| 摘要 |
PURPOSE:To attain optical communication even when one of plural optical transmission lines is interrupted by providing a master station having plural light emitting and receiving ports and a slave station having plural light emitting and receiving ports so as to provide the plural optical transmission lines. CONSTITUTION:An electric signal is inputted externally to an outside IF112 of a slave station 4x and converted into an optical signal by data conversion sections 6A, 6B via a control section 92, a communication section 72 and sent from light emitting and receiving ports 3A, 3B. The signal is received by the light emitting and receiving ports 1A, 1B of a master station 2 and inputted to a communication control section 71 via conversion sections 5A, 5B. One reception signal is stored tentatively in an elastic memory 81. The signal is compared with an output of the control section 71 at a control section 91. When one of optical transmission lines between the slave station and the master station is interrupted, it is discriminated by observing the mark hold. When the both are in the mark hold state, an alarm is raised from an alarm section 101 and retransmission is requested to the slave station 4x. The result of discrimination by the control section 91 is sent to an external device by the IF 111. The optical transmission line with high quality is obtained. |
