Optical Fiber Magnetic Field Sensor Research Articles

U-bent single-mode–multimode–single-mode fiber optic magnetic field sensor based on magnetic fluid

A magnetic field sensor based on a U-bent single-mode–multimode–single-mode (SMS) fiber structure and magnetic fluid (MF) is presented and demonstrated experimentally. The U-bent and straight sensors are compared, and the influence of the diameter of the no-core fiber (NCF) on the sensitivity of the U-bent sensor is investigated. The experimental results show that the sensitivity of the sensor can be improved by bending the NCF and decreasing the NCF diameter. The following magnetic field sensitivities have been achieved: 3185.2 pm/mT and 5.6 dB/mT, based on dip wavelength and transmission loss demodulations, respectively.

Low temperature sensitive intensity-interrogated magnetic field sensor based on modal interference in thin-core fiber and magnetic fluid

A fiber-optic magnetic field sensor based on the thin-core modal interference and magnetic fluid (MF) has been proposed and experimentally demonstrated. The magnetic field sensor is spliced with a thin-core fiber (TCF) between two conventional single-mode fibers immersed into the MF. The transmission spectra of the proposed sensor under different magnetic field intensities have been measured and theoretically analyzed. The results show that the magnetic field sensitivity reaches up to −0.058 dB/Oe with the linear range from 75 Oe to 300 Oe. Due to the small thermal expansion of the TCF material, the attenuation wavelength and the transmission power remain almost unchanged as the temperature varies. The proposed magnetic field sensor has several advantages such as intensity-interrogation, low temperature sensitivity, low cost, compact size, and ease of fabrication. And particularly, the temperature cross-sensitivity could be effectively resolved, which makes it a promising candidate for strict temperature environments. Therefore, it would find potential applications in the magnetic field measurement.

Magnetic field sensor based on asymmetric optical fiber taper and magnetic fluid

We report an optical fiber magnetic field sensor by merging the advantages of magnetic fluid and a core–cladding–mode interferometer which is directly fabricated on a standard single-mode fiber by using an arc fusion splicing machine. The sensing performances of the sensors are controllable by designing the parameters of the asymmetric-tapered structure. Experimental results show that the sensor with axial offset of 168μm and taper waist diameter of 45μm not only has good optical properties but also a relatively high magnetic-field sensitivity of ∼162.06pm/mT ranging from 0 to 21.4mT. The proposed sensors would find potential applications in weak magnetic sensing fields.

Magnetic Fluid-Filled Optical Fiber Fabry–Pérot Sensor for Magnetic Field Measurement

Magnetic fluid is a new type of optical functional material, which has interesting optical characteristics under an external magnetic field. In this letter, the magneto-optical characteristic of the magnetic fluid was adopted to form a novel fiber-optic magnetic field sensor. The sensor probe was composed of an extrinsic fiber Fabry-Perot interferometer and magnetic fluid. The refractive index of the magnetic fluid would be changed with the increase of magnetic field. Preliminary experiment was carried out to verify the feasibility of the sensor. The magnetic field measurement sensitivity was 0.0431 nm/Gs in the experiment. The measurement resolution was better than 0.5 Gs at the measurement range from 0 to 400 Gs. The sensor has the advantages of simple structure, compact size, and easy fabrication.

Fiber-optic in-line magnetic field sensor based on the magnetic fluid and multimode interference effects

A compact magnetic field sensor has been proposed based on multimode interference effects. It consists of typical multimode interferometer (MMI) immersed into the magnetic fluid (MF) which is formed by a section of square no-core fiber (NCF) spliced between two single-mode fibers. The transmission spectral characteristics of this MMI have been analyzed, and the spectral magnetic response of the proposed sensor has been investigated by immersing the NCF into the MF environment. The transmission response of the interference maxima exhibits a sensitivity of −0.01939 dB/Oe in the relatively linear range. Due to its low cost and compactness, this sensor would find potential applications in the measurement of magnetic field.

Optical fiber magnetic field sensor based on single-mode–multimode–single-mode structure and magnetic fluid

An optical fiber magnetic field sensor based on the single-mode-multimode-single-mode (SMS) structure and magnetic fluid (MF) is proposed and demonstrated. By using a piece of no-core fiber as the multimode waveguide in the SMS structure and MF sealed in a capillary tube as the magnetic sensitive media, which totally immersing the no-core fiber, an all-fiber magnetic sensor was fabricated. Interrogation of the magnetic field strength can be achieved either by measuring the dip wavelength shift of the transmission spectrum or by detecting the transmission loss at a specific wavelength. A demonstration sensor with sensitivities up to 905 pm/mT and 0.748 dB/mT was fabricated and investigated. A theoretical model for the design of the proposed device was developed and numerical simulations were performed.

Ampere force based magnetic field sensor using dual-polarization fiber laser

A magnetic field sensor is proposed by placing a dual-polarization fiber grating laser under a copper wire. With a perpendicular magnetic field applied, an electrical current flowing through the copper wire can generate Ampere force to squeeze the fiber grating laser, resulting in the birefringence change inside the laser cavity and hence the change of the beat note frequency. When an alternating current is injected into the copper wire, the magnetic field induced beat note frequency change can be discriminated from environment disturbances. A novel fiber-optic magnetic field sensor is therefore demonstrated with high sensitivity and inherent immunity to disturbances.

Remotely-Interrogated Three-Axis Fiber Laser Magnetometer

A fiber optic magnetic field sensor node designed for seabed-mounted surveillance arrays, incorporating three orthogonally mounted magnetic field sensors and a microelectomechancial systems inclinometer, is described. Each sensor comprises a current carrying nonmagnetic bridge, which experiences the Lorentz force generated in a magnetic field. A metalized fiber laser attached to the bridge measures the induced strain. The operating principle and fundamental performance of the sensor as well as relevant performance parameters are described. Measured data illustrating the sensor and node performance in laboratory tests are presented. Less than 2 nanoTesla/Hz1/2 resolution at frequencies from 0.002 to 10 Hz is achieved with only 75 mA-rms of current. The sensor node is separated from the interrogation electronics with a 1-km fiber optic cable (extendable to 10 km) and qualified to an operating depth of 100 m. Methods to further improve the magnetometer performance are also discussed.

Optical fiber magnetic field sensors with TbDyFe magnetostrictive thin films as sensing materials

Different from usually-used bulk magnetostrictive materials, magnetostrictive TbDyFe thin films were firstly proposed as sensing materials for fiber-optic magnetic field sensing characterization. By magnetron sputtering process, TbDyFe thin films were deposited on etched side circle of a fiber Bragg Grating (FBG) as sensing element. There exists more than 45pm change of FBG wavelength when magnet field increase up to 50 mT. The response to magnetic field is reversible, and could be applicable for magnetic and current sensing.

Experimental Investigation on Temperature Dependence of the Performance in a Magnetostrictive Fiber-Optic Interferometric Magnetic Field Sensor

This paper studies the temperature dependence of the performance in magnetostrictive fiber-optic Michelson interferometric magnetic field sensors. Experiments are carried out and the results show that the sensor system output, system sensitivity and transducer's mechanical resonant frequency are strongly affected by the ambient temperature. Fitted expressions are provided and compensation methods are demonstrated with experimental verification.

Experimental Study of Some Key Issues on Fiber-Optic Interferometric Sensors Detecting Weak Magnetic Field

This paper presents some key issues in fiber-optic interferometric magnetic field sensors. Practically applicable methods to design and implement fiber-optic Michelson interferometer and transducers are described with experimental verifications. Detection scheme of traditional hardware demodulation is improved, and a new software demodulation method is addressed. Transducers were implemented by using the proposed methods and the performance was tested. The results show significant performance improvement. The minimum detectable magnetic field using hardware demodulation scheme is about 0.10 nT/Hz1/2 at 1 Hz without any mumetal shield in the laboratory environment.

Fiberoptic heterodyne magnetic field sensor for long-pulsed fusion devices

A heterodyne polarimeter which measures the Faraday effect has been under development as a magnetic field sensor for long-pulsed fusion devices. The wavelength of laser beam was chosen to be 850 nm since the radiation-induced loss in optical fibers is significant below 800 nm while the Faraday rotation angle decreases with increasing wavelength. By the use of a distributed Bragg reflector laser diode and a Faraday isolator, excellent stability of phase measurement was attained. The phase resolution was raised to up to 0.02° by the digital complex demodulation and digital bandpass filtering of beat signals. Although the Verdet constant of heavily Tb3+-doped paramagnetic glass is larger than that of ZnSe by about a factor of 1.4, ZnSe is superior to the former in terms of negligible temperature dependence. With a 40-mm-long ZnSe sensing rod, resolutions of the magnetic field strength of about 5 and 2 G were found to be possible with time responses of 1 and 10 ms, respectively.

Layer-by-layer electrostatic self-assembly of nanoscale Fe3O4 particles and polyimide precursor on silicon and silica surfaces

Monolayer and multilayer ultrathin films comprised of nanosized iron oxide (Fe3O4) particles and polyimide molecules have been fabricated on single crystal silicon and quartz substrates by a novel layer-by-layer electrostatic self-assembly process. This process involves the alternate dipping of a substrate into an aqueous solution of anionic polyimide precursor (polyamic acid salt, PAATEA), followed by dipping into an aqueous solution of polycation polydiallyldimethylammonium chloride (PDDA) which coats on nanoscale Fe3O4 particles as a stabilizer. The growth process and the structure have been characterized using UV-vis spectroscopy, contact angle, and ellipsometry measurements. The results suggest that well-ordered uniform monolayer and multilayer magnetic films have been formed on silicon and silica surfaces. A recently developed highly sensitive fiber optic magnetic field sensor was used to probe the small magnetic field intensity produced by the multilayer films.

Doped sillenite crystals applicable for fiber-optic magnetic sensors

The spectral dependencies of the optical rotatory power (ORP-ϱ) and the Verdet coefficient ( V) of undoped and Fe- and Cr-doped Bi 12SiO 20 ( BSO) crystals are studied in the spectral range of 440–800 nm. The results show that Cr decreases ϱ about 4–5% in the range 600–700 nm, but below 560 nm ϱ strongly increases up to 180–200% compared to the ORP of undoped BSO, which could be related to the earlier observed absorption spectra. Like the ORP, the values of V are lower by about 1–3% at 700-600 nm, whereas below 590 nm V increases about 2%. The influence of Fe on ϱ and V strongly depends on the dopant concentration. For example, at larger concentrations (2.2 mol%) ϱ and V decrease up to 4% and 12%, respectively, whereas at 0.9 mol% Fe ϱ and V increase 3% and 9%, respectively. The influence of the annealung and the illumination on the gyrotropy of undoped BSO are also studied. Some assumption about the nature of the sillenite optical and magneto-optical rotation are made. The possibilities to use these materials for fiber optic magnetic field sensors or to improve their characteristics for photorefractive applications are discussed, too.

Optical fiber magnetic field sensors with ceramic magnetostrictive jackets

Optical fibers coated by magnetostrictive ceramic films were tested with a Mach-Zehnder interferometer in an open-loop mode. The sensors exhibited excellent linearity and good sensitivity. The response of ceramic-jacketed fibers was not affected by small dc fluctuations that are due to the linear behavior of tested ceramic coatings in low magnetic fields. Tested ceramic materials included magnetite, γ-Fe(2) O(3), nickel ferrite, and cobalt-doped nickel ferrite (NCF2) jackets. The latter showed the best performance. A minimum detectable field of 3.2 × 10(-3) A/m for optical fiber jacketed with 2-μm-thick and 1-m-long NCF2 material has been achieved. The capability of detecting magnetic fields as low as 2.6 × 10(-7) A/m with a 10-μm-thick cobalt-doped nickel ferrite jacket is proposed.

Stabilization of temperature dependence of verdet constant of bi‐doped garnet and development of high sensitive optical fiber magnetic field sensor

AbstractBi‐doped garnet is a rare metal iron garnet made up of a ferrimagnetic substance, of which some portion of the rare metal element is replaced with bismuth. It illustrates a strong Faraday effect and has been applied to optical isolators. In magnetic field sensing applications, however, a shortcoming is apparent: Faraday rotation of Bi‐doped garnet reveals temperature dependencies when the garnet is not magnetically saturated. Close attention has been paid to the magnetization of each rare earth element's different temperature characteristics; garnet compositions have been investigated by calculations and experiments in order to find a garnet that shows flat temperature characteristics between −10 and 80°C. The liquid phase epitaxy (LPE) method was established to obtain a single crystal of the garnet [Bi13(Y, La)0.9Ho0.8Fe4.5Ga0.5O12]. A magnetic field sensor of fiber optic based on the Faraday effect of this single crystal is highly accurate in detecting conductor currents of power cables. The developed sensor is small and lightweight compared to conventional current transformers; additionally, optical fiber transmission of detected current signals is free from both electric and magnetic noise.

Magnetic field detection enhancement in an external cavity fiber Fabry-Perot sensor

The sensitivity of an extrinsic fiber-optic magnetic field sensor using a gallium doped yttrium iron garnet (Ga:YIG) bulk optic crystal has been significantly improved by incorporating a Fabry-Perot resonator around the crystal.

High sensitivity fiber-optic magnetic field sensors based on iron garnets

Ferrimagnetic iron garnet crystals form the basis of magnetooptic magnetic field sensors which offer high sensitivity, broad-band frequency response, and compatibility with fiber optics. Recent developments at NIST promise still greater performance for these devices in the near term. Specifically, new designs for magnetic field sensors, electric current sensors, and novel experimental iron garnet compositions demonstrate the potential for significantly improving the performance of these devices.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Fiber optic CdMnTe magnetic field sensor made by the laser ablation deposition technique

A Cd/sub 1-x/Mn/sub x/Te (CMT) fiber optic magnetic field sensor has been developed with the use of a laser ablation deposition technique: pulsed laser evaporation and epitaxy (FLEE). This method of growth yields high-quality material and due to the low-temperature deposition it enables integration of CMT in optoelectronic systems. A disk-shaped sensor structure of diameter and thickness less than 3 mm and 75 /spl mu/m, respectively, is incorporated in a fiber optic system. A linear response of the sensor held at room temperature has been measured in the magnetic field up to 0.8 T; however, its usefulness for measurements of the field above 25 T is expected. Due to its small physical dimension and the potential of high-speed operation in the gigahertz range, the sensor can be particularly useful in the measurements of spatial and temporal uniformity of the magnetic field. >

Fiber-optic DC magnetic field sensor with balanced detection technique

The authors describe a balanced detection technique that suppresses undesirable effects due to residual signals for the detection of DC and low-frequency magnetic fields with intermetric fiber-optic sensors using metallic glass. The detection technique utilizes a square-wave magnetic field modulation that translates the residual signal outside of the detection bandwidth. Experimental results are presented that show effective suppression of the residual signal.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>