Cryogenic temperature sensor based on fiber optic Sagnac interferometer with a panda polarization-maintaining fiber

•A cryogenic temperature sensor based on fiber optic Sagnac interferometer was proposed and experimentally demonstrated.•The proposed sensor had an average temperature sensitivity of 1.74 nm/K in a wide temperature range of 320–170 K.•Free spectral range (FSR) was used to calibrate the dip wavelength as the variation of temperature exceeded an FSR. Accurate measurement of cryogenic temperature is crucial for various scientific and technological applications. In this paper, we experimentally investigated a fiber optic cryogenic temperature sensor based on a Sagnac interferometer (SI) with a panda polarization-maintaining fiber (PPMF). The PPMF used as the temperature sensing probe in SI enhanced the cryogenic temperature measurement sensitivity by two orders of magnitude compared to most of the published literature. The value of free spectral range (FSR) was used to label the dip wavelength as the movement of the spectrum exceeding an FSR in a large temperature variation scale. Experimental results demonstrated that the proposed sensor achieved an average measurement sensitivity of 1.8 nm/K in a wide temperature range of 170–320 K. Owing to high sensitivity, low hysteresis, and easy fabrication, our proposed sensor emerges as an ideal solution for cryogenic temperature detection.