An ultra-sensitive photonic crystal fiber magnetic field sensor based on Vernier effect using two parallel Sagnac loops

Magnetic field detection is of significant importance in various fields, including military, industrial, and power transmission systems. In this paper, we propose a novel ultra-sensitive photonic crystal fiber (PCF) magnetic field sensor based on the Vernier effect, employing two parallel Sagnac loops. Since magnetic field detection relies on the magneto-optical effect of magnetic fluids, all air holes in the PCF are assumed to filled with magnetic fluids. By inserting two slightly different lengths of PCFs into two parallel Sagnac loops, the Vernier effect can be excited to improve the sensitivity of magnetic field detection. The sensing characteristics of the PCF magnetic field sensor are theoretically studied using the finite element method (FEM). Moreover, the influences of the wavelength and magnetic field intensity on the sensing performance are also analyzed. The results show that the sensitivity and resolution of the PCF magnetic field sensor can reach 11.9 nm Oe-1 and 8.4 x 10-3 Oe, respectively, within the magnetic field intensity range of 80-150 Oe. To our best knowledge, the proposed magnetic field sensor exhibits the highest sensitivity among existing magnetic field sensors based on optical fiber interferometers. The proposed magnetic field sensor possesses ultra-high sensitivity and resolution, which exhibits good application prospects in the field of magnetic field detection.