All-fiber optic magnetic sensor based on PS-FLRD technique with superior environmental stability

Abstract

This paper proposes and experimentally demonstrates a highly stable and sensitive all-fiber magnetic field sensor based on the phase-shifted loop ring-down (PS-FLRD) technique. The sensor leverages the Faraday effect, employing a single polarization coupler to construct a loop structure with reduced sensitivity to external environmental variations. It transforms the Faraday rotation angle changes induced by the magnetic field into optical intensity variations, eliminating the need for transducing elements such as magnetic fluids or magnetostrictive materials. Additionally, this scheme offers a larger measurement range compared to the two aforementioned approaches. A pseudo-reflective loop architecture was implemented to achieve enhanced system performance. To address the long-term effects of the electro-optic modulator, a reference photodetector PD is incorporated to provide phase compensation and correct demodulation errors. Experimental results demonstrate that the sensor achieves a sensitivity of $0.03\text{deg}/{\text{Gs}}^2$, with a phase variation of only 0.27 deg over a temperature range between $-50{}^{\circ }\text{C}$ and $50{}^{\circ }\text{C}$, and exhibits excellent anti-interference performance under vibrations with an amplitude of 20 mm. The proposed sensor features a simple structure, high stability, and is suitable for magnetic field measurements in complex environments.