A diaphragm-free fiber Fabry-Perot gas pressure sensor

A diaphragm-free fiber gas pressure sensor based on the extrinsic Fabry-Perot interferometer (EFPI) is proposed and experimentally demonstrated. The sensor is fabricated by fusion splicing a sandwich structure of a single mode fiber, a hollow core fiber (HCF), and a coreless fiber. A femtosecond (fs) laser is employed to drill a micro-channel on the side wall of the HCF to allow gas entering/exiting the HCF. The refractive index of the gas has a linear relationship with the gas pressure. Thus, the gas pressure can be detected by investigating the optical path difference of the EFPI. The experimental results show that the proposed sensor exhibits a high gas pressure sensitivity of ∼1.80 µm/MPa from vacuum to 10 MPa at room temperature. Pressure responses under high temperatures are also investigated. The proposed sensor has properties of robust structure, miniature size, large measuring range, and high sensitivity.