Security pre-warning system of underground pipelines based on BOTDR

The security pre-warning system of underground pipelines was traditionally designed by electronic sensors, usually suffering from intrinsic flawssuch as too scattered monitoring points and poor anti-interference performance. To overcome these disadvantages, a distributed optical fiber temperature and strain sensing system based on Brillouin Optical Time Domain Reflectometer (BOTDR) is designed and developed for underground pipelines security monitoring. In this paper, the sensing mechanism of temperature and strain sensing is analyzed and a BOTDR experimental scheme is presented. Meanwhile, the kernel software program is developed for signal demodulation. Then, the integrated BOTDR instrument is designed compactly and evaluated by temperature and strain measurement experiments, for respectively simulating pipeline leakage and deformation. The experimental results show that the sensing range of 10.268 km is achieved with a spatial resolution of 1.15 m. The nonlinear error is less than 1% FSS over the temperature and strain change of 30~90°C and 0-15000με.