sing the use of fiber within a building. In Chapter 8, our concluding chapter, we will examine the use of fiber modems, fiber multiplexers, and even WDM within a building. This page intentionally left blank. mean, Team-Fly® CHAPTER Understanding Light Chapter Two Information is transmitted over different types of fiber by means of light. If we compare fiber to a copper conductor, we can note several similarities between the two. In a fiber environment, a light source replaces the electronic transmitter that generates pulses and is used by a copper-based digital transmission system, while the conductor is a glass or plastic fiber in place of a twisted-pair wire or coaxial-cable conductor. Because of the central role of light in a fiber-optic trans- mission system, it is important to inquire into what we normally take for granted. In this chapter we will literally focus our eyes and attention on light. In SO doing, we will discuss how light can be described in terms of par- ticles and waves, and where different colors are located in the frequency spectrum. As we discuss light we will introduce several terms that may appear new to many readers while serving as a refresher for others. Because this book is oriented toward communications applications, we will also discuss such terms as bandwidth, signaling rates, power measure- ments, and channel capacity. One or more topics covered in this chapter may leave you scratching our head in an attempt to determine how the topic relates to communications over a fiber. To paraphrase Indiana Jones, this author will say, "Trust me." Describing Light If you previously took a course covering physics, you probably read a chapter covering light. Although this may have been illuminating (no pun intended), you probably noted that light can be described as a par- ticle or as a wave, which in itself is a somewhat obscure idea. Light as a Particle If you consider light to represent a flow of particles, each particle is referred to as a photon (from the Greek word photos, meaning light). 