A Fabry-Perot Interferometer Sensor Based on a Microsphere Tellurite Fiber Probe for Temperature and Hydraulic Pressure Measurement

In this article, a tellurite fiber (TF) was fabricated into a microsphere structure via discharge and sequentially coupled with a multimode fiber and a single-mode fiber (SMF) to form a Fabry-Perot interferometer (FPI) sensor. Changes in temperature and hydraulic pressure cause the microsphere to deform, altering the interference length of reflected lights and establishing their dependency relationship. Experimental results showed that the proposed FPI sensor had temperature sensitivity of 157 pm/°C and hydraulic pressure sensitivity of 11.4 pm/MPa. In addition, repetitive experiments and stability tests were conducted, and the maximum relative standard deviation (RSD) was calculated to be $4.34\times 10^{-4}$ for temperature and $4.48\times 10^{-4}$ for hydra- ulic pressure. This FPI sensor is characterized by small size, compact structure, high sensitivity, long-term accuracy, and good stability and repeatability. All these features render it suitable for real-time temperature and hydraulic pressure monitoring in complex environments. In addition, the tellurite compositions can be adjusted to help adapt the FPI sensor to specific external environmental conditions, which provides valuable theoretical and technical insights for the development of high-performance sensing devices.