ABSTRACT
Optical communication systems employ lightwaves to transmit information from one place to another separated across distances that range from a few kilometers to thousands of kilometers. These systems deliver information from central exchanges to homes and vice versa or to and between major cities, respectively. Furthermore, these distances are now transoceanic distances, reaching several thousands of kilometers as shown in Figure 1.1. Figure 1.2 shows a map from KDD Submarine Cable Systems Inc. that shows the submarine cable infrastructure in the Asian region in 1996. More details of the —ber cable networks in South East Asia and Australia-Oceania region are given. The connection and the cable from Australia to America and Europe is the longest and is considered to be the most extensively laid out one of all the optical transmission systems. The lightwave frequency is in the range of nearly 200 THz for a wavelength of 1550 nm, and several wavelength channels can be multiplexed to make the total capacity reach few tens of terabytes/second over this spectral band. This band is only a very small part of the optical spectrum. Fortunately, this region is the lowest attenuation spectral window of silica —ber which is the critical guiding medium with minimum broadening effects on transmitted data pulse sequences. The electromagnetic spectrum for communications is shown in Figure 1.3. As observed, the spectrum of optical communication based on silica —ber occupies only a small fraction of the electromagnetic spectrum but extensive bandwidth and capacity will be made available in the years to come.
