| 摘要 |
PROBLEM TO BE SOLVED: To realize a passive optical network that is able to continue communication even at the time of the occurrence of a fault.SOLUTION: There is a fault detection optical transmission path 17a which extends clockwise relative to a ring-type optical transmission path 11 and a fault detection optical transmission path 17b which extends anti-clockwise along the ring. The fault detection optical transmission path 17a is folded back at the position of a closure 12b-2 and extends anti-clockwise along the ring. Also, the fault detection optical transmission path 17b is folded back at the position of the closure 12b-2 and extends clockwise along the ring. In addition, optical couplers 170 are inserted into the fault detection optical transmission paths 17a, 17b at the position of each closure 12b and the fault detection optical transmission paths 17a, 17b branch off branches 171a-c. A fault place of the optical transmission path 11 can be detected by receiving or not receiving signals from the fault detection optical transmission paths 17a, 17b and branches 171a-c, and on the basis of that the transmission path is switched and communication can be continued even if a fault occurs on the optical transmission path 11. |
