Device and method for measuring magnetization intensity of optical fiber magnetic fluid

Abstract

The invention discloses an optical fiber magnetic fluid magnetization intensity measuring device and method, and relates to the technical field of optical fiber sensing. The device comprises a broadband light source, an optical fiber circulator, a sensing head, a magnetic field regulation and control device and a spectrum analyzer, wherein the sensing head comprises a first single-mode optical fiber, a hollow-core optical fiber, a UV adhesive film, a second single-mode optical fiber and a quartz tube. The broadband light source emits a detection light signal; the optical fiber circulator transmits a detection optical signal to a first single-mode optical fiber of the sensing head; the magnetic field regulation and control device applies a directional magnetic field to the sensing head; the sensing head determines an interference spectrum of the magnetic fluid to be detected according to the detection light signal and the directional magnetic field; the interference spectrum is determined based on a reflected light signal reflected by a Fabry-Perot interferometer; and the spectrum analyzer receives and demodulates the interference spectrum to obtain the magnetization intensity of the magnetic fluid to be detected. According to the invention, accurate measurement of the magnetization intensity of the magnetofluid can be realized.

Description

Technical Field

[0001] The present application relates to the field of optical fiber sensing technology, and in particular to a device and method for measuring the magnetization intensity of an optical fiber magnetic fluid. Background Art

[0002] As a new type of superparamagnetic liquid functional material, ferrofluid has attracted extensive attention from researchers for its superior magneto-optical properties. Various sensors based on ferrofluid have been developed and applied in many fields such as biomedicine, environmental testing, geological exploration, etc. However, the absorption / refractive properties of ferrofluids cause serious light loss when detecting their magnetization intensity using traditional optical measurement methods, resulting in low detection sensitivity and difficulty in accurately measuring magnetization intensity. Summary of the invention

[0003] The purpose of this application is to provide a device and method for measuring the magnetization intensity of an optical fiber magnetic fluid, which can achieve accurate measurement of the magnetization intensity of a magnetic fluid.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] In a first aspect, the present application provides a device for measuring the magnetization intensity of an optical fiber magnetic fluid, the device comprising: a broadband light source, an optical fiber circulator, a sensor head, a magnetic field control device and a spectrum analyzer; wherein the sensor head comprises a first single-mode optical fiber, a hollow-core optical fiber, a UV adhesive film, a second single-mode optical fiber and a quartz tube;

[0006] The broadband light source, the sensor head and the spectrum analyzer are all connected to the optical fiber circulator; the sensor head is arranged between the N pole and the S pole of the magnetic field control device;

[0007] The first single-mode optical fiber is fused with the hollow-core optical fiber; the UV adhesive film is provided at the end of the hollow-core optical fiber; the fusion surface between the first single-mode optical fiber and the hollow-core optical fiber is a first reflection surface; the critical surface between the air in the hollow-core optical fiber and the UV adhesive film is a second reflection surface; the first reflection surface and the second reflection surface constitute a Fabry-Perot interferometer; the Fabry-Perot interferometer and the second single-mode optical fiber are placed inside the quartz tube at intervals, and the quartz tube is provided with an opening at the intervals;

[0008] The broadband light source is used to emit a detection light signal;

[0009] The optical fiber circulator is used to transmit the detection light signal to the first single-mode optical fiber of the sensor head;

[0010] The magnetic field control device is used to apply a directional magnetic field to the sensor head;

[0011] The sensor head is used to determine the interference spectrum of the magnetic fluid to be measured according to the detection light signal and the directional magnetic field; the magnetic fluid to be measured enters the quartz tube through the opening; the interference spectrum is determined based on the reflected light signal reflected by the Fabry-Perot interferometer;

[0012] The optical fiber circulator is also used to transmit the interference spectrum to the spectrum analyzer;

[0013] The spectrum analyzer is used to receive and demodulate the interference spectrum to obtain the magnetization intensity of the magnetic fluid to be measured.

[0014] Optionally, the end of the second single-mode optical fiber is cut at an angle of 45 degrees to 60 degrees.

[0015] Optionally, the core diameters of the first single-mode optical fiber and the second single-mode optical fiber are both in the range of 8 μm to 9 μm, and the outer diameters of the first single-mode optical fiber and the second single-mode optical fiber are both 125 μm.

[0016] Optionally, the core diameter of the hollow-core optical fiber is 70 microns, and the outer diameter of the hollow-core optical fiber is 125 microns; the inner diameter of the quartz tube is 125 microns, and the outer diameter of the quartz tube is 200 microns.

[0017] Optionally, the length of the hollow core optical fiber ranges from 50 microns to 100 microns; the interval between the UV adhesive film and the second single-mode optical fiber ranges from 100 microns to 150 microns; and the thickness of the UV adhesive film ranges from 5 microns to 10 microns.

[0018] Optionally, the openings on the quartz tube correspond to opening diameters in a range of 20 micrometers to 25 micrometers, and the opening density ranges from 20 / mm to 25 / mm.

[0019] In a second aspect, the present application provides a method for measuring the magnetization intensity of an optical fiber magnetic fluid, which is implemented by using an optical fiber magnetic fluid magnetization intensity measuring device; the method for measuring the magnetization intensity of an optical fiber magnetic fluid comprises:

[0020] Controlling the broadband light source to emit a detection light signal, and controlling the magnetic field control device to apply a directional magnetic field to the sensor head;

[0021] Obtaining the interference spectrum of the magnetic fluid to be measured; the interference spectrum is determined by the sensor head according to the detection light signal and the directional magnetic field, based on the reflected light signal reflected by the Fabry-Perot interferometer; the magnetic fluid to be measured enters the quartz tube in the sensor head through the opening;

[0022] The interference spectrum is demodulated to obtain the magnetization intensity of the magnetic fluid to be measured.

[0023] Optionally, the function expression corresponding to the interference spectrum is:

[0024] I=A 2 +B 2 +2ABcos(2Φ);

[0025] A=R1 1 / 2 ;

[0026] B=(1-α)(1-R1)R2 1 / 2 ;

[0027] Φ=2πnL / λ;

[0028] Wherein, I is the function corresponding to the interference spectrum; A is the mathematical expression corresponding to the first reflection surface; B is the mathematical expression corresponding to the second reflection surface; Φ is the phase difference between the two light beams in the Fabry-Perot interferometer cavity; R1 is the reflectivity of the first reflection surface; α is the intracavity transmission loss of the Fabry-Perot interferometer; R2 is the reflectivity of the second reflection surface; n is the refractive index of the cavity medium of the Fabry-Perot interferometer; L is the cavity length of the Fabry-Perot interferometer; λ is the wavelength of the incident light.

[0029] Optionally, demodulating the interference spectrum to obtain the magnetization intensity of the magnetic fluid to be measured specifically includes:

[0030] According to the oriented magnetic field, the force applied to the UV film by the oriented extension of the magnetic fluid to be tested under the action of the oriented magnetic field is determined; the expression of the force applied to the UV film is:

[0031] P=μ0HL MF c·m;

[0032] According to the force applied to the UV film, the deformation amount of the UV film is determined, and the change in the cavity length of the Fabry-Perot interferometer is obtained; the expression of the change in the cavity length is:

[0033]

[0034] Where P is the force applied to the UV film; μ0 is the vacuum magnetic permeability; H is the strength of the directional magnetic field; L MF is the spacing length between the UV film and the second single-mode optical fiber; c is the concentration of the magnetic fluid to be measured; m is the magnetization intensity of the magnetic fluid to be measured; ΔL is the change in cavity length; E is the Young's modulus of the UV film; υ is the Poisson's ratio of the UV film; r is the film radius of the UV film; h is the film thickness of the UV film;

[0035] Based on the interference spectrum, the force applied to the UV adhesive film and the change in cavity length, the relationship between the wavelength drift and the magnetization intensity of the magnetic fluid to be measured is determined to obtain the magnetization intensity of the magnetic fluid to be measured.

[0036] Optionally, the relationship between the wavelength drift and the magnetization intensity of the magnetic fluid to be measured corresponds to the expression:

[0037]

[0038] Where Δλ is the wavelength shift.

[0039] According to the specific embodiments provided in this application, this application has the following technical effects:

[0040] The present application provides a device and method for measuring the magnetization intensity of an optical fiber magnetic fluid, the device comprising: a broadband light source, an optical fiber circulator, a sensor head, a magnetic field control device and a spectrum analyzer; wherein the sensor head comprises a first single-mode optical fiber, a hollow-core optical fiber, a UV film, a second single-mode optical fiber and a quartz tube. The broadband light source emits a detection light signal; the optical fiber circulator transmits the detection light signal to the first single-mode optical fiber of the sensor head; the magnetic field control device applies a directional magnetic field to the sensor head; the sensor head determines the interference spectrum of the magnetic fluid to be measured according to the detection light signal and the directional magnetic field; the interference spectrum is determined based on the reflected light signal reflected by the Fabry-Perot interferometer; the spectrum analyzer receives and demodulates the interference spectrum to obtain the magnetization intensity of the magnetic fluid to be measured. Based on the characteristics of magnetic fluid and UV film and the principle of Fabry-Perot interferometer, the present application detects the magnetization intensity of the magnetic fluid to be measured by demodulating the deformation of the UV film at the end of the Fabry-Perot interferometer, avoiding the loss of the detection light due to the absorption / refraction of the magnetic fluid, thereby accurately measuring the magnetization intensity of the magnetic fluid to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the drawings required for use in the embodiments 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 work.

[0042] Figure 1 A schematic diagram of the optical fiber magnetic fluid magnetization intensity measurement device provided in this application;

[0043] Figure 2 A schematic diagram of the structure of the sensor head provided in this application;

[0044] Figure 3 The working principle diagram of the sensor head provided for this application;

[0045] Figure 4 Interference spectrum diagram of the sensor head provided by this application;

[0046] Figure 5This is a spectrum diagram of the sensor head provided in this application under different magnetic fluid filling conditions.

[0047] Figure numerals: broadband light source -1, optical fiber circulator -2, sensor head -3, magnetic field control device -4, spectrum analyzer -5; first single-mode optical fiber -31, hollow core optical fiber -32, UV adhesive film -33, second single-mode optical fiber -34, quartz tube -35, opening -36. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0049] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0050] In an exemplary embodiment, Figure 1 As shown, a device for measuring the magnetization intensity of an optical fiber magnetic fluid is provided. The device comprises: a broadband light source 1, an optical fiber circulator 2, a sensor head 3, a magnetic field control device 4 and a spectrum analyzer 5.

[0051] The broadband light source 1 , the sensor head 3 and the spectrum analyzer 5 are all connected to the optical fiber circulator 2 ; the sensor head 3 is arranged between the N pole and the S pole of the magnetic field control device 4 .

[0052] like Figure 2 As shown, the sensor head 3 includes a first single-mode optical fiber 31 , a hollow-core optical fiber 32 , a UV adhesive film 33 , a second single-mode optical fiber 34 and a quartz tube 35 .

[0053] The first single-mode optical fiber 31 is fused with the hollow-core optical fiber 32; a UV adhesive film 33 is provided at the end of the hollow-core optical fiber 32. Figure 3 As shown, the fusion surface of the first single-mode optical fiber 31 and the hollow-core optical fiber 32 is the first reflection surface; the critical surface between the air in the hollow-core optical fiber 32 and the UV adhesive film 33 is the second reflection surface; the first reflection surface and the second reflection surface constitute a Fabry-Perot interferometer. Figure 3 The arrows in the figure represent the direction of optical signal transmission. Figure 2 As shown, the Fabry-Perot interferometer and the second single-mode optical fiber 34 are placed inside the quartz tube 35 at intervals, and the quartz tube 35 is provided with an opening 36 at the interval. That is, the quartz tube 35 is provided with an opening 36 at the interval between the Fabry-Perot interferometer and the second single-mode optical fiber 34, which is used to achieve magnetic fluid filling and external environment communication.

[0054] The broadband light source 1 is used to emit a detection light signal; the optical fiber circulator 2 is used to transmit the detection light signal to the first single-mode optical fiber 31 of the sensor head 3. The magnetic field control device 4 is used to apply a directional magnetic field to the sensor head 3; the sensor head 3 is used to determine the interference spectrum of the magnetic fluid to be measured based on the detection light signal and the directional magnetic field. The magnetic fluid to be measured enters the quartz tube 35 through the opening 36; the interference spectrum is determined based on the reflected light signal reflected by the Fabry-Perot interferometer.

[0055] The optical fiber circulator 2 is also used to transmit the interference spectrum to the spectrum analyzer 5; the spectrum analyzer 5 is used to receive and demodulate the interference spectrum to obtain the magnetization intensity of the magnetic fluid to be measured.

[0056] In one embodiment, the end of the second single-mode optical fiber 34 is cut at a 45-60 degree angle. The core diameters of the first single-mode optical fiber 31 and the second single-mode optical fiber 34 are both in the range of 8 microns to 9 microns, and the outer diameters of the first single-mode optical fiber 31 and the second single-mode optical fiber 34 are both 125 microns.

[0057] The core diameter of the hollow core optical fiber 32 is 70 micrometers, and the outer diameter of the hollow core optical fiber 32 is 125 micrometers; the inner diameter of the quartz tube 35 is 125 micrometers, and the outer diameter of the quartz tube 35 is 200 micrometers.

[0058] The length of the hollow core optical fiber 32 ranges from 50 microns to 100 microns; the interval between the UV adhesive film 33 and the second single-mode optical fiber 34 ranges from 100 microns to 150 microns; and the thickness of the UV adhesive film 33 ranges from 5 microns to 10 microns.

[0059] The corresponding opening diameters of the openings 36 on the quartz tube 35 range from 20 micrometers to 25 micrometers, and the density of the openings 36 ranges from 20 / mm to 25 / mm.

[0060] This application solves the problems of low sensitivity, complex device, and difficulty in accurately measuring the magnetization intensity of magnetic fluids caused by the existing optical magnetic fluid magnetization intensity detection methods, serious absorption / refractive loss of magnetic fluids, etc. This application proposes a fiber-optic magnetic fluid magnetization intensity measurement device based on the characteristics of magnetic fluids and UV glue and the principle of fiber-optic Fabry-Perot interferometer. It is simple to make, has a stable structure, and high sensitivity, and can be used for accurate measurement of the magnetization intensity of magnetic fluids.

[0061] Specifically, in practical applications, the optical fiber magnetic fluid magnetization intensity measuring device includes a broadband light source 1, an optical fiber circulator 2, a sensor head 3, a magnetic field control device 4 and a spectrum analyzer 5; the broadband light source 1 is connected to the first port of the optical fiber circulator 2, and the broadband light source 1 is used to provide a detection light signal; the sensor head 3 is connected to the second port of the optical fiber circulator 2, and the sensor head 3 is used to determine the interference spectrum of the magnetic fluid to be measured, so as to subsequently measure the magnetization intensity of the magnetic fluid to be measured; the spectrum analyzer 5 is connected to the third port of the optical fiber circulator, and the spectrum analyzer 5 is used to receive and demodulate the reflected light signal.

[0062] The quartz tube is provided with an opening 36 at the interval between the Fabry-Perot interferometer and the second single-mode optical fiber 34 for achieving magnetic fluid filling and communication with the external environment.

[0063] The detection light signal emitted by the broadband light source 1 enters the sensor head 3 through the optical fiber circulator 2; the incident light signal is transmitted to the hollow-core optical fiber 32 through the first single-mode optical fiber 31, and part of the incident light signal is reflected back to the first single-mode optical fiber 31 at the first reflection surface; another part of the incident light signal is transmitted into the hollow-core optical fiber 32, and is reflected back to the first single-mode optical fiber 31 at the second reflection surface; the total reflected light signal enters the optical spectrum analyzer 5 through the optical fiber circulator 2, and is received and demodulated by the optical spectrum analyzer 5.

[0064] When measuring the magnetization intensity of the magnetic fluid, the magnetic fluid to be measured enters the interior of the quartz tube 35 through the opening 36; a directional magnetic field is applied to the sensor head 3 through the magnetic field control device 4; the magnetic fluid to be measured extends in a directional manner under the action of the magnetic field, generating a force applied to the UV film 33; the UV film 33 is deformed by the force, thereby changing the cavity length of the Fabry-Perot interferometer; the magnetization intensity of the magnetic fluid to be measured can be detected by demodulating the interference spectrum of the sensor head 3.

[0065] In an exemplary embodiment, a method for measuring the magnetization intensity of an optical fiber magnetic fluid is provided, and the method for measuring the magnetization intensity of an optical fiber magnetic fluid is implemented by using an optical fiber magnetic fluid magnetization intensity measuring device. The method for measuring the magnetization intensity of an optical fiber magnetic fluid comprises:

[0066] The broadband light source is controlled to emit a detection light signal, and the magnetic field control device is controlled to apply a directional magnetic field to the sensor head.

[0067] Obtain the interference spectrum of the magnetic fluid to be measured; the interference spectrum is determined by the reflected light signal reflected by the sensor head based on the detection light signal and the directional magnetic field and the Fabry-Perot interferometer; the magnetic fluid to be measured enters the quartz tube in the sensor head through the opening.

[0068] The interference spectrum is demodulated to obtain the magnetization intensity of the magnetic fluid to be tested.

[0069] In one embodiment, the function expression corresponding to the interference spectrum is:

[0070] I=A 2 +B 2 +2ABcos(2Φ).

[0071] A=R1 1 / 2 .

[0072] B=(1-α)(1-R1)R2 1 / 2 .

[0073] Φ=2πnL / λ.

[0074] Wherein, I is the function corresponding to the interference spectrum; A is the mathematical expression corresponding to the first reflection surface; B is the mathematical expression corresponding to the second reflection surface; Φ is the phase difference between the two light beams in the Fabry-Perot interferometer cavity; R1 is the reflectivity of the first reflection surface; α is the intracavity transmission loss of the Fabry-Perot interferometer; R2 is the reflectivity of the second reflection surface; n is the refractive index of the cavity medium of the Fabry-Perot interferometer; L is the cavity length of the Fabry-Perot interferometer; λ is the wavelength of the incident light.

[0075] As an optional implementation, the interference spectrum is demodulated to obtain the magnetization intensity of the magnetic fluid to be measured, specifically including:

[0076] According to the oriented magnetic field, the force applied to the UV film generated by the oriented extension of the magnetic fluid to be tested under the action of the oriented magnetic field is determined; the expression of the force applied to the UV film is:

[0077] P=μ0HL MF c.m.

[0078] According to the force applied to the UV film, the deformation amount of the UV film is determined, and the change in the cavity length of the Fabry-Perot interferometer is obtained; the expression of the change in the cavity length is:

[0079]

[0080] Where P is the force applied to the UV film; μ0 is the vacuum magnetic permeability; H is the strength of the directional magnetic field; L MF is the spacing length between the UV film and the second single-mode optical fiber; c is the concentration of the magnetic fluid to be measured; m is the magnetization intensity of the magnetic fluid to be measured; ΔL is the change in cavity length; E is the Young's modulus of the UV film; υ is the Poisson's ratio of the UV film; r is the film radius of the UV film; and h is the film thickness of the UV film.

[0081] Based on the interference spectrum, the force applied to the UV adhesive film and the change in cavity length, the relationship between the wavelength drift and the magnetization intensity of the magnetic fluid to be measured is determined to obtain the magnetization intensity of the magnetic fluid to be measured.

[0082] In one embodiment, the relationship between the wavelength shift and the magnetization intensity of the magnetic fluid to be measured is expressed as follows:

[0083]

[0084] Among them, Δλ is the wavelength drift.

[0085] The working principle of the sensor head provided in this application can be analyzed by a double-beam interference model, and its interference spectrum is as follows: Figure 4 As shown. The interference spectrum function of the sensor head can be expressed as:

[0086] I=A 2 +B 2 +2ABcos(2Φ) (1)

[0087] In formula (1), A=R1 1 / 2 , B=(1-α)(1-R1)R2 1 / 2 , Φ=2πnL / λ. R1 and R2 are the reflectivities of the first reflection surface and the second reflection surface respectively, α is the intracavity transmission loss of the Fabry-Perot interferometer, n is the intracavity medium refractive index of the Fabry-Perot interferometer, L is the cavity length of the Fabry-Perot interferometer, and λ is the wavelength of the incident light.

[0088] When the sensor head is used to measure the magnetization intensity of magnetic fluid, the magnetic fluid to be measured enters the quartz tube through the opening. A directional magnetic field H is applied to the sensor head through the magnetic field control device. The magnetic fluid to be measured extends in a directional manner under the action of the magnetic field H, generating a force P applied to the UV film, which can be expressed as:

[0089] P=μ0HL MF c·m (2)

[0090] In formula (2), μ0 is the vacuum magnetic permeability, H is the strength of the applied directional magnetic field, and L is MF is the spacing length between the UV adhesive film and the second single-mode optical fiber, c is the concentration of the magnetic fluid to be measured, and m is the magnetization intensity of the magnetic fluid to be measured.

[0091] The UV film is deformed by the force P exerted by the magnetic fluid to be measured, thereby changing the cavity length L of the fiber Fabry-Perot interferometer. The cavity length change ΔL can be expressed as:

[0092]

[0093] In formula (3), E is the Young's modulus of the UV film, υ is the Poisson's ratio of the UV film, r is the film radius of the UV film, and h is the film thickness of the UV film.

[0094] The magnetization intensity m of the magnetic fluid to be measured can be detected by demodulating the interference spectrum of the sensor head. The relationship between the wavelength drift Δλ of the interference spectrum of the sensor head and the magnetization intensity m of the magnetic fluid to be measured can be expressed as:

[0095]

[0096] From formula (4), we can know that by demodulating the wavelength drift Δλ of the sensor head interference spectrum, we can accurately measure the magnetization intensity m of the magnetic fluid to be measured. We can also compare it with the database spectrum to analyze the composition of the magnetic fluid to be measured. The spectra of the sensor head under different magnetic fluid filling conditions are as follows: Figure 5 shown.

[0097] The beneficial effects of this application are:

[0098] Based on the characteristics of magnetic fluid and UV glue and the principle of optical fiber Fabry-Perot interferometer, the present application proposes a device for measuring the magnetization intensity of optical fiber magnetic fluid; the present application utilizes the characteristics of UV glue film deformation under force and magnetic fluid directional extension with magnetic field, and detects the magnetization intensity of the magnetic fluid to be measured by demodulating the deformation of the UV glue film at the end of the Fabry-Perot interferometer, thereby avoiding the loss of detection light due to magnetic fluid absorption / refraction, thereby achieving accurate measurement of the magnetization intensity of the magnetic fluid to be measured; the optical fiber magnetic fluid magnetization intensity measurement device provided by the present application is simple to manufacture, stable in structure, and highly sensitive, and provides a feasible solution for high-precision, stable and reliable detection of the magnetization intensity of magnetic fluid.

[0099] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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.

[0100] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. An optical fiber magnetic fluid magnetization intensity measuring device, characterized in that: The optical fiber magnetic fluid magnetization intensity measuring device comprises: a broadband light source, an optical fiber circulator, a sensor head, a magnetic field control device and a spectrum analyzer; wherein the sensor head comprises a first single-mode optical fiber, a hollow-core optical fiber, a UV adhesive film, a second single-mode optical fiber and a quartz tube; The broadband light source, the sensor head and the spectrum analyzer are all connected to the optical fiber circulator; the sensor head is arranged between the N pole and the S pole of the magnetic field control device; The first single-mode optical fiber is fused with the hollow-core optical fiber; the UV adhesive film is provided at the end of the hollow-core optical fiber; the fusion surface between the first single-mode optical fiber and the hollow-core optical fiber is a first reflection surface; the critical surface between the air in the hollow-core optical fiber and the UV adhesive film is a second reflection surface; the first reflection surface and the second reflection surface constitute a Fabry-Perot interferometer; the Fabry-Perot interferometer and the second single-mode optical fiber are placed inside the quartz tube at intervals, and the quartz tube is provided with an opening at the intervals; The broadband light source is used to emit a detection light signal; The optical fiber circulator is used to transmit the detection light signal to the first single-mode optical fiber of the sensor head; The magnetic field control device is used to apply a directional magnetic field to the sensor head; The sensor head is used to determine the interference spectrum of the magnetic fluid to be measured according to the detection light signal and the directional magnetic field; the magnetic fluid to be measured enters the quartz tube through the opening; the interference spectrum is determined based on the reflected light signal reflected by the Fabry-Perot interferometer; The optical fiber circulator is also used to transmit the interference spectrum to the spectrum analyzer; The spectrum analyzer is used to receive and demodulate the interference spectrum to obtain the magnetization intensity of the magnetic fluid to be measured.

2. The optical fiber magnetic fluid magnetization intensity measuring device according to claim 1, characterized in that: The end of the second single-mode optical fiber is cut at an angle of 45 degrees to 60 degrees.

3. The optical fiber magnetic fluid magnetization intensity measuring device according to claim 1, characterized in that: The core diameters of the first single-mode optical fiber and the second single-mode optical fiber are both in the range of 8 microns to 9 microns, and the outer diameters of the first single-mode optical fiber and the second single-mode optical fiber are both 125 microns.

4. The optical fiber magnetic fluid magnetization intensity measuring device according to claim 1, characterized in that: The core diameter of the hollow-core optical fiber is 70 microns, and the outer diameter of the hollow-core optical fiber is 125 microns; the inner diameter of the quartz tube is 125 microns, and the outer diameter of the quartz tube is 200 microns.

5. The optical fiber magnetic fluid magnetization intensity measuring device according to claim 1, characterized in that: The length of the hollow core optical fiber ranges from 50 microns to 100 microns; the interval between the UV adhesive film and the second single-mode optical fiber ranges from 100 microns to 150 microns; and the thickness of the UV adhesive film ranges from 5 microns to 10 microns.

6. The optical fiber magnetic fluid magnetization intensity measuring device according to claim 1, characterized in that: The openings on the quartz tube have opening diameters corresponding to a range of 20 micrometers to 25 micrometers, and a density of the openings is in a range of 20 to 25 per millimeter.

7. A method for measuring the magnetization intensity of optical fiber magnetic fluid, characterized in that: The optical fiber magnetic fluid magnetization intensity measurement method is implemented by using the optical fiber magnetic fluid magnetization intensity measurement device according to any one of claims 1 to 6; The optical fiber magnetic fluid magnetization intensity measurement method comprises: Controlling the broadband light source to emit a detection light signal, and controlling the magnetic field control device to apply a directional magnetic field to the sensor head; Obtaining the interference spectrum of the magnetic fluid to be measured; the interference spectrum is determined by the sensor head according to the detection light signal and the directional magnetic field, based on the reflected light signal reflected by the Fabry-Perot interferometer; the magnetic fluid to be measured enters the quartz tube in the sensor head through the opening; The interference spectrum is demodulated to obtain the magnetization intensity of the magnetic fluid to be measured.

8. The method for measuring the magnetization intensity of optical fiber magnetic fluid according to claim 7, characterized in that: The function expression corresponding to the interference spectrum is: I=A 2 +B 2 +2ABcos(2Φ); A=R1 1 / 2 ; B=(1-α)(1-R1)R2 1 / 2 ; Φ=2πnL / λ; Wherein, I is the function corresponding to the interference spectrum; A is the mathematical expression corresponding to the first reflection surface; B is the mathematical expression corresponding to the second reflection surface; Φ is the phase difference between the two light beams in the Fabry-Perot interferometer cavity; R1 is the reflectivity of the first reflection surface; α is the intracavity transmission loss of the Fabry-Perot interferometer; R2 is the reflectivity of the second reflection surface; n is the refractive index of the cavity medium of the Fabry-Perot interferometer; L is the cavity length of the Fabry-Perot interferometer; λ is the wavelength of the incident light.

9. The method for measuring the magnetization intensity of optical fiber magnetic fluid according to claim 7, characterized in that: Demodulating the interference spectrum to obtain the magnetization intensity of the magnetic fluid to be measured specifically includes: According to the oriented magnetic field, the force applied to the UV film by the oriented extension of the magnetic fluid to be tested under the action of the oriented magnetic field is determined; the expression of the force applied to the UV film is: P=μ0HL MF c·m; According to the force applied to the UV film, the deformation amount of the UV film is determined, and the change in the cavity length of the Fabry-Perot interferometer is obtained; the expression of the change in the cavity length is: Where P is the force applied to the UV film; μ0 is the vacuum magnetic permeability; H is the strength of the directional magnetic field; L MF is the spacing length between the UV film and the second single-mode optical fiber; c is the concentration of the magnetic fluid to be measured; m is the magnetization intensity of the magnetic fluid to be measured; ΔL is the change in cavity length; E is the Young's modulus of the UV film; υ is the Poisson's ratio of the UV film; r is the film radius of the UV film; h is the film thickness of the UV film; Based on the interference spectrum, the force applied to the UV adhesive film and the change in cavity length, the relationship between the wavelength drift and the magnetization intensity of the magnetic fluid to be measured is determined to obtain the magnetization intensity of the magnetic fluid to be measured.

10. The method for measuring the magnetization intensity of optical fiber magnetic fluid according to claim 9, characterized in that: The relationship between the wavelength drift and the magnetization intensity of the magnetic fluid to be measured is expressed as follows: Where Δλ is the wavelength shift.

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