Optical fiber temperature and magnetic field measurement sensor of GMMC-FBG collaborative architecture

Abstract

The invention provides an optical fiber temperature and magnetic field measurement sensor of a GMMC-FBG collaborative architecture. The optical fiber temperature and magnetic field measurement sensor comprises an ASE light source (1), a sensing unit (2), a spectrometer (3), a demodulation module (4) and a computer (5). The sensing unit (2) comprises a single-mode fiber (2-1), a conical seven-core fiber (2-2), a GMMC (2-3) and an FBG (2-4). Through the innovative design, the cascade structure that the GMPC wraps the FBG is adopted, the integration level and stability of the sensor are considered, the interaction with the external environment is enhanced through the micro-nanofiber structure, and the sensitivity of the sensor is remarkably improved. Meanwhile, by developing the GMPC-coated FBG cascade S-TSCF-S structure, the eddy current loss caused by low resistivity of the magnetostrictive material is effectively reduced, and efficient and accurate magnetic field detection is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber optic sensing, and particularly relates to a fiber optic temperature and magnetic field measurement sensor with a GMPC-FBG collaborative architecture. Background Art

[0002] Currently, the sensors used for magnetic field detection mainly include electrical magnetic field sensors and fiber optic magnetic field sensors. Fiber optic sensing technology is a sensing technology with strong anti-interference ability, good insulation, resistance to extreme environments, and easy to realize online monitoring. However, in the current field of magnetic field monitoring, fiber optic sensing technology is difficult to meet the monitoring requirements of low interference, real-time, and easy demodulation for equipment monitoring. Therefore, the research on fiber optic magnetic field sensing technology has important application significance.

[0003] Compared with electrical magnetic field sensors, although the technology is relatively mature and widely used, most of them are point detectors and need to be equipped with a specific platform to achieve large-scale magnetic field monitoring. In addition, there are also problems such as high cost, need for power supply and external temperature control systems. Therefore, electrical magnetic field sensors are difficult to meet the requirements of online monitoring in large areas of the sea and multi-parameter integrated sensing. Fiber optic magnetic field sensors have low cost and small volume, and have great application potential in various application fields. For example, Ye Wenhao et al. (Design of a GMM-FBG alternating current sensor based on an improved PI hysteresis model [D]. Yanshan University, 2022) built an experimental system for a GMM-FBG current sensor, analyzed the frequency doubling effect and hysteresis problem of giant magnetostrictive material (GMM) in an alternating magnetic field, made full use of the advantages of optical current sensors, and utilized the high magnetostrictive characteristics of GMM to enhance the sensitivity of optical current sensors. The constant temperature environment in the experiment could not be fully realized, and according to the temperature characteristics of GMM and Bragg grating (FBG), some practical operation errors would be brought in this regard; Dong Funing et al. (A current sensor based on magnetostrictive effect and fiber grating [J]. Dong Funing; Yang Qing; Luo Mandan; Chen Ning; Liao Wei. Acta Optica Sinica, 2022(08)) proposed a method of using an iron-based nanocrystalline soft magnetic material with excellent magnetic conductivity to aggregate the magnetic field generated by the input current and act on GMM, causing it to deform and drive the center wavelength of the FBG adhered to it to shift, strengthening the magnetic line density and distribution uniformity in the sensing FBG adhesion area, and improving the linearity and sensitivity of the sensor. However, important performance such as its sensing frequency and input-output linearity will be limited by the inherent hysteresis problem of GMM, and the sensing range will be limited by the magnetic saturation characteristics of GMM. Summary of the Invention

[0004] At present, researchers have achieved magnetic field measurement by combining magnetostrictive materials with fiber Bragg gratings. However, due to the inherent hysteresis problem of GMM materials and the eddy current loss caused by their low resistivity, the sensing range is limited. In addition, if the constant temperature condition cannot be achieved, it will further affect the measurement accuracy of the sensing unit. To solve the defects of the existing technology, the present invention proposes a fiber optic temperature and magnetic field measurement sensor with a GMPC-FBG collaborative architecture that is highly sensitive, low-cost, and has a simple structure.

[0005] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0006] Technical solution: A fiber optic temperature and magnetic field measurement sensor with a GMPC-FBG collaborative architecture, characterized in that it includes an ASE light source (1), a sensing unit (2), a spectrometer (3), a demodulation module (4), and a computer (5);

[0007] The sensing unit (2) includes a single-mode optical fiber (2-1), a tapered seven-core optical fiber (2-2), a GMPC (2-3), and an FBG (2-4), where:

[0008] In the sensing unit (2), the FBG (2-4), the single-mode optical fiber (2-1), and the seven-core optical fiber (SCF) are cascaded with the single-mode optical fiber (2-1) to form an optical fiber composite structure. In addition, the GMPC (2-3) coats the FBG (2-4);

[0009] The specific preparation process of the sensing unit (2) includes the production of the optical fiber composite structure and the preparation of the GMPC (2-3) material;

[0010] Among them, the fabrication of the fiber composite structure includes the fabrication of FBG (2-4), single-mode fiber (2-1), the cascaded structure of seven-core fiber (SCF) and single-mode fiber (2-1), and the fabrication of tapered seven-core fiber (2-2); First, the fabrication of FBG (2-4), single-mode fiber (2-1), the cascaded structure of seven-core fiber (SCF) and single-mode fiber (2-1) includes: successively fusing the single-mode fiber (2-1), SCF, and single-mode fiber (2-1) using an optical fiber fusion splicer to form an S-SCF-S optical fiber structure; Secondly, the fabrication of tapered seven-core fiber (2-2) includes: using a hydrogen-oxygen flame melting and tapering machine to taper the SCF part in the S-SCF-S structure to form an S-TSCF-S structure. During the tapering process, hydrogen and oxygen are generated through the reaction of potassium hydroxide solution, and these gases are released from the burner head of the tapering machine and ignited to form a hydrogen-oxygen flame; When performing the tapering operation, first fix the SCF to be tapered on the operating table, and then, by precisely controlling the movement of the operating table, while the hydrogen-oxygen flame heats the SCF, the operating table gradually stretches the optical fiber towards both ends; During the stretching process, continuously monitor the change of the spectrum to ensure the precise formation of the tapered structure; Finally, we obtained a tapered seven-core fiber (2-2) with a diameter of 8.8 μm at its lumbar part; Further, an FBG (2-4) with a wavelength of 1550 nm is etched at one end of its single-mode fiber (2-1) to form an FBG (2-4) cascaded S-TSCF-S optical fiber structure. Finally, prepare GMPC (2-3) and coat it on FBG (2-4) to form a sensing unit (2) of FBG (2-4) coated with GMPC (2-3) cascaded S-TSCF-S;

[0011] The magnetic particles Tb in GMPC (2-3) in the sensing unit (2) x Dy 1-x Fe 2 When the concentration of Tb in it is near 0.25, the magnetic moment of the material is maximized at 88.684 μB, and at the same time its ductility and toughness are optimal. Therefore, the most widely used Terfenol-D powder (Tb 0.27 Dy 0.73 Fe 2 ) is selected as the magnetic particles during the preparation process of GMPC (2-3) material, and the optimal mass fraction of the magnetic particles in GMPC (2-3) is obtained as 91%;

[0012] The preparation method of the GMPC (2-3) material in the sensing unit (2) is as follows: Select an epoxy resin and curing agent mixture accounting for 70% as the binder of the GMPC (2-3) material (i.e., the matrix material). Weigh magnetic particles (Terfenol-D powder) so that its mass fraction in the GMPC (2-3) material composed of the matrix material is 91% (Terfenol-D powder: mixture is 10:1). Then, fully mix and stir the magnetic particles and the matrix material, and pour them into a pre-prepared hollow cylinder mold with a radius of 3 mm and a height of 20 mm. Place an FBG (2-4) with a grating length of 10 mm and a central wavelength of 1550 nm in the mold, and fix the FBG (2-4) to be aligned with the center of the mold height. After applying pressure to the filled mold, place it in a magnetic field environment and let it stand for 48 hours (in a vacuum environment), and then demold to take out the shaped sensing unit (2) with GMPC (2-3) coating the FBG (2-4).

[0013] Furthermore, the fiber optic temperature and magnetic field measurement sensor with a GMPC-FBG collaborative architecture is further characterized in that:

[0014] The ASE light source (1) emits a light beam that is transmitted to the sensing unit (2). When the temperature changes, it causes changes in the refractive indices of the core mode and the cladding mode in the fiber composite structure, resulting in wavelength drift. At the same time, the wavelength drift is linearly related to the temperature. When the magnetic field intensity changes, it triggers the magnetostrictive effect in the GMPC (2-3), which further causes axial tension on the FBG (2-4), resulting in slight changes in size or shape. The sensing unit (2) is connected to the spectrometer (3) through an optical fiber jumper. When the temperature and magnetic field change, a wave valley generated by S-TSCF-S is denoted as dip A and the wave valley generated by the FBG (2-4) is denoted as dip FBG in the temperature response spectrum. When the temperature rises in a gradient manner, the wavelengths of dip A and dip FBG show a red-shift phenomenon. As the magnetic field gradient increases, since S-TSCF-S does not have magnetic field sensitivity, the wave valley dip A basically does not drift, and dip FBG shows a blue-shift phenomenon. The changes are transmitted to the demodulation module (4), and the temperature change amount ΔT and the magnetic field change amount ΔH are obtained through the demodulation matrix and data processing is performed in the computer (5).

[0015] Furthermore, the ASE light source (1) is a broadband light source with a central wavelength of 1550 nm for generating optical signals.

[0016] When the sensing unit (2) measures temperature, the refractive index changes of the core mode and the cladding mode in the fiber composite structure are measured to achieve temperature measurement; when measuring magnetic field, the GMPC (2-3) generates magnetostrictive effect and deforms to achieve magnetic field measurement.

[0017] Structural invention: An optical fiber temperature and magnetic field measurement sensor with a GMPC-FBG collaborative architecture.

[0018] Compared with the existing calculations, the beneficial effects of this invention patent are:

[0019] In the present invention, by preparing the GMPC (2-3) material, the consumption of rare earth materials is reduced by replacing the use of GMM material, as well as the eddy current loss caused by the low resistivity of GMM.

[0020] In the GMPC (2-3) material of the present invention, the magnetic particles are Tb 0.27 Dy 0.73 Fe, Tb x Dy 1-x Fe 2 When x is near the concentration of 0.25, the magnetosensitive performance of the material is higher, and the better ductility is more suitable for engineering applications.

[0021] In the present invention, the lumbar diameter D of the seven-core single-mode optical fiber is 8.8 μm, and the evanescent field intensity is large. Therefore, the interaction effect with the external environment is also the strongest, greatly improving the sensitivity of the sensor.

[0022] In the GMPC (2-3) coated FBG (2-4) cascaded S-TSCF-S multi-parameter sensing structure of the present invention, the highest temperature sensitivity is 1.33 times that of the temperature sensitivity of the cascaded structure of multiple FBG (2-4).

[0023] In the FBG (2-4) cascaded S-TSCF-S structure of the present invention, the characteristic peak generated by S-TSCF-S has only temperature-sensitive characteristics, reducing cross-interference and making it easier to achieve multi-parameter independent demodulation. Description of the drawings

[0024] Figure 1 It is a structural diagram of an optical fiber temperature and magnetic field measurement sensor with a GMPC-FBG collaborative architecture.

[0025] Figure 2 It is a structural diagram of the sensing unit of an optical fiber temperature and magnetic field measurement sensor with a GMPC-FBG collaborative architecture. Detailed implementation manners

[0026] The following embodiments will describe the specific implementation manners of an optical fiber temperature and magnetic field measurement sensor with a GMPC-FBG collaborative architecture proposed by the present invention in conjunction with the drawings.

[0027] As shown Figure 1 in the figure, it is a structural diagram of a fiber optic temperature and magnetic field measurement sensor with a GMPC-FBG collaborative architecture. The ASE light source (1) emits a light beam and transmits it to the sensing unit (2). When the temperature changes, it causes changes in the refractive indices of the core mode and the cladding mode in the fiber composite structure, resulting in wavelength drift. At the same time, the wavelength drift is linearly related to the temperature. When the magnetic field strength changes, it triggers the magnetostrictive effect in the GMPC (2-3), and then causes axial tension on the FBG (2-4), resulting in a slight change in size or shape. The sensing unit (2) is connected to the spectrometer (3) through an optical fiber jumper. When the temperature and magnetic field change, a wave trough generated by the S-TSCF-S is denoted as dip A , and the wave trough generated by the FBG (2-4) is denoted as dip FBG in the temperature response spectrum. When the temperature increases gradually, the wavelengths of dip A , dip FBG show a red shift phenomenon. As the magnetic field gradient increases, since the S-TSCF-S does not have magnetic field sensitivity characteristics, therefore, the wave trough dip A basically does not drift, and dip FBG shows a blue shift phenomenon. The changes are transmitted to the demodulation module (4), and the temperature change amount ΔT and the magnetic field change amount ΔH are obtained through the demodulation matrix and data processing is performed in the computer (5);

[0028] As shown Figure 2 in the figure, it is a structural diagram of the sensing unit of a fiber optic temperature and magnetic field measurement sensor with a GMPC-FBG collaborative architecture. In the sensing unit (2), the GMPC (2-3) material is simulated. Under a steady magnetic field, the magnetic field required in three-dimensional space is obtained by Ampere's law as follows:

[0029] B = μ 0 μ r H + B r

[0030] where: μ 0 is the magnetic permeability in space, μ r is the relative magnetic permeability, B is the magnetic flux density, B r is the residual magnetic flux density. Let the μ rThe value is 5. To ensure that the optical fiber is not broken due to the influence of the material thickness, a GMPC(2-3) material with a radius of 3 mm and a height of 20 mm is selected for finite element simulation and experimental design. When the length of the GMPC(2-3) material is 20 mm, the required saturation magnetic field strength is the largest. Therefore, the GMPC(2-3) material with a length of 20 mm has a larger magnetic field detection range. When the magnetic field is less than 2000 mT, the GMPC material does not reach magnetic saturation, and the magnetostriction increases with the increase of the magnetic field.

[0031] The method for preparing the GMPC(2-3) coated FBG(2-4) cascaded S-TSCF-S structure in the sensing unit (2) is as follows: First, weld the S-SCF-S optical fiber structure, and select the SCF length to be 25 mm. Similarly, the single-mode optical fibers (2-1) at both ends of this structure are denoted as F1 and F2 respectively; after the S-SCF-S optical fiber structure is prepared, then taper the seven-core optical fiber part with a fiber taper machine to make its lumbar diameter 8.8 μm to form the S-TSCF-S optical fiber structure, and then perform encapsulation; further etch the FBG(2-4) with a wavelength of 1550 nm at the single-mode optical fiber F1 end to form the FBG(2-4) cascaded S-TSCF-S optical fiber structure. After the optical fiber structure is made, finally prepare the GMPC(2-3) material and coat the FBG(2-4) part of the FBG(2-4) cascaded S-TSCF-S optical fiber structure.

Claims

1. A GMPC-FBG collaborative optical fiber temperature and magnetic field measurement sensor, characterized in that: It includes an ASE light source (1), a sensor unit (2), an optical fiber coupler (3), a photoelectric converter (4), and a computer (5); The sensing unit (2) comprises a single-mode optical fiber (2-1), a tapered seven-core optical fiber (2-2), a GMPC (2-3), and a FBG (2-4), wherein: The specific preparation process of the sensing unit (2) includes the preparation of the optical fiber composite structure and the preparation of the GMPC (2-3) material; The preparation of the optical fiber composite structure includes the preparation of the cascade structure of FBG (2-4), single-mode optical fiber (2-1), seven-core optical fiber (SCF) and single-mode optical fiber (2-1), and the preparation of tapered seven-core optical fiber (2-2); firstly, the preparation of the cascade structure of FBG (2-4), single-mode optical fiber (2-1), seven-core optical fiber (SCF) and single-mode optical fiber (2-1) includes: using a fiber fusion splicer to sequentially fuse the single-mode optical fiber (2-1), SCF and single-mode optical fiber (2-1) to form an S-SCF-S optical fiber structure; secondly, the preparation of the tapered seven-core optical fiber (2-2) includes: using a hydrogen-oxygen flame melting taper machine to perform a taper process on the SCF part of the S-SCF-S structure to form an S-TSCF-S structure. During the taper drawing process, hydrogen and oxygen are generated by the reaction of potassium hydroxide solution. These gases are released from the flame of the taper drawing machine and ignited to form a hydrogen-oxygen flame. When performing the taper drawing operation, the SCF to be tapered needs to be fixed on the operating table first, and then the movement of the operating table is precisely controlled so that the hydrogen-oxygen flame heats the SCF while the operating table gradually stretches the optical fiber to both ends. During the stretching process, the changes in the spectrum are continuously monitored to ensure the precise formation of the tapered structure. Finally, we obtained a tapered seven-core optical fiber (2-2), the diameter of its lumbar part reached 8.8μm. Further, FBG (2-4) with a wavelength of 1550nm was etched at one end of its single-mode optical fiber (2-1) to form a FBG (2-4) cascaded S-TSCF-S optical fiber structure. Finally, GMPC (2-3) was prepared and coated with FBG (2-4) to form a GMPC (2-3) coated FBG (2-4) cascaded S-TSCF-S sensing unit (2). Magnetic particles Tb in GMPC (2-3) in the sensing unit (2) x Dy 1-x When the concentration of Tb in Fe2 is around 0.25, the magnetic moment of the material is 88.684μB, and its ductility and toughness are optimal. Therefore, the most widely used Terfenol-D powder (Tb 0.27 Dy 0.73 Fe2) was used as magnetic particles in the preparation process of GMPC (2-3) materials, and the best mass fraction of magnetic particles in GMPC (2-3) was 91%; The preparation method of the GMPC (2-3) material in the sensor unit (2) is as follows: a mixed material of epoxy resin and curing agent accounting for 70% is selected as a binder (i.e., a matrix material) of the GMPC (2-3) material, magnetic particles (Terfenol-D powder) are weighed so that the mass fraction of the GMPC (2-3) material composed of the matrix material is 91% (Terfenol-D powder: mixture is 10:1), and then the magnetic particles and the matrix material are fully mixed and stirred, and then poured into a pre-prepared hollow cylindrical mold with a radius of 3 mm and a height of 20 mm, and a FBG (2-4) with a grid area length of 10 mm and a central wavelength of 1550 nm is placed in the mold, and the FBG (2-4) is fixedly aligned with the height center of the mold, and then pressure is applied to the filled mold, and it is placed in a magnetic field environment, and after being left to stand for 48 hours (in a vacuum environment), the mold is removed to remove the GMPC (2-3) coated with the FBG (2-4) sensor unit (2).

2. The optical fiber temperature and magnetic field measurement sensor with GMPC-FBG collaborative architecture according to claim 1, characterized in that: The ASE light source (1) emits a light beam which is transmitted to the sensing unit (2). When the temperature changes, the refractive index of the core mode and the cladding mode in the optical fiber composite structure changes, and the wavelength drifts. At the same time, the wavelength drift is linearly related to the temperature. When the magnetic field intensity changes, the GMPC (2-3) is induced to produce a magnetostrictive effect, which in turn causes axial stretching of the FBG (2-4), resulting in a slight change in size or shape. The sensing unit (2) is connected to the spectrometer (3) through an optical fiber jumper. When the temperature and magnetic field change, a trough generated by the S-TSCF-S is recorded as a dip. A , and the trough generated by FBG (2-4) is denoted as dip FBG The temperature response spectrum shows that when the temperature increases gradually, the dip A 、dip FBG The wavelength shows a red shift phenomenon; and as the gradient of the magnetic field increases, since S-TSCF-S is not sensitive to magnetic fields, the dip A Basically no drift occurs, dip FBG The blue shift phenomenon is generated and the change is transmitted to the demodulation module (4). The ΔT temperature change and ΔH magnetic field change are obtained and data processing is performed in a computer (5).

3. The optical fiber temperature and magnetic field measurement sensor with GMPC-FBG collaborative architecture according to claim 1, characterized in that: The ASE light source (1) is a broadband light source with a central wavelength of 1550 nm and is used to generate optical signals.

4. The optical fiber temperature and magnetic field measurement sensor with GMPC-FBG collaborative architecture according to claim 1, characterized in that: When the sensing unit (2) measures temperature, the refractive index of the core mode and the cladding mode in the optical fiber composite structure changes, thereby achieving temperature measurement; and when measuring the magnetic field, the GMPC (2-3) produces a magnetostrictive effect and deforms, thereby achieving magnetic field measurement.

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