Cascaded MI and FPI Based Optical Fiber Sensor for Simultaneous High-Temperature and High-Pressure Monitoring

An optical fiber sensor based on Michelson interferometer (MI) cascaded with Fabry–Perot interferometer (FPI) is proposed for simultaneous monitoring of high-temperature and high-pressure. The MI comprises a tapered single-mode fiber (SMF) spliced with a section of no-core fiber (NCF), while the FPI cavity is formed by sealing the fiber MI into a silica capillary tube. The temperature and pressure can be detected by monitoring the spectral features of the MI and FPI, respectively. The experimental results demonstrate that the sensor achieves a temperature sensitivity of 42.95 pm/°C and a pressure sensitivity of −195.38 nm/MPa in a temperature range of 25–150 °C and a pressure range of 0–35 MPa. The sensor has the advantages of high sensitivity, cost-effectiveness, and ease of preparation.