JPS643384B

PURPOSE:To simplify the circuit constitution, by transmitting frequency division multiplex signal with optical fibers and reducing the number of conversion stages, through the selection of line pilot frequency to the attenuation area of pass filter of each basic group. CONSTITUTION:A signal from the distribution group MGDF of the basic main group MG is converted into the basic main supergroup SMG with a transmission converter 16, and the frequency division multiplex signal fed to a photosignal transmitter 11 via the distribution frame SMGDF is converted into optical signal and transmitted on the transmission fiber 14. Further, the photo signal received via the reception fiber 15 is converted into the signal of the basic main supergroup SMG being electric signal, fed to the reception converter 17 via the distribution frame SMGDF and converted into the basic main group MG. Further, the signal received at the reception fiber 15 and transmitted on the transmission fiber 14' is fed to the photo signal transmitter 11' the same type device as the device 11 via the pass filter 13, and the pilot signal included in the reception signal is rejected at the filter 13 and transmitted to the terminal device.