Coherent detection offers several advantages, including improved signal quality, increased data rates, and enhanced spectral efficiency. We review detection methods, including noncoherent, differentially coherent, and coherent detection, as well as a hybrid method. What modulation formats are supported by coherent detection? Coherent detection supports a wide range of modulation. While direct detection works well for short-distance links, it has limitations in terms of capacity and sensitivity. It cannot efficiently use phase information and is more vulnerable to signal impairments such as dispersion. These systems, unlike their conventional counterparts, employ advanced signal processing techniques that leverage the phase, amplitude, and frequency of light.
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