Optical Magnetic Field Sensor Research Articles

Fiber optic magnetic field sensor based on a magnetic-fluid-induced phase-shift FLRD

A magnetic field sensing system based on a phase-shift fiber loop ring-down (FLRD) technique and multi-mode interferometer (MI) coated with magnetic fluid (MF) is proposed and demonstrated. The MI is constructed by splicing a segment of no-core fiber between two sections of single-mode fibers, which is then immersed in MF to serve as a sensing head with the advantages of simple fabrication and specific magnetic sensitivity. Due to the magnetic refractive index tunable properties of the MF, the magnetic-field-dependent loss will be introduced in the fiber loop by the sensing head. Such magnetic-induced loss would be accumulated during the round trip of the optical carrier and reflected on the phase information of the modulated signal. The phase-shift changes with the applied magnetic field strength, enabling magnetic field sensing through phase-shift measurements. The sensing system is experimentally demonstrated and a sensitivity of 0.704×10−3deg/Gs in the linear region is achieved. Moreover, the stability and repeatability of the system are verified, leading to a promising method for magnetic field measurements.

A novel flexible optical fiber magnetic field sensor based on integrated Fe3O4 nanoparticles

We propose a new flexible optical fiber magnetic field sensor (FOMS) based on the combination of Michelson interferometer and the PDMS polymer-based optical fiber. The flexible optical fiber magnetic field sensor is made of stretchable elastomer. It uses a stepped refractive index core-cladding structure to achieve effective light confinement, thus enabling stable transmission of light in the waveguide. When the magnitude of the external magnetic field is changed, the micro bending of the sensing region of the optical fiber causes its equivalent refractive index to change, which leads to a drift in the interference spectrum. It is shown that the magnetic field sensitivity of this optical fiber magnetic field sensor reaches −62.8 pm/mT for wavelength detection in the measurement range of 0–200 mT. The FOMS has the characteristics of high sensitivity, good linearity, good temperature response capability, sensitive response, and resistance to electromagnetic interference. In the future, the sensor will have a broad application prospect in medical, geography, aerospace and other fields.

Ultra-sensitive axial strain and magnetic field sensor based on three reflection surface interference and harmonic vernier effect

A high-sensitivity fiber optic strain and magnetic field (MF) sensor is designed by two Fabry-Perot interferometers (FPI) cascading and harmonic Vernier effect. Two cascaded FPIs consist of an intrinsic FPI1 and an extrinsic FPI2. FPI1 is fabricated by femtosecond laser pulse ablation on the single-mode fiber core. Then, FPI1 and another single-mode fiber are inserted into a quartz capillary from both sides to form FPI2. By adjusting the cavity length of FPI2, the cascaded FPI1 and FPI2 can form a harmonic Vernier effect sensor. Due to FPI1 being a cantilever beam, it is not subjected to axial strain. The strain of the sensor acts on a longer capillary, resulting in an extension of the effective length of the strain and a many fold increase in the strain sensitivity of the sensor. Due to the compact cascading of FPI1 and FPI2, this strain sensor has a very small structural size. The sensor average strain sensitivity obtained from the experiment reached 260.05 pm/με. Due to the extremely high axial strain sensitivity of this strain sensor, adhering it to the magnetostrictive material results in the average MF sensitivity of 6.82 nm/mT, and the minimum MF intensity detected by the MF sensor is 0.1 mT. The temperature crosstalk of the MF sensor is 0.3 mT/°C.

An Optical Magnetic Field Sensor With Improved Sensitivity Based on Multiloop Antenna Loaded With LiNbO₃ Crystal

An Optical Magnetic Field Sensor With Improved Sensitivity Based on Multiloop Antenna Loaded With LiNbO₃ Crystal

Photonic crystal fiber sensors to excite surface plasmon resonance based on elliptical detection channels are used for highly sensitive magnetic sensing

To improve the detection performance of fiber optic magnetic field sensors a new photonic crystal fiber (PCF) based on surface plasmon resonance (SPR) was designed and investigated. The designed sensor uses an elliptical detection channel, and the modal transmission characteristics and magnetic field sensing characteristics of this fiber optic sensor are analyzed using the full vector finite element method (FVFEM). In addition, the effect of the detection channel on the detection accuracy at different curvatures was investigated. Compared with previous optical fiber magnetic field (MF) sensors, the designed sensor meets the requirements of both refractive index (RI) and MF measurements, and the MF sensitivity, RI sensitivity, and amplitude sensitivity (AS) of the sensor reach 0.739 nm/Oe, 12043.8 nm/RIU, and 754.88RIU−1, respectively. The designed sensor expands the application range of optical fiber sensors and reduces the cost. It has great potential for application in complex environments.

Distributed optical fiber magnetic field sensor based on polarization-sensitive OFDR.

A distributed optical fiber magnetic field sensor based on a polarization-sensitive optical frequency domain reflectometer (POFDR) is proposed. It extracts the accumulated Faraday rotation by combining the Stokes vectors and the backward Mueller matrices from the measured states of polarization (SOPs) and obtains the magnetic field component. This method avoids adjusting the input polarization during the magnetic field sensing process. It overcomes the drawback of the conventional POFDR scheme, which requires at least two sets of different input SOPs for each sensing. Finally, the aforementioned effectiveness has been experimentally verified by using a single-mode sensing fiber. The results show that the sensor has good repeatability and linearity. The measurement error of the magnetic field sensor is 19.4 mT. The measured magnetic field variations agree with the applied ones with similarities higher than 0.98.

Highly sensitive magnetic field sensor using magnetic fluid filled dual-core photonic crystal fiber

A high sensitivity fiber optic magnetic field sensor that utilizes a dual-core photonic crystal fiber (DC-PCF) filled with magnetic fluid (MF) has been proposed and validated to simultaneously detect magnetic field intensity and temperature. DC-PCF is a multimode fiber that supports various modes of light transmission and induces intermodal interference within fiber core. The numerical analysis of the mode characteristics of DC-PCF is conducted. The sensing structure relies on the use of a DC-PCF with air holes filled with a suitable material, such as MF substance. The analysis of the working principle of the DC-PCF for sensing and measurement is conducted by considering its structural characteristics and mode characteristics. The effective refractive index (ERI) of MF is affected by external magnetic field intensity and temperature. To extract the effective frequency points, the fast Fourier transform (FFT) method can be employed. Additionally, the inverse fast Fourier transform (IFFT) method can be utilized to determine the magnetic field sensitivity, which can reach up to 1.562 nm/mT. Furthermore, the temperature sensitivity can be as high as −1.043 nm/°C. The sensor demonstrates excellent repeatability and showcases low detection limits of 0.0128 mT and 0.0192 °C, respectively. Additionally, the proposed sensor exhibits substantial potential for further development in the field of high sensitivity magnetic field detection applications.

Optical Fiber Vector Magnetic Field Sensors Based on Magnetic Fluid: A Review

Optical Fiber Vector Magnetic Field Sensors Based on Magnetic Fluid: A Review

Inversion of Target Magnetic Moments Based on Scalar Magnetic Anomaly Signals

As a key physical property of underwater ferromagnetic targets, magnetic moment can reflect important information such as the mass and heading of the target. However, most of the current magnetic moment estimation methods rely on vector magnetic field sensors or sensor arrays to measure the magnetic field, which limits its application in remote target magnetic moment calculation on mobile platforms to some extent. To solve this problem, a real-time magnetic moment inversion method based on the high-precision scalar magnetic measurement data of a high-speed moving platform is proposed in this paper. The method allows the estimation of the magnetic moment of underwater ferromagnetic targets by the scalar magnetic measurement data of an optical pump magnetic field sensor mounted on a high-speed moving platform. The experimental results show that this method has high precision in estimating magnetic moment; the average error of the magnetic moment amplitude was only 5.85%, while the average errors of the magnetic moment inclination and magnetic moment deflection were 1.58° and 2.79°, respectively. These results provide a new and effective way to estimate the magnetic moment of underwater ferromagnetic targets and are expected to have important practical applications.

An Optical Fiber Magnetic Field Sensor Based on Mach–Zehnder Interferometer Composed of Two Peanut-Shaped Structures and Tapered No-Core Fiber

An Optical Fiber Magnetic Field Sensor Based on Mach–Zehnder Interferometer Composed of Two Peanut-Shaped Structures and Tapered No-Core Fiber

Comparative study of geometry effect for magnetic field sensor based on multi-mode optical fiber

Experimentally and numerically, measurements have been presented for new type of magnetic field sensor based on combining multimode optical fiber and magnetic ferrofluid. The ferrofluid was filled in a capillary tube around a 15 mm uncladded region of optical fiber. Three uncladded geometries cylindrical, D-shaped and 2D-shaped, have been investigated to study the effect of geometry on sensing performance. Results illustrate that the geometry of the optical fiber has a significant impact on the evanescent waves which propagate from the sensing region into the ferrofluid tube. The obtained results expressed that among all studied cases, the D-shaped configuration has the best performance designing an optical fiber-based magnetic field sensor, since the best measured sensor features such as linearity, sensitivity, response time and recovery time for this case are R2 = 0.9865, 0.01795 μW/mT, 3.15 s and 0.26 s, respectively.

Characterization of Fiber-Optic Vector Magnetic Field Sensors Based on the Magneto-Strictive Effect.

Fiber-optic magnetic field sensors have garnered considerable attention in the field of marine monitoring due to their compact size, robust anti-electromagnetic interference capabilities, corrosion resistance, high sensitivity, ease of multiplexing and integration, and potential for large-scale sensing networks. To enable the detection of marine magnetic field vector information, we propose an optical fiber vector magnetic field sensor that integrates three single-axis sensors in an orthogonal configuration. Theoretical analysis and experimental verification are conducted to investigate its magnetic field and temperature sensing characteristics, and a sensitivity matrix is established to address the cross-sensitivity between the magnetic field and temperature; experimental tests were conducted to assess the vector response of the three-dimensional (3D) vector sensor across the three orthogonal axes; the obtained experimental results illustrate the commendable magnetic field vector response exhibited by the sensor in the orthogonal axes, enabling precise demodulation of vector magnetic field information. This sensor presents several advantages, including cost-effectiveness, easy integration, and reliability vectorially. Consequently, it holds immense potential for critical applications in marine magnetic field network detection.

Magnetic Field and Temperature Two-Parameter Sensor Based on Mach–Zehnder Interferometer and Faraday Rotation Effect

A novel combination of structural design and sensing theory is proposed for an optical fiber magnetic field and temperature two-parameter sensor based on the Mach-Zehnder interferometer (MZI) and Faraday rotation effect. The sensor structure includes a polydimethylsiloxane (PDMS) microcavity and a small section of offset spliced fiber. Numerical analysis shows that the sensor exhibits high temperature sensitivity, which has been experimentally verified. The sensor has a temperature sensitivity of -846 pm/°C in the 20 to 35°C and a magnetic field intensity sensitivity of 190 pm/Gs in the range of 0 to 150 Gs. The temperature and magnetic field intensity responses of the sensor are linear and have been optimized for sensitivity demodulation. The sensor is well-suited for standardized monitoring of temperature and magnetic field in applications requiring accurate measurements.

High Sensitivity Surface Plasmon Resonance Magnetic Field Sensor Based on Au/Gold Nanoparticles/Magnetic Fluid in the Hollow Core Fiber

A type of surface plasmon resonance (SPR) magnetic field sensor based on Au/gold nanoparticles/magnetic fluid (MF)-processed hollow core fiber is proposed in this work, which fully utilizes SPR’s high sensitivity to RI and the magnetron refractive index characteristic of MF. The metal material Au excites SPR and gold nanoparticles excite the localized surface plasmon resonance (LSPR). The coupling of surface plasmon polariton (SPP) with localized surface plasmon (LSP) increases the local electric field strength, thus improving the sensor’s sensitivity. Both the theoretical analysis on the sensing mechanism and the experimental findings demonstrate that this novel SPR magnetic field sensor has a wide measurement range and high sensitivity. In the range of magnetic field strength from 0 to 603 Gs, the sensitivity can reach up to 156 pm/Gs, and the linearity is good (the coefficient of determination is 0.996). Compared with other optical fiber magnetic field sensors, the sensor proposed in this paper has the benefits of easy fabrication, excellent sensitivity, simple structure, strong anti-interference ability, and wide measurement range, exhibiting significant application potentials in the fields of military drills, aerospace, etc.

A high-sensitivity magnetic field sensor using spindly optical fiber taper

In this paper, a high-sensitivity magnetic field sensor is proposed. The sensor consists of a spindly optical fiber taper (SOFT) coated with magnetic fluid. The SOFT structure is made through fusing taper method and connected to a fiber loop for magnetic field sensing. The experiment results show that the sensor is barely dependent on laser wavelength within the range of 1520 nm to 1575 nm. When the magnetic field of 180 Oe is applied, the transmission change reaches up to 3.324 dB at 1550 nm. Additionally, the magnetic field sensitivity of the sensor is −23.4μs/Oe in the linear region of 10 Oe−80 Oe. Compared with the traditional fiber optic magnetic field sensor with the fiber loop ring-down (FLRD), the proposed SOFT sensor could achieve higher magnetic field sensitivity.

Optical magnetic field sensors based on nanodielectrics: From biomedicine to IoT‐based energy internet

AbstractSmart sensors with excellent performance are accelerating the development of biomedicine and the Internet of Energy. Nanodielectrics exhibit unique electrical and mechanical properties. As the predominant materials in optical magnetic field sensor (MFS), they can not only exert the anti‐interference of optical sensing, but improve the measuring characteristics of optical sensors. For instance, the optical fibre quantum probe for the magnetic field can obtain a higher sensitivity of 0.57 nT/Hz1/2, while the measurement range of the sensor that uses Co‐doped ZnO nanorods as cladding is 17–180 mT. Here, these exciting recent achievements in the realm of optical sensing methods for magnetic field detection are reviewed, with a focus on nanodielectrics, which provide an emerging opportunity to achieve higher sensitivity and a wider measurement range of MFS.

Magnetic flux leakage detection based on a sensitivity-enhanced fiber Bragg grating magnetic field sensor.

We propose a sensitivity-enhanced fiber Bragg grating (FBG) magnetic field sensor for magnetic flux leakage (MFL) detection. The testing system consists of the FBG, suspended strain concentration structure, and two ceramic tubes bonded on a Terfenol-D base. We show the relation between the MFL and the width and depth of the crack, the lift-off of the sensor away from the surface of the workpiece, and the angle between the orientation of the sensor and the magnetization direction. The experimental results are very consistent with those obtained from finite element analysis simulations. The sensitivity of the sensor is increased to 81.11pm/mT for increasing magnetic fields and 91.55pm/mT for decreasing magnetic fields. The MFL test demonstrates that the sensor can identify a crack with a width of 0.5mm and depth of 2mm in an 8mm thick workpiece. To the best of our knowledge, the magnetic field sensor proposed in this work has the highest sensitivity compared with the same types of sensors. Moreover, the application of an FBG-Terfenol-D based magnetic field sensor in the MFL test shows good performance. Compared with traditional electrical MFL testing technologies, the sensitivity-enhanced optical fiber magnetic field sensor has a higher resolution and longer survival time in harsh environments.

Computational Modeling of Magnetic Field Optical Fiber Sensor Considering Temperature Effects

Due to the vast area of application and reliability, fiber optic magnetic field sensors have been the subject of several studies, however, some of these application areas are submitted to temperature variations, which can hinder the sensors in monitoring the magnetic field. With this panorama, this work analyzes through computational modeling a fiber optical magnetic field sensor, using the magneto-optical Faraday effect and observing temperature effects in the sensor response. For modeling, a numerical model built in COMSOL Multiphysics is used. The results show a value for cross-sensitivity of 3.27 mT/°C in a non-optimized configuration of the sensor and of 2.47 mT/°C for an optimized configuration. A methodology for optimizing the sensor to operate in a certain temperature range, 55 to 75 °C, is also discussed. The results presented in this work show that the temperature is an important factor to be considered to improve the selectivity and to obtain the correct sensitivity of the sensor.

Optical Fiber Magnetic Field Sensors Based on 3 × 3 Coupler and Iron-Based Amorphous Nanocrystalline Ribbons

Optical fiber interferometric magnetic field sensors based on magnetostrictive effects have several advantages, e.g., high sensitivity, strong adaptability to harsh environments, long distance transmission, etc. They also have great application prospects in deep wells, oceans, and other extreme environments. In this paper, two optical fiber magnetic field sensors based on iron-based amorphous nanocrystalline ribbons and a passive 3 × 3 coupler demodulation system were proposed and experimentally tested. The sensor structure and the equal-arm Mach-Zehnder fiber interferometer were designed, and the experimental results showed that the magnetic field resolutions of the optical fiber magnetic field sensors with sensing length of 0.25 m and 1 m were 15.4 nT/√Hz @ 10 Hz and 4.2 nT/√Hz @ 10 Hz, respectively. This confirmed the sensitivity multiplication relationship between the two sensors and the feasibility of improving the magnetic field resolution to the pT level by increasing the sensing length.

Fiber Optic All-Polarization Weak Magnetic Field Sensor Based on Sagnac Interferometer

A novel fiber-optic magnetic field sensor, based on a Sagnac structure, is proposed with the approach of polarization interference detection. The sensor takes advantage of common path interference, combining with a high magnetic field sensitivity sensing unit, composed of magneto-optical crystal, and magnetic field concentrators, to achieve high resolution, high stability, and large dynamic measurement of DC magnetic field signals. In this paper, the theoretical model is established and the related theory is derived in detail. The key technologies in the system are thoroughly investigated and verified. Experimental research on the proposed system is demonstrated and the results show that a DC magnetic field resolution of 5.6 nT and a dynamic range of larger than 70 dB is achieved. Furthermore, the linearity of the system is greater than 99.8% and the instability is less than 0.5%.