Demonstration of a scalable fault surveillance scheme for WDM transmission links

In long haul WDM transmission systems, some kind of surveillance scheme is needed for the status monitoring of the in-line erbium-doped fiber amplifiers (EDFAs) and the identification of fiber breaks to guarantee the quality of service. Previous surveillance schemes based on using the combination of fiber Bragg gratings (FBGs) and amplified spontaneous emission (ASE) as monitoring source were proposed. In these schemes, FBGs of various distinct wavelengths are inserted at the inputs of all in-line EDFAs to reflect selectively the ASE for monitoring purposes. These schemes, however, are not scalable and can only be applied to long-haul transmission systems with limited distances, as each FBGs wavelength has to be unique. Here, we propose a scalable surveillance scheme, which is based on a novel monitoring-wavelength reuse concept. The proposed scheme is demonstrated experimentally.