Design and fabrication of a differential-pressure optical fiber grating sensor for monitoring the flow rate of fluid

Abstract

A fiber Bragg grating (FBG) flow sensor is designed and fabricated, in which two FBGs are fixed on the front and other side of the metal diaphragm, and differential pressure is used to monitor the flow rate of fluid. The temperature sensitivity of these two FBGs is 0.030 and 0.029 nm/°C, which is almost the same, suggesting that the influence of temperature on the flow measurement can be effectively eliminated. The static pressure sensitivity of these two FBGs can be up to 86.7 nm/MPa and 68.6 nm/MPa, respectively; accordingly, the static pressure sensitivity of the sensor overall is 155.3 nm/MPa. Furthermore, the flow rate sensitivity is 0.00029 L/s. This FBG flow sensor exhibits high sensitivity, high accuracy, and a low start-up flow rate. Furthermore, the cross effect between the temperature and strain on the sensing sensitivity is eliminated, which makes this FBG flow sensor suitable for real-time monitoring of the trace flow rate in oil and gas wells.