| 摘要 |
PURPOSE:To transmit monitoring information with a service bit even when one line is interrupted by constituting the subject device so that a decoding circuit extracts service bit monitoring information and a coding circuit sends a data while main signal bits except the service bit are brought into all zero. CONSTITUTION:When one of optical transmission lines 4 is disconnected, the light receiving circuit 5 of an optical transmission circuit equipment A generates an optical interruption detection signal. A coding circuit 2 receiving the signal sends an optical signal making all main signal bits except the service bit of monitoring information to '0' from an optical transmission circuit 3 to the transmission line 4 which is not disconnected. The optical reception circuit 5 of an optical transmission line equipment B does not detect optical interruption, converts the received optical signal into an electric signal and sends the result to a decoding circuit 6, which extracts the service bit to acquire the monitoring information and gives a signal detecting that all main signal bits are '0' except the service bit to the coding circuit 2. The coding circuit 2 in response to thereto sends the signal of all '0' of the main signal bits to the transmission line 4 via the optical transmission circuit 3. |
