Cavity-Grate Integrated All-Fiber Optic High Temperature Pressure Sensor with Enhanced Contrast and Sensitivity

An all-fiber dual-parameter pressure–temperature sensor with enhanced contrast and sensitivity is proposed, fabricated, and experimentally validated for gas monitoring in high-temperature environments. The sensing structure combines a Fabry–Pérot interferometer (FPI) for pressure detection and a fiber Bragg grating (FBG) for temperature measurement. A collimation-enhancement mechanism, based on the self-focusing effect of the graded-index fiber, is employed to improve signal contrast. The diaphragm-based closed-end FPI cavity is fabricated using precision mechanical cutting and arc discharge techniques. To further enhance the pressure sensitivity, the fiber end-face is treated using mechanical grinding followed by femtosecond laser roughening. The sensor's performance was evaluated at ambient conditions and under extreme conditions of 700 °C and 5 MPa. At 700 °C, the sensor exhibits a temperature sensitivity of 11.61 pm/°C and a pressure sensitivity of 46.96 nm/MPa. The full-temperature drift of the pressure sensitivity is less than 3 nm/MPa, with a maximum full-scale error of 2.95%. Owing to its high mechanical robustness and sensitivity, the proposed sensor is well suited for simultaneous gas temperature and pressure monitoring in harsh, high-temperature environments.