Reflective fiber-optic magnetic field sensor based on a magnetic-fluid-filled capillary probe structure

Abstract

A novel reflective magnetic field sensor is presented and experimentally demonstrated. The sensing probe is fabricated by splicing a section of uncoated four-core fiber (FCF) between two sections of no-core fibers (NCFs), and the end face of the last NCF is coated by silver. The sensor structure is sealed in a magnetic fluid (MF)-filled capillary, so that the NCF-FCF-NCF magnetic field sensing probe structure is obtained. The NCF is used to excite the high-order modes of the FCF's cladding. Combined with the adjustable refractive index of MF, the sensor is sensitive to the magnetic field and temperature. Experimental results indicate that the presented sensor can measure the low magnetic field and high magnetic field. In the low magnetic field ranges of 0-10 mT and 10-18 mT, the wavelength near 1548 nm varies linearly with the magnetic field intensity, and the sensitivities are −7.43 pm mT −1 and −60 pm mT −1 , respectively. The sensitivity of the interference intensity is −0.30782 dB mT −1 in the low magnetic field intensity range of 0-18 mT. The sensor under low magnetic field is also affected by temperature. In the temperature range of 20 • C-70 • C, the temperature sensitivity of the wavelength shift around 1548 nm is 62.33 pm • C −1 , and the corresponding sensitivities of the interference intensity are −0.03888 dB • C −1 and −0.02076 dB • C −1 in the range of 30 • C-50 • C and 50 • C-70 • C, respectively. However, the effect of temperature on the sensor in the high magnetic field (18-36 mT) can be ignored. Within the high magnetic field intensity range of 26-36 mT, the sensitivity of the interference intensity near 1598 nm is −1.20993 dB mT −1 . The dual-parameter matrix is used to eliminate the cross-sensitivity of temperature in the low magnetic field. This sensor, with the advantages of easy fabrication, high sensitivity and low cost, has the potential application in the magnetic field monitoring.

An Intensity-Demodulated Fiber-Optic Magnetometer Based on Nanostructured Magnetic Fluid-Filled Fluidic Photonic Crystal Fibers

“…The structure achieved stronger mode coupling with magnetic fluid and obtained a sensitivity of 0.336 dB/mT. Tao et al [ 17 ] proposed a fiber-optic magnetometer in which SMF-No core Fiber (NCF)-Few mode fiber (FMF)-NCF structure integrated with magnetic fluid is used. The magnetometer has a sensitivity of 0.30782 dB mT in the range of 0–18 mT.…”

2D-Vector Magnetic Sensing Based on Ring-Shaped Fiber-Optic Structure Coated with Magnetic Fluid

“…By tapering FBG, the sensor can generate a powerful evanescent field in the sensing region. In 2021, Yu Tao et al [24] reported a reflective fiber magnetic field sensor. The fiber sensor is composed of an SMF-NCF-Few core fiber (FCF)-NCF structure and encapsulated by MF.…”