In-service passive surveillance system for optically-amplified branched networks

The authors experimentally demonstrate a passive surveillance system for in-service fault identification in optically-amplified branched networks. The proposed scheme only requires fibre Bragg gratings to be placed on different fibre branches and needs no extra laser source as required in conventional and multiwavelength OTDR. The reflected monitoring channels are demultiplexed by an array-waveguide grating and detected by a power sensor array. The link status of all fibre branches can be monitored continuously and simultaneously through the Internet.