installed about 1.5 miles under downtown Chicago and each optical fiber carried the equivalent of 672 voice channels. In 1979, single-mode fibers with a loss of only 0.2 dB/km at 1550 nm were fabricated [3]. The availability of low-loss fibers combined with the advent of semiconductor lasers led to a new era of optical fiber communication. Today, more than 80% of the world's long-distance traffic is carried over optical fiber cable and about 25 million kilometers of optical fiber has been installed worldwide.

This chapter deals with light propagation in optical fibers. Multi-mode and single-mode fibers are discussed using a ray-optics description in Section 2.3. A rigorous solution of the wave equation is derived ...