Fiber-optic systems are no longer passive pipes that merely carry optical signals from point to point. Signals may be modulated in intensity, switched between fibers, shifted in wavelength, and modified in other ways. The potential of “optical networking” was over-promoted during the telecommunications bubble, but the need to operate on signals is growing with the volume of traffic and the size of the global telecommunications network. The devices that perform these operations on signals are called active components.
You have already learned about several types of active components. Light sources,
transmitters, receivers, optical amplifiers, and wavelength converters are all active components. In this chapter you’ll learn about optical modulators, optical switches, and other components that dynamically affect optical signals.
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