This document discusses various optical modulation and demodulation schemes. It describes modulation techniques such as amplitude shift keying, frequency shift keying, and phase shift keying that encode information by varying the amplitude, frequency, or phase of an optical. The invention of the laser by Schawlow, Townes and Maiman [1,2] ushered in the era of deep-space optical communications. Here was a source of intense, highly directed optical energy that could produce coherent radiation, like radio frequency (RF) transmitters, but at much higher optical. Optical modulation allows one to control an optical wave or to encode information on a carrier optical wave. Optical modulation enables many key functions in. Abstract: Performance and implementation complexity of various binary and nonbinary modulation methods with coherent, differentially coherent and noncoherent detection are compared. A modulation scheme continuously alters the property or properties of a waveform.
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