DETECTOR FOR DISCONNECTION OF OPTICAL TRANSMISSION LINE

摘要

PURPOSE:To detect immediately a disconnection of optical transmission line with respect to an adjacent station by sending a signal received by the adjacent station to a transmission station and allowing the transmission station to detect that a period without the reception signal exceeds a setting time. CONSTITUTION:An adjacent station sends a reception signal via an optical fiber 105 and an optical receiver 108 to a transmission station via a selector 1a, an optical transmitter 107 and an optical fiber 106 through loopback. The transmission station receives the transmission signal of its own station sent by the adjacent station through loopback via the optical receiver 108. An output of the optical receiver 108 is applied to an AND gate 4b via a carrier sense 2b. Since other input to the AND gate 4b is a transmission signal 6b generated by a signal controller 3, the condition of AND not being zero indicates it that the transmission station sends a signal and cannot receive the loopback signal from an adjacent station. In this case, a timer 5b is operated and a disconnection detection signal 7b is outputted after the lapse of the confirmation time.