Optical network architectures

Telecommunication networks in all their various shapes are indispensable to bring information quickly anywhere and anytime, which is a vital need of our modern global society. Since the invention of the electrical telegraph by Samuel Morse in 1837, the variety of telecommunication services has grown at an increasing pace, as illustrated in Figure 2.1. In addition, the services are becoming ever more individualized, and along with the penetration of video-based services (“a picture says more than a thousand words”) the request for information transport capacity has exploded and is continuing to do so. Since the early 1990s, the introduction of the worldwide Internet has drastically promoted this information transport explosion. The number of Internet hosts is still increasing exponentially; from January 1992 to January 1997 to January 2002, it grew from 727 thousand to 19.5 million to 147 million worldwide. This is causing data traffic to take an ever-larger share of the telecommunication network capacity; since a few years, it has surpassed the volume of the traditional voice traffic (but not yet its revenues). Wireless mobile telecommunication is attracting ever more users, and enables a fast roll-out of services to the end users without the need to install extensive first-mile customer access networks. The telecommunication market liberalization has provided ample opportunities to the entry of more operators and service providers, and the resulting national and international competition is pressing for very efficient high-capacity telecommunication networks.