Optical Networks: A Practical Perspective - Part 8. This book describes a revolution within a revolution, the opening up of the capacity of the now-familiar optical fiber to carry more messages, handle a wider variety of transmission types, and provide improved reliabilities and ease of use. In many places where fiber has been installed simply as a better form of copper, even the gigabit capacities that result have not proved adequate to keep up with the demand. The inborn human voracity for more and more bandwidth, plus the growing realization that there are other flexibilities to be had by imaginative use of the fiber, have led people. | 40 Introduction to Optical Networks networks are now widely deployed. Today it is common to have high-speed optical interfaces on a variety of other devices such as IP routers and ATM switches. As these first-generation networks were being deployed in the late 1980s and early 1990s people started thinking about innovative network architectures that would use fiber for more than just transmission. Most of the early experimental efforts were focused on optical networks for local-area network applications but the high cost of the technology for these applications has hindered commercial viability of such networks. Research activity on optical packet-switched networks and local-area optical networks continues today. Meanwhile wavelength-routing networks became a major focus area for several researchers in the early 1990s as people realized the benefits of having an optical layer. Optical add drop multiplexers and crossconnects are now available as commercial products and are beginning to be introduced into telecommunications networks stimulated by the fact that switching and routing high-capacity connections is much more economical at the optical layer than in the electrical layer. At the same time the optical layer is evolving to provide additional functionality including the ability to set up and take down lightpaths across the network in a dynamic fashion and the ability to reroute lightpaths rapidly in case of a failure in the network. A combination of these factors is resulting in the introduction of intelligent optical ring and mesh networks which provide lightpaths on demand and incorporate built-in restoration capabilities to deal with network failures. There was also a major effort to promote the concept of fiber to the home FTTH and its many variants such as fiber to the curb FTTC in the late 1980s and early 1990s. The problems with this concept were the high infrastructure cost and the questionable return on investment resulting from customers reluctance to
