| 摘要 |
PURPOSE:To realize a loopback circuit in which the insertion loss of a main signal system is remarkably reduced by inputting a loopback signal branched by a light demultiplexer to the light multiplexer of an opposite circuit through a light amplifier. CONSTITUTION:The light multiplexer 5 and the light demultiplexer 9 are arranged at the input part and the output part of a light repeater 1 respectively, and a signal branched by the light demultiplexer 9 is inputted to the light multiplexer 6 of the opposite circuit through the light amplifier 13. When the signal is desired to loop back form the light repeater 1 to the light repeater 2 of the opposite circuit, the light amplifier 13 is turned on. By adjusting the amplification degree of the light amplifier 13, the loss of the loopback signal system of the light demultiplexer 9 and the light multiplexer 6 can be compensated, and the loopback signal of a sufficient level can be transmitted to the repeater 2. Thus, since the loss of the loopback signal system can be compensated by the light amplifier 13, the braching ratios of the light demultiplexer 9 and the light multiplexer 6 can be made large, and the insertion loss of the main signal system can be reduced. |
