| 摘要 |
PROBLEM TO BE SOLVED: To prevent the influences to other subscriber circuits by placing the optical breakers at many branches of a multi-branch type optical-coupler and detecting a circuit that received the disturbance light from a subscriber device to break only the relevant circuit. SOLUTION: Optical breakers 21 to 28 are placed at the branches of a multi- branch type optical coupler 3, and each of breakers 21 to 28 has an optical coupler 201. The coupler 201 branches the optical input received from a subscriber device into two parts to connect one of both parts to the coupler 3 via an optical delay circuit 202 and an optical switch 203 with the other part detected by a photodiode 204 and amplified by an amplifier 205 respectively. When a high level detection circuit 206 identifies a high optical level or a low frequency detection circuit 207 identifies the frequency different from that of the signal light against the disturbance light given from the subscriber devices 11 to 18, the switch 203 is actuated to cut off the output given from the circuit 202 and to prevent the disturbance light from reaching an end office. When the output of the circuit 202 is cut, a low frequency optical signal generator 209 transmits a channel identification signal. |
