brief introduction: Receiver: its role is opposite to the role of the transmitter, mainly to receive the signal in the channel, and transform it into the same physical form of information when sending, and then transmitted to the host, that is, to complete the so-called decoding process. The basic requirement of the receiver is to be able to extract the source output information from the disturbed signal to the maximum extent and reproduce the source output as much as possible. Optical receiver: in optical fiber co