Study of Cryogenic Temperature Sensing Based on an All-Fiber Sagnac Loop With High Sensitivity and Wide Measurement Range

Fiber optic-based cryogenic temperature sensing has vital applications in aerospace, biomedicines, food, and energy storage. However, the current fiber optic-based cryogenic temperature sensors have the problems of low sensitivity and narrow sensing range. In this study, we experimentally investigated the cryogenic temperature sensing based on an all-fiber Sagnac loop using a panda polarization maintaining fiber (PPMF) and a fiber Bragg grating (FBG). Modeling simulation of PPMF under cryogenic temperature proved that it could be used for cryogenic temperature sensing in Sagnac loop. FBG, which showed a low but linear temperature response, was used to mark the dip wavelength in Sagnac loop as the movement of dip wavelength exceeding a free spectrum range (
FSR
). The proposed sensor showed a temperature measurement sensitivity of 0.943 nm/°C and a wide measurement range of −103.15–46.85 °C. Furthermore, the proposed sensor also depicted good hysteresis and stability. The study in this paper, which provides an idea to detect cryogenic temperature with high sensitivity and wide measurement range, offers a choice for remote and precise monitoring of cryogenic temperature.