Research of Magnetic Shielding on the Closing Gap of Optical Fiber Current Sensor

Abstract

Reflective optical fiber current sensors have been widely used in electric power and metallurgy. However, the closing gaps between the $\lambda /4$ wave plate and the reflector leads to a strong background current when they are used in strong magnetic fields. In this paper, a mathematical model of the background current was analyzed, and the relationship between the external magnetic field and the background current was identified through experiments. Therefore, a method to reduce the background current by magnetic shielding was proposed. A magnetic ring to shield the magnetic field effectively was designed, and the effects of the structure and relative permeability of the magnetic ring on its shielding rate were established by experiments and numerical simulations. The results showed that the shielding rate exceeded 95% when the length, thickness, and inner diameter of the magnetic ring were 50 mm, 2 mm, and 13 mm, respectively. Overall, this work provided a comprehensive framework that is useful for the analysis and optimization of magnetic shielding and improved the measurement accuracy of optical fiber current sensors in strong magnetic fields.