Optical fiber sensor, preparation method thereof and optical fiber magnetic field sensing device

Abstract

The invention provides an optical fiber sensor and a preparation method thereof and an optical fiber magnetic field sensing device.The optical fiber sensor comprises an optical fiber, a fixing part and a plurality of magnetic parts, the optical fiber is provided with a macro-bending section formed by bending, and the optical fiber is fixed through the fixing part so that the macro-bending section can be kept in a bending state; the plurality of magnetic members are respectively connected to the macro-bending section at intervals along the macro-bending section. When the optical fiber sensor is arranged in a magnetic field, the magnetic part is subjected to the action of the magnetic field, so that the macro-bending section is further bent and deformed, the macro-bending diameter and the effective refractive index difference correspondingly change, and spectrum drift is caused. The magnetic field intensity and the direction can be measured by representing the wavelength drift distance and the drift direction in the spectrum. The optical fiber sensor has the advantages of simple structure, flexible and adjustable performance, low cost, high stability and the like, and can realize accurate measurement of magnetic field intensity and direction in a complex environment.

Description

Technical Field

[0001] The present application belongs to the technical field of optical fiber sensors, and more specifically, relates to an optical fiber sensor and a preparation method thereof. In addition, the present application also relates to an optical fiber magnetic field sensing device. Background Art

[0002] In the modern information revolution, magnetic field sensors have an important impact on scientific research, manufacturing and daily life, such as bridge inspection, military engineering, biomedical engineering and power systems. Therefore, it is necessary to develop sensors that can accurately monitor magnetic fields in complex environments.

[0003] Optical fiber is a very good waveguide for light transmission. It has the advantages of light weight, small size, and long transmission distance, which makes it widely used in communications. External factors such as the bending state of the optical fiber, coupling conditions, and refractive index distribution often cause changes in the light intensity in the optical fiber. These characteristics can be used to measure various physical quantities. This is the detection principle of optical fiber sensors. Optical fiber sensors have attracted the interest of researchers due to their ultra-high sensitivity, chemical resistance, and compact structure, and have been widely used in various fields such as military, industry, and civil use. However, due to the anti-electromagnetic interference characteristics of optical fiber itself, it is difficult to respond to changes in the magnetic field. How to accurately measure the intensity and direction of the magnetic field through optical fiber sensors has become a technical problem. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide an optical fiber sensor and a method for preparing the same, and an optical fiber magnetic field sensing device, so as to solve the technical problem in the prior art that it is difficult for optical fibers to respond to magnetic field changes for magnetic field measurement.

[0005] To achieve the above-mentioned purpose, the technical solution adopted in the present application is: to provide an optical fiber sensor, which includes an optical fiber, a fixing part and a plurality of magnetic parts, wherein the optical fiber has a macrobend section formed by bending, and the optical fiber is fixed by the fixing part so that the macrobend section maintains a bent state, and the plurality of magnetic parts are respectively arranged in the macrobend section at intervals along the macrobend section.

[0006] According to an embodiment, the macrobending section passes through each of the magnetic members.

[0007] According to one embodiment, at least three magnetic members are provided; wherein the first magnetic member is provided at a position of the macrobending section away from the fixing member, and the second magnetic member and the third magnetic member are symmetrically provided at the macrobending section on both sides of the first magnetic member.

[0008] According to one embodiment, the fixing member is a hollow tube, and both ends of the optical fiber pass through the interior of the hollow tube, so that the optical fiber is bent to form a macrobend section and fixed in the hollow tube.

[0009] According to an embodiment, the macrobend diameter of the macrobend section is 8 mm.

[0010] According to another aspect of the present application, the present application also provides a fiber optic magnetic field sensing device, which includes any of the fiber optic sensors described above, and also includes a light source and a spectrometer, wherein the light source and the spectrometer are respectively connected to both ends of the optical fiber.

[0011] According to another aspect of the present application, the present application also provides a method for preparing an optical fiber sensor, which is used to prepare any of the optical fiber sensors described above, comprising the following steps:

[0012] Setting step: setting a plurality of magnetic members at intervals on the outer periphery of the optical fiber;

[0013] Bending step: bending the portion of the optical fiber provided with the magnetic member to form a macrobend section, and fixing the optical fiber by a fixing member to keep the macrobend section in a bent state.

[0014] According to one embodiment, the setting step includes:

[0015] forming a plurality of grooves spaced apart from each other on a substrate;

[0016] Adding magnetic particles into the organic solution according to a predetermined ratio and stirring evenly;

[0017] An organic solution mixed with magnetic particles is poured into the groove, and a section between the two ends of the optical fiber is buried in the groove;

[0018] The substrate is heated to solidify the organic solution, thereby forming a magnetic component on the periphery of the optical fiber. After cooling, the optical fiber and the magnetic component are taken out to obtain the optical fiber sensor.

[0019] According to one embodiment, the fixing member is a hollow tube, and the bending step comprises:

[0020] Pipe threading step: passing both ends of the optical fiber through the interior of the hollow tube, so that the optical fiber is bent to form a macrobend section;

[0021] Fixing steps: Inject UV glue into the hollow tube and irradiate it with UV lamp to fix the optical fiber.

[0022] According to one embodiment, the bending step further comprises:

[0023] Debugging steps: After the tube threading step and before the fixing step, connect the light source and the spectrometer to the two ends of the optical fiber respectively, adjust the bending degree of the macrobend section to change the macrobend diameter, observe and record the spectrum measured by the spectrometer under different macrobend diameters, and select the macrobend diameter corresponding to the spectrum with the largest peak as the selected macrobend diameter.

[0024] The beneficial effect of the optical fiber sensor provided by the present application is that: compared with the prior art, the optical fiber sensor of the present application forms a macrobend section by bending the optical fiber, and fixes the optical fiber by a fixing member so that the macrobend section remains in a bent state, and multiple magnetic parts are arranged at intervals on the periphery of the macrobend section, so that when the optical fiber sensor is placed in a magnetic field, the multiple magnetic parts are affected by the magnetic field, so that the macrobend section is further bent and deformed, so that the macrobend diameter and the effective refractive index difference at the macrobend section change accordingly, so that the light intensity and wavelength change accordingly after the light passes through the macrobend section, thereby causing spectral drift. When there are magnetic forces in different directions, the deformation of the macrobend section is also manifested in different ways, so the magnetic field strength and direction can be measured by characterizing the wavelength drift amount and drift direction in the spectrum. The optical fiber sensor has the advantages of simple structure, flexible and adjustable performance, low cost and high stability, and can achieve accurate measurement of magnetic field strength and direction in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0026] Figure 1 A schematic diagram of the structure of the optical fiber magnetic field sensing device provided in an embodiment of the present application;

[0027] Figure 2 The deformation performance of the optical fiber sensor in the optical fiber magnetic field sensing device provided in the embodiment of the present application under the action of magnetic fields in the first direction and the second direction, respectively, wherein the first direction and the second direction are two directions located on the same plane and perpendicular to each other;

[0028] Figure 3 are spectra respectively measured by a spectrometer in the optical fiber magnetic field sensing device when the optical fiber sensor is subjected to magnetic fields of different intensities in the first direction;

[0029] Figure 4 are spectra respectively measured by a spectrometer in the optical fiber magnetic field sensing device when the optical fiber sensor is subjected to magnetic fields of different intensities in the second direction;

[0030] Figure 5 Based on Figure 3 and Figure 4 The scatter plot between the wavelength drift and magnetic field strength of the measured results;

[0031] Figure 6 It is a top view of the optical fiber sensor when the magnetic component is solidified and formed on the outer periphery of the optical fiber during the preparation process;

[0032] Figure 7 This is a front cross-sectional view of the optical fiber sensor when the magnetic component is solidified and formed on the outer periphery of the optical fiber during the preparation process;

[0033] Figure 8 Spectral diagram of the optical fiber sensor provided in the embodiment of the present application at different macrobend diameters during the debugging step;

[0034] Among them, the reference numerals in the figure are:

[0035] 1-fiber sensor; 11-optical fiber; 111-macrobend section; 12-fixing member; 13-magnetic member; 2-light source; 3-spectrometer; 300-substrate; 301-groove. DETAILED DESCRIPTION

[0036] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0037] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0038] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0039] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0040] like Figure 1 As shown, the embodiment of the present application provides a fiber optic magnetic field sensing device for measuring the magnetic field strength and direction of a two-dimensional magnetic field. The fiber optic magnetic field sensing device comprises a fiber optic sensor 1, a light source 2 and a spectrometer 3.

[0041] Furthermore, the optical fiber sensor 1 comprises an optical fiber 11, a fixing member 12 and a plurality of magnetic members 13. The optical fiber 11 may be a single-mode optical fiber or a multi-mode optical fiber, and is used as a light transmission waveguide. The optical fiber 11 has a macrobend section 111 formed by bending, for example, Figure 1 In the embodiment, a position between the two ends of the optical fiber 11 is bent to form a spherical macrobend section 111, and the macrobend diameter at the macrobend section 111 is D.

[0042] The fixing member 12 keeps the macrobend section 111 in a bent state. For example, the fixing member 12 is a fixing fixture that can fix both ends of the macrobend section 111, so that the macrobend section 111 keeps in a bent state, so that in the absence of external force, the macrobend diameter D at the macrobend section 111 remains unchanged.

[0043] The plurality of magnetic components 13 are connected to the macrobend section 111 at intervals along the macrobend section 111. Specifically, all the magnetic components 13 can be arranged at equal intervals on the periphery of the macrobend section 111. For example, the magnetic component 13 can be a hollow ring or a tube. In specific applications, the magnetic component 13 can also be a flat plate or a block. The magnetic component 13 is sleeved on the periphery of the macrobend section 111 of the optical fiber 11. The macrobend section 111 passes through each of the magnetic components 13, and each of the magnetic components 13 is distributed at intervals. The number of magnetic components 13 can be reasonably set according to the size of the macrobend diameter at the macrobend section 111 and the sensitivity requirements for the magnetic field response. For example, in Figure 1 In the embodiment, the number of magnetic parts 13 is three, and in other embodiments, the number of magnetic parts 13 may also be two, four or five. In the present embodiment, the first magnetic part 13 is arranged at a position of the macrobend section 111 away from the fixing part 12, that is, the magnetic part 13 is arranged opposite to the fixing part 12, and the second and third magnetic parts 13 are symmetrically arranged on the macrobend section 111 on both sides of the first magnetic part 13, that is, the connection line between the first magnetic part 13 and the fixing part 12, and the connection line between the second and third magnetic parts 13 may be in a cross shape. In specific applications, the arrangement of the magnetic parts 13 may also adopt other arrangement forms.

[0044] The light source 2 and the spectrometer 3 are respectively connected to the two ends of the optical fiber 11. In this way, the light signal emitted by the light source 2 is transmitted to the other end of the optical fiber 11 through one end, and the spectrometer 3 can receive the light signal and measure the spectrum.

[0045] The optical fiber 11 may include a core located at the center, a cladding wrapped around the core, and a coating coated around the cladding. The cladding is a layer of glass or other transparent material covering the core. The cladding has a slightly lower light refractive index than the core to provide a reflection surface or light isolation, so that light can be confined to propagate in the core. The coating is generally an opaque material composed of acrylate, silicone rubber, nylon, etc., which plays a protective role.

[0046] When the light signal emitted by the light source 2 propagates in the optical fiber 11 and reaches the macrobend section 111, part of the light will escape from the core to the cladding and excite the cladding mode, that is, part of the light will be refracted at the interface between the core and the cladding, thereby entering the cladding for propagation. Moreover, since the coating is an opaque material, the light escaping to the cladding will not escape further to the outside of the coating. When the light leaves the macrobend section 111, the light in the cladding will meet the light in the core again. Since the effective refractive index of the core and the cladding is different, an optical path difference will be generated, thereby forming Mach-Zehnder interference. The spectrometer 3 connected to the other end of the optical fiber 11 can measure the spectrum after interference.

[0047] We know that when the optical fiber 11 is macrobent, based on the photoelastic effect, with the central axis of the optical fiber 11 as the dividing line, the effective refractive index of the macrobend section 111 away from the bending direction (referred to as the away side) is higher than that of the original straight optical fiber, while the effective refractive index of the macrobend section 111 facing the bending direction (referred to as the facing side) is lower than that of the original straight optical fiber. The distribution of the effective refractive index of the macrobend section 111 along the direction perpendicular to the central axis of the optical fiber can be expressed by the following formula:

[0048] Divergence side: n′(x)=n(x)(1+2x / D)

[0049] Towards the side: n′(x) = n(x)(1-2x / D)

[0050] Wherein, n′(x) and n(x) are the effective refractive indices of the optical fiber 11 when macrobending occurs and when macrobending does not occur at position x, respectively; x represents the distance from the central axis of the optical fiber 11; and D is the macrobend diameter.

[0051] It can be seen that, in the macrobend section 111 of the optical fiber 11, for the away side, the farther away from the central axis of the optical fiber 11, the higher the effective refractive index n'(x), while the closer to the central axis of the optical fiber 11, the lower the effective refractive index n'(x). In addition, the larger the macrobend diameter D, the lower the effective refractive index n'(x).

[0052] When the optical fiber sensor 1 is not placed in a magnetic field, the initial macrobend diameter at the macrobend section 111 is D, and the initial interference spectrum can be observed through the spectrometer 3. When the optical fiber sensor 1 is placed in a two-dimensional magnetic field, the magnetic component 3 will be affected by the magnetic field, thereby driving the macrobend section 111 to further deform, so that the macrobend diameter changes from the original D to D', and the effective refractive index difference also changes accordingly. The interference spectrum observed by the spectrometer 3 is also different from the initial one, but a spectrum drift occurs. By characterizing the wavelength drift amount and drift direction of the spectrum, the magnetic field strength and direction can be specifically calculated.

[0053] Specifically, Figure 3 As shown in the figure, the interference curve with a magnetic field strength of 0 mT (milli-Tesla) is the initial interference spectrum measured by the spectrometer 3 when the optical fiber sensor 1 is not placed in the magnetic field. At this time, the macrobend diameter at the macrobend section 111 is D. When the optical fiber sensor 1 is placed in a magnetic field with a magnetic field strength of 5 mT in the first direction, the magnetic element 13 is acted upon by the magnetic force in the first direction, causing the optical fiber 11, which has been bent into a quasi-spherical shape, to undergo a significant deformation in the first direction, such as Figure 2 As shown by the dotted fiber profile, the macrobend diameter becomes larger, from the original macrobend diameter D to D′, and the effective refractive index difference also changes accordingly, causing the interference wavelength to blue shift (i.e., the frequency becomes higher and the wavelength becomes shorter). At this time, the interference spectrum measured by the spectrometer 3 is as follows: Figure 3 The interference curve with a magnetic field strength of 5 mT is shown in the figure. Figure 3 The interference curves measured by the spectrometer 3 when the magnetic field strengths are 10 mT, 25 mT and 45 mT are also exemplarily indicated. By comparing these multiple interference curves, it can be seen that the stronger the magnetic field strength, the greater the wavelength drift.

[0054] Likewise, if Figure 4 As shown in the figure, the interference curve with a magnetic field strength of 0 mT is the initial interference spectrum measured by the spectrometer 3 when the optical fiber sensor 1 is not placed in the magnetic field. At this time, the macrobend diameter at the macrobend section 111 is D. When the optical fiber sensor 1 is placed in a magnetic field with a second direction and a magnetic field strength of 5 mT, the magnetic member 13 is subjected to a magnetic force in the second direction, wherein the second direction is perpendicular to the first direction and is located in the same plane, so that the optical fiber 11, which has been bent into a spherical shape, is significantly deformed in the second direction, as shown in FIG. Figure 2 As shown by the dotted fiber outline in the figure, the macrobend diameter becomes larger, and the macrobend diameter changes from the original D to D'. The effective refractive index difference also changes accordingly, causing the interference wavelength to redshift (i.e., the frequency becomes lower and the wavelength becomes longer). At this time, the interference spectrum measured by the spectrometer 3 is as follows: Figure 4 The interference curve with a magnetic field strength of 5 mT is shown in the figure. Figure 42 also exemplarily indicates the interference curves measured by the spectrometer 3 when the magnetic field strength is 10 mT, 25 mT, and 45 mT, respectively. By comparing these multiple interference curves, it can be seen that the stronger the magnetic field strength, the greater the wavelength drift.

[0055] In this way, when the optical fiber sensor 1 is placed in a plurality of known magnetic fields of different magnitudes and directions, the drift direction and wavelength drift magnitude of the interference spectrum are measured by the spectrometer 3, and then the data results measured by the multiple tests are fitted to form a chart as shown in FIG. Figure 5 As shown. Figure 5 It can be seen that under the action of the magnetic field in the first direction, the drift direction of the interference pattern is opposite to that under the action of the magnetic field in the second direction; and the greater the magnetic field intensity, the greater the wavelength drift; specifically, Figure 5 In the wavelength range of the experiment, the magnetic field strength and wavelength drift are basically linear. Through such a chart, the different directions and strengths of the magnetic field can be identified according to the drift direction and wavelength drift of the interference pattern.

[0056] Compared with the prior art, the optical fiber sensor provided in the embodiment of the present application creatively arranges a plurality of magnetic parts 13 at intervals on the outer periphery of the macrobend section 111 formed by bending, so that the magnetic parts 13 will cause the macrobend section 111 to further deform when subjected to the magnetic field, and the macrobend diameter D will also change accordingly, thereby changing the effective refractive index and causing spectral drift. The magnetic field strength and direction are measured by characterizing the wavelength drift amount and drift direction of the spectrum. Such an optical fiber sensor has a simple structure, low preparation cost, and accurate measurement.

[0057] In one embodiment of the present application, the magnetic component 13 is formed by solidifying an organic solution mixed with magnetic particles. For example, the magnetic component 13 is formed by solidifying a polydimethylsiloxane solution mixed with magnetic particles. Specifically, a polydimethylsiloxane solution is prepared with a mass ratio of water: polydimethylsiloxane of 10:1, and then 30% of the mass of the solution of ferrosoferric oxide nanoparticles is added to the prepared polydimethylsiloxane solution, and stirred evenly, and then the optical fiber 11 is immersed in the polydimethylsiloxane solution and heated, and the polydimethylsiloxane solution will be solidified on the periphery of the optical fiber 11, thereby forming the magnetic component 13. Alternatively, the polydimethylsiloxane solution mixed with magnetic particles can be poured into a mold and heated to solidify to form a hollow tubular magnetic component 13, and then the magnetic component 13 can be directly sleeved on the periphery of the optical fiber 11.

[0058] Since polydimethylsiloxane is a magnetostrictive material and is flexible after curing, the magnetic component 13 is also a flexible component and can bend with the optical fiber 11. In this way, when the macrobending section 111 is deformed, the magnetic component 13 will not limit the deformation of the optical fiber 11. Through the combination of the optical fiber 11 and the magnetostrictive material, the magnetic field strength and direction are judged, and the accuracy of the optical fiber sensor 1 is improved. In other embodiments, other organic glue solutions can also be used instead of the polydimethylsiloxane solution.

[0059] It is understandable that, depending on the different sensitivity requirements for the magnetic field response, the proportion of the magnetic particles mixed in the organic solution and the size of the magnetic part 13 formed after solidification may also be different accordingly, thereby adjusting the magnitude of the magnetic force exerted on the magnetic part 13, and further achieving the regulation of the magnetic field sensing performance of the optical fiber sensor 1.

[0060] In one embodiment of the present application, the optical fiber 11 is a single-mode optical fiber. A single-mode optical fiber is an optical fiber with a very thin central glass core and only one transmission mode. The use of a single-mode optical fiber can minimize the transmission mode of light at the macrobend diameter 111, reduce other complex transmission modes and light leakage, and thus improve the accuracy of the optical fiber sensor 1.

[0061] In another embodiment of the present application, the coating layer of the optical fiber 11 at the macrobending section 111 is stripped. The coating layer of the original optical fiber 11 at the macrobending section 111 is stripped, so that the magnetic member 13 is directly arranged on the outer periphery of the cladding of the macrobending section 111, so that the surface of the optical fiber 11 corresponding to the magnetic member 13 can be flat, making the optical fiber 11 more stable.

[0062] In another embodiment of the present application, the fixing member 12 is a hollow tube, and both ends of the optical fiber 11 pass through the interior of the hollow tube, so that the optical fiber 11 is bent to form a macrobend section 111 and is fixed in the hollow tube by ultraviolet glue.

[0063] like Figure 1 and Figure 2 As shown, the fixing member 12 is a hollow tube made of glass. The two ends of the optical fiber 11 are placed side by side and passed into the hollow tube from the same end of the hollow tube and passed out from the other end of the hollow tube, so that the optical fiber 11 is bent to form a macrobend section 111. Then, ultraviolet glue is injected into the hollow tube to fix the optical fiber 11 and the inner wall of the hollow tube together, so that the optical fiber 11 is fixed, thereby maintaining the bending state, and the macrobend diameter D of the macrobend section 111 remains unchanged without the action of external force.

[0064] In other embodiments, the two ends of the optical fiber 11 may be respectively inserted into the interior of the hollow tube from different ends of the hollow tube, and respectively exit from the other opposite end of the hollow tube. That is, one end of the optical fiber 11 enters the interior of the hollow tube from the first end of the hollow tube and exits from the second end of the hollow tube; and the other end of the optical fiber 11 enters the interior of the hollow tube from the second end of the hollow tube and exits from the first end of the hollow tube. This method also enables the optical fiber 11 to be bent to form a macrobend section 111. Ultraviolet glue is then injected into the hollow tube to fix the optical fiber 11 and the inner wall of the hollow tube together, and the optical fiber 11 is fixed, thereby maintaining the bending state. In the absence of external force, the macrobend diameter D of the macrobend section 111 remains unchanged.

[0065] The fixing member 12 is a hollow tube, which can not only fix the optical fiber 11 , but also facilitate pulling the optical fiber 11 along the hollow tube as needed during the preparation of the optical fiber sensor 1 , thereby adjusting the macrobend diameter D of the macrobend section 111 .

[0066] According to another aspect of the present application, the present application also provides a method for preparing the above-mentioned optical fiber sensor 1, comprising the following steps:

[0067] Setting step: setting a plurality of magnetic members 13 at intervals on the outer periphery of the optical fiber 11;

[0068] Bending step: bending the portion of the optical fiber 11 provided with the magnetic member 13 to form a macrobend section 111, and fixing the optical fiber 11 by the fixing member 12 to keep the macrobend section 111 in a bent state.

[0069] Specifically, in the setting step, a plurality of magnetic members 13 are arranged at intervals on the outer periphery of the optical fiber 11, and a predetermined spacing is provided between two adjacent magnetic members 13. All magnetic members 13 can be arranged approximately at the center of the optical fiber 11. The magnetic member 13 can be a hollow ring or a tube, and the magnetic member 13 is sleeved on the outer periphery of the optical fiber 11.

[0070] In the bending step, the portion of the optical fiber 11 provided with the magnetic member 13 is bent to form a macrobend section 111, so that the magnetic members 13 are spaced and distributed on the periphery of the macrobend section 111. At this time, the macrobend diameter at the macrobend section 111 is D. The optical fiber 11 is then fixed by the fixing member 12. For example, a fixing clamp can be used to fix the two ends of the macrobend section 111, so that the macrobend section 111 remains in a bent state. In the absence of external force, the macrobend diameter D remains unchanged.

[0071] In an embodiment of the present application, the setting step specifically includes:

[0072] A plurality of grooves 301 are formed on a substrate 300 and are spaced apart from each other;

[0073] Adding magnetic particles into the organic solution according to a predetermined ratio and stirring evenly;

[0074] Pour an organic solution mixed with magnetic particles into the groove 301, and bury a section between the two ends of the optical fiber 11 into the groove 301;

[0075] The substrate 300 is heated to solidify the organic solution, thereby forming a magnetic member 13 on the periphery of the optical fiber 11 , and the optical fiber 11 is taken out after cooling.

[0076] For example, Figure 6 and Figure 7 As shown, a stainless steel plate can be used as the substrate 300, and three rectangular grooves 301 are etched on the substrate 300 by laser micromachining. The three grooves 301 are spaced 5 mm apart from each other, and the size of the groove 301 is 2 mm*1 mm*0.5 mm, that is, the outer size of the magnetic component 3 is 2 mm*1 mm*0.5 mm; the surface of the substrate 300 can also be processed to form an optical fiber groove, and the optical fiber groove can connect the rectangular grooves 301 in series, and the optical fiber groove is used to accommodate the optical fiber.

[0077] A polydimethylsiloxane solution is prepared with a mass ratio of water to polydimethylsiloxane of 10:1, and then 30% of the mass of the solution of ferrosoferric oxide nanoparticles are added to the prepared polydimethylsiloxane solution, and stirred evenly;

[0078] The polydimethylsiloxane solution mixed with magnetic particles (ferroferric oxide nanoparticles) is uniformly filled into each groove 301 of the substrate 300. Then, a section between the two ends of the optical fiber 11, preferably the central area, is immersed in the polydimethylsiloxane solution in the groove 301. During the operation, the optical fiber 11 is placed in the middle of the groove 301 as much as possible, so that the polydimethylsiloxane solution can be evenly filled around the optical fiber 11, which is conducive to forming a regular and symmetrical magnetic part 3. In addition, the overflowed polydimethylsiloxane solution can be scraped off with a blade so that the polydimethylsiloxane solution is only filled in the groove 301;

[0079] The substrate 300 is heated at 120° C. for 5 minutes, so that the polydimethylsiloxane solution in the groove 301 is completely solidified and coated on the outer periphery of the optical fiber 11, thereby forming the magnetic member 13. After cooling, the optical fiber 11 is removed from the substrate 300 with tweezers.

[0080] In other embodiments, the number, size, and spacing of the grooves 301 etched on the substrate 300 are different according to the number and size of the designed magnetic parts 13. The temperature and time of heating the substrate 300 are different according to the type and amount of the organic solution mixed with magnetic particles. In addition, before immersing the optical fiber 11 in the polydimethylsiloxane solution, the coating layer of about 20 mm in length of the optical fiber 11 can be stripped, and then the part of the optical fiber stripped of the coating layer can be immersed in the polydimethylsiloxane solution. After removing the coating layer, the surface of the optical fiber 11 corresponding to the magnetic part 13 can be made flat, and the optical fiber 11 can be more stable.

[0081] The magnetic component 13 is obtained by adding magnetic particles into an organic solution and coating the magnetic component 11 with the aid of heat curing. Not only is the process simple and easy to operate, but the sensitivity of the magnetic component 13 to the magnetic field response can also be adjusted by controlling the proportion of the magnetic particles mixed in the organic solution and the size of the magnetic component 13.

[0082] In one embodiment of the present application, the fixing member 12 is a hollow tube, and the bending step includes:

[0083] Pipe threading step: both ends of the optical fiber 11 are passed through the interior of the hollow tube, so that the optical fiber 11 is bent to form a macrobend section 111;

[0084] Fixing step: injecting ultraviolet glue into the hollow tube and irradiating it with ultraviolet light to fix the optical fiber 11.

[0085] Specifically, the fixing member 12 is a hollow tube made of glass. The two ends of the optical fiber 11 are placed side by side and penetrated into the interior of the hollow tube from the same end of the hollow tube, and then both pass out from the other end of the hollow tube. In this way, the optical fiber 11 is bent to form a macrobend section 111 and is confined in the hollow tube, and cannot return to a straight state by itself. Then, ultraviolet glue is injected into the hollow tube and irradiated with an ultraviolet lamp for ten seconds, so that the ultraviolet glue is cured, and the optical fiber 11 is fixed to the inner wall of the hollow tube, so that the macrobend section 111 remains in a bent state. In the absence of external force, the macrobend diameter D of the macrobend section 111 remains unchanged.

[0086] In other embodiments, one end of the optical fiber 11 is inserted into the hollow tube from the first end of the hollow tube and then passes out from the second end of the hollow tube; the other end of the optical fiber 11 is inserted into the hollow tube from the second end of the hollow tube and then passes out from the first end of the hollow tube. In other words, the two ends of the optical fiber 11 are respectively inserted into the hollow tube from different ends of the hollow tube and respectively pass out from the other opposite end of the hollow tube. This method can also bend the optical fiber 11 to form a macrobend section 111. Then, ultraviolet glue is injected into the hollow tube and irradiated with an ultraviolet lamp for ten seconds, so that the ultraviolet glue is cured, and the optical fiber 11 is fixed to the inner wall of the hollow tube, so that the macrobend section 111 remains in a bent state. In the absence of external force, the macrobend diameter D of the macrobend section 111 remains unchanged.

[0087] It should be noted that, since the UV adhesive expands during the curing process, the macrobend diameter of the manufactured spherical macrobend section 111 will change slightly, resulting in a slight difference between the peak measured after fixing and the peak measured before fixing.

[0088] When a hollow tube is used as the fixing member 12, before the UV glue is provided, the optical fiber 11 can be pulled along the hollow tube to gradually tighten the macrobend section 111, thereby gradually adjusting the size of the macrobend diameter D. After the macrobend diameter D is adjusted and determined, the UV glue is injected into the hollow tube for curing.

[0089] In one embodiment of the present application, the bending step further includes:

[0090] Debugging steps: After the tube threading step and before the fixing step, the light source 2 and the spectrometer 3 are respectively connected to the two ends of the optical fiber 11, and the bending degree of the macrobend section 111 is adjusted to change the macrobend diameter D. The spectrum measured by the spectrometer 3 under different macrobend diameters is observed and recorded, and the macrobend diameter corresponding to the spectrum with the largest peak is selected, and then the macrobend diameter is adjusted to the selected value.

[0091] Specifically, the bending degree of the macrobend section 111 of the optical fiber 11 is gradually adjusted to change the size of the macrobend diameter D, so that the effective refractive index difference at the macrobend section 111 will change accordingly, and the wavelength and light intensity of the optical signal measured by the spectrometer 3 connected to the optical fiber 11 will also be different, thereby presenting different spectrum graphs. The spectrum graphs measured by the spectrometer 3 under different macrobend diameters are recorded, such as Figure 8 As shown, the fluctuation amplitude, peak value and wave shape of the spectrum curve measured under different macrobend diameters are all different. The macrobend diameter corresponding to the spectrum curve with the largest peak is selected. The macrobend diameter of the macrobend section 111 can be 7 to 9 mm, preferably 7.5 to 8.5 mm. For example, Figure 8From the several spectral curves in FIG. 1 , it can be seen that the peak of the corresponding spectral curve is the largest when the macrobend diameter is 8 mm, so the macrobend diameter D of the optical fiber 11 is adjusted to 8 mm. The macrobend diameter of the macrobend section 111 can be set to different ranges according to actual conditions.

[0092] Through the debugging steps, the macrobend diameter corresponding to the spectral curve with the largest peak is selected as the final macrobend diameter of the macrobend section 111. This macrobend diameter value is the optimal value, which can facilitate the resolution of the collected data and improve the accuracy of the optical fiber sensor 1.

[0093] In one embodiment of the present application, in the debugging step, the optical fiber 11 is fixed on the translation stage by using an optical fiber clamp, and then the translation stage is moved so that both ends of the optical fiber 11 move away from the hollow tube. Due to the presence of the hollow tube, the macrobend section 111 of the optical fiber 11 gradually shrinks, and the macrobend diameter D gradually decreases, thereby forming a spherical macrobend section 111. By controlling the moving distance of the translation stage, the size of the macrobend diameter D can be accurately adjusted, and the operation is simple.

[0094] In summary, the optical fiber sensor 1 and optical fiber magnetic field sensing device provided by the present application have the advantages of simple structure, flexible and adjustable performance, low cost and high stability, and can achieve accurate measurement of magnetic field strength and direction in complex environments. The preparation process of the optical fiber sensor 1 is also simple and easy to operate.

[0095] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. An optical fiber sensor, characterized in that: The optical fiber comprises an optical fiber, a fixing part and a plurality of magnetic parts. The optical fiber has a macrobending section formed by bending, and the optical fiber is fixed by the fixing part so that the macrobending section maintains a bending state. The plurality of magnetic parts are respectively connected to the macrobending section at intervals along the macrobending section.

2. The optical fiber sensor according to claim 1, characterized in that The macrobending section passes through each of the magnetic members.

3. The optical fiber sensor according to claim 1 or 2, characterized in that: There are at least three magnetic members, wherein the first magnetic member is arranged at a position of the macrobending section away from the fixing member, and the second magnetic member and the third magnetic member are symmetrically arranged at the macrobending section on both sides of the first magnetic member.

4. The optical fiber sensor according to claim 1 or 2, characterized in that: The fixing member is a hollow tube, and both ends of the optical fiber pass through the interior of the hollow tube, so that the optical fiber is bent to form the macrobend section and is fixed in the hollow tube.

5. The optical fiber sensor according to claim 1 or 2, characterized in that: The macrobend diameter of the macrobend section is 8 mm.

6. An optical fiber magnetic field sensing device, characterized in that: The optical fiber sensor comprises the optical fiber sensor as claimed in any one of claims 1 to 5, and further comprises a light source and a spectrometer, wherein the light source and the spectrometer are respectively connected to two ends of the optical fiber.

7. A method for preparing an optical fiber sensor, characterized in that: The method for preparing the optical fiber sensor according to any one of claims 1 to 5 comprises the following steps: Setting step: setting a plurality of magnetic members at intervals on the outer periphery of the optical fiber; Bending step: bending the portion of the optical fiber provided with the magnetic member to form a macrobend section, and fixing the optical fiber by a fixing member to keep the macrobend section in a bent state.

8. The method for preparing the optical fiber sensor according to claim 7, characterized in that: The setting steps include: forming a plurality of grooves spaced apart from each other on a substrate; Adding magnetic particles into the organic solution according to a predetermined ratio and stirring evenly; An organic solution mixed with magnetic particles is poured into the groove, and a section between the two ends of the optical fiber is buried in the groove; The substrate is heated to solidify the organic solution, thereby forming a magnetic component on the periphery of the optical fiber. After cooling, the optical fiber and the magnetic component are taken out to obtain the optical fiber sensor.

9. The method for preparing the optical fiber sensor according to claim 7 or 8, characterized in that: The fixing member is a hollow tube, and the bending step comprises: Pipe-threading step: passing both ends of the optical fiber through the interior of the hollow tube, so that the optical fiber is bent and forms the macrobend section; Fixing step: injecting ultraviolet glue into the hollow tube and irradiating it with ultraviolet light to fix the optical fiber.

10. The method for preparing an optical fiber sensor according to claim 9, characterized in that: The bending step further comprises: Debugging steps: After the tube threading step and before the fixing step, the light source and the spectrometer are respectively connected to the two ends of the optical fiber, the bending degree of the macrobend section is adjusted to change the macrobend diameter, the spectrum measured by the spectrometer under different macrobend diameters is observed and recorded, and the macrobend diameter corresponding to the spectrum with the largest peak is selected as the selected macrobend diameter.

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