Microwave photonic FLRD based on phase shifting for high-sensitivity magnetic sensing

We propose a magnetic field sensing system that employs a phase-shifting fiber loop ring-down technique enhanced by microwave photonics, and it has been experimentally demonstrated. The system integrates a fiber Bragg grating (FBG) attached to a magnetostrictive material within the fiber loop, enabling the conversion of magnetic field variations into changes in loss. We performed theoretical and numerical analyses of the system’s output characteristics, confirming the feasibility of magnetic field measurements at various modulation frequencies. The sensitivity can be flexibly adjusted by modifying the modulation frequency. Experimental results demonstrate that this method achieves a sensitivity of 0.014 deg/Gs within the 0-350 Gs range. Including two identical FBGs allows for temperature compensation, ensuring excellent temperature stability. The magnetic field information from the two channels can be independently obtained by utilizing loss-insensitive points, eliminating crosstalk. This proposed scheme provides a dual-channel magnetic field measurement approach characterized by high sensitivity and robust stability.