A fiber-optic magnetic sensor based on magnetic hydrogel

Abstract

The application discloses a kind of optical fiber magnetic sensor based on magnetic hydrogel, comprising: first transmission section, with the first transmission section integral type communication first tapered optical fiber transition section, with the first tapered optical fiber transition section integral type communication tapered optical fiber waist area, with the tapered optical fiber waist area integral type communication second tapered optical fiber transition section and with the second tapered optical fiber transition section integral type communication second transmission section, one end of first transmission section is connected with broadband light source, and second transmission section is connected with spectrometer;Tapered optical fiber waist area is coated with capillary tube, and the capillary tube is covered in first tapered optical fiber transition section and second tapered optical fiber transition section;Capillary tube is filled with magnetic hydrogel.According to the application, it has the same superparamagnetic as magnetic fluid Magnetic nano-particle and responds well to external magnetic field, improve sensitivity.

Description

Technical Field

[0001] This invention relates to the technical field of fiber optic magnetic sensors, and particularly to a fiber optic magnetic sensor based on magnetic hydrogel. Background Technology

[0002] Magnetic fields are an unavoidable and objectively existing physical quantity in nature, exerting various influences on machines used in production and daily life, and even affecting the normal operation of machinery. Therefore, magnetic field measurement technology is extremely important in many fields. Fiber optic magnetic field sensors are favored by many experts and scholars due to their advantages such as small size, fast magnetic field response, high sensitivity, low power consumption, strong corrosion resistance, remote detection capability, strong reusability, and strong resistance to electromagnetic interference. Fiber optic magnetic field sensing detects magnetic fields in the external environment by detecting changes in parameters such as wavelength, intensity, phase, amplitude, and loss of light transmitted through the optical fiber. Fiber optic magnetic field sensors are mainly fabricated by integrating magnetostrictive materials and magneto-optical materials with optical fibers. Under the influence of an external magnetic field, the solid particles inside a magnetofluid aggregate and align themselves along the direction of the external magnetic field, causing a change in the refractive index of the magnetofluid. This type of magnetofluid-based fiber optic magnetic field sensor has advantages such as high sensitivity and light weight, but its magnetic field measurement range is affected by the saturation magnetization of the magnetofluid, limiting its sensing range in high magnetic fields. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a fiber optic magnetic sensor based on magnetic hydrogels, possessing superparamagnetism similar to that of magnetic nanoparticles in magnetofluids and exhibiting good response to external magnetic fields, thereby improving sensitivity. To achieve the above-mentioned objectives and other advantages of the present invention, a fiber optic magnetic sensor based on magnetic hydrogels is provided, comprising:

[0004] A first transmission segment, a first tapered fiber transition segment integrally connected to the first transmission segment, a tapered fiber waist region integrally connected to the first tapered fiber transition segment, a second tapered fiber transition segment integrally connected to the tapered fiber waist region, and a second transmission segment integrally connected to the second tapered fiber transition segment. One end of the first transmission segment is connected to a broadband light source, and the second transmission segment is connected to a spectrometer.

[0005] The waist region of the tapered fiber is surrounded by a capillary tube, which covers both the first tapered fiber transition section and the second tapered fiber transition section.

[0006] The capillary is filled with magnetic hydrogel.

[0007] Preferably, the optical fiber is drawn from single-mode optical fiber, and the lengths of the first tapered fiber transition section and the second tapered fiber transition section are both 3 mm.

[0008] Preferably, the waist region of the tapered optical fiber has a length of 6 mm and a diameter of 11.8 micrometers.

[0009] Preferably, the magnetic hydrogel is prepared by mixing polyvinyl alcohol hydrogel material with iron oxide magnetic nanoparticles and sodium oleate as a dispersant.

[0010] Preferably, the capillary has a diameter of 3 mm, and both ends of the capillary are cured and encapsulated with UV adhesive, with magnetic hydrogel injected and wrapped in the capillary located in the tapered structure region of the tapered optical fiber.

[0011] A method for fabricating an optical fiber magnetic sensor based on magnetic hydrogel includes the following steps:

[0012] S1. Clean the surface of the single-mode fiber and remove the coating layer from the multimode fiber;

[0013] S2. Taper the single-mode fiber;

[0014] S3. Specific solutions and pale yellow, clear sodium oleate solution before preparing PVA hydrogel;

[0015] S4. Place Fe3O4 particles in sodium oleate solution, use a magnet to attract Fe3O4 particles to the bottom of the beaker, pour off the upper waste liquid, and remove the remaining sodium oleate impurities on the surface.

[0016] S5. Mix the treated Fe3O4 particles with the PVA hydrogel pretreatment solution to obtain a PVA / Fe3O4 magnetic hydrogel solution.

[0017] S6. Wrap the capillary tube around the waist region of the tapered optical fiber and the transition section between the first and second tapered optical fibers. Inject the prepared PVA / Fe3O4 magnetic hydrogel solution into the capillary tube and seal both ends with UV glue for UV curing.

[0018] S7. The tapered optical fiber wrapped in the encapsulated magnetic hydrogel is frozen and then placed at room temperature to obtain a tapered optical fiber magnetic field sensor based on magnetic hydrogel.

[0019] S8. Connect a broadband light source and a spectrometer to the two ends of the optical fiber in the sensing element to obtain the tapered optical fiber magnetic field sensor based on magnetic hydrogel.

[0020] Compared with existing technologies, the advantages of this invention are as follows: By mixing hydrogel with magnetic nanoparticles to prepare a magnetic hydrogel, and then encapsulating the magnetic hydrogel in the tapered structural region of a tapered optical fiber, a broadband light source and a spectrometer are connected to the two ends of the tapered optical fiber, respectively, thus creating an optical fiber magnetic field sensor with a higher magnetic field sensing range. The magnetic hydrogel can change its refractive index according to changes in the external environmental magnetic field. The output spectrum of the tapered optical fiber magnetic field sensor will exhibit wavelength shift with changes in the external environmental magnetic field. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the tapered optical fiber of the optical fiber magnetic sensor according to the present invention;

[0022] Figure 2 This is a schematic diagram of the tapered optical fiber of the fiber optic magnetic sensor based on magnetic hydrogel according to the present invention;

[0023] Figure 3 The transmission spectrum of the fiber optic magnetic sensor based on magnetic hydrogel according to the present invention at room temperature is shown.

[0024] Figure 4 The image shows the wavelength variation of the fiber optic magnetic sensor based on magnetic hydrogel under different magnetic fields according to the present invention. Detailed Implementation

[0025] 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.

[0026] Reference Figure 1-4 A fiber optic magnetic sensor based on magnetic hydrogel includes: a first transmission segment 1, a first tapered fiber transition segment 2 integrally connected to the first transmission segment 1, a tapered fiber waist region 3 integrally connected to the first tapered fiber transition segment 2, a second tapered fiber transition segment 4 integrally connected to the tapered fiber waist region 3, and a second transmission segment 7 integrally connected to the second tapered fiber transition segment 4. One end of the first transmission segment 1 is connected to a broadband light source, and the second transmission segment 7 is connected to a spectrometer. The tapered fiber waist region 3 is surrounded by a capillary tube 5, which encloses both the first tapered fiber transition segment 2 and the second tapered fiber transition segment 4. The capillary tube 5 is filled with magnetic hydrogel 6. When the broadband light source enters the first tapered fiber transition section 2, two modes of light, the core mode and the cladding mode, propagate in the fiber. The effective refractive index of the cladding mode light is affected by the refractive index of the magnetic hydrogel, and couples with the core mode light in the second tapered fiber transition section 4, forming interference. Under the influence of a magnetic field, the refractive index of the magnetic hydrogel 6 changes with the magnetic field. This change in refractive index modulates the phase information of the fiber optic sensing structure, causing a shift in the interference spectrum, which in turn causes a shift in the sensor's transmission spectrum. By analyzing the changes in the transmission spectrum, the changes in the external magnetic field can be determined.

[0027] Furthermore, the optical fiber is drawn from single-mode optical fiber, and the lengths of the first tapered fiber transition section 2 and the second tapered fiber transition section 4 are both 3 mm.

[0028] Furthermore, the waist region 3 of the tapered optical fiber has a length of 6 mm and a diameter of 11.8 micrometers.

[0029] Furthermore, the magnetic hydrogel 6 was prepared by mixing polyvinyl alcohol hydrogel material with iron oxide magnetic nanoparticles and sodium oleate as a dispersant.

[0030] Furthermore, the capillary 5 has a diameter of 3 mm, and both ends of the capillary 5 are sealed with UV adhesive. Magnetic hydrogel 6 is injected and wrapped in the capillary located in the tapered structure region of the tapered optical fiber.

[0031] A method for fabricating an optical fiber magnetic sensor based on magnetic hydrogel includes the following steps:

[0032] S1. Clean the surface of the single-mode fiber with alcohol; remove the coating from a 2 cm long section of multimode fiber.

[0033] S2. Place the single-mode fiber on the fusion splicer and perform tapering using fusion tapering technology. The preferred settings are a tapered transition zone length of 3 mm, a waist diameter of 11.8 micrometers, and a length of 6 mm. Figure 1 As shown;

[0034] S3. Dissolve 9g of PVA powder in 45g of deionized water, and stir at 85℃ under a magnetic stirrer for 30min to obtain a clear and transparent PVA hydrogel pre-solution.

[0035] Take 3g of sodium oleate powder, dissolve it in 30g of deionized water, and stir vigorously with a mechanical stirrer in a 90℃ water bath until a light yellow clear sodium oleate solution is obtained.

[0036] S4. Take 1.6g of Fe3O4 particles with a diameter of 15nm, place them in sodium oleate solution, stir vigorously with a mechanical stirrer for 30min, then use a magnet to attract the Fe3O4 particles to the bottom of the beaker, pour off the upper waste liquid, and wash the Fe3O4 particles with alcohol several times to remove the remaining sodium oleate impurities on the surface.

[0037] S5. Mix the treated Fe3O4 particles with the PVA hydrogel pretreatment solution, stir evenly, and ultrasonically vibrate to remove air bubbles to obtain PVA / Fe3O4 magnetic hydrogel solution.

[0038] S6. Wrap the capillary tube around the waist region 3 of the tapered optical fiber and the transition section 2 and the transition section 4 of the first tapered optical fiber. Inject the prepared PVA / Fe3O4 magnetic hydrogel solution into the capillary tube and seal both ends with UV glue for UV curing.

[0039] S7. Place the tapered optical fiber wrapped in the encapsulated magnetic hydrogel into a -20℃ freezer for 24 hours, take it out, and place it at room temperature for 2 hours to obtain a tapered optical fiber magnetic field sensor based on magnetic hydrogel.

[0040] S8. Connect a broadband light source and a spectrometer to the two ends of the optical fiber in the sensing element, respectively, to obtain the tapered optical fiber magnetic field sensor based on magnetic hydrogel, as shown below. Figure 2 As shown.

[0041] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention, and applications, modifications and variations thereof will be apparent to those skilled in the art.

[0042] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A fiber optic magnetic sensor based on magnetic hydrogel, characterized in that, include: The first transmission segment (1), the first tapered fiber transition segment (2) integrally connected with the first transmission segment (1), the tapered fiber waist region (3) integrally connected with the first tapered fiber transition segment (2), the second tapered fiber transition segment (4) integrally connected with the tapered fiber waist region (3), and the second transmission segment (7) integrally connected with the second tapered fiber transition segment (4), one end of the first transmission segment (1) is connected to a broadband light source, and the second transmission segment (7) is connected to a spectrometer; The waist region (3) of the tapered fiber is surrounded by a capillary tube (5), and the capillary tube (5) covers both the first tapered fiber transition section (2) and the second tapered fiber transition section (4). The capillary (5) is filled with magnetic hydrogel (6); The two ends of the capillary (5) are encapsulated by UV adhesive curing, and magnetic hydrogel (6) is injected and wrapped in the capillary located in the tapered structure region of the tapered optical fiber.

2. The fiber optic magnetic sensor based on magnetic hydrogel as described in claim 1, characterized in that, The optical fiber is drawn from single-mode optical fiber, and the lengths of the first tapered fiber transition section (2) and the second tapered fiber transition section (4) are both 3 mm.

3. The fiber optic magnetic sensor based on magnetic hydrogel as described in claim 2, characterized in that, The waist region (3) of the tapered fiber has a length of 6 mm and a diameter of 11.8 μm.

4. The fiber optic magnetic sensor based on magnetic hydrogel as described in claim 1, characterized in that, The magnetic hydrogel (6) was prepared by mixing polyvinyl alcohol hydrogel material with iron oxide magnetic nanoparticles and sodium oleate as a dispersant.

5. The fiber optic magnetic sensor based on magnetic hydrogel as described in claim 4, characterized in that, The diameter of the capillary (5) is 3 mm.

6. A method for fabricating an optical fiber magnetic sensor based on magnetic hydrogel as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Clean the surface of the single-mode fiber and remove the coating layer from the multimode fiber; S2. Taper the single-mode fiber; S3. Specific solutions and pale yellow, clear sodium oleate solution before preparing PVA hydrogel; S4. Place Fe3O4 particles in sodium oleate solution, use a magnet to attract Fe3O4 particles to the bottom of the beaker, pour off the upper waste liquid, and remove the remaining sodium oleate impurities on the surface. S5. Mix the treated Fe3O4 particles with the PVA hydrogel pretreatment solution to obtain a PVA / Fe3O4 magnetic hydrogel solution. S6. Wrap the capillary around the waist region (3) of the tapered fiber and the transition section (2) of the first tapered fiber and the transition section (4) of the second tapered fiber. Inject the prepared PVA / Fe3O4 magnetic hydrogel solution into the capillary and seal both ends with UV glue for UV curing. S7. The tapered optical fiber wrapped in the encapsulated magnetic hydrogel is frozen and then placed at room temperature to obtain a tapered optical fiber magnetic field sensor based on magnetic hydrogel. S8. Connect a broadband light source and a spectrometer to the two ends of the optical fiber in the sensing element to obtain the tapered optical fiber magnetic field sensor based on magnetic hydrogel.

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