A variety of components manipulate optical signals in fiber-optic systems. They fall into two broad categories: passive components that require no outside power supply, and active components that draw external power. This chapter covers couplers and other passive components that are not involved in wavelength-division multiplexing. Chapter 15 covers WDM optics including couplers, and Chapter 16 covers switches, modulators, and other active components.
Couplers split input signals into two or more outputs, or combine two or more
inputs into one output. As you will learn, optical coupling is more complex than its
electronic counterpart because of the nature of optical signals. This chapter will explain how optical couplers work and describe the technologies used. It also will cover other important passive components not intended specifically for WDM applications, including attenuators and optical isolators.
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