An FBG Pressure Sensor Based on Spring-Diaphragm Elastic Structure for Ultimate Pressure Detection

We demonstrate a fiber Bragg grating (FBG) pressure sensor based on a spring-diaphragm elastic structure (SDES) for measuring ultimate pressure. The spring-diaphragm elastic structure model can effectively prevent the fiber Bragg grating from being broken under large pressure situations. The geometrical parameters of the sensor are optimally optimized by analyzing the structure of the spring and the diaphragm. By analyzing the results based on the spring-diaphragm elastic structure, the pressure sensor is manufactured and experimentally verified for extreme pressure conditions. For the first time, the fiber Bragg grating pressure sensor was operated at the ultimate pressure. The ultimate pressure experiment demonstrates a stable linear relationship between the fiber Bragg grating central wavelength and external pressure in the range of 0–100 MPa, and the sensitivity of the pressure sensor is 79.7 pm/MPa with a linear correlation coefficient of 0.9998. In addition, the relative temperature sensitivity coefficients of the FBGs were obtained as ${K}_{P} =5.99 \times 10^{-6}/^{\circ }\text{C}$ and ${K}_{T} =6.265 \times 10^{-6}/^{\circ }\text{C}$ respectively to eliminate the temperature cross-sensitivity effect. The pressure sensor can be used for ultimate pressure detection, especially for deep sea detection, oil exploration, and chemical monitoring.