The previous three chapters have shown how transmitters and receivers send and receive signals in a fiber-optic system. Sometimes signals need a boost or special processing somewhere along the line to reach the final receiver in intelligible form. Optical amplifiers, repeaters, and regenerators give them that needed boost. Signals also may need to be converted from one wavelength to another as they are transmitted through a system.
In this chapter, you will learn about the differences among repeaters, regenerators, optical amplifiers, and wavelength converters; the functions they perform; and the technologies they use. Repeaters and regenerators are electro-optic devices, closely related to transmitters and receivers because they convert optical signals to electronic form. Optical amplifiers are purely optical devices, related to the lasers described in Chapter 9. Optical regeneration also is possible, but not widely used. Wavelength conversion is a separate function that may be performed optically or electro-optically.
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