Magnetic Field Sensor Using the Magnetic Fluid-Encapsulated Long-Period Fiber Grating Inscribed in the Thin-Cladding Fiber

Abstract

Optical magnetic field current sensors could overcome the shortcomings of traditional sensors based on electrical principles, such as large volume, insufficient sensitivity, and limitations of working environment, which can be applied to medical, military, and other fields with higher sensing requirements. We demonstrated experimentally the inscription of the long-period fiber gratings (LPFGs) in the thin-cladding fiber (TCF). The magnetic field current sensor is fabricated by encapsulating the TCF–LPFG with magnetic fluid (MF) nanoparticles. The principle of the sensor is based on the refractive index tunability of the MF with the magnetic field (current). The measurement of the external magnetic field (current) can be obtained by detecting the wavelength shift of the coated TCF–LPFG, which changes with the applied magnetic field. In the intensity range of 0 ∼ 11 mT, the experimental sensitivity of magnetic field measurement is up to −0.31 nm/mT. The proposed magnetic field current sensor has potential applications in practical measurement of magnetic field.