Centimeter Spatial Resolution Distributed Temperature Sensor Based on Polarization-Sensitive Optical Frequency Domain Reflectometry

Abstract

A centimeter-level spatial resolution distributed temperature sensor (DTS) based on polarization-sensitive optical frequency domain reflectometry (OFDR) is proposed. Polarization-maintaining fiber (PMF) is employed as the sensing fiber. The birefringence along the PMF is detected from the Rayleigh backscattering (RBS) spectral difference between the two orthogonal polarization axes, which is retrieved by short-time Fourier transform and distributed cross-correlation algorithm, and thus the large error induced by the auto-correlation is eliminated. Since the birefringence is roughly uniform for the same type of PMF, relationship between the absolute temperature and the birefringence calibrated on a small fiber section can be applied to the whole fiber, or even the same batch of fiber, which brings convenience in practice. The linear relationship between the absolute temperature and the RBS spectral difference is experimentally verified, and distributed temperature measurements are implemented with a high spatial resolution of 1.3 cm along the 94 m sensing fiber. The absolute temperature measurement uncertainty is $\boldsymbol {\pm 4.5\, ^{\circ}\text{C}}$ in the experiment, which is mainly limited by the birefringence non-uniformity. In some cases the impact of birefringence non-uniformity can be eliminated, and thus the temperature measurement uncertainty can be improved up to $\boldsymbol {\pm 0.8\, ^{\circ}\text{C}}$ , which is limited by the random noise in the proposed system.