A device and method for measuring the magnetization of a fiber optic magnetofluid

Abstract

The application discloses a kind of optical fiber magnetic fluid magnetization intensity measuring device and method, it is related to optical fiber sensing field.The device includes: broadband light source, optical fiber circulator, sensor head, magnetic field regulation device and spectrum analyzer;Wherein, sensor head includes first single-mode optical fiber, hollow optical fiber, UV glue film, second single-mode optical fiber and quartz tube.Broadband light source emits probe light signal;Optical fiber circulator transmits probe light signal to the first single-mode optical fiber of sensor head;Magnetic field regulation device applies directional magnetic field to sensor head;Sensor head determines the interference spectrum of the magnetic fluid to be measured according to probe light signal and directional magnetic field;Interference spectrum is determined based on the reflected light signal that Fabry-Perot interferometer is reflected;Spectrum analyzer receives and demodulates interference spectrum, obtains the magnetization intensity of the magnetic fluid to be measured.The application can realize the accurate measurement of magnetic fluid magnetization intensity.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of optical fiber sensing, in particular to a device and method for measuring the magnetization intensity of a magnetic fluid. BACKGROUND

[0002] As a new type of superparamagnetic liquid functional material, the magnetic fluid has attracted extensive attention of researchers due to its superior magneto-optical performance. Various sensors based on the magnetic fluid have been developed and applied in many fields such as biological medicine, environmental detection and geological exploration. However, the light absorption / refraction characteristics of the magnetic fluid result in serious light loss when the traditional optical measurement method is used to detect the magnetization intensity, thereby leading to low detection sensitivity and difficulty in accurately measuring the magnetization intensity. SUMMARY

[0003] The application aims to provide a device and method for measuring the magnetization intensity of a magnetic fluid, which can realize accurate measurement of the magnetization intensity of the magnetic fluid.

[0004] To achieve the above-mentioned purpose, the application provides the following solutions.

[0005] In a first aspect, the application provides a device for measuring the magnetization intensity of a magnetic fluid, which comprises a broadband light source, a fiber circulator, a sensing head, a magnetic field regulating device and a spectrum analyzer; wherein the sensing head comprises a first single-mode optical fiber, a hollow-core optical fiber, a UV glue film, a second single-mode optical fiber and a quartz tube.

[0006] The broadband light source, the sensing head and the spectrum analyzer are connected with the fiber circulator; the sensing head is arranged between the N-pole and the S-pole of the magnetic field regulating device.

[0007] The first single-mode optical fiber is fused with the hollow-core optical fiber; the end of the hollow-core optical fiber is provided with the UV glue film; the fusion surface of the first single-mode optical fiber and the hollow-core optical fiber is a first reflecting surface; the critical surface of the air in the hollow-core optical fiber and the UV glue film is a second reflecting surface; the first reflecting surface and the second reflecting surface constitute a Fabry-Perot interferometer; the Fabry-Perot interferometer and the second single-mode optical fiber are spaced apart and arranged inside the quartz tube, and the quartz tube is provided with an opening at the spacing.

[0008] The broadband light source is used for emitting a probe light signal.

[0009] The fiber circulator is used for transmitting the probe light signal to the first single-mode optical fiber of the sensing head.

[0010] The magnetic field regulating device is used for applying a directional magnetic field to the sensing head.

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

[0012] The optical fiber circulator is further configured to transmit the interference spectrum to the optical spectrum analyzer.

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

[0014] Optionally, the second single-mode optical fiber end is subjected to a 45-degree to 60-degree inclined cutting.

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

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

[0017] Optionally, the length of the hollow optical fiber is in a range of 50 micrometers to 100 micrometers; the interval between the UV adhesive film and the second single-mode optical fiber is in a range of 100 micrometers to 150 micrometers; and the thickness of the UV adhesive film is in a range of 5 micrometers to 10 micrometers.

[0018] Optionally, the opening on the quartz tube corresponds to an opening diameter in a range of 20 micrometers to 25 micrometers, and the density of the openings is in a range of 20 per millimeter to 25 per millimeter.

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

[0020] controlling a broadband light source to emit a probe light signal, and controlling a magnetic field control device to apply a directional magnetic field to a sensing head;

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

[0022] demodulating the interference spectrum to obtain the magnetization intensity of the to-be-measured magnetic fluid.

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

[0029] Optionally, the interference spectrum is demodulated to obtain the magnetization of the magnetic fluid to be measured, and the method specifically comprises:

[0030] According to the directional magnetic field, it is determined that the magnetic fluid to be measured extends directionally under the action of the directional magnetic field, and a force applied to the UV film is generated; and an 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, it is determined that a deformation amount of the UV film is generated, and a cavity length change amount of the Fabry-Perot interferometer is obtained; and an expression of the cavity length change amount is:

[0033]

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

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

[0036] Optionally, the relationship between the wavelength shift and the magnetization of the magnetic fluid to be measured is as follows:

[0037]

[0038] Wherein, Δλ is the wavelength shift.

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

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

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the application or the related art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0042] Figure 1 A schematic diagram of the device for measuring the magnetization of a magnetic fluid provided by the application;

[0043] Figure 2 A structural schematic diagram of the sensor head provided by the application;

[0044] Figure 3 A working principle diagram of the sensor head provided by the application;

[0045] Figure 4 An interference spectrum diagram of the sensor head provided by the application;

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

[0047] Reference 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 this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0049] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to 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; the end of the hollow-core optical fiber 32 is provided with a UV adhesive film 33. 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 spaced apart and placed inside a quartz tube 35, and the quartz tube 35 has an opening 36 at the interval. In other words, the quartz tube 35 has an opening 36 at the interval between the Fabry-Perot interferometer and the second single-mode optical fiber 34, which is used to enable magnetic fluid filling and communication with the external environment.

[0054] The broadband light source 1 is used for emitting a probe light signal; the fiber circulator 2 is used for transmitting the probe light signal to the first single-mode optical fiber 31 of the sensing head 3. The magnetic field regulating device 4 is used for applying a directional magnetic field to the sensing head 3; the sensing head 3 is used for determining an interference spectrum of the to-be-detected magnetic fluid according to the probe light signal and the directional magnetic field. The to-be-detected magnetic fluid enters the quartz tube 35 through the opening 36; the interference spectrum is determined based on a reflected light signal reflected by a Fabry-Perot interferometer.

[0055] The fiber circulator 2 is also used for transmitting the interference spectrum to the spectrum analyzer 5; the spectrum analyzer 5 is used for receiving and demodulating the interference spectrum to obtain the magnetization intensity of the to-be-detected magnetic fluid.

[0056] In an embodiment, the second single-mode optical fiber 34 is subjected to a 45-degree-60-degree oblique cutting at the end. 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-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 microns, and the outer diameter of the hollow-core optical fiber 32 is 125 microns; the inner diameter of the quartz tube 35 is 125 microns, and the outer diameter of the quartz tube 35 is 200 microns.

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

[0059] The opening 36 on the quartz tube 35 corresponds to an opening diameter in the range of 20 microns-25 microns, and the density of the opening 36 is in the range of 20-25 per millimeter.

[0060] The present application solves the problems of low sensitivity, complex device, and difficulty in accurately measuring the magnetization intensity caused by serious light absorption / refraction loss of the existing optical magnetic fluid magnetization intensity detection method. Based on the characteristics of the magnetic fluid and the UV glue and the principle of the fiber Fabry-Perot interferometer, the present application proposes a fiber magnetic fluid magnetization intensity measurement device, which is simple to manufacture, stable in structure, and high in sensitivity, and can be used for precise measurement of the magnetization intensity of the magnetic fluid.

[0061] Specifically, in actual application, the optical fiber magnetorheological fluid magnetization strength measurement device comprises a broadband light source 1, a fiber loop 2, a sensor head 3, a magnetic field regulating device 4 and a spectrum analyzer 5; the broadband light source 1 is connected with the first port of the fiber loop 2, and the broadband light source 1 is used to provide a probe light signal; the sensor head 3 is connected with the second port of the fiber loop 2, and the sensor head 3 is used to determine the interference spectrum of the magnetorheological fluid to be measured, so as to subsequently measure the magnetization strength of the magnetorheological fluid to be measured; the spectrum analyzer 5 is connected with the third port of the fiber loop 2, 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 of the Fabry-Perot interferometer and the second single-mode optical fiber 34, so as to realize the filling of the magnetorheological fluid and the communication with the external environment.

[0063] The probe light signal emitted by the broadband light source 1 enters the sensor head 3 through the fiber loop 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 reflected back to the first single-mode optical fiber 31 at the second reflection surface; the total reflected light signal enters the spectrum analyzer 5 through the fiber loop 2 and is received and demodulated by the spectrum analyzer 5.

[0064] When the magnetization strength of the magnetorheological fluid is measured, the magnetorheological fluid to be measured enters the inside of the quartz tube 35 through the opening 36; the directional magnetic field is applied to the sensor head 3 by the magnetic field regulating device 4; the magnetorheological fluid to be measured is directionally extended under the action of the magnetic field, so as to generate the force applied to the UV adhesive film 33; the UV adhesive film 33 is deformed under the force, so as to change the cavity length of the Fabry-Perot interferometer; the detection of the magnetization strength of the magnetorheological fluid to be measured can be realized by demodulating the interference spectrum of the sensor head 3.

[0065] In an exemplary embodiment, an optical fiber magnetorheological fluid magnetization strength measurement method is provided, and the optical fiber magnetorheological fluid magnetization strength measurement method is realized by using an optical fiber magnetorheological fluid magnetization strength measurement device. The optical fiber magnetorheological fluid magnetization strength measurement method comprises the following steps.

[0066] Controlling the broadband light source to emit a probe light signal, and controlling the magnetic field regulating device to apply a directional magnetic field to the sensor head.

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

[0068] Demodulating the interference spectrum to obtain the magnetization strength of the magnetorheological fluid to be measured.

[0069] In an embodiment, the function expression corresponding to the interference spectrum is as follows:

[0070] I = A + B 2 + 2ABcos(2Φ). 2

[0071] A = R1 1 / 2 .

[0072] B = (1 - α)(1 - R1)R2 1 / 2 .

[0073] Φ = 2πnL / λ.

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

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

[0076] According to the directional magnetic field, it is determined that the magnetic fluid to be measured is subjected to directional extension under the action of the directional magnetic field, and a force applied to the UV adhesive film is generated; the expression of the force applied to the UV adhesive film is:

[0077] P = μ0HL MF c·m.

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

[0079]

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

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

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

[0083]

[0084] where Δλ is the wavelength shift.

[0085] The working principle of the sensor head provided in the present application can be analyzed by a double-beam interference model, and the interference spectrum thereof is shown in Figure 4 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 - a)(1 - R1)R2 1 / 2 , and Φ = 2πnL / λ. R1 and R2 are the reflectivities of the first and second reflecting surfaces, respectively, a is the in-cavity transmission loss of the Fabry-Perot interferometer, n is the in-cavity 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 for measuring the magnetization of a magnetic fluid, the magnetic fluid to be measured enters the interior of the quartz tube through the opening. A directional magnetic field H is applied to the sensor head by the magnetic field regulating device. The magnetic fluid to be measured is oriented under the action of the magnetic field H, and a force P is generated on the UV film, which can be expressed as:

[0089] P = μ0HL MF c · m (2)

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

[0091] The UV film deforms under the force P applied by the magnetic fluid to be measured, thereby changing the cavity length L of the optical 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 sensing head, and the relationship between the wavelength shift Δλ of the interference spectrum of the sensing head and the magnetization intensity m of the magnetic fluid to be measured can be represented as:

[0095]

[0096] As can be seen from formula (4), the magnetization intensity m of the magnetic fluid to be measured can be accurately measured by demodulating the wavelength shift Δλ of the interference spectrum of the sensing head, and the composition analysis of the magnetic fluid to be measured can be realized by comparing with the database spectrum. Figure 5

[0097] The application has the following beneficial effects:

[0098] The application is based on the characteristics of the magnetic fluid and the UV glue and the principle of the fiber Fabry-Perot interferometer, and proposes a fiber magnetic fluid magnetization intensity measuring device; the application utilizes the stress deformation of the UV glue film and the directional extension of the magnetic fluid along the magnetic field, 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, avoids the loss of the detection light caused by the light absorption / refraction of the magnetic fluid, and thus realizes the accurate measurement of the magnetization intensity of the magnetic fluid to be measured; the fiber magnetic fluid magnetization intensity measuring device provided by the application is simple in manufacturing, stable in structure, and high in sensitivity, and provides a feasible scheme for the high-precision, stable and reliable detection of the magnetization intensity of the magnetic fluid.

[0099] The technical features of the above embodiments can be combined in any manner, and to make the description concise, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present application.

[0100] The principles and implementation modes of the application are described by using specific examples in this paper, and the above embodiment descriptions are only used to help understand the method and core idea of the application; meanwhile, for those skilled in the art, according to the idea of the application, the specific implementation modes and application ranges will be changed. In conclusion, the content of the specification should not be understood as a limitation of the application.​

Claims

1. A device for measuring the magnetization intensity of an optical fiber magnetic fluid, characterized in that: The optical fiber magnetic fluid magnetization intensity measuring device includes: a broadband light source, an optical fiber circulator, a sensor head, a magnetic field control device and a spectrum analyzer; wherein the sensor head includes 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 interface 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 an interval, and the quartz tube is provided with an opening at the interval; 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 based on 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 further 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; Demodulating the interference spectrum to obtain the magnetization intensity of the magnetic fluid to be measured specifically includes: According to the directional magnetic field, the force applied to the UV film by the magnetic fluid to be tested being directional extended under the action of the directional 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 of the UV film is determined, and the change in the cavity length of the Fabry-Perot interferometer is obtained. The expression of the cavity length change is: Where P is the force applied to the UV film; μ0 is the vacuum magnetic permeability; H is the intensity 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; Determining the relationship between the wavelength shift and the magnetization intensity of the magnetic fluid to be measured based on the interference spectrum, the force applied to the UV adhesive film, and the change in cavity length to obtain the magnetization intensity of the magnetic fluid to be measured; 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 and L is the cavity length of the Fabry-Perot interferometer.

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 a corresponding opening diameter ranging from 20 micrometers to 25 micrometers, and a density of the openings ranging from 20 / mm to 25 / mm.

7. A method for measuring the magnetization intensity of an optical fiber magnetic fluid, characterized in that: The method for measuring the magnetization intensity of an optical fiber magnetic fluid is implemented by using the device for measuring the magnetization intensity of an optical fiber magnetic fluid according to any one of claims 1 to 6; The method for measuring the magnetization intensity of optical fiber magnetic fluid 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 an interference spectrum of the magnetic fluid to be measured; the interference spectrum is determined by a reflected light signal reflected by a sensor head based on the detection light signal and the directional magnetic field and a Fabry-Perot interferometer; the magnetic fluid to be measured enters the quartz tube in the sensor head through an opening; Demodulating the interference spectrum to obtain the magnetization intensity of the magnetic fluid to be measured; Demodulating the interference spectrum to obtain the magnetization intensity of the magnetic fluid to be measured specifically includes: According to the directional magnetic field, the force applied to the UV film by the magnetic fluid to be tested being directional extended under the action of the directional 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 of the UV film is determined, and the change in the cavity length of the Fabry-Perot interferometer is obtained. The expression of the cavity length change is: Where P is the force applied to the UV film; μ0 is the vacuum magnetic permeability; H is the intensity 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; Determining the relationship between the wavelength shift and the magnetization intensity of the magnetic fluid to be measured based on the interference spectrum, the force applied to the UV adhesive film, and the change in cavity length to obtain the magnetization intensity of the magnetic fluid to be measured; 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 and L is the cavity length of the Fabry-Perot interferometer.

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 intra-cavity transmission loss of the Fabry-Perot interferometer; R2 is the reflectivity of the second reflection surface; n is the refractive index of the intra-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.

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