| 摘要 |
PURPOSE:To avoid external electromagnetic induction by providing repeaters with filters differing in center frequency, by sending out a search signal modulated by the center frequency of each filter from a terminal station to a main signal line and then by making repeater detect a fault and send a detection signal to the terminal station through an optical fiber. CONSTITUTION:Terminal station T and another terminal station are connected together by optical fibers 1 and 5 and repeaters 2a and 2c, respective repeaters 2a- 2c are provided with BPFs 3a-3c differing in center frequency, and electro-photo converting element 4 is connected to output sides of BPFs 3a-3c. On detecting a fault, terminal station T sends a search signal modulated by a corresponding center frequcncy to fiber 2 and this search signal is selected by BPFs 3a-3c; and a search result from element 4 of repeaters 2a-2c corresponding to the search signal is sent to fiber 5 through coupler 6 to attain fault search by detection circuit Ta of terminal T without external electromagnetic induction. |
