Performance improvement of a self-heterodyne detection BOTDR system employing broad-band laser

Distributed optical fiber sensor based on Brillouin scat- tering was fn＇st proposed by Farahi et al in 1989[1], and has attracted intense interest due to the potential applica- tion in monitoring large civil structures, power cables, oil and gas pipelines and geological disaster[2＇3]. One of the subjects mainly investigated is Brillouin optical time domain reflectometer （BOTDR） for single-fiber-ended measurement only and simple implementation. The backscattered spontaneous light is used to measure the round-trip time of optical pulses entering into the sens- ing fiber and the optical intensity at each sampling point. By analyzing the measured round-trip time and the spon- taneous Brillouin intensity, the distributed physical quantities, such as temperature and strain, can be ob- tained [4,5].