A Novel Weak-Scattering Michelson Interferometer Based on PBS for Long-Distance Disturbance Localization

Optical fiber interferometer could achieve various dynamic measurements by transforming phase change into intensity change. In this paper, a novel Michelson interferometer (MI) based on two polarization beam splitters (PBSs) is proposed. Two thirds of Rayleigh backscattering (RB) is separated from the signal light by using PBS and Faraday rotating mirror (FRM) due to the difference polarization properties between RB and signal light in optical fibers. And the signal-to-noise ratio (SNR) of system has been significantly improved. Within the detection range of 50 km, the localization experiments on this new interferometer show that the SNR is increased by 6.69 dB compared with traditional MI on the condition of 500 kHz sampling rate. And the positioning accuracy can achieve ±100 m in the first-order null-frequency. The sensing distance also increases from 36.17 km to 49.42 km with a SNR of 15 dB. This proposed sensing system exhibits high sensitivity in the low frequency region, which is of great importance for long-distance buried optical cable detection and location.