High-Sensitivity Temperature Sensor Based on Vernier-Effect and Cascaded Polarization Mode Interferometers

In this paper, a highly sensitive fiber optic temperature sensor (FOTS) based on two cascaded polarization mode interferometers (PMIS) cascaded is proposed and experimentally demonstrated. One PMI is fabricated by splicing a polarization-maintaining fiber (PMF) with a polarizer by an angle of 45 -degree of polarization axes, which is applied as a reference interferometer (RI). The other PMI is constituted by splicing a PMF with the former PMI by an angle of 45 -degree of polarization axes, which is used as a sensing interferometer (SI). The end face of the SI is well cleaved, which has a 4 % end face reflection. The Vernier effect is generated by controlling the FSR of SI through the PME length. Experimental results show that the temperature sensitivity of the cascaded sensor can reach $19.067 \mathrm{~nm} /{}^{\circ} \mathrm{C}$, which is 15.376 times of that of the single SI. The sensor has the advantages of high sensitivity, simple fabrication, and good stability, which has a potential application prospect in aerospace and industrial production.