| 摘要 |
<P>PROBLEM TO BE SOLVED: To keep superior quality of a signal light to be transmitted in any other block, which is not associated with the failure block, in a simple configuration, even when an input signal to an optical add/drop multiplexer is interrupted by any failure. <P>SOLUTION: For an optical add/drop multiplexer branching unit(OADM-BU) 20 on a main transmission path L1, there are input decision circuits 23A-23D are provided for detecting power of lights from the main transmission path L1 and a branch transmission path L2 and determining whether each of the lights is lost based on the detection results; and optical path switching units 24A-24D forming a loop-back path, when a corresponding input decision circuit determines a state of losing an input light, by connecting an optical path, on which an output light to a transmission path corresponding to the relevant input light is propagated, to an opposite-side optical path, through a switching operation of an optical switch. <P>COPYRIGHT: (C)2011,JPO&INPIT |
