| 摘要 |
PURPOSE:To prevent overload, to make the installation work and the maintenance efficient and to improve the reliability by controlling automatically the optical input to an APD. CONSTITUTION:An O/E conversion circuit 3 is provided with an alarm circuit outputting an alarm signal when a reverse bias voltage of an APD is decreased to a prescribed value or below, an E/O conversion circuit 4 is provided with an alarm transmission means inserting the alarm signal to an overhead bit of a transmission signal and sending the result to an opposite station, an O/E conversion circuit 2 is provided with an alarm reception means receiving the alarm signal and outputting it, and an EGO conversion circuit 1 is provided with an optical output attenuation means decreasing a sender side optical output level automatically by a prescribed quantity by means of the alarm signal. |
