Temperature-compensated fiber Bragg grating pressure sensor utilizing square diaphragm-based stress transfer structure

A fiber Bragg grating (FBG) pressure sensor using square diaphragm, dowel bar, and constant-strength cantilever beam (CSCB) as the stress transfer structure is proposed in this paper. The measurement principle involving pressure to strain transduction is described. Comparative finite element simulations of two diaphragms show square diaphragm’s superior pressure responsivity, demonstrating a central deflection approximately 30% greater than that of the circular diaphragm. The performance of this design over the range of 0 to 2 MPa is experimentally evaluated, achieving a pressure sensitivity of 273.72 pm/MPa, excellent coefficient of determination (R²) of 0.9992, 0.688% full scale (FS) hysteresis, and 3.368% FS repeatability errors. Furthermore, the utilization of difference in central wavelength shifts between dual Bragg gratings enables effective temperature compensation, resulting in a relative error of 2%. The cost-effective sensor can be adopted for the pressure measurement of gases or liquids within pipelines.