High-sensitivity temperature sensing system based on frequency demodulation technology of high birefringence fibers

This paper proposes and validates a highly sensitive temperature detection system based on polarization mode beat frequency signal (PMBFS) demodulation. The system incorporates high birefringence fiber to enhance the stability of the PMBFS, while the low birefringence single-mode fiber (SMF) resonator is optimized for temperature measurement. Theoretical research demonstrates that the difference in the refractive index between the fast and slow axes of PANDA polarization-maintaining fiber (PMF) exhibits a strong linear response to external temperature, resulting in PMBFS drift. By monitoring this drift, we characterize the external temperature. In this study, we introduce Panda PMF with lengths of 10 cm, 14 cm, and 20 cm into the resonant cavity as the temperature-sensing structure. The experimental results confirm that as the length of the panda polarization-maintaining optical fiber increases, the sensitivity of the sensor to temperature also improves. When PMF is 20 cm long, the maximum sensitivity reaches 3.53409 MHz/°C, and the resolution reaches 0.01 °C. This method utilizes only PMF for temperature sensing, featuring adjustable sensitivity and resolution. It offers significant advantages such as high sensitivity, high precision, and a simple structure during the temperature monitoring process. Given its excellent performance, the sensor has great potential for applications in biochemical reactions.