Abstract: In a communication system between an exchange station and terminal equipment through an optical fiber cable, a power supply for operating the terminal equipment is supplied from the exchange station through the optical fiber cable in a form of an optical energy. The optical fiber cable is utilized both for transmitting a voice signal between terminal equipment and the exchange station, and for transmitting the power supply from the exchange station to terminal equipment on a time divisional basis. When the terminal equipment is inactive, the exchange station transmits no energy, or transmits intermittently an optical pulse. The duration that the optical pulse is transmitted when the terminal equipment is inactive, is less than 1/10 of the total time.