Three-axis magnetic field surveying and mapping method and system based on magnetostrictive strain modulation optical fiber interference

Abstract

The invention discloses a three-axis magnetic field surveying and mapping method and system based on magnetostrictive strain modulation optical fiber interference, and the method comprises the steps: preparing a soft magnetic elastomer, coating the surface of a single-mode optical fiber with the soft magnetic elastomer, and obtaining the single-mode optical fiber with a soft magnetic elastomer coating; performing structure processing to form an eggbeater-shaped optical fiber sensing probe; an optical sensing system is built, the eggbeater-shaped optical fiber sensing probe is placed in a magnetic field environment to be detected, optical signals emitted by a light source are detected, and transmission interference spectrums under different magnetic field intensities and magnetic field directions are recorded; extracting the wavelength valley offset of the resonant wavelength, and calculating the three-axis component of the magnetic field to be detected based on the preset corresponding relation between the wavelength valley offset and the magnetic field intensity and the magnetic field direction; surveying and mapping of the three-axis magnetic field are completed. The eggbeater-shaped optical fiber sensing probe provided by the invention is simple in structure, strong in anti-interference capability, high in measurement precision and high in strain transmission efficiency, and improves the three-dimensional surveying and mapping precision and efficiency of a magnetic field in combination with a three-axis component resolving algorithm.

Description

Technical Field

[0001] This invention relates to the field of magnetic field mapping technology, and in particular to a three-axis magnetic field mapping method and system based on magnetostrictive strain modulated fiber optic interferometry. Background Technology

[0002] Three-dimensional magnetic field mapping is a core supporting technology in modern technological fields such as intelligent robot control, human-computer interaction, and wearable electronic devices. In the precise control of joint postures in intelligent robots, real-time capture of the three-dimensional magnetic field distribution is required to achieve closed-loop motion adjustment. In human-computer interaction scenarios, rapid magnetic field perception is crucial for gesture command recognition and motion trajectory tracking. Wearable electronic devices place stringent requirements on the miniaturization, flexibility, and low interference resistance of sensors. As these fields develop towards higher precision, higher real-time performance, and greater integration, traditional single-axis or dual-axis magnetic field measurement can no longer meet the needs for acquiring full-dimensional magnetic field information. Developing three-axis magnetic field mapping technology that combines high sensitivity, rapid response, and a compact structure has become an urgent industry need.

[0003] Existing magnetic field measurement technologies are mainly divided into two categories: traditional sensors and fiber optic sensors. Traditional Hall effect sensors are widely used due to their small size, but they are susceptible to electromagnetic interference and suffer from temperature drift. Electromagnetic induction sensors, on the other hand, have drawbacks such as low sensitivity and slow response, making them unsuitable for dynamic magnetic field monitoring. Fiber optic sensors have become a research hotspot due to their strong anti-interference capabilities, small size, and ease of integration, with fiber optic interferometric sensors based on the magnetostrictive effect being particularly prominent. Existing triaxial fiber optic magnetic field measurement schemes mainly include two types: one is to orthogonally combine three independent single-axis fiber optic sensors and achieve three-dimensional measurement through multi-channel signal fusion; the other is to design integrated sensitive structures such as spirals and butterflies, utilizing magnetostrictive materials and the fiber optic interference principle to achieve multi-directional response.

[0004] However, existing technologies still have many key drawbacks: multi-single-axis sensor combination schemes are complex in structure and large in size, cumbersome in installation and debugging, and prone to cross-interference, affecting measurement accuracy; in integrated structures, the bonding between magnetostrictive material and optical fiber interface is not tight, resulting in low strain transfer efficiency and weak response in some magnetic field directions. At the same time, the anisotropy of a single sensing structure makes the three-axis magnetic field response uneven, making it impossible to achieve uniform sensing in all directions. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides a three-axis magnetic field mapping method and system based on magnetostrictive strain modulation fiber optic interferometry. The provided egg beater-shaped fiber optic sensing probe has a simple structure, strong anti-interference ability, high measurement accuracy, and high strain transfer efficiency. Combined with a three-axis component solution algorithm, it improves the accuracy and efficiency of three-dimensional mapping of the magnetic field.

[0006] This invention provides a method for triaxial magnetic field mapping based on magnetostrictive strain modulated fiber interferometry, the method comprising: A soft magnetic elastomer is prepared, and the soft magnetic elastomer is coated on the surface of a single-mode optical fiber to obtain a single-mode optical fiber with a soft magnetic elastomer coating. The single-mode optical fiber with a soft magnetic elastomer coating is structurally processed to form an egg beater-shaped optical fiber sensing probe. An optical sensing system is constructed, and the egg beater-shaped fiber optic sensing probe is placed in the magnetic field environment to be detected. The light signal emitted by the light source is detected based on the egg beater-shaped fiber optic sensing probe, and the transmission interference spectrum under different magnetic field strengths and magnetic field directions in the magnetic field environment to be detected is recorded by a spectral detection device. The wavelength valley offset of the resonant wavelength is extracted from the transmission interference spectrum, and the triaxial components of the magnetic field to be detected are calculated based on the preset correspondence between the wavelength valley offset and the magnetic field strength and magnetic field direction. The triaxial magnetic field is mapped based on the triaxial components of the magnetic field to be detected.

[0007] Furthermore, the preparation of the soft magnetic elastomer, which involves coating the soft magnetic elastomer onto the surface of a single-mode optical fiber to obtain a single-mode optical fiber with a soft magnetic elastomer coating, includes: Polydimethylsiloxane resin and curing agent are mixed in a mass ratio of 10:1 to obtain a polydimethylsiloxane mixture. The polydimethylsiloxane mixture was subjected to vacuum treatment for 20 minutes to obtain a uniformly mixed polydimethylsiloxane solution. Adding iron oxide nanoparticles to the polydimethylsiloxane solution and stirring thoroughly forms a soft magnetic elastomer, wherein the mass ratio of the iron oxide nanoparticles is 10%-50%. The soft magnetic elastomer is injected into a capillary tube, and the single-mode optical fiber is inserted and fixed inside the capillary tube. After heating and curing, the single-mode optical fiber with a soft magnetic elastomer coating is obtained after demolding.

[0008] Furthermore, the structural processing of the single-mode optical fiber with a soft magnetic elastomer coating to form a whisk-shaped optical fiber sensing probe includes: The two ends of the single-mode optical fiber with a soft magnetic elastomer coating are inserted into a glass tube, and the soft magnetic elastomer coating in the middle region of the single-mode optical fiber with a soft magnetic elastomer coating is peeled off. The near end of the partially coated single-mode fiber, the coated area, and the glass tube are fixed on three independent micro-positioning stages to form a quasi-spherical single-mode fiber. Two quasi-spherical single-mode optical fibers with identical structural parameters were fabricated. The spatial orientation of the two quasi-spherical single-mode optical fibers was adjusted so that their axes of symmetry were perpendicular to each other, and then they were mechanically fixed to form an orthogonal cascaded structure. After verifying the integrity of two orthogonally cascaded quasi-spherical single-mode optical fibers, an eggbeater-shaped optical fiber sensing probe was formed.

[0009] Furthermore, the construction of the optical sensing system includes: A tunable single-wavelength laser is selected as the light source, and the input end of the egg beater-shaped fiber optic sensing probe is connected to the output end of the light source through a fiber optic adapter. An optical spectrum analyzer was selected as the spectral detection device, and the output end of the egg beater-shaped fiber optic sensing probe was connected to the input end of the spectral detection device via a fiber optic adapter. After the setup is complete, the optical sensing system is calibrated.

[0010] Furthermore, the step of placing the whisk-shaped fiber optic sensing probe in the magnetic field environment to be detected, detecting the light signal emitted by the light source based on the whisk-shaped fiber optic sensing probe, and recording the transmission interference spectrum under different magnetic field strengths and directions in the magnetic field environment to be detected using a spectral detection device includes: The egg beater-shaped fiber optic sensor probe is fixed in the magnetic field area of ​​the magnetic field environment to be detected, so that the center of the egg beater-shaped fiber optic sensor probe coincides with the center of the magnetic field of the magnetic field environment to be detected. Excite the light source and adjust its operating wavelength to the preset range. The magnetic field strength of the magnetic field to be detected is adjusted so that the magnetic field strength is continuously adjustable within a preset range. Adjust the magnetic field direction of the magnetic field to be detected so that the magnetic field direction is continuously adjustable within a preset range; Dynamic response testing was performed on the adjusted magnetic field to be tested; Under each combination of magnetic field strength within the preset range of magnetic field strength and magnetic field direction within the preset range of magnetic field direction, the transmission interference spectrum corresponding to the magnetic field environment of the magnetic field under different combinations of magnetic field strength and magnetic field direction is recorded by a spectral detection device.

[0011] Furthermore, after recording the transmission interference spectra under different magnetic field strengths and directions in the magnetic field environment to be detected using a spectral detection device, the method further includes: The bending radius of the stripped coating area on the two quasi-spherical single-mode optical fibers in the egg beater-shaped optical fiber sensing probe is adjusted, and the transmission interference spectrum corresponding to different bending radii of the stripped coating area is recorded by a spectral detection device. When the transmission peak of the transmission interference spectrum corresponding to different bending radii of the stripped coating area reaches a preset threshold, the two quasi-spherical single-mode optical fibers are cured.

[0012] Furthermore, the wavelength valley shift for extracting the resonant wavelength from the transmission interference spectrum includes: The transmission interference spectrum is preprocessed to eliminate noise in the transmission interference spectrum; Identify the valley values ​​of two consecutive resonant wavelengths in the transmission interference spectrum and label them as the first valley value and the second valley value, respectively; The transmission interference spectrum under a magnetic field-free environment was retrieved, and the initial wavelengths corresponding to the first valley value and the second valley value were extracted. The transmission interference spectrum under each magnetic field environment is retrieved, and the actual wavelengths corresponding to the first valley value and the second valley value are extracted. Based on the initial wavelength and actual wavelength corresponding to the first valley value, and the initial wavelength and actual wavelength corresponding to the second valley value, the wavelength valley value offset corresponding to the first valley value and the wavelength valley value offset corresponding to the second valley value are calculated respectively.

[0013] Furthermore, the calculation of the triaxial components of the magnetic field to be detected based on the preset correspondence between the wavelength valley offset and the magnetic field strength and direction includes: The preset sensitivity parameters are used to calculate the detection limit for each magnetic field direction of the magnetic field to be detected; Substitute the wavelength valley offset corresponding to the first valley value and the wavelength valley offset corresponding to the second valley value into the sensitivity formula for the corresponding magnetic field direction to calculate the initial value of the magnetic field strength in each magnetic field direction. Based on the variation law of magnetic field direction and wavelength valley offset, the x, y, and z components of the magnetic field to be detected are calculated for the initial value of magnetic field strength in each magnetic field direction.

[0014] Furthermore, the mapping of the triaxial magnetic field based on the triaxial components of the magnetic field to be detected includes: Record the voltage response curve of the egg beater-shaped fiber optic sensor probe, and identify the initial response stage, quasi-equilibrium stage, and recovery stage in the voltage response curve; Based on the preset amplitude of the stable voltage value, the rise time and fall time in the x, y, and z axes are calculated, and the dynamic response time is obtained by analyzing the rise time and fall time in the x, y, and z axes. The three-axis components of the magnetic field to be detected are calibrated in the time dimension based on the dynamic response time. The three-axis magnetic field was mapped based on the three-axis components calibrated according to the time dimension.

[0015] This invention also provides a triaxial magnetic field mapping system based on magnetostrictive strain modulated fiber interferometry, the system being used to implement the above-mentioned triaxial magnetic field mapping method based on magnetostrictive strain modulated fiber interferometry, the system comprising: An optical fiber fabrication module is used to fabricate a soft magnetic elastomer, which is then coated onto the surface of a single-mode optical fiber to obtain a single-mode optical fiber with a soft magnetic elastomer coating. A sensor probe fabrication module is used to process the single-mode optical fiber with a soft magnetic elastomer coating to form an egg beater-shaped optical fiber sensor probe. A transmission interference spectroscopy detection module is used to build an optical sensing system. The egg beater-shaped fiber optic sensing probe is placed in the magnetic field environment to be detected. The light signal emitted by the light source is detected by the egg beater-shaped fiber optic sensing probe, and the transmission interference spectrum under different magnetic field strengths and directions in the magnetic field environment to be detected is recorded by a spectral detection device. The three-axis component calculation module is used to extract the wavelength valley offset of the resonant wavelength from the transmission interference spectrum, and calculate the three-axis components of the magnetic field to be detected based on the preset correspondence between the wavelength valley offset and the magnetic field strength and magnetic field direction. The three-axis magnetic field mapping module is used to complete the mapping of the three-axis magnetic field based on the three-axis components of the magnetic field to be detected.

[0016] This invention provides a triaxial magnetic field mapping method and system based on magnetostrictive strain modulated fiber optic interferometry. It employs a single-mode fiber coated with a soft magnetic elastomer, and through structural processing, forms a whisk-shaped fiber optic sensing probe composed of two orthogonally cascaded near-spherical single-mode fibers. The magnetostrictive strain material is tightly integrated with the fiber, resulting in a simple structure, strong anti-interference capability, and high strain transfer efficiency. Furthermore, it exhibits balanced triaxial response, achieving uniform sensing in all directions and ensuring comprehensive capture of three-dimensional magnetic field information. By adjusting the bending radius of the stripped coating area on the fiber and combining it with a curing process, the structural stability of the sensing probe is improved. A triaxial component calculation algorithm considering multiple factors such as the valley of the resonant wavelength, offset, sensitivity, and voltage response is used to address the resonant wavelength caused by residual stress, resulting in high calculation accuracy. This improves the accuracy and efficiency of three-dimensional magnetic field mapping, making it suitable for a wide range of scenarios and effectively filling the application gap in flexible, high-precision triaxial magnetic field mapping. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the triaxial magnetic field mapping method based on magnetostrictive strain modulation fiber interferometry in Embodiment 1 of the present invention; Figure 2 This is a flowchart of the preparation of a single-mode optical fiber with a soft magnetic elastomer coating in Embodiment 1 of the present invention; Figure 3 This is a flowchart illustrating the fabrication process of the egg beater-shaped fiber optic sensor probe structure in Embodiment 1 of the present invention. Figure 4 This is a schematic diagram of the egg beater-shaped fiber optic sensing probe structure in Embodiment 1 of the present invention; Figure 5 This is a flowchart of the construction of the optical sensing system in Embodiment 1 of the present invention; Figure 6 This is a flowchart of the transmission interference spectrum for detecting the magnetic field to be detected in Embodiment 1 of the present invention; Figure 7 This is a flowchart illustrating the extraction of wavelength valley offset of resonant wavelength in transmission interference spectrum as described in Embodiment 1 of the present invention; Figure 8 This is a flowchart of calculating the three-axis components of the magnetic field to be detected in Embodiment 1 of the present invention; Figure 9 This is a flowchart of the three-axis magnetic field mapping based on three-axis components in Embodiment 1 of the present invention; Figure 10 This is a diagram of the architecture of the three-axis magnetic field mapping system based on magnetostrictive strain modulation fiber interferometry in Embodiment 2 of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In this invention, it should be understood that terms such as “comprising” or “having” are intended to indicate the presence of features, figures, steps, behaviors, components, portions or combinations thereof disclosed in this specification, and are not intended to exclude the possibility that one or more other features, figures, steps, behaviors, components, portions or combinations thereof are present or added.

[0021] It should also be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] Example 1 Embodiment 1 of the present invention provides a method for triaxial magnetic field mapping based on magnetostrictive strain modulated fiber interferometry, the method comprising: A soft magnetic elastomer is prepared, and the soft magnetic elastomer is coated on the surface of a single-mode optical fiber to obtain a single-mode optical fiber with a soft magnetic elastomer coating. The single-mode optical fiber with a soft magnetic elastomer coating is structurally processed to form an egg beater-shaped optical fiber sensing probe. An optical sensing system is constructed, and the egg beater-shaped fiber optic sensing probe is placed in the magnetic field environment to be detected. The light signal emitted by the light source is detected based on the egg beater-shaped fiber optic sensing probe, and the transmission interference spectrum under different magnetic field strengths and magnetic field directions in the magnetic field environment to be detected is recorded by a spectral detection device. The wavelength valley offset of the resonant wavelength is extracted from the transmission interference spectrum, and the triaxial components of the magnetic field to be detected are calculated based on the preset correspondence between the wavelength valley offset and the magnetic field strength and magnetic field direction. The triaxial magnetic field is mapped based on the triaxial components of the magnetic field to be detected.

[0023] In one optional implementation of this embodiment, such as Figure 1 As shown, Figure 1 The flowchart of the triaxial magnetic field mapping method based on magnetostrictive strain modulation fiber interferometry in Embodiment 1 of the present invention is shown, including the following steps: S101. Prepare a soft magnetic elastomer, coat the soft magnetic elastomer onto the surface of a single-mode optical fiber, and obtain a single-mode optical fiber with a soft magnetic elastomer coating. In one optional implementation of this embodiment, a soft magnetic elastomer is prepared and coated onto the surface of a single-mode fiber to form a single-mode fiber with a soft magnetic elastomer coating, thereby achieving magnetostrictive strain modulation.

[0024] Specifically, such as Figure 2 As shown, Figure 2 The flowchart illustrating the fabrication of a single-mode optical fiber with a soft magnetic elastomer coating according to Embodiment 1 of the present invention is shown, including the following steps: S201. Mix polydimethylsiloxane resin and curing agent in a mass ratio of 10:1 to obtain polydimethylsiloxane mixture. In an optional implementation of this embodiment, it is necessary to ensure that the soft magnetic elastomer (SME) has suitable flexibility and controllable curing rate. Polydimethylsiloxane resin (PDMS) and curing agent are mixed in a mass ratio of 10:1 and the mixture is obtained by manual or mechanical stirring to obtain a polydimethylsiloxane mixture.

[0025] S202. The polydimethylsiloxane mixture is subjected to vacuum treatment for 20 minutes to obtain a uniformly mixed polydimethylsiloxane solution. In one optional implementation of this embodiment, the uniformly mixed polydimethylsiloxane mixture is subjected to vacuum treatment for 20 minutes. The vacuum environment eliminates bubbles and impurities in the mixture, making the solution highly uniform and reducing the generation of interface defects during subsequent coating processes.

[0026] Furthermore, vacuum treatment can be achieved using rotary vacuum drying equipment or static vacuum chambers.

[0027] S203. Add iron oxide nanoparticles to the polydimethylsiloxane solution and stir thoroughly to form a soft magnetic elastomer. The mass ratio of the iron oxide nanoparticles is 10%-50%. In an optional implementation of this embodiment, iron oxide nanoparticles are added to the polydimethylsiloxane solution formed after vacuum treatment, and then the solution is stirred thoroughly again to form a soft magnetic elastomer.

[0028] Furthermore, the iron oxide nanoparticles are magnetic metal nanoparticles with a mass ratio of 10%-50%. This concentration of iron oxide nanoparticles optimizes the balance between magnetostrictive strain response and mechanical properties, resulting in a soft magnetic elastomer with strong magnetostrictive strain performance, ensuring the effective generation and transmission of strain under the action of a magnetic field.

[0029] S204. Inject the soft magnetic elastomer into the capillary tube, insert and fix the single-mode optical fiber into the capillary tube, perform heat curing treatment, and obtain a single-mode optical fiber with a soft magnetic elastomer coating after demolding.

[0030] In one optional implementation of this embodiment, the soft magnetic elastomer is injected into a capillary tube, a single-mode optical fiber is inserted into a single capillary tube into which the soft magnetic elastomer has been injected, the mixture in the capillary tube is cured by heating, and a single-mode optical fiber with a soft magnetic elastomer coating is obtained after demolding.

[0031] Specifically, by using a capillary tube as a constraint mold to forcefully guide a soft magnetic elastomer to form a coating that is applied to a single-mode optical fiber, the coating uniformly wraps the surface of the single-mode optical fiber, forming a gapless and highly fitted coating structure.

[0032] Here, by precisely controlling the mass ratio of polydimethylsiloxane resin to curing agent, stable physicochemical properties of the elastomer matrix are ensured. Subsequent vacuum treatment effectively removes air bubbles from the mixture, laying the foundation for uniform coating. When adding iron oxide nanoparticles, their mass ratio is strictly limited to the range of 10%-50% to ensure sufficient magnetic response while maintaining the material's flexibility and interfacial adhesion. Finally, a capillary tube is used as a mold for heating and curing, forcing the soft magnetic elastomer to uniformly coat the fiber surface, achieving a tight molecular-level bond. This organic combination of process steps fundamentally solves the problem of loose bonding between the soft magnetic elastomer and the fiber, enabling efficient transmission of magnetostriction to the fiber. This ensures uniform sensing of the triaxial magnetic field in all directions, significantly improves the interfacial bonding strength between the soft magnetic elastomer and the fiber, effectively improves strain transmission efficiency, and makes the magnetic field response more uniform in all directions, thereby improving the reliability and accuracy of subsequent triaxial magnetic field mapping.

[0033] S102. The single-mode optical fiber with a soft magnetic elastomer coating is structurally processed to form an egg beater-shaped optical fiber sensing probe. In one optional implementation of this embodiment, such as Figure 3 As shown, Figure 3 The following is a flowchart illustrating the fabrication process of the egg beater-shaped fiber optic sensing probe structure according to Embodiment 1 of the present invention, including the following steps: S301. Insert both ends of the single-mode optical fiber with a soft magnetic elastomer coating into a glass tube, and peel off the soft magnetic elastomer coating in the middle region of the single-mode optical fiber. In an optional implementation of this embodiment, the two ends of the single-mode optical fiber with a soft magnetic elastomer coating are inserted into a glass tube, and the glass tube provides rigid support to fix the ends of the optical fiber, preventing displacement or damage to the ends of the optical fiber during processing.

[0034] Furthermore, taking the center point of the single-mode optical fiber with the soft magnetic elastomer coating as the diffusion point, the soft magnetic elastomer coating on the middle area enclosed by the same distance on both sides of the center point is stripped using an optical fiber stripper. The coating material in the middle section of the optical fiber is selectively removed to expose the surface of the optical fiber to form a magnetostrictive strain sensitive area, thereby avoiding interference of the residual coating with the optical signal.

[0035] S302. Fix the near end of the partially coated single-mode fiber, the coated area, and the glass tube on three independent micro-positioning stages to form a quasi-spherical single-mode fiber. In one optional implementation of this embodiment, the near end (i.e. the end closest to the light source), the midpoint of the stripped coating area (i.e. the area exposed on the fiber surface), and the glass tubes attached to both ends of the fiber are respectively fixed on three independent micro-positioning stages to form a quasi-spherical single-mode fiber.

[0036] S303. Prepare two quasi-spherical single-mode optical fibers with identical structural parameters, adjust the spatial orientation of the two quasi-spherical single-mode optical fibers so that their axes of symmetry are perpendicular to each other, and then mechanically fix them to form an orthogonal cascaded structure. In an optional implementation of this embodiment, steps S301 and S302 are repeated to prepare two quasi-spherical single-mode optical fibers with identical structural parameters, i.e., the stripped coating areas are completely overlapped. The spatial orientation of the two quasi-spherical single-mode optical fibers is adjusted by a micro-positioning stage to make their axes of symmetry perpendicular to each other, ensuring that the two sensing units are matched in geometry and material properties. After alignment, mechanical fixation is performed to lock the adjustment mechanism of the micro-positioning stage, and the two quasi-spherical single-mode optical fibers are cascaded to form an orthogonal cascaded structure composed of two quasi-spherical single-mode optical fibers.

[0037] S304. After verifying the integrity of two single-mode optical fibers forming an orthogonal cascaded spherical structure, an egg beater-shaped optical fiber sensing probe is formed.

[0038] In one optional implementation of this embodiment, after performing integrity verification on two single-mode optical fibers forming an orthogonal cascaded spherical structure, including but not limited to integrity verification processes such as structure, transmission spectrum signal-to-noise ratio, or clarity of interference fringes, a complete eggbeater-shaped optical fiber sensing probe is formed.

[0039] Here, a collaborative design is established by inserting both ends of a single-mode optical fiber with a soft magnetic elastomer coating into a glass tube and peeling off the middle coating. This design, featuring rigid support at both ends and exposure of the sensitive area in the middle, precisely limits the strain range and improves the magnetostrictive strain transfer efficiency. Subsequently, relevant components are fixed on three independent micro-positioning stages to form a quasi-spherical structure. Based on the principle of multi-point independent control, the bending shape of the optical fiber is precisely calibrated, ensuring the high symmetry of the quasi-spherical structure. Next, two quasi-spherical structures with identical parameters are fabricated and fixed after being adjusted so that their axes of symmetry are perpendicular to each other. Through parameter consistency and strict alignment of spatial orientation, the two sensing units respond independently along their respective sensitive axes without directional coupling. Finally, integrity verification is performed to confirm the functional integrity of the orthogonal cascaded structure. These steps are executed sequentially and are interconnected, jointly ensuring the balance and reliability of the eggbeater-shaped optical fiber sensing probe in triaxial magnetic field measurement. This effectively solves the problems of insufficient stability of the quasi-spherical structure and lack of accuracy in orthogonal cascade, achieving balance and measurement reliability in the triaxial magnetic field response and avoiding cross-interference.

[0040] In one optional implementation of this embodiment, such as Figure 4 As shown, Figure 4 A schematic diagram of the egg beater-shaped fiber optic sensing probe structure in Embodiment 1 of the present invention is shown. The egg beater-shaped fiber optic sensing probe includes a first type of spherical single-mode fiber 1 and a second type of spherical single-mode fiber 2 arranged in orthogonal cascade. Both ends of the first type of spherical single-mode fiber 1 and both ends of the second type of spherical single-mode fiber 2 are inserted into the glass tube 3 and fixed by the glass tube 3.

[0041] S103. Build an optical sensing system, place the egg beater-shaped fiber optic sensing probe in the magnetic field environment to be detected, detect the light signal emitted by the light source based on the egg beater-shaped fiber optic sensing probe, and record the transmission interference spectrum under different magnetic field strengths and magnetic field directions in the magnetic field environment to be detected through a spectral detection device. In one optional implementation of this embodiment, an optical sensing system consisting of a light source, a sensing probe, and a spectral detection device is constructed to detect the magnetic field environment to be detected.

[0042] Specifically, such as Figure 5 As shown, Figure 5 The flowchart of building an optical sensing system according to Embodiment 1 of the present invention is shown, including the following steps: S401. Select an adjustable single-wavelength laser as the light source, and connect the input end of the egg beater-shaped fiber optic sensing probe to the output end of the light source through a fiber optic adapter. In one optional implementation of this embodiment, a laser source capable of outputting a single wavelength and with tunable wavelength is selected as the light source in this embodiment. A semiconductor laser, fiber laser, or external cavity laser can be used to provide a stable and tunable monochromatic light signal, avoiding the interference fringe blurring problem caused by multi-wavelength light sources, and ensuring the clarity and repeatability of the transmission interference spectrum.

[0043] S402. Select an optical spectrum analyzer as the spectral detection device, and connect the output end of the egg beater-shaped fiber optic sensor probe to the input end of the spectral detection device through a fiber optic adapter. In one optional implementation of this embodiment, the optical spectrum analyzer refers to a detection device capable of measuring spectral characteristics at high resolution. Specifically, it can be a grating scanning spectrometer or a Fourier transform spectrometer, which accurately captures subtle changes in the transmission interference spectrum and provides a high-fidelity data basis for the subsequent extraction of wavelength valley offset.

[0044] S403. After the setup is complete, calibrate the optical sensing system.

[0045] In one optional implementation of this embodiment, after connecting the light source, the spectral detection device, and the whisk-shaped fiber optic sensing probe, the completed optical sensing system is calibrated.

[0046] Specifically, standard wavelength light source calibration or zero magnetic field environment calibration can be used to eliminate optical path differences and equipment drift caused by setup accuracy issues, and establish a reliable measurement benchmark.

[0047] Here, a stable monochromatic light signal is provided by a tunable single-wavelength laser, avoiding interference fringe blurring caused by multi-wavelength interference. A fiber optic adapter is used to achieve precise connection between the whisk-shaped fiber optic sensing probe and the light source and spectral detection equipment, ensuring low-loss coupling of the optical signal during transmission. An optical spectrum analyzer is used to perform high-resolution detection of the transmission interference spectrum, accurately capturing subtle spectral changes. Finally, a unified reference standard is established through system calibration to eliminate inherent equipment drift. These components work together to construct a stable optical signal detection path, forming a closed-loop optimized system of light source output, signal transmission, and spectral detection. This effectively suppresses noise and signal drift in the transmission interference spectrum, significantly reducing noise levels and signal drift, and improving the accuracy of wavelength valley offset extraction. This ensures the accuracy of magnetic field strength and direction calculations, providing a reliable data foundation for triaxial magnetic field mapping.

[0048] In one optional implementation of this embodiment, such as Figure 6 As shown, Figure 6 The flowchart of detecting the transmission interference spectrum of the magnetic field to be detected in Embodiment 1 of the present invention is shown, including the following steps: S501. Fix the egg beater-shaped fiber optic sensor probe in the magnetic field area of ​​the magnetic field environment to be detected, so that the center of the egg beater-shaped fiber optic sensor probe coincides with the center of the magnetic field of the magnetic field environment to be detected. In an optional implementation of this embodiment, the whisk-shaped fiber optic sensor probe is fixed within the magnetic field area of ​​the magnetic field environment to be detected, so that the center of the whisk-shaped fiber optic sensor probe coincides with the center of the magnetic field of the magnetic field environment to be detected, thereby ensuring the detection accuracy of the sensor probe.

[0049] S502. Excite the light source to adjust its operating wavelength to the preset range. In one optional implementation of this embodiment, the light source is excited so that the operating wavelength of the light source is adjusted to a preset range.

[0050] Specifically, in this embodiment, the preset range of the working band is set between 1450nm and 1650nm.

[0051] S503. Adjust the magnetic field strength of the magnetic field to be detected so that the magnetic field strength is continuously adjustable within a preset range. In one optional implementation of this embodiment, the control parameters of the electromagnet that forms the magnetic field to be detected are adjusted so that the strength of the formed magnetic field is continuously adjustable within a preset range.

[0052] Specifically, in this embodiment, the adjustment step size of the preset range of magnetic field strength is set to 10mT.

[0053] S504. Adjust the magnetic field direction of the magnetic field to be detected so that the magnetic field direction is continuously adjustable within a preset range. In one optional implementation of this embodiment, the control parameters of the electromagnet that forms the magnetic field to be detected are adjusted so that the direction of the magnetic field is cyclically adjusted in steps of 30° within the range of 0°-360°, and covers the three planes XY, YZ, and ZX.

[0054] S505. Perform dynamic response testing on the adjusted magnetic field to be tested; In one optional implementation of this embodiment, dynamic response tests are performed on the magnetic field to be detected with different magnetic field strengths and directions after adjustment, to evaluate the sensor's response capability when the magnetic field changes rapidly. This may include step response or frequency response test methods, with the aim of verifying the real-time performance reliability of the system in a dynamic magnetic field environment.

[0055] S506. Under each combination of magnetic field strength within the preset range of magnetic field strength and magnetic field direction within the preset range of magnetic field direction of the magnetic field to be detected, the transmission interference spectrum corresponding to the magnetic field environment under different combinations of magnetic field strength and magnetic field direction of the magnetic field to be detected is recorded by a spectral detection device.

[0056] In an optional implementation of this embodiment, for the magnetic field to be detected, the transmission interference spectra corresponding to the magnetic field environments under different combinations of magnetic field strength and magnetic field direction in steps S503 and S504 are recorded by a spectral detection device.

[0057] This method precisely aligns the whisk-shaped fiber optic sensor probe with the center of the magnetic field, eliminating measurement benchmark inaccuracies caused by positional deviations. It optimizes the light source's operating wavelength to match the sensor's optical characteristics, improving the quality of optical signal detection. The system continuously adjusts the magnetic field strength and direction, covering all possible combinations of magnetic field states to avoid missing critical response ranges in discrete point measurements. Dynamic response testing verifies the system's reliability under rapidly changing magnetic fields. Transmission interference spectra are recorded at each combination of magnetic field strength and direction, comprehensively capturing spectral response data under different conditions. This systematic measurement process, through the organic coordination of each step, ensures precise control of magnetic field measurement conditions and data integrity. It effectively solves the problem of uneven three-axis magnetic field response, achieving precise probe alignment, optimized light source operating wavelength, and continuous adjustment of magnetic field strength and direction. This effectively addresses the uneven three-axis magnetic field response caused by positional deviations, light source mismatch, and discontinuous adjustments, thus improving the accuracy of magnetic field mapping.

[0058] In an optional implementation of this embodiment, after recording the transmission interference spectra under different magnetic field strengths and directions in the magnetic field environment to be detected using a spectral detection device, the method further includes: The bending radius of the stripped coating area on the two quasi-spherical single-mode optical fibers in the egg beater-shaped optical fiber sensing probe is adjusted, and the transmission interference spectrum corresponding to different bending radii of the stripped coating area is recorded by a spectral detection device. When the transmission peak of the transmission interference spectrum corresponding to different bending radii of the stripped coating area reaches a preset threshold, the two quasi-spherical single-mode optical fibers are cured.

[0059] Specifically, by fixing three micro-positioning stages on the quasi-spherical single-mode optical fiber, the bending radius of the stripped coating area on the two quasi-spherical single-mode optical fibers in the eggbeater-shaped optical fiber sensing probe is adjusted. This is the radius of curvature of the fiber in the stripped coating area. The transmission interference spectra corresponding to different bending radii in the stripped coating area are recorded using a spectral detection device. The purpose is to explore the optimal optical path through physical deformation to avoid response blind spots. The preset threshold can be understood as the critical optimization point of the transmission peak intensity, which can be set based on the spectral signal-to-noise ratio or peak stability. The purpose is to determine the curing timing based on actual spectral feedback rather than empirical parameters. In practical applications, curing refers to the process of fixing the quasi-spherical structure in its optimal geometric shape. This can be achieved using ultraviolet curing or thermal curing methods, with the aim of locking the geometry of the orthogonal cascaded structure to maintain the continuity of strain transfer.

[0060] Furthermore, when the desired transmission peak is reached, UV adhesive is introduced into the glass tubes at both ends of the single-mode fiber, and the structure is cured under ultraviolet light.

[0061] First, after recording the magnetic field response spectrum, the bending radius of the peeled coating area is dynamically adjusted. By altering the fiber interference effect through physical deformation, the optical performance under different geometric parameters is explored. Simultaneously, the transmission interference spectra corresponding to different bending radii are recorded in real time to establish a dynamic correlation between bending geometric parameters and spectral characteristics, providing traceable data support for performance optimization. When the transmission peak reaches a preset threshold, it indicates that the transmission efficiency has reached the critical optimization point. At this point, the quasi-spherical structure is solidified to lock the geometry of the orthogonal cascaded structure, ensuring the continuity and consistency of strain transmission under the action of the magnetic field, thereby ensuring the accuracy of the triaxial component calculation. This effectively avoids the anisotropy problem caused by the fixed bending radius, enabling the egg beater-shaped fiber optic sensing probe to maintain high sensitivity in omnidirectional magnetic field sensing and ensuring the accuracy of the triaxial magnetic field component calculation.

[0062] S104. Extract the wavelength valley offset of the resonant wavelength from the transmission interference spectrum, and calculate the triaxial components of the magnetic field to be detected based on the preset correspondence between the wavelength valley offset and the magnetic field strength and magnetic field direction. In an optional implementation of this embodiment, the interference mechanism of the whisk-shaped fiber optic sensing probe is analyzed. The internal interference is caused by the change in refractive index distribution due to the bending of the fiber. When the fiber bends, a portion of the core light leaks into the cladding, generating interference. The refractive index distribution along the x-direction (i.e., parallel to the bend in the fiber) is shown by the following formula:

[0063] In the formula, This represents the distance parallel to the axis at the bend in the optical fiber. It is the bending radius of the area on the optical fiber where the coating has been stripped. and These represent the refractive index distributions of straight and curved optical fibers, respectively.

[0064] Furthermore, by employing an equivalent transformation, the quasi-spherical single-mode fiber is converted into an equivalent straight fiber. When light propagates through the curved region, the core mode and the cladding mode will couple, forming an interference pattern similar to that of a Mach-Zehnder interferometer.

[0065] In an optional implementation of this embodiment, the transmission intensity for a single quasi-spherical single-mode fiber is expressed as:

[0066]

[0067] In the formula, The light intensity in the core mode. The light intensity in cladding mode. It is the phase difference between the core mode and the cladding mode. For effective bending length, The refractive index difference between the core mode and the cladding mode. This is the operating wavelength.

[0068] Destructive interference occurs when the phase difference satisfies the following conditions:

[0069] when At that time, the resonant wavelength The calculation formula is:

[0070] When a quasi-spherical single-mode optical fiber deforms, the refractive index difference... Changes occur, altering the transmittance and causing a shift in the output spectrum. When two quasi-spherical single-mode optical fibers are orthogonally cascaded to form a whisk-shaped fiber optic sensing probe, the transmittance is expressed as:

[0071]

[0072]

[0073]

[0074]

[0075] In the formula, This represents the core mode light intensity of the first quasi-spherical single-mode fiber. This represents the cladding mode intensity of the first quasi-spherical single-mode fiber. This represents the core mode light intensity of the second quasi-spherical single-mode fiber. This represents the light intensity of the cladding mode in the second quasi-spherical single-mode fiber. This represents the phase difference between the core mode and the cladding mode in the first quasi-spherical single-mode fiber. This represents the phase difference between the core mode and the cladding mode of the second quasi-spherical single-mode fiber.

[0076] Furthermore, when two quasi-spherical single-mode optical fibers are orthogonally cascaded to form a whisk-shaped optical fiber sensing probe, it is equipped with a symmetry axis aligned with the z-axis. The iron oxide nanoparticles in the whisk-shaped optical fiber sensing probe are magnetized along the z-axis, causing deformation. The two cascaded quasi-spherical single-mode optical fibers effectively compensate for the limited magnetic field response observed in three directions by a single quasi-spherical single-mode optical fiber. The three-axis response is balanced, achieving uniform sensing in all directions and ensuring comprehensive capture of three-dimensional magnetic field information.

[0077] In one optional implementation of this embodiment, such as Figure 7 As shown, Figure 7 The flowchart illustrating the extraction of wavelength valley shift in a transmission interference spectrum according to Embodiment 1 of the present invention is shown, including the following steps: S601. Preprocess the transmission interference spectrum to eliminate noise in the transmission interference spectrum; In an optional implementation of this embodiment, wavelet transform filtering or moving average filtering is used to preprocess the transmission interference spectrum and eliminate noise in the transmission interference spectrum.

[0078] S602. Identify the valley values ​​of two consecutive resonant wavelengths in the transmission interference spectrum and label them as the first valley value and the second valley value, respectively. In an optional implementation of this embodiment, the positions of adjacent valleys in the transmission interference spectrum are identified, and the valley values ​​of the resonant wavelengths corresponding to these two consecutive valleys are extracted and marked as the first valley value and the second valley value, respectively.

[0079] S603. Retrieve the transmission interference spectrum under a magnetic field-free environment, and extract the initial wavelength corresponding to the first valley value and the initial wavelength corresponding to the second valley value; In one optional implementation of this embodiment, reference data is acquired in a magnetic field-free environment, including the initial wavelength corresponding to the first valley value and the initial wavelength corresponding to the second valley value.

[0080] S604. Retrieve the transmission interference spectrum under each magnetic field environment, and extract the actual wavelength corresponding to the first valley value and the actual wavelength corresponding to the second valley value; In one optional implementation of this embodiment, transmission interference spectra are retrieved for combinations of different magnetic field strengths and directions. Several data points are selected, and the actual wavelengths corresponding to the first valley value and the second valley value in the corresponding transmission interference spectra are extracted.

[0081] S605. Based on the initial wavelength and actual wavelength corresponding to the first valley value, and the initial wavelength and actual wavelength corresponding to the second valley value, calculate the wavelength valley value offset corresponding to the first valley value and the wavelength valley value offset corresponding to the second valley value, respectively.

[0082] In an optional implementation of this embodiment, the difference between the initial wavelength and the actual wavelength corresponding to the first valley value, and the difference between the initial wavelength and the actual wavelength corresponding to the second valley value are calculated to obtain the wavelength valley value offset corresponding to the first valley value and the wavelength valley value offset corresponding to the second valley value.

[0083] Specifically, the scheme in this application eliminates random noise through a preprocessing step to ensure that valley value identification is not interfered with. Based on this, two consecutive valley values ​​are identified and labeled as the first and second valley values, and cross-validation is performed using the relative stability of adjacent valley values. Further, the initial wavelength is extracted from the transmission interference spectrum under a magnetic field-free environment, using the zero magnetic field state as an absolute reference to eliminate zero-point drift. Simultaneously, the actual wavelength is extracted from the transmission interference spectrum under a magnetic field environment, establishing a dynamic correlation between the magnetic field effect and wavelength change. Finally, the wavelength valley value offset is calculated independently based on the two valley values, and the cumulative deviation introduced by single calculation is avoided through cross-verification of dual-channel data. Each step is executed sequentially and closely linked to form a complete wavelength offset extraction process, ensuring the accuracy and robustness of the offset calculation, effectively solving the problem of valley value ambiguity caused by noise interference, and improving the accuracy and reliability of triaxial magnetic field mapping.

[0084] In one optional implementation of this embodiment, such as Figure 8 As shown, Figure 8 The flowchart illustrating the calculation of the three-axis components of the magnetic field to be detected in Embodiment 1 of the present invention is shown, including the following steps: S701. Call the preset sensitivity parameters to calculate the detection limit of each magnetic field direction of the magnetic field to be detected; In an optional implementation of this embodiment, the sensitivity in the x-direction corresponding to the first valley value is set to -50 pm / mT, the sensitivity in the y-direction corresponding to the first valley value is set to 24.8 pm / mT, and the sensitivity in the z-direction corresponding to the first valley value is set to 242.1 pm / mT. The sensitivity in the x-direction corresponding to the second valley value is set to -4.8 pm / mT, the sensitivity in the y-direction corresponding to the second valley value is set to -41.8 pm / mT, and the sensitivity in the z-direction corresponding to the second valley value is set to 147.5 pm / mT.

[0085] Furthermore, based on the minimum resolution and sensitivity of the aforementioned spectral detection device, the minimum resolution achievable by the egg beater-shaped fiber optic sensing probe is determined as follows:

[0086] In the formula, This represents the minimum resolution of the spectral detection equipment. Sensitivity.

[0087] The detection limit of the magnetic field in each direction of the magnetic field to be detected is evaluated using the minimum resolution achievable by the egg beater-shaped fiber optic sensing probe.

[0088] S702. Substitute the wavelength valley offset corresponding to the first valley value and the wavelength valley offset corresponding to the second valley value into the sensitivity formula for the corresponding magnetic field direction to calculate the initial value of the magnetic field strength in each magnetic field direction. In an optional implementation of this embodiment, the wavelength valley offset corresponding to the first valley value and the wavelength valley offset corresponding to the second valley value are substituted into the sensitivity formula for the corresponding magnetic field direction to calculate the initial value of the magnetic field strength in each magnetic field direction.

[0089] S703. Based on the variation law of magnetic field direction and wavelength valley offset, calculate the x, y, and z axis components of the magnetic field to be detected for the initial value of magnetic field strength in each magnetic field direction.

[0090] In one optional implementation of this embodiment, the x, y, and z-axis components of the magnetic field to be detected are calculated by combining the functional relationship between the wavelength valley offset and the magnetic field direction, and the initial values ​​of the magnetic field strength in each magnetic field direction.

[0091] This process first determines the detection limits for each magnetic field direction by calling preset sensitivity parameters, ensuring calculations are performed only within the effective measurement range. Then, the initial magnetic field strength is calculated by substituting the dual-valley offsets into the direction-dependent sensitivity formula, effectively compensating for the differences in strain transfer efficiency of the soft magnetic elastomer in different directions. Finally, the initial value is solved by combining the law of offset variation with magnetic field direction, and the coupling effect between the components of each axis is corrected through a mathematical model, thus achieving accurate separation of the three-axis magnetic field components. This process is based on the independent response characteristics of two resonant wavelengths in fiber optic interferometry. By applying the direction-dependent sensitivity formula, the accuracy of the initial value calculation is significantly improved. Furthermore, the nonlinear characteristics of the offset variation with the magnetic field direction are analyzed in depth, ultimately achieving accurate calculation of the x, y, and z-axis components. This effectively overcomes the problem of unbalanced three-axis magnetic field response caused by the anisotropy of the soft magnetic elastomer coating, achieving high-precision three-axis magnetic field component calculation and significantly improving the accuracy of magnetic field mapping.

[0092] S105. Based on the three-axis components of the magnetic field to be detected, the three-axis magnetic field is mapped.

[0093] In one optional implementation of this embodiment, such as Figure 9 As shown, Figure 9 The flowchart of triaxial magnetic field mapping based on triaxial components in Embodiment 1 of the present invention is shown, including the following steps: S801. Record the voltage response curve of the egg beater-shaped fiber optic sensor probe, and identify the initial response stage, quasi-equilibrium stage and recovery stage in the voltage response curve. In an optional implementation of this embodiment, during actual testing, the voltage response curve of the whisk-shaped fiber optic sensing probe exhibits a continuous periodic voltage response in the x, y, and z directions, with a peak-to-peak voltage difference. As the voltage amplitude increases, the soft magnetic elastomer coating deviates from the fixed capillary, leading to an increase in the diameter displacement of the spherical fiber structure, with the z-direction showing the highest response amplitude. Furthermore, an abnormal increase in the response voltage is observed during voltage drops, which may be attributed to the hysteresis effect of the structure.

[0094] Furthermore, the magnetic response of the whisk-shaped fiber optic sensing probe comprises three stages: an initial response stage, a quasi-equilibrium stage, and a recovery stage. The initial response stage is characterized by the soft magnetic elastomer coating deflecting outward and rapidly displacing upon magnetic field activation. Subsequently, due to the balance between magnetic tensile force and elastic resistance, the displacement gradually saturates, entering the quasi-equilibrium stage. A slow, ramp-like curve is observed before reaching the final stable stage, which may be due to the hysteresis or viscoelastic properties of the soft magnetic elastomer coating. Once the magnetic field is deactivated, the soft magnetic elastomer coating rapidly returns to its initial position.

[0095] S802. Based on the preset amplitude of the stable voltage value, calculate the rise time and fall time in the x, y, and z axes, and analyze and obtain the dynamic response time based on the rise time and fall time in the x, y, and z axes. In one optional implementation of this embodiment, the rise time and fall time in the x, y, and z axes are calculated based on 10% and 90% amplitudes of the stable voltage value, and the dynamic response time is obtained by analyzing the rise time and fall time in the x, y, and z axes.

[0096] Specifically, the rise time refers to the time required for the voltage to reach a preset stable value from its initial value. It can be calculated based on the timestamp of the voltage signal, with the aim of quantifying the sensor's response speed to an increase in magnetic field. The fall time refers to the time required for the voltage to recover from its stable value to the preset initial value. It is also calculated using timestamps, with the aim of quantifying the sensor's recovery characteristics to a decrease in magnetic field. The dynamic response time is a parameter that comprehensively characterizes the sensor's response characteristics in three axes. It can be obtained by weighted averaging or maximum value analysis of the rise and fall times of the x, y, and z axes, with the aim of uniformly quantifying the differences in response across axes.

[0097] S803. Based on the dynamic response time, perform time dimension calibration on the three-axis components of the magnetic field to be detected; In one optional implementation of this embodiment, the three-axis components of the magnetic field to be detected are time-series adjusted based on the dynamic response time. Calibration can be achieved through a time offset compensation algorithm to eliminate data asynchrony caused by different response speeds of each axis.

[0098] S804. The three-axis magnetic field is mapped based on the three-axis components after time-dimensional calibration.

[0099] First, the initial response phase, quasi-equilibrium phase, and recovery phase are identified by recording the voltage response curve, providing key timing anchors for quantifying the response timing. Then, the rise and fall times of each axis are calculated based on a preset amplitude of the stable voltage value, using the preset amplitude as a unified benchmark to ensure the accuracy of parameter calculations. Next, the dynamic response time is obtained by analyzing the rise and fall times of each axis, comprehensively characterizing the sensor's response characteristics in different directions. Based on this, the dynamic response time is used as a compensation parameter to align the original three-axis components, eliminating data asynchrony caused by uneven response speeds across axes. Finally, mapping is completed based on the calibrated three-axis components, ensuring the results strictly correspond to the true instantaneous state of the magnetic field. This process, through a closed-loop mechanism of dynamic characteristic capture, parameter quantization, and data correction, achieves accurate restoration of the time dimension, effectively eliminating the time misalignment problem caused by differences in the response speeds of the whisk-shaped fiber optic sensor probe across axes. This allows the three-axis magnetic field mapping results to accurately reflect the instantaneous state of the magnetic field, significantly improving the real-time performance and reliability of measurements, especially in scenarios with rapidly changing magnetic fields.

[0100] In summary, Embodiment 1 of this invention provides a three-axis magnetic field mapping method based on magnetostrictive strain modulation fiber interferometry. It employs a single-mode fiber coated with a soft magnetic elastomer, and through structural processing, forms a whisk-shaped fiber optic sensing probe composed of two orthogonally cascaded near-spherical single-mode fibers. The magnetostrictive strain material is tightly integrated with the fiber, resulting in a simple structure, strong anti-interference capability, and high strain transfer efficiency. Furthermore, the three-axis response is balanced, achieving uniform sensing in all directions and ensuring comprehensive capture of three-dimensional magnetic field information. By adjusting the bending radius of the stripped coating area on the fiber and combining it with a curing process, the structural stability of the sensing probe is improved. In addition, a three-axis component calculation algorithm considering multiple factors such as the valley of the resonant wavelength, offset, sensitivity, and voltage response is used to address the resonant wavelength caused by residual stress, resulting in high calculation accuracy. This improves the accuracy and efficiency of three-dimensional magnetic field mapping, and is applicable to a wide range of scenarios, effectively filling the application gap of existing technologies in flexible, high-precision three-axis magnetic field mapping.

[0101] Example 2 Embodiment 2 of the present invention provides a triaxial magnetic field mapping system based on magnetostrictive strain modulation fiber interferometry. The system is used to implement the triaxial magnetic field mapping method based on magnetostrictive strain modulation fiber interferometry described in Embodiment 1. The system includes an optical fiber fabrication module, a sensor probe fabrication module, a transmission interferometry spectroscopy detection module, a triaxial component calculation module, and a triaxial magnetic field mapping module.

[0102] In one optional implementation of this embodiment, such as Figure 10 As shown, Figure 10The diagram shows the architecture of a triaxial magnetic field mapping system based on magnetostrictive strain modulation fiber interferometry according to Embodiment 2 of the present invention, which includes the following modules: The optical fiber fabrication module 10 is used to fabricate a soft magnetic elastomer, coat the soft magnetic elastomer onto the surface of a single-mode optical fiber, and obtain a single-mode optical fiber with a soft magnetic elastomer coating. The sensing probe fabrication module 20 is used to process the single-mode optical fiber with a soft magnetic elastomer coating to form an egg beater-shaped optical fiber sensing probe. Transmission interference spectroscopy detection module 30 is used to build an optical sensing system. The egg beater-shaped fiber optic sensing probe is placed in the magnetic field environment to be detected. The light signal emitted by the light source is detected by the egg beater-shaped fiber optic sensing probe, and the transmission interference spectrum under different magnetic field strengths and magnetic field directions in the magnetic field environment to be detected is recorded by the spectral detection device. The triaxial component calculation module 40 is used to extract the wavelength valley offset of the resonant wavelength from the transmission interference spectrum, and calculate the triaxial components of the magnetic field to be detected based on the preset correspondence between the wavelength valley offset and the magnetic field strength and magnetic field direction. The triaxial magnetic field mapping module 50 is used to complete the mapping of the triaxial magnetic field based on the triaxial components of the magnetic field to be detected.

[0103] In summary, Embodiment 2 of this invention provides a triaxial magnetic field mapping system based on magnetostrictive strain modulated fiber optic interferometry. This system implements the triaxial magnetic field mapping method based on magnetostrictive strain modulated fiber optic interferometry described in Embodiment 1. It employs a single-mode fiber coated with a soft magnetic elastomer and processes it to form a whisk-shaped fiber optic sensing probe composed of two orthogonally cascaded near-spherical single-mode fibers. The magnetostrictive material is tightly bonded to the fiber, resulting in a simple structure, strong anti-interference capability, and high strain transfer efficiency. Furthermore, the system exhibits balanced triaxial response, achieving uniform sensing in all directions and ensuring comprehensive capture of three-dimensional magnetic field information. By adjusting the bending radius of the stripped coating area on the fiber and combining it with a curing process, the structural stability of the sensing probe is improved. A triaxial component calculation algorithm considering multiple factors such as the valley of the resonant wavelength, offset, sensitivity, and voltage response is used to address the resonant wavelength caused by residual stress, resulting in high calculation accuracy and improved accuracy and efficiency of three-dimensional magnetic field mapping. This system is applicable to a wide range of scenarios and effectively fills the application gap in flexible, high-precision triaxial magnetic field mapping.

[0104] The above provides a detailed description of a triaxial magnetic field mapping method and system based on magnetostrictive strain modulation fiber interferometry provided by the present invention. Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, which may include: read-only memory (ROM), random access memory (RAM), disk or optical disk, etc.

[0105] Furthermore, the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for mapping a three-axis magnetic field based on magnetostrictive modulation of an optical fiber interferometer, characterized in that, The method comprises: Preparation of soft magnetic elastomer, coating the soft magnetic elastomer on the surface of a single-mode optical fiber, and obtaining a single-mode optical fiber with a soft magnetic elastomer coating; Structural processing of the single-mode optical fiber with the soft magnetic elastomer coating to form a whisk-like optical fiber sensing probe; Building an optical sensing system, placing the whisk-like optical fiber sensing probe in a magnetic field environment to be detected, detecting the light signal emitted by the whisk-like optical fiber sensing probe, and recording the transmission interference spectrum under different magnetic field strengths and directions in the magnetic field environment to be detected through a spectrum detection device; Extracting the wavelength valley value offset of the resonance wavelength from the transmission interference spectrum, and calculating the three-axis components of the magnetic field to be detected based on the preset correspondence between the wavelength valley value offset and the magnetic field strength and direction; Mapping the three-axis magnetic field based on the three-axis components of the magnetic field to be detected.

2. The method of claim 1, wherein the magnetostrictive modulation fiber-optic interferometer is a fiber Bragg grating (FBG) sensor. The preparation of the soft magnetic elastomer, coating the soft magnetic elastomer on the surface of a single-mode optical fiber, and obtaining a single-mode optical fiber with a soft magnetic elastomer coating comprises: Mixing polydimethylsiloxane resin and curing agent at a mass ratio of 10:1 to obtain a polydimethylsiloxane mixture; Vacuum treatment of the polydimethylsiloxane mixture for 20 minutes to obtain a uniformly mixed polydimethylsiloxane solution; Adding ferriferrous oxide nanoparticles to the polydimethylsiloxane solution, and forming a soft magnetic elastomer after sufficient stirring, the mass ratio of the ferriferrous oxide nanoparticles being 10%-50%; Injecting the soft magnetic elastomer into a capillary tube, inserting the single-mode optical fiber into the capillary tube, and performing heating and curing treatment to obtain a single-mode optical fiber with a soft magnetic elastomer coating.

3. The method of claim 1, wherein the magnetostrictive modulation fiber optic interferometer is a fiber Bragg grating (FBG) sensor. The structural processing of the single-mode optical fiber with the soft magnetic elastomer coating to form a whisk-like optical fiber sensing probe comprises: Inserting both ends of the single-mode optical fiber with the soft magnetic elastomer coating into a glass tube, and stripping the soft magnetic elastomer coating from the middle region of the single-mode optical fiber with the soft magnetic elastomer coating; Fixing the proximal end of the single-mode optical fiber with the stripped coating, the stripped coating region, and the glass tube on three independent micro-positioning stages to form a spherical structure single-mode optical fiber; Preparing two spherical structure single-mode optical fibers with consistent structural parameters, adjusting the spatial attitude of the two spherical structure single-mode optical fibers so that their symmetry axes are perpendicular to each other, and mechanically fixing them to form an orthogonal cascade structure; After verifying the integrity of the two spherical structure single-mode optical fibers forming the orthogonal cascade structure, a whisk-like optical fiber sensing probe is formed.

4. The method of claim 1, wherein the magnetostrictive modulation fiber optic interferometer is a fiber Bragg grating (FBG) sensor. The building of the optical sensing system comprises: Selecting an adjustable single-wavelength laser as a light source, and connecting the input end of the whisk-like optical fiber sensing probe and the output end of the light source through a fiber adapter; Selecting an optical spectrum analyzer as a spectrum detection device, and connecting the output end of the whisk-like optical fiber sensing probe and the input end of the spectrum detection device through a fiber adapter; After the completion of the building, calibrate the optical sensing system.

5. The method of claim 1, wherein the magnetostrictive modulation fiber-optic interferometer is a fiber Bragg grating (FBG) sensor. The beater-shaped optical fiber sensing probe is placed in a magnetic field environment to be detected, a light signal emitted by a light source is detected based on the beater-shaped optical fiber sensing probe, and a transmission interference spectrum under different magnetic field strengths and magnetic field directions in the magnetic field environment to be detected is recorded by a spectrum detection device. The beater-shaped optical fiber sensing probe is fixed in the magnetic field action region of the magnetic field environment to be detected, so that the probe center of the beater-shaped optical fiber sensing probe coincides with the magnetic field center of the magnetic field environment to be detected. The light source is excited, and the working waveband of the light source is adjusted in the preset range of the working waveband. The magnetic field strength of the magnetic field to be detected is adjusted so that the magnetic field strength is continuously adjustable in the preset range of the magnetic field strength. The magnetic field direction of the magnetic field to be detected is adjusted so that the magnetic field direction is continuously adjustable in the preset range of the magnetic field direction. Dynamic response testing is performed on the adjusted magnetic field to be detected. Under each combination of the magnetic field strength in the preset range of the magnetic field strength and the magnetic field direction in the preset range of the magnetic field direction of the magnetic field to be detected, the transmission interference spectrum corresponding to the magnetic field environment under the combination of different magnetic field strengths and magnetic field directions of the magnetic field to be detected is recorded by the spectrum detection device.

6. The method of claim 3, wherein the magnetic strain-induced modulation fiber-optic interferometer is a fiber-optic interferometer based on a fiber Bragg grating (FBG) or a long period grating (LPG). After recording the transmission interference spectrum under different magnetic field strengths and magnetic field directions in the magnetic field environment to be detected by the spectrum detection device, the method further comprises: The bending radius of the stripped coating region of the two class-spherical structure single-mode optical fibers in the beater-shaped optical fiber sensing probe is adjusted, and the corresponding transmission interference spectrum under different bending radii of the stripped coating region is recorded by the spectrum detection device. When the transmission peaks of the transmission interference spectrum under different bending radii of the stripped coating region reach a preset threshold, the two class-spherical structure single-mode optical fibers are solidified.

7. The method of claim 1, wherein the method is a magnetostrictive strain- based modulation fiber-optic interferometric triaxial magnetic field mapping method, characterized in that, The wavelength valley value offset of the resonance wavelength from the transmission interference spectrum comprises: The transmission interference spectrum is preprocessed to eliminate noise in the transmission interference spectrum; The two continuous resonance wavelengths in the transmission interference spectrum are identified, and are marked as a first valley value and a second valley value, respectively; The transmission interference spectrum under a non-magnetic field environment is called, and the initial wavelength corresponding to the first valley value and the initial wavelength corresponding to the second valley value are extracted; The transmission interference spectrum under each magnetic field environment is called, and the actual wavelength corresponding to the first valley value and the actual wavelength corresponding to the second valley value are extracted; Based on the initial wavelength and the actual wavelength corresponding to the first valley value, and the initial wavelength and the actual wavelength corresponding to the second valley value, the wavelength valley value offset corresponding to the first valley value and the wavelength valley value offset corresponding to the second valley value are calculated, respectively.

8. The method of claim 7, wherein the magnetostrictive modulation fiber optic interferometer is a fiber Bragg grating (FBG) sensor. Based on the preset correspondence between the wavelength valley value offset, the magnetic field strength, and the magnetic field direction, the three-axis components of the magnetic field to be detected are calculated. The preset sensitivity parameters are called to calculate the detection limit of each magnetic field direction of the magnetic field to be detected; The wavelength valley value offset corresponding to the first valley value and the wavelength valley value offset corresponding to the second valley value are substituted into the sensitivity formula of the corresponding magnetic field direction, respectively, to calculate the initial value of the magnetic field strength in each magnetic field direction. The initial value of the magnetic field strength of each magnetic field direction is calculated according to the change rule of the magnetic field direction and the wavelength valley value offset, and the x, y and z three-axis components of the magnetic field to be detected are calculated.

9. The method of claim 1, wherein the method is a magnetostrictive strain- based modulation fiber-optic interferometric triaxial magnetic field mapping method, characterized in that, The three-axis magnetic field mapping based on the three-axis components of the magnetic field to be detected comprises: The voltage response curve of the whisk-shaped optical fiber sensing probe is recorded, and the initial response stage, quasi-equilibrium stage and recovery stage in the voltage response curve are identified; Based on the preset amplitude of the stable voltage value, the rise time and fall time of the x, y and z three-axis directions are calculated, and the dynamic response time is analyzed and obtained based on the rise time and fall time of the x, y and z three-axis directions; The three-axis components of the magnetic field to be detected are calibrated in time dimension based on the dynamic response time; The three-axis magnetic field mapping based on the three-axis components after time dimension calibration.

10. A three-axis magnetic field mapping system based on magnetostrictive modulation of fiber optic interferometry, characterized in that, The system is used to realize the three-axis magnetic field mapping method based on magnetostrictive strain modulation optical fiber interference according to any one of claims 1-9, and the system comprises: An optical fiber preparation module is used to prepare a soft magnetic elastomer, coat the soft magnetic elastomer on the surface of a single-mode optical fiber, and obtain a single-mode optical fiber with a soft magnetic elastomer coating; A sensing probe preparation module is used to process the structure of the single-mode optical fiber with a soft magnetic elastomer coating to form a whisk-shaped optical fiber sensing probe; A transmission interference spectrum detection module is used to build an optical sensing system, place the whisk-shaped optical fiber sensing probe in a magnetic field environment to be detected, detect the light signal emitted by the light source based on the whisk-shaped optical fiber sensing probe, and record the transmission interference spectrum under different magnetic field strengths and magnetic field directions in the magnetic field environment to be detected through a spectrum detection device; A three-axis component calculation module is used to extract the wavelength valley value offset of the resonant wavelength from the transmission interference spectrum, and calculate the three-axis components of the magnetic field to be detected based on the preset corresponding relationship between the wavelength valley value offset and the magnetic field strength and the magnetic field direction; A three-axis magnetic field mapping module is used to complete the three-axis magnetic field mapping based on the three-axis components of the magnetic field to be detected.

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