38 Introduction to Optical Networks 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 pay for a bevy of new services such as video to the home. However, telecommunications deregulation, coupled with the increasing demand for broadband services such as
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