High-Precision Distributed Temperature Sensor Based on Phase-Shifted FBGs Interrogated by OFDR

We proposed and demonstrated a high precision distributed temperature sensing system by utilizing the intricate spectral characteristics of phase-shifted fiber Bragg gratings (PSFBG). By employing optical frequency domain reflectometry, we have achieved exceptional localization accuracy with 20.5 μm and spectral reconstruction with the wavelength accuracy of 0.1 pm. In the experiment, we characterized the temperature sensing property of a strong standard PSFBG and an array of 1,974 ultra-weak PSFBGs, respectively. The temperature sensitivity of the single PSFBG is approximately 10.4 pm/°C with an average temperature precision of 0.05 °C and a minimum precision of 0.01 °C, which is significantly improved over the traditional FBG sensors. In the case of the sensor array, the average temperature precision is 0.13 °C and the minimum precision reaches 0.06 °C, with a sensing spatial resolution of 20 mm. These results indicate that the proposed system is highly suitable for precision measurement tasks, offering both precise positioning and temperature sensing.