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Chapter 1 Introduction to Optical Networ... > 1.1 Telecommunications Network Archi... - Pg. 2

2 Introduction to Optical Networks cost of bandwidth. This reduced cost of bandwidth in turn spurs the development of a new set of applications that make use of more bandwidth and affects behavioral patterns. A simple example is that as phone calls get cheaper, people spend more time on the phone. This development in turn drives the need for more bandwidth in the network. This positive feedback cycle shows no sign of abating in the near future. Another factor causing major changes in the industry is the deregulation of the telephone industry. It is a well-known fact that monopolies impede rapid progress. Monopolistic companies can take their time adapting to changes and have no incen- tive to reduce costs and provide new services. Deregulation of these monopolies has stimulated competition in the marketplace, which in turn has resulted in lower costs to end users and faster deployment of new technologies and services. Deregulation has also resulted in creating a number of new start-up service providers as well as start-up companies providing equipment to these service providers. Also, traffic in a network is dominated by data as opposed to traditional voice traffic. In the past, the reverse was true, and so legacy networks were designed to efficiently support voice rather than data. Today, data transport services are perva- sive and are capable of providing quality of service to carry performance sensitive applications such as real-time voice and video. These factors have driven the development of high-capacity optical networks and their remarkably rapid transition from the research laboratories into commercial deployment. This book aims to cover optical network technologies, systems, and networking issues, as well as economic and other deployment considerations. 1.1 Telecommunications Network Architecture Our focus in this book is primarily on the so-called public networks, which are networks operated by service providers, or carriers, as they are often called. Carriers use their network to provide a variety of services to their customers. Carriers used to be essentially telephone companies, but today there are many different breeds of carriers operating under different business models, many of whom do not even provide telephone service. In addition to the traditional carriers providing telephone and leased line services, today there are carriers who are dedicated to interconnecting Internet service providers (ISPs), carriers that are in the business of providing bulk bandwidth to other carriers, and even virtual carriers that provide services without owning any infrastructure. In many cases, the carrier owns the facilities (for example, fiber links) and equip- ment deployed inside the network. Building fiber links requires right-of-way priv- ileges. Not anybody can dig up streets! Fiber is deployed in many different ways