| 摘要 |
PURPOSE:To surely detect the occurrence of a fault such as the disconnection of an optical fiber in an optical transmission line by providing a polarity inversion circuit inverting signal polarity to each of a transmission circuit and a reception circuit in one direction in the bidirection of transmission directions. CONSTITUTION:When a fault such as the disconnection of the takes place in an optical transmission line 51, a transmission signal from a transmission circuit 52 is reflected fully at the disconnection point and reaches a reception circuit 57 of its own station, and since the arrived signal is inverted for the polarity by a polarity inversion circuit 54, the line is in the state of the code rule violation. Thus, the reception circuit 57 detects the occurrence of a fault immediately by the code rule violation to raise an alarm. Moreover, the reception circuit 53 detects the occurrence of a fault because of the interruption of the arrived signal from the transmission circuit 52. Thus, the disconnection of the line due to the occurrence of a fault in the optical fiber is surely detected by both the sender side and the receiver side. |
