Novel in-service supervisory system using OTDR for long-haul WDM transmission link including cascaded in-line EDFAs

We propose and demonstrate a novel optical supervisory system for long-haul wavelength-division-muitiplexing (WDM) transmission link including cascaded erbium-doped fiber amplifiers (EDFAs). By employing a modified optical time domain reflectometry technique with a wavelength selective bidirectional EDFA, it was possible to monitor the status of the WDM transmission link and EDFA at in-service states with negligible power penalty. Proof of the concept with a 2.5 Gb/s/spl times/eight-channel WDM transmission system [single-mode fiber, 320 km] shows clear trace of the transmission line loss/gain/reflection map with minimal signal power penalty of 0.3 dB.