High Sensitivity All Sapphire-Based Optical Fiber Fabry–Perot Pressure Sensor for Harsh Environment
Zhiqiang Shao, M.C. Chen, 卓二 外山, Zhiqiang Sun, Yan Wang, Lei Yan, Yiqun Wang, Bin Liu
Abstract
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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40~\mu $ </tex-math></inline-formula>m to improve the pressure sensitivity dramatically, while maintaining its dimensions to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.877~\mu $ </tex-math></inline-formula>m/mPa under room temperature to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.193~\mu $ </tex-math></inline-formula>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.