Fiber Optic Vector Magnetic Field Sensor Based on Highly Localized Point-by-Point Fiber Bragg Grating

A kind of compact fiber optic vector magnetic field sensor is proposed. This sensor features a highly localized eccentric point-by-point fiber Bragg grating as its core component, with a gold-coated end facet to enhance cladding mode reflection. Eccentric local modulation points disrupt the axial symmetry of the fiber core, enabling the excitation of significant higher-order cladding modes as the core mode passes through the modulation points. Among these, the cut-off mode is exceptionally sensitive to changes in the refractive index near the fiber surface, with a sensitivity of approximately 536 nm/RIU. The sensor supports vector magnetic field sensing, achieving a maximum magnetic field sensitivity of 0.24 dB/mT in the range of 0-21 mT. The sensor is characterized by rapid fabrication, high stability, and holds significant potential for applications in vector magnetic field sensing.