A Magnetic Field Sensor Based on a Magnetic Fluid-Filled FP-FBG Structure

Abstract

Based on the characteristic magnetic-controlled refractive index property, in this paper, a magnetic fluid is used as a sensitive medium to detect the magnetic field in the fiber optic Fabry-Perot (FP) cavity. The temperature compensation in fiber Fabry-Perot magnetic sensor is demonstrated and achieved. The refractive index of the magnetic fluid varies with the applied magnetic field and external temperature, and a cross-sensitivity effect of the temperature and magnetic field occurs in the Fabry-Perot magnetic sensor and the accuracy of magnetic field measurements is affected by the thermal effect. In order to overcome this problem, we propose a modified sensor structure. With a fiber Bragg grating (FBG) written in the insert fiber end of the Fabry-Perot cavity, the FBG acts as a temperature compensation unit for the magnetic field measurement and it provides an effective solution to the cross-sensitivity effect. The experimental results show that the sensitivity of magnetic field detection improves from 0.23 nm/mT to 0.53 nm/mT, and the magnetic field measurement resolution finally reaches 37.7 T. The temperature-compensated FP-FBG magnetic sensor has obvious advantages of small volume and high sensitivity, and it has a good prospect in applications in the power industry and national defense technology areas.

Magnetic field sensors in fused silica fabricated by femtosecond laser micromachining

“…Figures 7 and 8 show the sensor response to the magnetic field magnitude, with the field applied parallel to the waveguide axis. The measurements were carried at 19.0°C±0.5°C, so index variations induced by thermal effects can be neglected; thermal cross talk can be completely avoided by adding a Bragg grating [26]. For field strengths below 9 mT, no significant variations are observed in the spectrum, as the exerted magnetic force is not enough to overcome diffusive forces and, in turn, form magnetic columns that cause the index variation [1].…”

Diaphragm-Free Fiber-Optic Fabry-Perot Interferometric Gas Pressure Sensor for High Temperature Application

“…So the light returned to the FBG is the interference light of the FP. The intensity of the output light can be defined as [ 18 ]: where and are the reflection coefficients of FBG and FP cavity. They are defined as [ 18 ]: where R 1 is the FBG peak reflectivity, is the FBG center wavelength, w is the bandwidth of the FBG reflection peak, R 2 is the reflectivity of the fiber end, and L is the length of the FP cavity: where , are the wavelength of adjacent peak-peak (or valley-valley).…”

Inversion Algorithm of Fiber Bragg Grating for Nanofluid Flooding Monitoring

“…On the basis of previous studies [5][6][7][8][9][10][11], employing nanoparticles can shift reservoir wettability from oil-wet to water-wet and reduce oil viscosity. At high temperatures, however, nanoparticles can create a massive diffusion-driving force caused by a large surface-to-volume ratio [12][13][14], with the penetration of these tiny particles into pore spaces observable by using currently available technologies [15][16][17][18].…”