Batch-Producible Fiber-Optic Fabry–Pérot Sensor for Simultaneous Pressure and Temperature Sensing

We demonstrated a simple and batch-producible fiber-optic sensor based on hybrid Fabry-Pérot (FP) configuration for simultaneous pressure and temperature sensing. The proposed sensor head chips are batch fabricated by double-sided anodic bonding of a through-holes-array-structured glass wafer and two silicon wafers. The silicon-glass-silicon sandwich bonding structure constructs two serially connected low-finesse FP cavities naturally. The first cavity (FP₁) is a silicon cavity and utilizes the refractive indices temperature dependence of silicon to achieve temperature sensing. The second cavity (FP₂) is a vacuum cavity and employs a thin silicon diaphragm as a pressure sensing element. The reflection spectra exhibit hybrid interference fringes with different frequencies produced by silicon and vacuum cavity, and the temperature and pressure are simultaneously measured. Experiment results demonstrate that the pressure sensitivity of FP₂ is 12.82 nm/kPa with a high linear pressure response over the range of 10-250 kPa, and the temperature sensitivity of FP₁ is 142.02 nm/°C under the range of -20 °C-70 °C.