| 摘要 |
PURPOSE:To decrease the circuit scale by detecting the intermission of a transmission signal with a non-signal detector on the occurrence of a fault and sending an optical signal representing the fault modulated by a frequency assigned to a repeater from an optical fiber amplifier so as to inform a fault block to a terminal station. CONSTITUTION:An optical signal to be sent normally is branched by an optical branching device 1, the one signal is inputted to an optical synthesizer 3 in an optical fiber amplifier 2, amplified by an exciting light source 4 and sent. Moreover, the other optical signal branched by an optical branching device 1 is inputted to a photodetector 5, in which the signal is converted into an electric signal and inputted to a non-signal detector 6. When the sent optical signal is interrupted, the non-signal detector 6 detects no signal and outputs a control signal operating a transmitter 7. The transmitter 7 is oscillated at a frequency allocated by the repeater 2 to modulates a bias current in the exciting light source 4 in the optical fiber amplifier 2. As a result, the optical fiber amplifier 2 sends a naturally stimulated light modulated by a frequency assigned to the repeater 2. |
