Vector Magnetic Field Sensing Characteristics of the Magnetofluid-Encapsulated Polarization-Maintaining Fiber Single-End Offset Fusion Spliced Hollow-Core Fiber Structure

This article proposes and demonstrates an optical fiber vector magnetic field sensor based on magnetofluid-encapsulated polarization-maintaining fiber (PMF) single-end offset fusion spliced hollow-core fiber (HCF) structure. Thanks to the unique fast and slow axes structure of the PMF, when the two axes are offset fused with HCF, respectively, the sensor exhibits different responses to the magnetic field variation surrounding the fiber sensing structure. Experimental results reveal that at a dislocation offset of $6 \mu \text{m}$ along the slow axis of the PMF with the HCF, a maximum magnetic field intensity sensitivity of −813 pm/mT and direction sensitivity of 245 pm/° within the range of 39–55 mT are obtained. Moreover, temperature-induced cross-sensitivity is effectively suppressed with a dislocation offset of the slow axis of the PMF fused with the HCF. The proposed magnetic field sensor has several advantages, such as low cost, easy manufacturing, immunity to electromagnet interference, all-optical fiber structure, and convenience of fiber optic multiplexing.