Demonstration of a low-cost 1625-nm OTDR monitoring for 350-km WDM networks with semiconductor optical amplifiers

A semiconductor optical amplifier (SOA)-based optical time-domain reflectometry (OTDR) monitoring system is successfully demonstrated for a 350-km wavelength-division-multiplexing (WDM) network operating at 1625 nm. The 1625-nm monitoring signal bypasses the amplifying stage for WDM signals and is amplified by an L-band SOA. No power penalty was observed in the 10-Gb/s WDM transmissions when the OTDR signal is on. This simple and low-cost system is an excellent candidate for the online monitoring of WDM transmission systems.