Introduction

Optical fiber communication is a communication approach to transport information from one point to another using light as a carrier and optical fibers as transmission media. In ancient times, in order to speed up information transmission, people learned how to use optical signals, such as smoke signals, semaphores, etc., to communicate. However, the utility of these methods was very limited. In the early 1960s, American physicists invented the ruby laser[

1

], and the proposals for optical communication via dielectric waveguides or glass optical fibers to avoid degradation of the optical signal by the atmosphere were made almost simultaneously in 1966 by Kao and Hockham[

2

] and Werts[

3

]. Initially the optical fibers exhibited very high attenuation (i.e., 1000dB/km) and were therefore not competitive with the coaxial cables which they were to replace (i.e., 5 to 10dB/km). In 1970, the Corning Company in America manufactured a fiber-optic with attenuation of 17dB/km, and the optical fiber losses at 1310 nm wavelength were reduced to 0.3dB/km[

4

] in 1974. In 1977, the field trial of the first commercial use of the multimode fibers between two telephone offices in Chicago 7000 meters distant was made successfully[

5

].