Optical Fiber Temperature Sensor Based on PDMS-Filled Air-Cavity Fabry–Perot Structure

Seawater temperature is one of the important basic parameters in oceanography, which involves many fields such as aquaculture, marine meteorology, and navigation. In this article, a high-sensitivity temperature sensor based on polydimethylsiloxane (PDMS) filled air-cavity fiber Fabry–Perot (FP) structure is proposed. It is composed of capillary quartz tube, single-mode fiber, and PDMS. According to the temperature experiments, the proposed sensor can achieve a high-temperature sensitivity (no less than 7.34611 nm/°C or even more) with good repeatability and good response time in the measurement range of 0 °C–40 °C. The standard deviation of probe 1 is 0.03903 nm (0.00483 °C) at 30 °C, while that of the actual environment temperature is 0.00452 °C. Only a small deviation existed between the proposed sensor’s result and the actual environment temperature. In addition, the proposed sensor still exhibits high stability in environments with temperatures of 10 °C and 20 °C. Moreover, it could easily achieve temperature measurement with high sensitivity and large range simultaneously by using the cavity length demodulation method.