nts, the goal of this book ultimately was to provide a practical guide to the operation and utilization of optical net- working devices. In this book we will focus on the various components that make up an optical transmission system, how each component oper- ates, and how all these components are integrated to form an optical net- Introduction TABLE 1.1 Network operator Fiber miles Network completion date Network Buildouts in Terms of Fiber Aerie Networks 8,885,376 2004 (projected) Miles 5,148,000 2001 (projected) Level 3 Communications 2,304,000 2001 (projected) Qwest 1,836,480 Completed Broadwing 1,507,200 Completed Global Crossing 480,000 Completed work. As we progress through this book, we will obtain an appreciation for the composition of light and how it flows down different types of optical fiber. We will note the use of different types of light sources that function as a transmitter in an optical system as well as the use of differ- ent types of photodetectors that function as light receivers. Through our coverage of operational information, we will obtain a foundation of knowledge that we will use to understand how optical transmission can be used in local and wide area networking environments as well as with- in a building to satisfy a variety of different networking requirements. Chapter Focus Until the late 1990s or SO, most persons associated optical networking with wide area networks (WANs) as communications carriers extended their infrastructure to support the growth in the use of the Internet, video- conferencing, and other bandwidth-intensive applications. What was not common knowledge is the fact that optical networking devices can and are being used in the office environment and are gaining momentum in providing communications to residences. To understand the reason for the growth in the use of optical networking devices, the first section of this chapter provides an overview of the rationale behind the use of opti- cal fiber. To ensure that readers do not have a biased impression that everyth