In coherent optical communication s

In coherent optical communication system, the selectivity of coherent receiver is also very good, which is another advantage of coherent optical communication system. In the coherent detection system, because the detected light is the mixing light, which is obtained by mixing the signal light and the mixing light. At this time, the light is the intermediate frequency light, so only the noise entering the system is only in the intermediate frequency band. Because the mixing light passes through the intermediate frequency micro wave amplifier with narrow bandwidth, the amplifier will also filter the noise outside the band. It can be seen that the filtering of coherent detection system is also very good. Dense wavelength division multiplexing (DWDM) is generated by the good selectivity of coherent detection, which can reduce the frequency interval of frequency division multiplexing system, so it can replace the traditional optical multiplexing technology of frequency interval.