A high-sensitivity optical fiber magnetic field sensor based on magnetostrictive effect

This paper introduces a high-sensitivity sensor integrated within a Michelson interferometer. Due to the low-loss and bending-insensitive characteristics of the thin-diameter single-mode optical fiber, it is coiled around a Terfenol-D rod to construct the sensing unit, enabling magnetostrictive strain of the rod converting into optical fiber phase shifts directly. As the length of the optical fiber in the sensing unit increases, the effective length affected by magnetostriction also extends, resulting in a larger phase difference and consequently enhanced magnetic field sensitivity. Simultaneously, the increased fiber-length applies greater pressure on the Terfenol-D rod, enhancing its prestress. The prestress mitigates magnetic hysteresis effect and minimizes the nonlinear response of the rod, thereby improving the linearity of the sensor. The highest sensitivity reaches 123 mrad/μT at 500 Hz for a fiber length of 300 m, with an AC magnetic field phase resolution of 121 pT/Hz^1/2. The sensor demonstrates high sensitivity, excellent linearity, and a simple structure, making it well-suited for detecting weak-magnetic targets and remote sensing applications.