Mitigating Polarization-Dependent Fluctuation of Single-Photon Raman Distributed Optical Fiber Temperature Sensor

Raman distributed optical fiber temperature sensor based on single-photon detection (RDTS-SPD) improves the spatial resolution in temperature sensing. However, the temperature accuracy of RDTS-SPD is hindered by the polarization and interference effects in the Raman spontaneous backscattering process. Existing methods only mitigate the influence of the polarization-sensitive single-photon detector, and commonly require the assistance of multiple single-photon detectors, complex cryogenic devices, or long measurement periods. In our work, we analyze the the interference between the Raman photons generated by the different polarization components of probe light, and propose a method based on orthogonal-polarization dual-pulse light to mitigate polarization-dependent fluctuation with a single measurement period. A proof-of-principle experimental demonstration is performed by using an InGaAs/InP-based single-photon avalanche diode (SPAD). The proposed method reduces the contrast of polarization-dependent fluctuations from $0.18\pm 0.01$ to $0.05\pm 0.01$. A temperature resolution of 0.5 $ ^{\circ }$C and a temperature accuracy of $\pm 0.9 ^{\;\circ }$C are achieved without any other denoising method. The spatial resolution is achieved to be 37 cm, which can be further improved by reducing the pulse laser width. Our approaches open opportunities for the RDTS-SPD system from experimental validations to practical application.