A Novel Fiber Optic Ring Cavity Oscillating DC Magnetic Field Sensing Technology Based on Phase Demodulation

Magnetic field sensing has important application value in multiple fields. In recent years, new application requirements for magnetic field sensing technology have been proposed, such as high accuracy, good linearity, small volume, and low cost. This paper proposes a sensing technology based on fiber optic ring cavity oscillation structure for DC magnetic field detection requirements. The magnetic sensing unit is composed of a micro-structure composed of single-mode optical fibers and coreless optical fibers, and is encapsulated with magnetic fluid and capillary tubes. The DC magnetic field size information can be obtained by detecting the strength of the phase-locked output signal at a specific frequency. The results indicate that within the range of the magnetic field intensity among 0-140Gs, its phase exhibits good linearity with magnetic field intensity, with a sensitivity of approximately 0.57 mrad/Gs. Over 140Gs, the response tends to saturate due to the influence of magnetic fluid saturation factors.