Temperature self-compensation sensitization fiber Bragg grating strain sensor while drilling

Aiming at the measurement requirements of WOB torque near the bit and the temperature-strain cross-sensitivity of fiber Bragg grating (FBG) in MWD, a diamond-shaped FBG sensor with hinge structure is proposed to realize temperature self-compensation and strain sensitization. The parametric modeling and static simulation of the sensor are carried out by using the finite element method. The influence of the hinge size on the grating strain and the maximum equivalent stress at the hinge is analyzed, and the optimal structural parameters are determined by response surface optimization design. Experiments show that the strain sensitivity of the sensor is 4.2 pm/με, and the temperature sensitivity is 2.381 pm/℃, which is 3.5 times and 4.8 times higher than that of the bare grating, respectively. The problem of low sensitivity is successfully solved, which provides a new scheme and research idea for the application of optical fiber sensing technology in the field of MWD.