Compact-Packaged and Diaphragm-Lever Structured Fiber-Optic Temperature and Pressure Sensors for Oil and Gas Well Applications

A small-sized sensor combined with a diaphragm structure and a lever structure is proposed for application in high-temperature and high-pressure environments. The feasibility of the structure is verified from both theory and simulation, and the relationship between the change of the Bragg wavelength and the pressure is established. Differential measurements of temperature and pressure are achieved using two fiber Bragg gratings (FBGs). The experimental data show that the pressure sensitivity of the sensor is 28.86 pm/MPa in the range of 0–30 MPa, and the correlation coefficient is 0.9969. The pressure sensitivity of the improved structure is 29.76 pm/MPa and the correlation coefficient is 0.9999. The sensor's temperature sensitivity is 32.66 pm/°C in the range of 50 °C–200 °C. The structure can be applied to the measurement of temperature and pressure in oil and gas wells.