| 摘要 |
PURPOSE:To supervise the reception state by returning a reception signal on an optional line designated by a transmission terminal station to the transmission terminal station from a reception terminal station so as to allow a supervisor in the transmission terminal station to compare a transmission signal with the reception signal. CONSTITUTION:Plural optical transmitters 1 are arranged to the transmission terminal station and each optical transmitter 1 converts an input signal into an optical signal and transmits the result to an optical fiber cable 3. Plural optical receiver 2 in the reception terminal station converts each reception optical signal into an electric signal and sends the signal to each subscriber through a coupler 6. Further, an output of each optical receiver 2 is branched respectively and inputted to a line selection receiver 5, which selects alternatively the output signal of an optional optical receiver 2 and sends it to the optical transmitter 1. The optical transmitter 1 converts the output of the line selection receiver 5 into an optical signal and returns it to the optical transmitter 1 via an optical fiber cable 3. A command to select an optical line is sent to the reception terminal station through one of the optical transmitters 1. The said command is inputted to the line selection receiver 5 by the reception terminal station, the receiver 5 selects an output of the optical receiver 2 of the designated line and inputs the signal to the optical transmitter 1. Thus, the output of the optical receiver 2 of the transmission terminal station supervises the reception state of the said line. |
