| 摘要 |
PURPOSE:To prevent the S/N of back scattering light deteriorating and to reduce insertion loss in a main line system by providing optical multiplexing/ demultiplexing means pre-arranged at the optical signal input sides of up and down optical repeaters, respectively, and looping back an optical signal to a landing station to measure the back scattering light generated at a faulty point. CONSTITUTION:The back scattering light L' generated in an optical fiber 1c with a back scattering light measuring pulse LP sent from the up optical repeater 5b passes the optical repeater 5b, and is amplified. After that, it is branched with an optical multiplexer/demultiplexer 22b, and passes a folding route 24, and is coupled with the down optical repeater 6b with an optical multiplexer/demultiplexer 23b. Since weak back scattering light L' is looped back to a down optical fiber 2c after being optically amplified with the optical repeater 5b once, the S/N at a reception terminal can be improved. |
