Ultra-sensitive air pressure sensor based on gelatin diaphragm-based Fabry-Peroy interferometers and Vernier effect

We proposed and experimentally demonstrated a gelatin film-based Fabry-Perot interferometer (FPI) structure ultra-sensitive fiber optic air pressure sensor. The Fabry-Perot (F-P) cavity of the sensing probe FPI1 is made of gelatin film, with a thickness of approximately 0.8 mu m and the probe length of approximately 136 mu m. The air pressure sensitivity of the probe obtained in the experiment is as high as 334 nm/MPa. In order to further improve the sensitivity of the probe, we fabricated an FPI2 with an air F-P cavity that is approximately the length of the FPI1 cavity, and then paralleled FPI2 with FPI1 to generate a Vernier effect. The sensitivity of the Vernier probe obtained in the experiment reached -2701.14 nm/MPa, which magnified the sensitivity of a single FPI1 by 8.1 times. The temperature cross-sensitivity is only 0.0035 MPa/degree celsius. This proposed air pressure sensor has the advantages of ultra-high sensitivity, simple manufacturing, low cost, good repeatability and stability, and has broad application prospects in high sensitivity pressure and acoustic detection.