| 摘要 |
PURPOSE:To easily constitute an optical loop-back and obtain high sensitivity by connecting a 2X2 optical fiber switch in the input side or output side of an optical reproduction repeating circuit. CONSTITUTION:When the command signal of a loop-back is sent from a transmitting side terminal station, an optical switch 4 is operated by a control circuit 11. The route of a light goes to be the route to be shown by a broken line. Then, an ascending optical signal proceeds in the route of 2a 5 4 8 3b 10 3c and it is sent to a descending line. Namely, the loop- back is constituted. Reversely, a descending optical signal proceeds in the route of 3a 6 4 7 2b 9 2c and it is sent to an ascending optical fiber. Then, also concerning this signal, the loop-back is constituted. |
