High-Temperature and High-Pressure Fiber Microsphere Fabry–Perot Sensor Based on Vernier Effect and FBG

A pressure and temperature sensor based on dual Fabry–Perot interferometers (F-PIs) using Vernier effect and fiber Bragg grating (FBG) in a hollow silica microsphere-cavity (HSMC) structure is demonstrated theoretically and experimentally. The sensor consists of an F-P cavity formed by inserting the FBG into the HSMC and a reference F-P cavity. Two structures are connected by a 50% coupler to generate the Vernier effect. The change of external pressure will change the length of the microsphere F-P cavity. Utilizing the characteristics that FBG is temperature-sensitive and not effected by pressure, the simultaneous detection of temperature and pressure can be realized by demodulating equation. With a pressure sensitivity of 49.5 nm/MPa and a temperature sensitivity of 14.3 pm/°C, the sensor achieves pressure detection at 300 °C ranging from 0 to 0.8 MPa. The sensor has the characteristics of temperature compensation, high production efficiency, low cost, strong robustness, self-encapsulation, and so on. It has a broad prospect in the field of high-temperature and high-pressure detection.