Optical fiber distributed acoustic sensing based on the self-interference of Rayleigh backscattering

In order to detect the weak underwater acoustic signal, a Distributed Acoustic Sensing (DAS) scheme based on the self-interference of Rayleigh backscattering is presented. Rayleigh backscattered light which contains a phase change induced by acoustic signal along the sensing fiber which is a standard telecom single-mode fiber is split and fed into an imbalance Michelson interferometer. With the self-interference of two Rayleigh backscattered beams, the phase change is amplified theoretically compared with phase-sensitive OTDR. We designed an experiment to prove the scheme, and successfully restored the acoustic information, meanwhile, the DAS system has preliminary realized around the acoustic phase sensitivity of −151 dB (re rad/μPa) at 600 Hz, and the minimum detectable acoustic pressure of 6 Pa in the experiment.