Abstract To address the demand for flow-induced vibration monitoring of steam generator heat transfer tubes in pressurized water reactors under high-temperature (350 °C) and high-pressure (17.5 MPa) conditions, a fiber-optic Fabry–Pérot interferometric accelerometer based on a composite Fabry–Pérot cavity structure is proposed. The sensor employs a symmetrically arranged multidirectional cantilever beam and a central proof mass to effectively reduce cross-axis sensitivity. Using a MEMS-based fabrication process, a three-layer sensing chip with a composite cavity is formed, mitigating the temperature drift problem of conventional single-cavity structures under elevated temperatures. A temperature calibration model is further incorporated to improve measurement accuracy. The optical path is folded by a 45° metallic mirror and hermetically sealed by laser welding, ensuring stable operation under high temperature, high pressure, and external mechanical shocks. Experimental results show that the sensor achieves a sensitivity of 4.53 nm/g, a resonant frequency of 7450 Hz, a cross-axis sensitivity as low as 0.281%, and a resolution of 4.4 mg, with an acceleration measurement range of ±238 g at room temperature. Under 350 °C and 17.5 MPa, the sensor exhibited cavity length drift below 0.1 nm during a 60-h stability test, demonstrating reliable dynamic performance and long-term stability in extreme conditions, which provides an effective tool for the continuous safety monitoring of critical heat transfer structures in pressurized water reactors.
Qin et al. (Tue,) studied this question.