OCP service card (Optical Channel Protection) is an optional part of the WDM system, which is primarily used in line protection and ring network protection networking. At the transmitting end, one optical signal is divided into two identical signals, which are transmitted through different specific wavelengths or different lines. At the receiving end, the signals of two specific wavelengths or different lines are received and sent to the subsequent processing according to the signal quality, which is the process of double transmitting and selective receiving.