METHOD AND APPARATUS FOR DISTRIBUTED SENSING WITH STROKES-LOCKED REFERENCE LASER

摘要

This invention relates to a method for distributed sensing with a Stokes-locked reference laser, comprising the steps of splitting an optical pump radiation in two beams, one for Brillouin pumping of an optical reference fiber and another for pulsed Brillouin pumping of a test fiber, locking a reference laser on reference fiber Stokes radiation for producing a stable seed signal which is launched into the test fiber, receiving a spontaneous back-scattered Stokes signal transmitted through the test fiber seed signal, calculating the temperature or strain distribution by sensing change in amplification of the seed signal or by processing the shift of the beat spectrum between the seed signal and the spontaneously scattered Stokes component along the test fiber. Brillouin based distributed sensors are very attractive and promising technique for truly distributed sensing of strain and/or temperature and widely used to monitor tunnels, bridges, dams, airplanes, buildings and etc. The Brillouin frequency shift is dependent on the temperature and strain conditions of the optical fiber, which provides the basis for a sensing technique capable of detecting these two parameters.