A flexible photonic crystal fiber magnetic field sensor, a preparation method and a detection system

Abstract

The application discloses a flexible photonic crystal fiber magnetic field sensor, a preparation method and a detection system, relates to the technical field of optical fiber sensing, and the flexible photonic crystal fiber magnetic field sensor comprises a flexible photonic crystal fiber, a first transmission optical fiber and a second transmission optical fiber, and the first transmission optical fiber and the second transmission optical fiber are coaxially inserted into and fixed in the flexible photonic crystal fiber from two ends respectively. The flexible photonic crystal fiber comprises a polymer base and microspheres of magnetostrictive material, the microspheres of magnetostrictive material are uniformly dispersed in the interior of the polymer base, and the microspheres of magnetostrictive material are periodically arranged in the polymer base. Wherein, the microspheres of magnetostrictive material can swell in volume under the action of a magnetic field, and change the arrangement period of the microspheres of magnetostrictive material in the polymer base. The application realizes the preparation of the flexible photonic crystal fiber magnetic field sensor at lower cost and higher efficiency, and helps to promote the industrialization process of the photonic crystal fiber magnetic field sensor.

Description

Technical Field

[0001] This application relates to the field of fiber optic sensing technology, and in particular to a flexible photonic crystal fiber magnetic field sensor, its preparation method, and a detection system. Background Technology

[0002] Magnetic fields, as common as electric fields and with a significant impact on human production activities, are widely recognized. Correspondingly, the detection of magnetic field strength has become a crucial technology. Among various detection technologies, fiber optic sensing technology has been developed and applied to the field of magnetic field detection due to its excellent resistance to electromagnetic interference and its ability to achieve remote real-time monitoring. In recent years, the emergence of photonic crystal fibers has brought about a new revolution in sensing and detection mechanisms. Its unique optical field manipulation capabilities have attracted widespread research attention, and with its ultra-high detection sensitivity and novel detection mechanism, it is considered to have great potential in magnetic field detection. However, despite the excellent sensing performance and promising prospects of photonic crystal fibers, their manufacturing process typically relies on expensive and sophisticated equipment, resulting in complex structures and high fabrication difficulty. Based on existing fabrication technologies, it is difficult to achieve mass production and industrial application. Therefore, developing a photonic crystal fiber with a simple fabrication process, low equipment dependence, and the ability to achieve mass production is of great significance for promoting the industrialization of photonic crystal fiber magnetic field sensors.

[0003] Currently, photonic crystal fibers are mainly fabricated using a special stacking and drawing method. This method requires stacking capillaries or glass rods into preforms according to a specific design, and then drawing them into fibers through heating. This process demands high precision and stability from the fabrication equipment, and its fabrication efficiency is relatively low. Regarding the specific implementation of photonic crystal fiber magnetic field sensors, existing technologies primarily construct sensing units by filling the drawn photonic crystal fiber with a magnetic fluid, or by doping the fiber with materials exhibiting magneto-optical effects before drawing the photonic crystal fiber. While these methods achieve higher detection sensitivity compared to traditional fiber optic magnetic field sensors, their fabrication processes are complex, inefficient, and costly, and they are highly dependent on specialized equipment. These factors, to some extent, limit the widespread application and adoption of photonic crystal fibers in the field of magnetic field detection, and also delay the industrialization and commercialization of photonic crystal fiber magnetic field sensors. Therefore, in view of the above-mentioned limitations of existing photonic crystal fiber magnetic field sensors, developing a novel photonic crystal fiber magnetic field sensor with a novel detection principle, simple fabrication process, low cost, low dependence on equipment, and easy mass production is expected to significantly promote the industrialization potential of photonic crystal fibers in the field of magnetic field sensing and detection, and provide important reference value for the technological research and development in this field. Summary of the Invention

[0004] The purpose of this application is to provide a flexible photonic crystal fiber magnetic field sensor, its fabrication method, and a detection system, which can realize the fabrication of flexible photonic crystal fiber magnetic field sensors at a lower cost and higher efficiency, and help promote the industrialization process of photonic crystal fiber magnetic field sensors.

[0005] To achieve the above objectives, this application provides the following solution:

[0006] In a first aspect, this application provides a flexible photonic crystal fiber magnetic field sensor, comprising:

[0007] A flexible photonic crystal fiber, a first transmission fiber, and a second transmission fiber are provided, wherein the first transmission fiber and the second transmission fiber are coaxially inserted into and fixed in the flexible photonic crystal fiber from both ends.

[0008] The flexible photonic crystal fiber includes a polymer substrate and magnetostrictive material microspheres. The number of magnetostrictive material microspheres is multiple. The magnetostrictive material microspheres are uniformly dispersed inside the polymer substrate and are arranged periodically in the polymer substrate.

[0009] The magnetostrictive material microspheres can expand in volume under the action of a magnetic field, thereby changing the lattice constant of the flexible photonic crystal fiber.

[0010] Optionally, the polymer substrate is a cured polydimethylsiloxane elastic solid.

[0011] Optionally, the magnetostrictive material microspheres are made of rare-earth super magnetostrictive material, and the surface of the magnetostrictive material microspheres is modified with amino functional groups.

[0012] Secondly, this application provides a method for fabricating a flexible photonic crystal fiber magnetic field sensor, comprising:

[0013] Prepare a polymer precursor and magnetostrictive material microspheres; the number of magnetostrictive material microspheres is multiple;

[0014] The magnetostrictive material microspheres and the polymer precursor were uniformly stirred to obtain an initial mixture.

[0015] The initial mixture was ultrasonically dispersed using an ultrasonic instrument probe to obtain a flexible photonic crystal precursor mixture.

[0016] The flexible photonic crystal precursor mixture is injected into a tubular mold using a peristaltic pump;

[0017] First, the first and second transmission optical fibers are inserted into the flexible photonic crystal precursor mixture from both ends of the tubular mold. Then, the tubular mold filled with the flexible photonic crystal precursor mixture is heated and cured to form a polymer substrate.

[0018] Remove the tubular mold to obtain the flexible photonic crystal fiber magnetic field sensor.

[0019] Optionally, the tubular mold is a polytetrafluoroethylene (PTFE) tube.

[0020] Optionally, the tubular mold filled with the flexible photonic crystal precursor mixture is heated and cured to form a polymer substrate, specifically:

[0021] Multiple tubular molds filled with the flexible photonic crystal precursor mixture are simultaneously heated and cured using a heater to form multiple polymer substrates.

[0022] Thirdly, this application provides a detection system using a flexible photonic crystal fiber magnetic field sensor, comprising:

[0023] The light source module is used to provide the incident light signal;

[0024] A flexible photonic crystal fiber magnetic field sensor is connected to the light source module through a first transmission fiber. It is used to receive the incident light signal and modulate the incident light signal under the action of an external magnetic field, and output a transmitted light signal carrying magnetic field strength information.

[0025] The signal acquisition and processing module is connected to the flexible photonic crystal fiber magnetic field sensor through the second transmission fiber, and is used to receive the transmitted light signal and extract the transmission spectrum information from the transmitted light signal;

[0026] The computer module is connected to the signal acquisition and processing module via a first data connection line. It is used to receive and display transmission spectrum information, calculate the wavelength shift of the loss peak based on the transmission spectrum information, and determine the magnetic field strength of the external magnetic field based on the wavelength shift of the loss peak.

[0027] Optionally, the computer module is also connected to the light source module via a second data connection line for controlling the incident light signal.

[0028] Optionally, the light source module is a broadband light source capable of providing incident light signals including ultraviolet light, visible light, and near-infrared light.

[0029] Optionally, the signal acquisition and processing module is a fiber optic grating demodulator, used to convert the transmitted light signal into transmission spectral information corresponding to wavelength and intensity.

[0030] According to the specific embodiments provided in this application, this application has the following technical effects:

[0031] This application provides a flexible photonic crystal fiber magnetic field sensor, its fabrication method, and a detection system. The sensor utilizes a flexible photonic crystal fiber as its core structure, which is composed of a polymer substrate and periodically arranged magnetostrictive material microspheres. By leveraging the volume expansion of the magnetostrictive material microspheres under a magnetic field, the sensor alters the lattice constant of the flexible photonic crystal fiber, influencing the modulation of the incident light signal. This allows for indirect detection of the magnetic field strength based on the modulation of the incident light signal, resulting in higher sensitivity magnetic field detection. Furthermore, this flexible photonic crystal fiber magnetic field sensor, through its periodic arrangement of magnetostrictive material microspheres in a polymer substrate, avoids the stacking and drawing process required in traditional photonic crystal fibers, thus reducing reliance on specialized precision drawing equipment. This enables the fabrication of flexible photonic crystal fiber magnetic field sensors at a lower cost and higher efficiency, contributing to the industrialization of photonic crystal fiber magnetic field sensors. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A flowchart illustrating the pre-fabrication process of the flexible photonic crystal fiber magnetic field sensor based on the magnetostrictive effect provided in Embodiment 2 of this application;

[0034] Figure 2 This is a flowchart illustrating the fabrication process of the flexible photonic crystal fiber magnetic field sensor based on the magnetostrictive effect provided in Embodiment 2 of this application.

[0035] Figure 3 This is a schematic diagram of the detection system based on a flexible photonic crystal fiber magnetic field sensor provided in Embodiment 3 of this application;

[0036] Figure 4 This is a schematic diagram of the detection principle of the flexible photonic crystal fiber magnetic field sensor based on the magnetostrictive effect provided in Embodiment 4 of this application.

[0037] Figure label:

[0038] 1-1 First data connection line; 1-2 Second data connection line; 2. Light source module; 3-1 First transmission optical fiber; 3-2 Second transmission optical fiber; 4. Optical fiber sensing unit; 5. Magnetic field environment; 6. Signal acquisition and processing module; 7. Computer module; 8. Polymer precursor; 9. Magnetostrictive material microspheres; 10. Ultrasonic uniform dispersion; 11. Ultrasonic instrument probe; 12. Extraction of flexible photonic crystal precursor mixture; 13. Peristaltic pump; 14. Tubular mold; 15. Tubular mold filled with flexible photonic crystal precursor mixture; 16. Optical fiber core; 17. Optical fiber cladding; 18. Heater; 19. Polymer matrix; 20. Incident light; 21. Transmitted light; 22. Weak magnetic field; 23. Strong magnetic field. Detailed Implementation

[0039] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] In one exemplary embodiment, a flexible photonic crystal fiber magnetic field sensor is provided. In this embodiment, the flexible photonic crystal fiber magnetic field sensor includes: a flexible photonic crystal fiber, a first transmission fiber, and a second transmission fiber. The first transmission fiber and the second transmission fiber are coaxially inserted into and fixed in the flexible photonic crystal fiber from both ends.

[0043] The flexible photonic crystal fiber includes a polymer substrate and magnetostrictive material microspheres. There are multiple magnetostrictive material microspheres, which are uniformly dispersed inside the polymer substrate and arranged periodically in the polymer substrate. The magnetostrictive material microspheres can expand in volume under the action of a magnetic field, thereby changing the lattice constant of the flexible photonic crystal fiber.

[0044] Furthermore, the polymer substrate is a cured polydimethylsiloxane (PDMS) elastic solid. The flexible photonic crystal fiber magnetic field sensor uses PDMS as a substrate, and its refractive index and physical properties can be adjusted by regulating the ratio of A and B adhesives in the PDMS. This not only reduces cost but also ensures that it does not react with external forces due to its excellent chemical stability and elasticity. It quickly returns to its initial state when external forces or internal stresses disappear, enabling it to operate in complex environments. In addition, its excellent sealing properties ensure that the internal magnetostrictive microspheres are isolated from the external environment, reducing environmental impact and extending the service life of the flexible photonic crystal fiber magnetic field sensor. Alternatively, other materials with similar functions can be used as substitutes.

[0045] For example, to enable sensing applications in more scenarios and for sensing more biomolecules, the polymer substrate can be replaced with a hydrogel (polyethylene glycol diacrylate). The flexible photonic crystal fiber optic magnetic field sensor uses a hydrogel (polyethylene glycol diacrylate) with good flexibility and biocompatibility as the substrate material. Its unique porous structure allows small molecules to permeate into the internal photonic crystal structure for specific sensing. Alternatively, hydrogel materials such as polyacrylamide can be used to provide unique properties to the flexible photonic crystal fiber optic magnetic field sensor, such as hydrophobicity, electromagnetic sensitivity, or birefringence, to enable sensing applications in a wider range of scenarios.

[0046] Furthermore, by using PDMS as the substrate of the flexible photonic crystal fiber magnetic field sensor, different substances can be doped into the PDMS precursor to improve its performance in various aspects (such as fluorination modification to resist oil) without affecting the magnetic field sensing performance. This allows the flexible photonic crystal fiber magnetic field sensor to adapt to more occasions and even achieve multi-parameter sensing, thereby increasing the functionality of the sensor.

[0047] Furthermore, the magnetostrictive material microspheres are made of rare-earth terfenol-D, and their surfaces are modified with amino functional groups. The flexible photonic crystal fiber magnetic field sensor uses magnetostrictive material microspheres prepared from terfenol-D as the magnetic field-sensitive material. These microspheres are periodically arranged in a polymer substrate to form a three-dimensional flexible photonic crystal structure. Through their unique magnetostrictive ability and extremely fast geomagnetic response speed, they can sensitively and quantitatively expand according to the magnetic field strength, thereby changing the lattice constant of the flexible photonic crystal fiber and achieving wavelength shift of the loss peak in the transmission spectrum. Different magnetostrictive materials can also be used for preparation (such as ferrite magnetostrictive materials), and the particle size can be adjusted according to the application and requirements. The sensitivity to magnetic fields and the upper limit of the detected magnetic field strength can be improved by adjusting the composition ratio and doping with other elements during the preparation of the magnetostrictive material microspheres, thus enhancing the detection range and sensitivity of the flexible photonic crystal fiber magnetic field sensor.

[0048] Furthermore, since some environments have a large amount of background light and stray light of considerable intensity, a non-antimagnetic reflective coating can be nested on the outside of the flexible photonic crystal fiber magnetic field sensor to prevent external light from interfering with the flexible photonic crystal fiber magnetic field sensor. It can also confine the modulated transmitted light in the optical path within the flexible photonic crystal fiber to enhance the intensity of the transmitted light signal.

[0049] Unlike existing technologies, the above technical solution has the following technical effects:

[0050] This application uses flexible photonic crystal fiber as the core structure of a flexible photonic crystal fiber magnetic field sensor. It achieves magnetic field detection by utilizing the principle that the lattice constant of the flexible photonic crystal fiber under a flexible polymer substrate changes with the magnetic field strength. Compared with existing photonic crystal fiber magnetic field sensors, it avoids the problem of magnetohydrodynamic instability and also makes up for the need for fiber drawing. The flexible photonic crystal fiber magnetic field sensor not only adopts a novel sensing principle, but also has a low dependence on expensive equipment in the fabrication process, effectively reducing costs. The fabrication process is simple and can be mass-produced, making it more likely to be industrialized.

[0051] This application uses PDMS as the substrate for a flexible photonic crystal fiber magnetic field sensor. PDMS possesses excellent flexibility and elasticity. When the lattice constant of the flexible photonic crystal fiber changes in the presence of a magnetic field, it can rapidly adjust its size. After the magnetic field disappears, it can quickly recover its initial state using its superior elasticity, without affecting the fast response characteristic of the flexible photonic crystal fiber magnetic field sensor. Furthermore, PDMS itself has good sealing properties, hydrophobicity, and chemical stability, effectively blocking the influence of the external environment on the sensitive material (magnetostrictive material microspheres). Even in harsh environments, it will not chemically react with most external substances, protecting the flexible photonic crystal structure composed of magnetostrictive material microspheres and extending the service life of the flexible photonic crystal fiber magnetic field sensor.

[0052] This application uses microspheres made of rare-earth giant magnetostrictive material (Terfenol-D) as the magnetic field sensitive material for a flexible photonic crystal fiber magnetic field sensor. Terfenol-D material itself has a magnetostrictive effect, and it will deform and elongate under the presence of a magnetic field. The degree of elongation is positively correlated with the magnetic field strength. After the microspheres are formed, they will expand in volume under the action of a magnetic field, which will cause a change in the lattice constant. After the magnetic field disappears, they can quickly recover their initial size. The performance and properties are relatively stable, and they are extremely sensitive to magnetic fields and respond quickly. Compared with existing photonic crystal fiber magnetic field sensors, this application uses a new detection principle and a more sensitive and stable material, which provides new reference for the design and manufacture of photonic crystal fiber magnetic field sensors.

[0053] Example 2

[0054] Based on the same inventive concept, such as Figures 1-2 As shown in the embodiments of this application, a method for fabricating the above-mentioned flexible photonic crystal fiber magnetic field sensor is also provided. The fabrication of the flexible photonic crystal fiber magnetic field sensor is divided into a pre-fabrication stage and a fabrication stage. The pre-fabrication stage mainly involves preparing the flexible photonic crystal precursor mixture and filling it into the mold. The pre-fabrication stage includes the following steps:

[0055] Step S1: Prepare polymer precursor 8 and magnetostrictive material microspheres 9; the number of magnetostrictive material microspheres is multiple, and the magnetostrictive material microspheres can be Terfenol-D microspheres with a particle size of 200-300nm and surface-modified amino groups prepared by chemical reduction and surface functionalization; the polymer precursor is a PDMS precursor containing A glue and B glue.

[0056] Step S2: The magnetostrictive material microspheres 9 and the polymer precursor 8 are stirred uniformly to obtain an initial mixture. The curing of the PDMS precursor is very slow under normal temperature conditions, so further operations are required on this basis.

[0057] Step S3: Use the ultrasonic instrument probe 11 to perform ultrasonic uniform dispersion on the initial mixture to obtain a flexible photonic crystal precursor mixture; specifically: use the ultrasonic instrument probe 11 to insert into the uniformly stirred PDMS precursor and surface-modified amino Terfenol-D microsphere mixture for 60 min of ultrasonic uniform dispersion 10. The ultrasonic vibration enables the surface-modified amino Terfenol-D microspheres to be uniformly dispersed in the PDMS precursor. The surface-modified amino groups provide electrostatic interaction sites, which enable them to achieve periodic uniform arrangement through self-assembly under the assistance of ultrasonic action, thus forming a flexible photonic crystal precursor mixture with the PDMS precursor.

[0058] Step S4: The flexible photonic crystal precursor mixture is injected into the tubular mold 14 using a peristaltic pump 13 (i.e., the flexible photonic crystal precursor mixture 12 is extracted); the tubular mold is a polytetrafluoroethylene tube. Removing the filled tubular mold 15 completes the pre-preparation process, resulting in a tubular mold 15 filled with the flexible photonic crystal precursor mixture. Multiple filled tubular molds 15 can be filled simultaneously, improving preparation efficiency.

[0059] After completing the pre-preparation process, a tubular mold 15 filled with a mixture of flexible photonic crystal precursors is obtained, which is then used for the preparation stage:

[0060] Step S5: First, insert the first transmission fiber 3-1 and the second transmission fiber 3-2 into the flexible photonic crystal precursor mixture from both ends of the tubular mold 14. Then, heat and solidify the tubular mold 15 filled with the flexible photonic crystal precursor mixture to form a polymer substrate. Multiple tubular molds 15 filled with flexible photonic crystal precursor mixtures can be simultaneously heated and solidified using the heater 18 to form multiple polymer substrates, achieving batch production. Specifically: Insert the first transmission fiber 3-1, which is connected to the light source module 2, and the second transmission fiber 3-2, which is connected to the signal acquisition and processing module 6, respectively. The fiber core 16 is inserted into the flexible photonic crystal precursor mixture, and the fiber cladding 17 is used to fix the tubular mold 14. Subsequently, it is placed under heater 18 for heating and curing for about 2 hours. Under high temperature, the polymer precursor 8 in the flexible photonic crystal precursor mixture will be rapidly cured and shaped to form a polymer substrate 19 with good mechanical properties, elasticity and chemical stability. The Terfenol-D microspheres 9 with amino-modified internal surfaces will also form a permanent periodic arrangement due to the shaping of the flexible photonic crystal precursor mixture, thus constituting a flexible photonic crystal fiber.

[0061] Step S6: Remove the tubular mold 14 to obtain the flexible photonic crystal fiber magnetic field sensor 4.

[0062] The flexible photonic crystal fiber magnetic field sensor can be prepared by pre-ultrasonic dispersion of a large amount of PDMS precursor and surface-modified amino Terfenol-D microsphere mixture, and the PDMS precursor and surface-modified amino Terfenol-D microsphere mixture can be simultaneously pumped by a peristaltic pump and filled into multiple polytetrafluoroethylene tubes and placed in the same heater for heating and curing to mass-produce flexible photonic crystal fiber magnetic field sensors, which greatly improves the preparation efficiency of flexible photonic crystal fiber magnetic field sensors.

[0063] The flexible photonic crystal fiber magnetic field sensor is fabricated using a mold method. PDMS can be heated and cured to shape the flexible photonic crystal fiber magnetic field sensor within a polytetrafluoroethylene (PTFE) tube. Due to the stable chemical and physical properties of PTFE, the tubular mold made of PTFE is easily removed after PDMS curing to complete the manufacturing process. Alternatively, molds of other shapes or made of materials that do not adhere to PDMS can be used to fabricate the flexible photonic crystal fiber magnetic field sensor, reducing reliance on high-precision, high-cost equipment.

[0064] Example 3

[0065] Based on the same inventive concept, such as Figure 3 As shown in the embodiments of this application, a detection system using a flexible photonic crystal fiber magnetic field sensor is also provided, comprising:

[0066] The light source module 2 is used to provide incident light signals. The light source module 2 is a broadband light source that can provide incident light signals including ultraviolet light, visible light and near-infrared light, to ensure that the fiber optic sensing unit 4 (i.e. the flexible photonic crystal fiber magnetic field sensor) modulates the incident light signals.

[0067] Fiber optic sensing unit 4 (flexible photonic crystal fiber magnetic field sensor) is connected to the light source module 2 via the first transmission fiber 3-1. It receives incident light signals and modulates these signals under the influence of an external magnetic field, outputting a transmitted light signal carrying magnetic field strength information. The fiber optic sensing unit 4 is constructed by combining a flexible photonic crystal fiber prepared using a mold method with a transmission fiber. Specifically, it is prepared by uniformly dispersing surface-modified amino-modified Terfenol-D microspheres in a PDMS precursor mixture using ultrasonic vibration, filling the mixture into a polytetrafluoroethylene tube, inserting transmission fibers at both ends, and heating to cure. The fiber optic sensing unit utilizes the Terfenol-D microspheres in the flexible photonic crystal fiber... Terfenol-D materials exhibit excellent magnetostrictive properties, producing a rapid magnetostrictive effect under the influence of a magnetic field. Because Terfenol-D microspheres are spherical, they expand uniformly in all directions, altering the lattice constant of the flexible photonic crystal. The degree of expansion of the Terfenol-D microspheres is positively correlated with the magnetic field strength. After the modulated incident light passes through the fiber optic sensing unit, the wavelength of the transmitted light loss peak shifts to varying degrees with the magnetic field strength. The amount of wavelength shift allows for qualitative and quantitative detection of the magnetic field strength, providing new ideas and insights for the design and fabrication of photonic crystal fiber optic magnetic field sensors, demonstrating the application potential and prospects of photonic crystal fiber optic magnetic field sensors.

[0068] The signal acquisition and processing module 6 is connected to the fiber optic sensing unit 4 (flexible photonic crystal fiber magnetic field sensor) through the second transmission fiber optic cable 3-2. It is used to receive the transmitted light signal and extract the transmission spectrum information from the transmitted light signal. The signal acquisition and processing module 6 is a fiber optic grating demodulator, which is used to convert the transmitted light signal into transmission spectrum information corresponding to wavelength and intensity.

[0069] Computer module 7 is connected to signal acquisition and processing module 6 via the first data connection line 1-1. It is used to receive and display transmission spectrum information, and calculate the wavelength shift of the loss peak based on the transmission spectrum information. Based on the wavelength shift of the loss peak, the magnetic field strength of the external magnetic field is determined. Specifically, the wavelength shift of the loss peak can be calibrated with the known magnetic field strength to obtain the relationship expression between the wavelength shift and the magnetic field strength. According to the relationship expression, the magnetic field strength of the unknown magnetic field can be calculated, realizing real-time qualitative and quantitative detection of magnetic field strength.

[0070] Computer module 7 is also connected to light source module 2 via second data connection line 1-2 for controlling incident light signal.

[0071] Example 4

[0072] Based on the same inventive concept, such as Figure 4As shown in the figure, this application embodiment also provides a detection principle diagram of a flexible photonic crystal fiber magnetic field sensor based on the magnetostrictive effect. The light source module 2 transmits the incident light 20 signal to the fiber sensing unit 4 through the fiber core 16 of the first transmission fiber 3-1. The incident spectrum of the incident light signal is the broadband spectrum generated by the light source module 2. When the incident light 20 signal passes through the fiber sensing unit 4, the flexible photonic crystal fiber composed of surface-modified amino Terfenol-D microspheres and PDMS will modulate the incident light 20. According to the modulation formula of the flexible photonic crystal fiber... ,in, The center wavelength of the photonic bandgap; The effective refractive index of flexible photonic crystal fiber; The lattice constant of the flexible photonic crystal fiber is given. The modulated transmitted light 21 will generate a wave with... The loss peak is at the center wavelength. When a magnetic field is applied to the fiber optic sensing unit 4, the amino-modified Terfenol-D microspheres undergo magnetostrictive expansion to varying degrees with changes in magnetic field strength. When the external magnetic field is a weak magnetic field 22, the Terfenol-D microspheres undergo weaker magnetostrictive expansion, and the lattice constant... Consequently, certain changes occur, while PDMS is insensitive to changes in magnetic field strength, and the effective refractive index of the photonic crystal structure... There will be no significant change, which affects the center wavelength that causes the loss peak. A certain amount of redshift (wavelength increase) occurs; when the external magnetic field is a strong magnetic field of 23, the Terfenol-D microspheres undergo significant magnetostrictive expansion, and the lattice constant... Significant changes occur in the center wavelength of the loss peak. This results in a significant increase and a substantial redshift; when the external magnetic field disappears, the Terfenol-D microspheres shrink back to their initial size, and the lattice constant... The center wavelength of the loss peak after restoring to its initial state. It also shrinks and restores the initial state, so it only needs to calibrate the center wavelength of the loss peak of the transmitted light 21 after passing through the fiber optic sensing unit 4. The relationship between the drift and the magnetic field strength can enable real-time qualitative and quantitative monitoring of unknown magnetic field strength.

[0073] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Unless otherwise specified, an element defined by the phrase "comprising..." or "including..." does not exclude the presence of additional elements in the process, method, article, or terminal device that includes said element. Additionally, in this document, "greater than," "less than," "exceeding," etc., are understood to exclude the stated number; "above," "below," "within," etc., are understood to include the stated number.

[0074] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0075] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A flexible photonic crystal fiber magnetic field sensor, characterized in that, The flexible photonic crystal fiber magnetic field sensor includes: a flexible photonic crystal fiber, a first transmission fiber, and a second transmission fiber, wherein the first transmission fiber and the second transmission fiber are coaxially inserted into and fixed in the flexible photonic crystal fiber from both ends; The flexible photonic crystal fiber comprises a polymer substrate and magnetostrictive material microspheres. The polymer substrate is a cured polydimethylsiloxane elastic solid or hydrogel. Multiple magnetostrictive material microspheres are uniformly dispersed within the polymer substrate and arranged periodically within it. The magnetostrictive material microspheres are made of rare-earth supermagnetostrictive material, and their surfaces are modified with amino functional groups. The flexible photonic crystal fiber magnetic field sensor is obtained by injecting the flexible photonic crystal precursor mixture into a tubular mold using a peristaltic pump, inserting the first and second transmission fibers into the flexible photonic crystal precursor mixture from both ends of the tubular mold, heating and curing multiple tubular molds filled with the flexible photonic crystal precursor mixture simultaneously using a heater, and finally removing the tubular molds. The magnetostrictive material microspheres can expand in volume under the action of a magnetic field, changing the lattice constant of the flexible photonic crystal fiber. When the lattice constant of the flexible photonic crystal fiber changes, the wavelength shift of the loss peak in the transmission spectrum information is adjusted. Combined with the relationship between the wavelength shift of the loss peak and the magnetic field strength, the magnetic field strength can be detected.

2. A method for fabricating a flexible photonic crystal fiber magnetic field sensor as described in claim 1, characterized in that, The preparation method includes: Prepare a polymer precursor and magnetostrictive material microspheres; the number of magnetostrictive material microspheres is multiple; The magnetostrictive material microspheres and the polymer precursor were uniformly stirred to obtain an initial mixture. The initial mixture was ultrasonically dispersed using an ultrasonic instrument probe to obtain a flexible photonic crystal precursor mixture. The flexible photonic crystal precursor mixture is injected into a tubular mold using a peristaltic pump; First, the first and second transmission optical fibers are inserted into the flexible photonic crystal precursor mixture from both ends of the tubular mold. Then, the tubular mold filled with the flexible photonic crystal precursor mixture is heated and cured to form a polymer substrate. Remove the tubular mold to obtain the flexible photonic crystal fiber magnetic field sensor.

3. The method for fabricating a flexible photonic crystal fiber magnetic field sensor according to claim 2, characterized in that, The tubular mold is a polytetrafluoroethylene tube.

4. The method for fabricating a flexible photonic crystal fiber magnetic field sensor according to claim 2, characterized in that, The tubular mold filled with the flexible photonic crystal precursor mixture is heated and cured to form a polymer substrate, specifically: Multiple tubular molds filled with the flexible photonic crystal precursor mixture are simultaneously heated and cured using a heater to form multiple polymer substrates.

5. A detection system using the flexible photonic crystal fiber magnetic field sensor of claim 1, characterized in that, The detection system includes: The light source module is used to provide the incident light signal; A flexible photonic crystal fiber magnetic field sensor is connected to the light source module through a first transmission fiber. It is used to receive the incident light signal and modulate the incident light signal under the action of an external magnetic field, and output a transmitted light signal carrying magnetic field strength information. The signal acquisition and processing module is connected to the flexible photonic crystal fiber magnetic field sensor through the second transmission fiber, and is used to receive the transmitted light signal and extract the transmission spectrum information from the transmitted light signal; The computer module is connected to the signal acquisition and processing module via a first data connection line. It is used to receive and display transmission spectrum information, calculate the wavelength shift of the loss peak based on the transmission spectrum information, and determine the magnetic field strength of the external magnetic field based on the wavelength shift of the loss peak.

6. The detection system according to claim 5, characterized in that, The computer module is also connected to the light source module via a second data connection line for controlling the incident light signal.

7. The detection system according to claim 6, characterized in that, The light source module is a broadband light source, capable of providing incident light signals including ultraviolet light, visible light, and near-infrared light.

8. The detection system according to claim 6, characterized in that, The signal acquisition and processing module is a fiber optic grating demodulator, used to convert the transmitted light signal into transmission spectral information corresponding to wavelength and intensity.

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