Diaphragm Structured Fiber-Optic Pressure Sensors for Oil Downhole Applications

We propose a fiber-optic Fabry-Pérot interferometer (FPI) pressure sensor that utilizes a diaphragm structure interfacing with the flat-cut end face of a single-mode fiber (SMF). The application of pressure results in the deformation of the diaphragm, which is analyzed using wavelength tracking and cavity length demodulation techniques. To compensate for temperature effects, Fiber Bragg Grating (FBG) is connected in series. The sensor exhibits a sensitivity of -763.33±4.33 pm/MPa when utilizing wavelength shift and -100.64±1.83 nm/MPa when measuring cavity length change within a pressure range of 0 - 80 MPa and a temperature of 150 °C. Due to its extensive dynamic range, heightened sensitivity, and excellent temperature resistance, this sensor is used to monitor pressure changes in 3500 meters deep oil wells.