They are responsible for converting electrical energy into optical energy or modulating optical signals. In contrast, passive devices do not generate light; they are only used to transmit, distribute, or filter optical signals, such as optical fibers, splitters, and filters. An optical filter is a device that selectively transmits light of different wavelengths, usually implemented as a glass plane or plastic device in the optical path, which are either dyed in the bulk or have interference coatings. The optical properties of filters are completely described by their. Section 10. The active devices described in this chapter include variable optical attenuators, tunable optical filters, dynamic gain equalizers, optical add/drop multiplexers, polarization controllers, and dispersion compensators.
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