FBG magnetic field sensors with a bias magnetic field or pre-compressive stress for enhanced sensitivity

In this study, fiber Bragg grating (FBG) magnetic field sensors with an improved sensitivity were achieved through magnetic field biasing and pre-stress regulation. Firstly, a multi-physics coupling model was developed by integrating magnetostrictive theory with FBG strain sensing principles. Three sensor structures were designed: a baseline without optimization, one optimized with a bias magnetic field, and one optimized with axial pre-compressive stress. Experimental results showed that the sensor's sensitivity under a bias magnetic field of 33.7 mT increased to 11.55 pm/mT, which was 68.18 % higher than that of the unoptimized case. When an axial pre-compressive stress of –10 MPa was applied, the sensitivity further increased to 14.17 pm/mT, which was total 106.26 % higher than that of the unoptimized case. This work offers a novel strategy for the sensitivity optimization in magnetic field sensors, suggesting its promising applications in miniaturized and highly integrated magnetic sensing systems.