Vector Magnetic Field Sensors Research Articles

Fiber-optic vector magnetic field sensor based on a magnetic-fluid-infiltrated large-core-offset Mach-Zehnder interferometer.

A fiber-optic vector magnetic field sensor based on a large-core-offset Mach-Zehnder interferometer (MZI) infiltrated by magnetic fluid (MF) is proposed and demonstrated in this paper. By large-core-offset fusion splicing of a short single-mode fiber (SMF) between a lead-in SMF and a coupling multi-mode fiber, the MZI with a sub-millimeter length is formed, which is then sealed in an MF-infiltrated glass capillary. Through the MF's refractive index modulation by external magnetic field, the phase of the light passing through the MZI is altered. As a result, the transmission spectrum can be monitored for the magnetic field measurement. Furthermore, from the axial-asymmetry of the large-core-offset MZI structure, the proposed sensor possesses vectorial magnetic-field-sensing ability. Experiments show that the MF-infiltrated large-core-offset MZI vector magnetic-field sensor can achieve a high wavelength sensitivity of 96.68 pm/Oe in a magnetic field range of 50-130 Oe.

High-Sensitivity and Low-Loss Vector Magnetic Field Sensor Based on the C-Type Optical Fiber

A low-loss all-straight optical fiber vector magnetic field sensor (OFVMS) based on magnetic fluid (MF) is designed and proposed. The sensing structure is composed of a Section of the C-type optical fiber (CTF) embedded in a pair of multi-mode optical fibers (MMF) and wrapped in a capillary with MF. The asymmetry of the CTF provides support for the vector magnetic field measurement whose direction is perpendicular to the optical transmission direction. According to the results of experiments, it can be obtained that the refractive index (RI) sensitivity of the sensing structure is as high as −15716.6072 nm/RIU. In addition, the intensity sensitivity of the OFVMS in the calibrated 90° direction can reach 202.23 pm/G between 0 and 123 G. At the same time, the transmission loss of the proposed sensor structure is not increased by the filling of MF. The sensor demonstrated has dominance in low cost, easy manufacture, and lower loss compared with the same type of sensor device, which has application prospects in vector magnetic field sensing.

An All-Optical Vector Magnetic Field Sensor Based on Magnetic Fluid and Side-Polished Hollow-Core Optical Fiber

We demonstrate an optical fiber vector magnetic field sensor based on Mach-Zehnder interferometer by splicing a section of side-polished hollow-core fiber between two sections of single-mode fiber. As a varied magnetic field is applied to the magnetic fluid encapsulated sandwiched structure, the transmission spectra of the sensor will vary with the intensity and the direction of the magnetic field. In our experiments, at the incident light wavelength around 1510 nm, the magnetic field orientation sensitivity and intensity sensitivity are 180 pm/° and 240 pm/mT, respectively. In addition, a high contrast of about 20 dB between the signal interference dip with the noise interference dip is obtained in our experiments. The proposed all-optical fiber magnetic field sensor has the advantages of simple structure, compact size, low cost and easy fabrication.

Vector magnetic field sensor based on orthogonal off-set spliced optical fiber cladded with magnetic fluid

Based on the anisotropic distribution of magnetic nanoparticles within magnetic fluid under an external magnetic field, a novel, to the best of our knowledge, vector magnetic field sensor based on an orthogonal offset spliced optical fiber structure cascaded with fiber taper has been proposed. The expression of interference dip wavelength with respect to external magnetic field is formulated, and the dual-parameter sensing matrix is established. Simultaneous measurement of magnetic field intensity and direction is realized. The corresponding physical principle is clarified. The sensing properties are experimentally investigated and theoretically verified. The theoretical results are in good agreement with the experimental ones.

Vector magnetic field measurement based on magnetic fluid and high-order cladding-mode Bragg grating

An optical fiber-based vector magnetic field sensor combining fiber Bragg gratings (FBGs) and magnetic fluids (MFs) is proposed and experimentally demonstrated. The Bragg gratings are inscribed on the core and the cladding of a multi-clad fiber (MCF). Splicing the MCF with a standard single-mode fiber (SMF) via core mismatch provides a cladding-mode generation mechanism. Then, the high-order cladding mode is excited with the increasing off-axis distance. There are two kinds of resonant modes in the reflection spectrum of the sensor, which are the high-order cladding mode and the fundamental core mode. The intensity of the first mode shows an excellent response to the magnetic field intensity and the direction. The intensity sensitivity of the magnetic field sensor is −0.143 dB/Oe in a linear range of 60–110 Oe. Furthermore, the second mode intensity is quite stable and varies with the ambient temperature. Thus, the proposed magnetic field sensor can simultaneously measure the magnetic field and the temperature.

Vector magnetic field sensor based on U-bent single-mode fiber and magnetic fluid.

A novel, compact, and easy fabrication vector magnetic field sensor has been proposed and investigated. The proposed sensor consists of a U-bent single-mode fiber fixed in a magnetic-fluid-filled vessel. Neither mechanical modification nor additional fiber grating is needed during the sensor fabrication. The results show that the response of magnetic fluid to magnetic field can be used to measure the direction and intensity of magnetic field via whispering gallery modes supported by the U-bent fiber structure with suitable bending radius. The sensitivity of direction is 0.251 nm/°, and the maximum magnetic field intensity sensitivity is 0.517 nm/mT. Besides, the results of this work prove the feasibility for realizing vector magnetic sensors based on other bending structures (such as bending multimode interference, bending SPR structure) in the future.

Vector Magnetic Field Sensors: Operating Principles, Calibration, and Applications

This review paper explores the most common technologies of vector magnetic field sensors. Specifically, the AMR, GMR, TMR, GMI, Hall, Fluxgate, Search Coil and SQUID sensors are considered. The physical phenomena that permit their operation as well as the structure and operating principles of each sensor are presented. In addition, the basic linear, time-invariant error sources of magnetic sensors are described along with some popular calibration techniques. Finally, some representative application examples of each sensor are described.

Temperature compensated three-dimension fiber optic vector magnetic field sensor based on an elliptical core micro fiber Bragg grating.

In this paper, a temperature-compensated three-dimension vector fiber optic magnetic field sensor based on an elliptical core micro fiber Bragg grating (FBG) has been proposed and experimentally demonstrated. The elliptical core fiber was tapered to form a microfiber, in which a FBG was inscribed. Due to the magnetism-manipulation of the anisotropic aggregation of ferromagnetism nanoparticles around the fiber surface, the effective refractive index of the evanescent field for two orthogonal polarization modes was modulated, and the magnetic field orientation can be detected by interrogating the wavelength interval between two reflection peaks. However, two reflection peaks show the identical response to ambient temperature. Hence the proposed sensor can achieve the measurements of the magnetic field intensity and the orientation simultaneously without the temperature cross-sensitivity. The experimental results show that the magnetic field orientation sensitivity of 15 pm/deg and intensity sensitivity of 81 pm/mT can be achieved, and the maximum standard variation of the temperature cross-sensitivity is only 0.02 nm. The proposed elliptical core micro FBG appears to have potential applications in navigation, vehicle detection, and current sensing.

Fiber-Optic Vector Magnetic Field Sensor Based on Mode Interference and Magnetic Fluid in a Two-Channel Tapered Structure

An innovative approach to high-sensitivity simultaneous intensity and direction measurement in a two-channel tapered sensor is proposed and demonstrated. The sensor is comprised of magnetic fluid (MF)- filled micro-capillary and two accompanying micro-fiber, thus enabling evanescent interaction to take place between the optical mode in the capillary and MF. Given the magnetic nanoparticles (MNPs) of MF manifest anisotropic magnetic field. Experimental and numerical simulations were performed simultaneously, which provided a better understanding of the interaction between light and MF in addition to clarifying the dynamic process of MNPs within MF with the assistance of varying magnetic field. The experimental results are well consistent with the numerical simulation results and show that the sensitivity of this sensor reaches up to 244 pm/mT, with the direction error being merely ±1.4°. Therefore, the proposed sensor exhibits a unique sensitivity for the measurement of magnetic field intensity and direction in 3D space, which makes it best suitable for applications in transportation, medicine, and smart device.

All-fiber-optic vector magnetic field sensor based on side-polished fiber and magnetic fluid.

A kind of compact all-fiber-optic vector magnetic sensor is proposed and demonstrated. The sensor consists of a side-polished-fiber (SPF)-integrated with singlemode-no core-singlemode (SNS) fiber structure. A section of side-polished fiber breaks the axially symmetry of the composite structure. The as-fabricated sensor supports vector sensing and has a magnetic field strength sensitivity of up to -2370 pm/mT over 2-6 mT range. The physical mechanism is that the modal interference is strongly influenced by the refractive index (RI) near the side-polished surface. The advantages of the proposed sensor lie in low cost, simple structure and easy manufacture, which make it attractive in the field of magnetic field vector sensing.

Highly Sensitivity Fiber-Optic Vector Magnetometer Based on Two-Mode Fiber and Magnetic Fluid

A compact fiber-optic vector magnetic field sensor combining a tapered two-mode fiber (TMF) and magnetic fluid is proposed and experimentally demonstrated. The modal interference effect is mainly caused by LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes, and an additional refractive-index-modulation (RIM) on TMF taper lateral is introduced by femtosecond laser for enhancing the interference intensity. Moreover, the RIM provides the sensor a significant direction-dependence due to its asymmetric position relatively to fiber axis. The spectral response to magnetic field intensity and direction of the proposed sensors has been investigated. And, the results show that the wavelength-referenced magnetic field sensitivity reaches up to 71.98 pm/Oe in the range of 40-120 Oe and the intensity-referenced sensitivity reaches up to 0.11 dB/Oe. Meanwhile, the sensor presents great directional resolution with intensity-reference (0.11 dB/deg).

Magnetoelectric effect in magnetostrictive-piezoelectric composites containing magnetite nanoparticles

We report the use of nanoparticle (NP) magnetite, Fe3O4, in magnetostrictive-piezoelectric composites in trilayer laminate and single layer form. The magnetoelectric (ME) effect in both structures is highly anisotropic and linear up to 9 kOe. A trilayer laminated Fe3O4-NPs/PZT/Fe3O4-NPs composite displays the highest dc magnetic field response sensitivity, with dVME,ac/dHdc reaching 42 nV/Oe at a resonance frequency of 19.43 kHz. A slightly lower dVME,ac/dHdc of 35 nV/Oe is found for a single layer mixed composite containing Fe3O4 nanoparticles and BaTiO3 nanopowder at a resonance frequency of 0.4 kHz. The lowest ME response is observed for a single layer composite that had Fe3O4 nanoparticles and PZT powder where dVME,ac/dHdc is 1.4 nV/Oe at resonance (0.335 kHz). Our results show that composites containing Fe3O4 nanoparticles have potential applications that include wide magnetic field range vector magnetic field sensors – parallel magnetic field sensing using a trilayer configuration and perpendicular magnetic field sensing using a single layer configuration.

High-sensitivity vector magnetic field sensor based on side-polished fiber plasmon and ferrofluid.

A high-sensitivity vector magnetic field is proposed and demonstrated. The sensor consists of a side-polished-fiber (SPF)-based surface plasmon resonance (SPR) structure integrated with ferrofluid. Because of the high refractive index sensitivity of the SPR scheme and the outstanding magneto optical properties of ferrofluid, the sensor shows a high sensitivity (up to 598.7 pm/Oe) to magnetic field intensity. Moreover, owing to the non-circular-symmetric geometry of the SPF and non-uniform distribution of the ferrofluid around the SPF, the sensor exhibits a sensitivity of -5.63 nm/deg to the orientation of the magnetic field. The proposed vector magnetic field sensor, integrating over magnetic, plasmonic, and fiber-optic schemes, is highly sensitive to both the intensity and orientation of the magnetic field simultaneously, and holds potential in applications in many fields, such as medicine, industry, and the military.

Equivalent Magnetic Noise in Magnetoelectric Laminates Comprising Bidomain LiNbO3 Crystals.

The anisotropic direct magnetoelectric (ME) properties of bilayered composites comprising magnetostrictive metglas foils and single-crystalline piezoelectric bidomain plates of 127°Y-cut LiNbO3 (LNO) have been studied theoretically and experimentally. The LNO plates possessed an engineered ferroelectric macrobidomain structure with opposite spontaneous polarization vectors. Impedance, ME effect, and equivalent magnetic noise density (EMND) measurements have been performed under quasi-static and resonant conditions. Whereas the quasi-static ME effect was only two times stronger in the bidomain samples compared to their unidomain and bonded bimorph counterparts, in the bending resonance mode, the effect was up to one order of magnitude stronger: ME coefficients of up to 578 V/( [Formula: see text]) were obtained at ca. 30 kHz under resonance using 0.5-mm-thick crystals. EMND measurements yielded values down to 153 pT/Hz 1/2 at 1 kHz and 524 fT/Hz 1/2 under resonant conditions. A further optimization of the fabrication techniques, laminate geometry, and detection circuit is expected to allow reducing these values down to at least 10 pT/Hz 1/2 and 250 fT/Hz 1/2 , respectively, and the resonance frequency by at least two orders of magnitude. Such systems may thus find use in simple and sensitive, passive and stable, low frequency and high-temperature vector magnetic field sensors.

Magnetic Field Multi-sensor Transducer for Detection of Defects in Steel Components

In this paper, a transducer allowing nondestructive evaluation of material state in various directions is presented. The axial-symmetry transducer is using a matrix of vector magnetic field sensors. Each sensor is utilized for the observation of three orthogonal components. First, the construction is shown and the general performance is evaluated. Then, the data processing and integration algorithm for reconstruction of the signals is presented. Finally, the operation of the transducer is verified using a low-carbon steel plate having notches of different depths and aligned at various angles to the scanning axis. The results are presented and discussed.

Concept of a microscale vector magnetic field sensor based on nitrogen-vacancy centers in diamond

A three-component magnetic field sensor scheme based on optically detected magnetic resonance (ODMR) in negatively charged nitrogen-vacancy centers is implemented and investigated experimentally. The central part of the scheme is a 0.01 mm3 diamond crystal, optically pumped and interrogated through an optical fiber; combined RF excitation of hyperfine triplets in the ODMR spectrum is used to increase the signal-to-noise ratio. Methods that allow for efficient identification of ODMR spectral lines while minimizing the number of the sensor “dead” zones are proposed and tested. The scheme’s sensitivity to magnetic field vector components, estimated on the basis of the signal-to-noise-to-linewidth ratio, is found to be 1.5 nT·Hz−1/2. The operational frequency range of the scheme is 0–100 Hz.

Prediction and removal of rotation noise in airborne EM systems

We aim to eliminate or reduce significant impediments to conductive target detection and conductive cover penetration in airborne electromagnetic (AEM) systems. Existing limitations come from the very high noise encountered at low base frequencies, caused by rotations of vector magnetic field sensors in the Earth’s magnetic field. We use the output of tri-axial rotation-rate sensors to predict and subtract the rotation noise from rigidly coupled ARMIT magnetic field sensors. The approach is successful in reducing rotation noise by one to two orders of magnitude at low frequencies.

Hall bar device processing on patterned substrates using optical lithography

Abstract A non-planar InP-based Hall bar device was manufactured using deep wet etching, epitaxial overgrowth and non-planar device processing with optical lithography. The Hall bar was defined in an n-doped InP layer at (1 1 0) and ( 1 1 0 ) quasi facets of mesa ridge patterns overgrown using organometallic vapour phase epitaxy (OMVPE). Initial galvanomagnetic measurements were carried out to test the device, which was designed to assist in the characterisation of non-planar epitaxial layers as well as in the development of a vector magnetic field sensor.

Adaptive methods for motion-noise compensation in extremely low frequency submarine receiving antennas

Motion-induced noise can be an overwhelming source of inteference in vector magnetic field sensors designed for submarine communications in the 30-130-Hz portion of the extremely low frequency (ELF) band. In the case of an ELF antenna constructed using three orthogonal superconducting quantum interference devices (SQUID's) as receiving elements, the removal of motion noise is complicated by the inability of SQUID sensors to determine the absolute value of the earth's field component along the axis of the sensor. An equation is derived that expresses the projection of the ELF signal vector on the earth's field in terms of the SQUID outputs, and an adaptive vector that is approximately equal to the earth's field vector. Two adaptive schemes using the methods of process parameter estimation are described which determine the adaptive vector. The Least Squares method requires no initial estimate of the adaptive vector but is an open-loop method which tends to be slow. The second adaptive scheme, the steepest descent method, is a close-loop technique that has the potential of being rapid, but requires an initial value of the adaptive vector that is close to the true value. Both techniques remove, to first order, sources of noise arising from sensor nonorthogonality, sensitivity differences and dc offset errors. From a computer simulation of both techniques, it is found that the optimum system is a combination of the two methods, using the Least Squares method for estimation of the coarse value of the adaptive vector, and using the Steepest Descent method for fine adjustment.