Fig. 1. Simulation of erbium-doped fiber material based on DFT. (a) Local microscopic model of Er-doped-3MR structure；(b) spin density distribution

Fig. 2. Magnetic moment curves of Er-doped fiber at different temperatures

Fig. 3. Schematic of magnetic field sensing system based on magneto-refractive effect of fibers

Fig. 4. Physical picture of magnetic field sensing system and interference spectral measurement with system. (a) Physical picture of system; (b) light source spectrum and interference spectrum

Fig. 5. Interference spectra of system with different equivalent fiber lengths

Fig. 6. Experimental results of magnetic field sensing. (a) Interference spectra under different magnetic fields; (b) resonance wavelength versus magnetic induction intensity

Fig. 7. Effect of temperature on magnetic field sensing. Change of interference valley with temperature under (a) 0, (b) 46.7 mT, and (c) 93.7 mT magnetic fields; (d) resonance wavelength versus magnetic induction intensity at different temperatures