High Sensitivity All Sapphire-Based Optical Fiber Fabry–Perot Pressure Sensor for Harsh Environment

In this paper, a high-sensitivity optical fiber Fabry-Perot sensor based on all-sapphire is proposed and fabricated for pressure sensing in ultrahigh temperature environments. Compared with other works, the pressure-sensing sapphire wafer’s thickness was reduced to about
$40~\mu $
m to improve the pressure sensitivity dramatically, while maintaining its dimensions to be
$2\times 2$
mm. The double-side wet-etching process was adopted to thin the sapphire wafer. The roughness of the wetted sides was modified by different etching processes to optimize the optical interference fringe. The all-sapphire sensor head was assembled with a directed bonding method, and the sapphire fiber was adopted to be the lead-in fiber to increase the sensor’s tolerance to high temperatures. Detailed experiment shows that the fabricated sensor can work stably under 1200 °C in the range of 0–3 mPa. The pressure sensitivity increased from
$0.877~\mu $
m/mPa under room temperature to
$1.193~\mu $
m/mPa under 1200 °C. The good performance of the proposed sensor under high temperatures ensures its good application in pressure sensing of aeroengine and gas turbine.