MEMS-Based High-Temperature Fiber-Optic Acoustic Pressure Sensor for Harsh Environment Monitoring

This paper presents a novel fiber-optic Fabry-Perot (FP) high-temperature acoustic pressure sensor for addressing the measurement of high acoustic pressure levels in a 350 °C environment. The sensor head, consisting of high-temperature-resistant silicon and high-boron-silicon wafer materials, is fabricated using micro-electro-mechanical system (MEMS), computer numerical control (CNC) machining, and laser micromachining technologies. CO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> laser welding is employed to achieve adhesive-free integration between the sensor head and optical fiber. The materials used in the sensor have similar thermal expansion coefficients, preventing thermal mismatch induced sensor failure in high-temperature environments. The pressure-equalizing holes in the sensor head eliminate the effect of static pressure on both sides of the diaphragm and enhance the efficiency of signal transmission. The micron-thick diaphragm is fabricated to improves both the sensitivity and measurement range of the sensor. Therefore, the sensor is capable of measuring high acoustic pressure levels in high-temperature environments. Experimental results show that the sensor achieves the measurement of acoustic pressures up to 170 dB at room temperature, with a sensitivity of 0.32 nm/Pa and a nonlinearity error of 0.23%. At 350 °C, the sensitivity increases to 0.61 nm/Pa, with a nonlinearity error of 0.33%. Stability tests demonstrate that under 350 °C and 120 dB acoustic pressure conditions, the maximum amplitude drift is less than 0.2 nm. The results indicate that this fiber-optic FP acoustic pressure sensor can achieve precise acoustic pressure measurements in high-temperature environments, providing reliable technical support for acoustic pressure parameter acquisition in harsh environments.