Room-temperature-fabricated TbDyFe-based fiber sensor for quasi-distributed magnetic field sensing.

Distributed magnetic field measurement is important for magnetic environment inversion and tracking the long-term evolution of magnetic fields. However, existing spatially resolved magnetic sensing schemes are largely based on serial interrogation of discrete point sensors or high-temperature fiber drawing, which limits measurement simultaneity, material choice, and magnetic-performance preservation. In this work, we propose a room-temperature quasi-distributed fiber-optic magnetic-field sensing strategy based on fiber Bragg grating (FBG) fibers longitudinally coated with a TbDyFe/UV-curable resin composite. The results show that the sensor achieves a sensitivity of 2.03 pm/mT and exhibits good linear response (R2 = 99.16%). Using a 22 m magnetically sensitive fiber, the system enables tracking of time-varying magnetic anomalies and reconstruction of spatially inhomogeneous magnetic fields, with a spatial resolution of 5.0 cm. This method offers a practical route for long-distance quasi-distributed spatiotemporal magnetic-field sensing with room-temperature fabrication, mechanical flexibility, and scalable architecture.