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A Magnetic Field Sensor Based on Birefringence Effect in Asymmetric Four-Hole Fiber

A Sagnacinterferometer-based magnetic field sensor is theoretically proposed and experimentally demonstrated by taking advantage of the high birefringence of an asymmetric four-hole fiber (AFHF) as well as the sensibility of magnetic fluid (MF) to magnetic field. A variation in the magnetic field intensity would induce a change in the RI of MF, leading to a birefringence change of MF-filled AFHF and resulting in a shift of the interference spectrum. The magnetic field sensing can be realized by monitoring the spectral shift. The proposed sensor has a high sensitivity of 226.2 pm/Gs (2.96 ∼ 89 Gs) with a measurement accuracy of 0.221 Gs, accompanied with competitive linearity, good repeatability and stability. In addition, it is insensitive to ambient temperature disturbance. The proposed sensor can be used in industry, biomedicine, aerospace and other fields which require a magnetic field measurement with high precision and good stability.