Sagnac Magnetic Field Sensor Based on Sinusoidal Modulation and Empirical Mode Decomposition

A direct current (DC) Sagnac magnetic field sensor is a kind of fiber sensor based on alternate current magnetic field (ACMF) demodulation and empirical mode decomposition (EMD) to detect the magnetic field by measuring the phase variety caused by direct current magnetic field (DCMF). Commonly, Sagnac DCMF sensors can improve the magnetic detection sensitivity by using high Verdet constant (HVC) medium, which is expensive to prepare, or optical resonant cavity. However, the polarization diffraction in cavity restricts the performance of these devices. Meanwhile, none of them can suppress the electrical noise of the system such as 1/f noise. In this paper, we use ACMF modulation to couple the phase containing the DCMF information into the amplitude of the fundamental frequency component of the interference signal. Then we demodulate the signal by EMD to extract the fundamental frequency component. The designed sensor demonstrates a sensitivity of 4.651 mV/µT with an accuracy of 1.649 nT in the magnetic field range of 0-40 mT. It has the advantages of high stability, anti-electromagnetic interference and miniaturization.