| 摘要 |
PURPOSE:To prevent the signal transmission of a cable without a fault from being stopped by stopping the superimposition of a low frequency signal onto an optical main signal at the occurrence of a faulty cable so as to stop the optical output. CONSTITUTION:If a faulty calbe takes place at a point A, the input interruption of an optical signal a1 is detected by an optoelectric converting circuit 3a of an optical terminal station equipment 1W and an alarm signal (b) of optical input interruption is outputted. An electrooptic converting circuit 2a of the optical terminal station equipment 1W receives an alarm signal (b) to stop the superimposing of a low frequency signal onto the optical signal a2. Thus, the optoelectric conversion circuit 3a of the optical terminal station equipment 1E detects the interruption of a low frequency signal and outputs a low frequency signal interruption alarm signal (c). The electrooptical converting circuit 2a receiving the signal (c) stops the output of the optical signal a1. |
