Optical fiber cavity optical force magnetic field sensor and direct current / alternating current magnetic field measuring system and method

Abstract

The invention relates to the technical field of magnetic field measurement, in particular to an optical fiber cavity optical force magnetic field sensor, a direct current / alternating current magnetic field measurement system and a direct current / alternating current magnetic field measurement method. The two capillary tubes are located on the two sides of an upper grating region of the fiber bragg grating respectively, a magnetic field response component is arranged below the fiber bragg grating, the positions, close to the two ends of the magnetic field response component, of the two capillary tubes are fixedly connected with the two ends of the magnetic field response component respectively, and the magnetic field response component is made of a material with a magnetostrictive effect. The axis of the fiber grating is parallel to the magnetostriction direction of the magnetic field response component. The advantages of cavity photomechanics and optical fiber sensing are combined, the grating region of the fiber bragg grating is used as an optical cavity, the magnetic field response component is used as a mechanical resonator, and the direct current / alternating current magnetic field measurement sensitivity is remarkably improved through a strain amplification mechanism.

Description

Technical Field

[0001] The present invention relates to the field of magnetic field measurement technology, and in particular to an optical fiber cavity optical force magnetic field sensor, a direct current / alternating current magnetic field measurement system and method. Background Art

[0002] With the continuous progress of society, magnetic field detection technology has shown its indispensable value in national security, health care, engineering construction and other industries. However, although traditional magnetic field measurement technologies, such as induction coils and Hall sensors, are widely used, they have significant limitations in terms of sensitivity, response speed and cost.

[0003] In recent years, in order to overcome these challenges, researchers have proposed a variety of new magnetic field measurement technologies, among which solutions based on superconducting quantum interferometers, atomic magnetometers, and sensors based on magnetostrictive materials have made significant progress in the field of magnetic field measurement. However, these technologies still face problems such as complex operating environment, high cost, or insufficient integration in practical applications.

[0004] As an emerging magnetic field measurement technology, cavity optical magnetometer mainly utilizes the resonance enhancement effect of optical cavity and mechanical mode, and has the characteristics of high sensitivity and wide dynamic range. However, since cavity optical magnetometer mainly uses on-chip optical whispering gallery mode such as micro-core ring cavity, the preparation process is complicated, special processing equipment is required, and low-cost mass production cannot be achieved, which limits its practical application.

[0005] Fiber optic magnetometer is another potential magnetic field measurement technology. By directly bonding the fiber grating to the surface of the magnetostrictive material, the change in the length of the magnetostrictive material under the action of the magnetic field is used to affect the phase or amplitude of the light field transmitted in the optical fiber to infer the change in magnetic field strength. Fiber optic magnetometer has the advantages of anti-electromagnetic interference, ultra-high electrical insulation, flame retardancy, explosion-proof, small size, low cost, light weight, and corrosion resistance. Therefore, it has been widely used in various fields of social production and life. However, since the fiber grating is directly bonded to the magnetostrictive material, the physical property upper limit of the saturated magnetostriction coefficient of these materials limits the further improvement of the sensitivity of magnetic field measurement. Summary of the invention

[0006] In view of the problem that the current optical fiber magnetometer cannot achieve high magnetic field measurement sensitivity due to the limitation of the physical properties of magnetostrictive materials, the present invention provides an optical fiber cavity optomechanics magnetic field sensor, a DC / AC magnetic field measurement system and method, which combine the advantages of cavity optomechanics and optical fiber sensing to achieve high-sensitivity magnetic field measurement, use the grating area of ​​the optical fiber Bragg grating as the optical cavity, and the magnetic field response component as the mechanical resonator, and significantly improve the magnetic field measurement sensitivity through the strain amplification mechanism, while having low cost and good distributed test scalability.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A fiber cavity optical force magnetic field sensor comprises a fiber Bragg grating, capillaries are fixedly sleeved on both ends of the fiber Bragg grating, the two capillaries are respectively located on both sides of the upper grating area of ​​the fiber Bragg grating, a magnetic field response component is arranged below the fiber Bragg grating, the two capillaries are respectively fixedly connected to the two ends of the magnetic field response component at positions close to the two ends of the magnetic field response component, the magnetic field response component is made of a material with a magnetostrictive effect, and the axis of the fiber Bragg grating is parallel to the magnetostrictive direction of the magnetic field response component.

[0009] Furthermore, the fiber grating is any one of a fiber Bragg grating, a phase-shifted fiber grating, a long-period fiber grating, a chirped fiber grating, and a fiber Bragg grating pair.

[0010] Furthermore, the inner diameter of the capillary is 10-30 microns larger than the diameter of the fiber grating to ensure that the fiber grating can be smoothly inserted without being damaged. The material of the capillary is any one of quartz, metal, alloy and plastic.

[0011] Furthermore, the material of the magnetic field response component is any one of pure nickel, iron oxide, iron-gallium alloy, iron-cobalt-vanadium alloy, iron-nickel alloy, terbium-dysprosium-iron alloy, and iron-gallium-boron alloy; the shape of the magnetic field response component is any one of a solid cylinder, a hollow cylinder, a solid cuboid, or a hollow cuboid.

[0012] The invention discloses a direct current magnetic field measurement system, comprising a broadband light source, a fiber circulator, a spectrometer, a fiber cavity optical force magnetic field sensor, a direct current solenoid and a direct current power supply, wherein the direct current solenoid is connected to the direct current power supply, the fiber cavity optical force magnetic field sensor is located in the direct current solenoid, the fiber circulator is connected to the broadband light source, the spectrometer and the fiber cavity optical force magnetic field sensor through a fiber connector, the broadband light source is used to provide the fiber cavity optical force magnetic field sensor with an optical signal covering its working band range, the fiber circulator is used to input the optical signal of the broadband light source and output the optical signal reflected by the fiber grating, the spectrometer is used to read the change of the reflection spectrum of the optical fiber through the optical fiber connector grating under different external direct current magnetic fields, the magnetic field strength of the calibrated direct current magnetic field generated by the direct current solenoid is adjusted by changing the output current of the direct current power supply, and the direct current magnetic field test sensitivity of the fiber cavity optical force magnetic field sensor is tested by using the calibrated direct current magnetic field.

[0013] The AC magnetic field measurement system comprises a continuously tunable light source, an optical fiber beam splitter, an optical fiber circulator, an optical attenuator, a balanced optical detector, an oscilloscope, a spectrometer, an optical fiber cavity optical force magnetic field sensor, an AC solenoid and a low-noise signal generator, wherein the AC solenoid is connected to the low-noise signal generator, the optical fiber cavity optical force magnetic field sensor is located in the AC solenoid, the optical fiber circulator is connected to the optical fiber beam splitter, the balanced optical detector and the optical fiber cavity optical force magnetic field sensor through an optical fiber connector, the two ends of the optical attenuator are respectively connected to the continuously tunable light source and the balanced optical detector, the oscilloscope and the spectrometer are both connected to the balanced optical detector through a coaxial cable, the continuously tunable light source is used to provide an optical signal, and the optical fiber beam splitter is used to connect the continuously tunable The optical signal emitted by the light source is divided into two beams, one of which enters the optical fiber circulator and the other enters the optical attenuator. The optical fiber circulator is used for continuously tunable optical signal input of the light source and output of optical fiber grating reflected optical signal. The optical attenuator is used to adjust the optical power entering one of the balanced optical detectors to facilitate effective balanced detection. The balanced optical detector is used to convert the optical signal into an electrical signal. The oscilloscope is used to record the reflection spectrum of the optical fiber grating output by the balanced optical detector or to monitor the level values ​​of the two electrical signals output by the monitoring end of the balanced optical detector. The spectrum analyzer is used to perform spectrum analysis on the AC component electrical signal output by the radio frequency end of the balanced optical detector to obtain the frequency domain response of the optical fiber cavity optical force magnetic field sensor with the change of the external AC magnetic field.

[0014] Furthermore, the relationship between the frequency of the low-noise signal generator and the characteristic mechanical resonant frequency of the magnetic field response component in the fiber cavity optical force magnetic field sensor is: the resonant frequency corresponding to the strongest vibration mode of the magnetic field response component is within the frequency range of the sinusoidal signal output by the low-noise signal generator.

[0015] The DC magnetic field measurement method comprises the following steps:

[0016] A broadband light signal is outputted through a broadband light source, and the broadband light signal enters the fiber cavity optical force magnetic field sensor through a fiber optic circulator. The reflected light of the fiber cavity optical force magnetic field sensor is detected by a spectrometer after passing through the fiber optic circulator. By changing the magnitude of the DC current output by the DC power supply, the DC solenoid generates magnetic fields of different intensities in the axial direction, and the spectrometer detects the reflection spectrum under different intensities of magnetic fields. The DC magnetic field test sensitivity of the fiber cavity optical force magnetic field sensor is obtained by dividing the drift of the central wavelength of the reflection spectrum by the change in the magnetic field intensity.

[0017] The AC magnetic field measurement method includes the following two stages:

[0018] In the first stage, the reflection spectrum of the fiber Bragg grating under the action of an uncalibrated AC magnetic field was tested:

[0019] A continuously changing optical signal is outputted through a continuously tunable light source, and the spectral bandwidth range of the optical signal needs to cover the reflection spectrum of the fiber cavity optical force and magnetic field sensor. The optical signal enters the fiber cavity optical force and magnetic field sensor through a fiber circulator, and after being reflected by the fiber grating in the fiber cavity optical force and magnetic field sensor, it enters the balanced optical detector through the fiber circulator again. The balanced optical detector converts the optical signal into an electrical signal and outputs it to an oscilloscope, and the oscilloscope records the reflection spectrum level value of the fiber grating;

[0020] In the second stage, the AC magnetic field test sensitivity of the fiber cavity optical force magnetic field sensor is tested:

[0021] Through a continuously tunable light source, a light signal of a specific single wavelength is output. With reference to the level values ​​of the two electrical signals output from the monitoring end of the balanced light detector displayed on the oscilloscope, the optical attenuator is adjusted to adjust the optical power of one of the balanced light detectors through the optical fiber beam splitter, so as to perform effective balanced detection. The balanced light detector performs balanced detection through two optical signal channels, subtracting the background optical noise of the continuously tunable light source. The two monitoring ends are used to output the electrical signals converted from the two optical signals, and the radio frequency end is used to output the AC component electrical signal after the balanced detection, which is used for analyzing the frequency domain response of the fiber cavity optical force magnetic field sensor. By changing the magnitude of the AC current with a continuously changing frequency output by the low-noise signal generator, the intensity of the AC magnetic field generated by the AC solenoid is changed. The AC component electrical signal output from the radio frequency end of the balanced light detector is analyzed by a spectrum analyzer to obtain the frequency domain response of the fiber cavity optical force magnetic field sensor with changes in the external AC magnetic field. By performing mathematical operations on the spectrum curve of the fiber cavity optical force magnetic field sensor when the AC magnetic field is applied and the spectrum curve of the device when the AC magnetic field is not applied, the AC magnetic field test sensitivity of the fiber cavity optical force magnetic field sensor is obtained.

[0022] Furthermore, the specific wavelength output by the continuously tunable light source in the second stage refers to one of two wavelength values ​​corresponding to one-quarter power intensity of the fiber grating reflection spectrum under the linearized power intensity.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The invention combines the advantages of cavity optomechanics and optical fiber sensing, uses the grating area of ​​the optical fiber Bragg grating as an optical cavity, and the magnetic field response component as a mechanical resonator, thereby significantly enhancing the sensitivity of AC magnetic field testing within a specific frequency range. When the external magnetic field changes, the magnetic field response component generates corresponding mechanical deformation, which is transmitted to the optical fiber Bragg grating through two sections of capillaries, causing the optical fiber Bragg grating to generate axial strain and positive stress inside the optical fiber Bragg grating. Since the reflection spectrum of the optical fiber Bragg grating will drift with the change of the positive stress, and the drift amount is proportional to the magnitude of the positive stress, the change of the magnetic field intensity can be measured by monitoring the change of the reflection spectrum of the optical fiber Bragg grating. In particular, the invention introduces a strain amplification mechanism to enhance the sensitivity to the change of the magnetic field. Specifically, the two capillaries in the invention are respectively located on both sides of the grating area of ​​the optical fiber Bragg grating. Since the cross-sectional area difference between the optical fiber Bragg grating and the capillary is large, the positive stress is concentrated on the grating area part of the optical fiber Bragg grating with a smaller cross-sectional area, thereby enhancing the sensitivity of the grating area part to the change of the magnetic field.

[0025] The present invention uses fiber Bragg grating as the sensing medium, which has a simpler manufacturing process, lower cost, easier integration, and higher test sensitivity than the existing on-chip cavity optomechanical magnetic field measurement system.

[0026] The present invention does not require low temperature or magnetic field shielding and has excellent application scenarios;

[0027] The present invention can realize multi-point or even gridded magnetic field / strain / temperature measurement by cascading a plurality of optical fiber cavity optical force magnetic field sensors with different central wavelengths. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the optical fiber cavity optical force magnetic field sensor of the present invention;

[0029] Figure 2 It is a structural schematic diagram of the DC magnetic field measurement system of the present invention;

[0030] Figure 3 It is a structural schematic diagram of the AC magnetic field measurement system of the present invention;

[0031] Figure 4 This is a comparison chart of the measurement results of different devices under a DC magnetic field;

[0032] Figure 5 The spectrum curve comparison diagram of different devices with and without AC magnetic field applied;

[0033] Figure 6 The spectrum curves of different devices without applying AC magnetic field;

[0034] Figure 7 A schematic diagram of a specific wavelength output by a continuously tunable light source in the second stage;

[0035] In the figure, there are a broadband light source 1, an optical fiber circulator 2, a spectrometer 3, an optical fiber cavity optical force and magnetic field sensor 4, a DC solenoid 5, a DC power supply 6, a continuously tunable light source 7, an optical fiber beam splitter 8, an optical attenuator 9, a balanced light detector 10, an oscilloscope 11, a spectrum analyzer 12, an AC solenoid 13, a low-noise signal generator 14, a fiber grating 401, a capillary 402, a grating region 403, and a magnetic field response component 404. DETAILED DESCRIPTION

[0036] In order to further illustrate the technical solution of the present invention, the present invention is further described below through embodiments.

[0037] A fiber cavity optical force magnetic field sensor comprises a fiber Bragg grating 401, capillaries 402 are fixedly sleeved at both ends of the fiber Bragg grating 401, the two capillaries 402 are respectively located at both sides of a grating area 403 on the fiber Bragg grating 401, a magnetic field response component 404 is arranged below the fiber Bragg grating 401, the two capillaries 402 are respectively fixedly connected to the two ends of the magnetic field response component 404 at positions close to the two ends of the magnetic field response component 404, the magnetic field response component 404 is made of a material having a magnetostrictive effect, and the axis of the fiber Bragg grating 401 is parallel to the magnetostrictive direction of the magnetic field response component 404. The fiber Bragg grating 401 is any one of a fiber Bragg grating, a phase-shifted fiber Bragg grating, a long-period fiber Bragg grating, a chirped fiber Bragg grating, and a fiber Bragg grating pair. The inner diameter of the capillary 402 is 10 to 30 microns larger than the diameter of the fiber Bragg grating 401 to ensure that the fiber Bragg grating 401 can be smoothly inserted without being damaged. The material of the capillary 402 is any one of quartz, metal, alloy, and plastic. The material of the magnetic field response component 404 is any one of pure nickel, iron oxide, iron gallium alloy, iron cobalt vanadium alloy, iron nickel alloy, terbium dysprosium iron alloy, and iron gallium boron alloy; the shape of the magnetic field response component 404 is any one of a solid cylinder, a hollow cylinder, a solid cuboid, or a hollow cuboid.

[0038] The DC magnetic field measurement system comprises a broadband light source 1, an optical fiber circulator 2, a spectrometer 3, an optical fiber cavity optical force magnetic field sensor 4, a DC solenoid 5 and a DC power supply 6, wherein the DC solenoid 5 is connected to the DC power supply 6, the optical fiber cavity optical force magnetic field sensor 4 is located in the DC solenoid 5, the optical fiber circulator 2 is connected to the broadband light source 1, the spectrometer 3 and the optical fiber cavity optical force magnetic field sensor 4 through an optical fiber connector, the broadband light source 1 is used to provide the optical fiber cavity optical force magnetic field sensor 4 with an optical signal covering its working band range, the optical fiber circulator 2 is used for the optical signal input of the broadband light source 1 and the output of the reflected optical signal of the optical fiber grating 401, the spectrometer 3 is used to read the change of the reflection spectrum of the optical fiber through the optical fiber connector grating under different external DC magnetic fields, the magnetic field strength of the calibrated DC magnetic field generated by the DC solenoid 5 is adjusted by changing the output current of the DC power supply 6, and the DC magnetic field test sensitivity of the optical fiber cavity optical force magnetic field sensor 4 is tested by using the calibrated DC magnetic field. The broadband light source 1 is any one of a fluorescent lamp, an incandescent lamp, a halogen lamp, an LED array, a supercontinuum light source, a broadband laser, a broadband LED light source, and a continuously tunable laser. The spectrometer 3 is any one of a grating spectrometer, a Fourier transform spectrometer, and a prism spectrometer.

[0039] The AC magnetic field measurement system includes a continuously tunable light source 7, an optical fiber beam splitter 8, an optical fiber circulator 2, an optical attenuator 9, a balanced optical detector 10, an oscilloscope 11, a spectrometer 12, an optical fiber cavity optical force magnetic field sensor 4, an AC solenoid 13 and a low-noise signal generator 14, wherein the AC solenoid 13 is connected to the low-noise signal generator 14, the optical fiber cavity optical force magnetic field sensor 4 is located in the AC solenoid 13, the optical fiber circulator 2 is connected to the optical fiber beam splitter 8, the balanced optical detector 10 and the optical fiber cavity optical force magnetic field sensor 4 through an optical fiber connector, the two ends of the optical attenuator 9 are respectively connected to the continuously tunable light source 7 and the balanced optical detector 10, the oscilloscope 11 and the spectrometer 12 are connected to the balanced optical detector 10 through a coaxial cable, the continuously tunable light source 7 is used to provide an optical signal, and the optical fiber beam splitter 8 is used to The optical signal emitted by the continuously tunable light source 7 is divided into two beams, one of which enters the optical fiber circulator 2 and the other enters the optical attenuator 9. The optical fiber circulator 2 is used for the input of the optical signal of the continuously tunable light source 7 and the output of the reflected optical signal of the optical fiber grating 401. The optical attenuator 9 is used to adjust the optical power of one of the paths entering the balanced optical detector 10 so as to perform effective balanced detection. The balanced optical detector 10 is used to convert the optical signal into an electrical signal. The oscilloscope 11 is used to record the reflection spectrum of the optical fiber grating 401 output by the balanced optical detector 10 or to monitor the level values ​​of the two paths of electrical signals output by the monitoring end of the balanced optical detector 10. The spectrum analyzer 12 is used to perform spectrum analysis on the AC component electrical signal output by the radio frequency end of the balanced optical detector 10 to obtain the frequency domain response of the optical fiber cavity optical force magnetic field sensor 4 with the change of the external AC magnetic field. The relationship between the frequency of the low-noise signal generator 14 and the characteristic mechanical resonant frequency of the magnetic field response component 404 in the optical fiber cavity optical force magnetic field sensor 4 is as follows: the resonant frequency corresponding to the strongest vibration mode of the magnetic field response component 404 is within the frequency range of the sinusoidal signal output by the low-noise signal generator 14. The optical attenuator 9 is any one of a mechanical adjustable optical attenuator, a thermo-optical adjustable attenuator, an electro-optical adjustable attenuator, a magneto-optical adjustable attenuator, an acousto-optical adjustable attenuator, and a liquid crystal adjustable attenuator; the continuously tunable light source 7 is any one of a semiconductor tunable laser, an optical parametric oscillator, a tunable fiber laser, a tunable vertical cavity surface emitting laser, and an electro-absorption modulated laser.

[0040] The DC magnetic field measurement method comprises the following steps:

[0041] A broadband light signal is outputted by a broadband light source 1, and the broadband light signal enters the fiber cavity optical force magnetic field sensor 4 through the fiber optic circulator 2. The reflected light of the fiber cavity optical force magnetic field sensor 4 is detected by the spectrometer 3 after passing through the fiber optic circulator 2. By changing the magnitude of the DC current output by the DC power supply 6, the DC solenoid 5 generates magnetic fields of different intensities in the axial direction, and the spectrometer 3 detects the reflection spectrum under different intensities of magnetic fields. The DC magnetic field test sensitivity of the fiber cavity optical force magnetic field sensor 4 is obtained by dividing the drift of the central wavelength of the reflection spectrum by the change in the magnetic field intensity.

[0042] The AC magnetic field measurement method includes the following two stages:

[0043] In the first stage, the reflection spectrum of the fiber Bragg grating 401 under the action of an uncalibrated AC magnetic field is obtained by testing:

[0044] A continuously changing optical signal is outputted through a continuously tunable light source 7, and the spectral bandwidth range of the optical signal needs to cover the reflection spectrum of the optical fiber cavity optical force and magnetic field sensor 4. The optical signal enters the optical fiber cavity optical force and magnetic field sensor 4 through the optical fiber circulator 2, and after being reflected by the optical fiber grating 401 in the optical fiber cavity optical force and magnetic field sensor 4, it enters the balanced optical detector 10 through the optical fiber circulator 2 again. The balanced optical detector 10 converts the optical signal into an electrical signal and outputs it to the oscilloscope 11. The oscilloscope 11 records the reflection spectrum level value of the optical fiber grating 401;

[0045] In the second stage, the AC magnetic field test sensitivity of the fiber cavity optical force magnetic field sensor 4 is tested:

[0046] Through the continuously tunable light source 7, a light signal of a specific single wavelength is output, and the level value of the two electrical signals output by the monitoring end of the balanced light detector 10 displayed on the oscilloscope 11 is referred to, and the optical attenuator 9 is adjusted to adjust the optical power of one of the balanced light detectors 10 through the optical fiber beam splitter 8, so as to perform effective balanced detection; the balanced light detector 10 performs balanced detection through two optical signal channels, subtracting the background optical noise of the continuously tunable light source 7, and the two monitoring ends are used to output the electrical signals converted from the two optical signals, and the radio frequency end is used to output the AC component electrical signal after the balanced detection, which is used for the optical force and magnetic field transmission of the optical fiber cavity. The frequency domain response of the optical fiber cavity optical force magnetic field sensor 4 is analyzed; the intensity of the AC magnetic field generated by the AC solenoid 13 is changed by changing the magnitude of the AC current with a continuously changing frequency output by the low noise signal generator 14; the frequency domain response of the optical fiber cavity optical force magnetic field sensor 4 with the change of the external AC magnetic field is obtained by spectrum analysis of the AC component electrical signal output by the RF end of the balanced light detector 10 by the spectrum analyzer 12; the AC magnetic field test sensitivity of the optical fiber cavity optical force magnetic field sensor 4 is obtained by performing mathematical operations on the spectrum curve of the optical fiber cavity optical force magnetic field sensor 4 when the AC magnetic field is applied and the spectrum curve of the device when the AC magnetic field is not applied. The specific wavelength output by the continuously tunable light source 7 in the second stage refers to one of the two wavelength values ​​corresponding to the quarter power intensity under the linearized power intensity of the reflection spectrum of the optical fiber grating 401.

[0047] In the structural design of this embodiment, the grating area 403 of the fiber grating 401 is exposed between two capillaries 402, and the length of the exposed optical fiber is L1; the two capillaries 402 are fixed on the magnetic field response component by glue, and the distance between the two glues is defined as L2, and the structural proportional factor Θ related to L1 and L2 is L2 / L1.

[0048] The DC magnetic field measurement system in this embodiment is used to perform measurement and calculate the structural proportional factor Θ related to L1 and L2.

[0049] like Figure 4 As shown, device No. 0 has no related structure, and the fiber Bragg grating is directly bonded to the magnetic field response component, Θ=1; device No. 1 and device No. 2 adopt the fiber cavity optical force magnetic field sensor structure of the present invention, wherein device No. 1 has Θ=7.71; device No. 2 has Θ=15.75;

[0050] The left side shows the spectrum drift test, and the right side shows the drift of the central wavelength. The DC magnetic field test sensitivities of devices No. 0, No. 1, and No. 2 are calculated to be 0.58pm / Gs, 5.17pm / Gs, and 8.47pm / Gs, respectively.

[0051] The AC magnetic field measurement system in this embodiment is used to perform measurement and calculate the structural proportional factor Θ related to L1 and L2.

[0052] Figure 5 The upper middle curve is the spectrum curve test diagram of different devices when AC magnetic field is applied, and the lower curve is the spectrum curve test diagram when no AC magnetic field is applied. Figure 6 The AC magnetic field test sensitivity curves of devices 0, 1 and 2 obtained by calculation are the highest at the characteristic mechanical resonance frequency of the magnetic field response component of 11.25kHz. The highest AC magnetic field test sensitivities of the three devices are 31.79pT / Hz 1 / 2 , 5.05pT / Hz 1 / 2 and 4.35pT / Hz 1 / 2 , the calculation results of AC magnetic field test sensitivity are as follows Figure 6 shown.

[0053] The above shows and describes the main features and advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0054] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A fiber cavity optical force magnetic field sensor (4), characterized in that: The invention comprises a fiber Bragg grating (401), capillaries (402) are fixedly sleeved at both ends of the fiber Bragg grating (401), the two capillaries (402) are respectively located at both sides of a grating area (403) on the fiber Bragg grating (401), a magnetic field response component (404) is arranged below the fiber Bragg grating (401), the two capillaries (402) are respectively fixedly connected to the two ends of the magnetic field response component (404) at positions close to the two ends of the magnetic field response component (404), the magnetic field response component (404) is made of a material having a magnetostrictive effect, and the axis of the fiber Bragg grating (401) is parallel to the magnetostrictive direction of the magnetic field response component (404).

2. The optical fiber cavity optical force magnetic field sensor (4) according to claim 1, characterized in that: The fiber grating (401) is any one of a fiber Bragg grating, a phase-shifted fiber grating, a long-period fiber grating, a chirped fiber grating, and a fiber Bragg grating pair.

3. The optical fiber cavity optical force magnetic field sensor (4) according to claim 1, characterized in that: The inner diameter of the capillary (402) is 10-30 microns larger than the diameter of the fiber grating (401) to ensure that the fiber grating (401) can be smoothly inserted without being damaged. The material of the capillary (402) is any one of quartz, metal, alloy and plastic.

4. The optical fiber cavity optical force magnetic field sensor (4) according to claim 1, characterized in that: The material of the magnetic field response component (404) is any one of pure nickel, iron oxide, iron-gallium alloy, iron-cobalt-vanadium alloy, iron-nickel alloy, terbium-dysprosium-iron alloy, and iron-gallium-boron alloy; the shape of the magnetic field response component (404) is any one of a solid cylinder, a hollow cylinder, a solid cuboid, or a hollow cuboid.

5. A DC magnetic field measurement system based on the optical fiber cavity optical force magnetic field sensor according to claim 1, characterized in that: The invention comprises a broadband light source (1), an optical fiber circulator (2), a spectrometer (3), an optical fiber cavity optical force magnetic field sensor (4), a direct current solenoid (5) and a direct current power supply (6), wherein the direct current solenoid (5) is connected to the direct current power supply (6), the optical fiber cavity optical force magnetic field sensor (4) is located in the direct current solenoid (5), the optical fiber circulator (2) is connected to the broadband light source (1), the spectrometer (3) and the optical fiber cavity optical force magnetic field sensor (4) via an optical fiber connector, the broadband light source (1) is used to provide the optical fiber cavity optical force magnetic field sensor (4) with an optical signal covering its working band range, the optical fiber circulator (2) is used to input the optical signal of the broadband light source (1) and output the reflected optical signal of the optical fiber grating (401), the spectrometer (3) is used to read the change of the reflected spectrum of the optical fiber through the optical fiber connector grating under different external direct current magnetic fields, the magnetic field strength of the calibrated direct current magnetic field generated by the direct current solenoid (5) is adjusted by changing the output current of the direct current power supply (6), and the direct current magnetic field test sensitivity of the optical fiber cavity optical force magnetic field sensor (4) is tested by using the calibrated direct current magnetic field.

6. An AC magnetic field measurement system based on the optical fiber cavity optical force magnetic field sensor according to claim 1, characterized in that: The invention comprises a continuously tunable light source (7), an optical fiber beam splitter (8), an optical fiber circulator (2), an optical attenuator (9), a balanced optical detector (10), an oscilloscope (11), a spectrometer (12), an optical fiber cavity optical force magnetic field sensor (4), an AC solenoid (13) and a low noise signal generator (14), wherein the AC solenoid (13) is connected to the low noise signal generator (14), the optical fiber cavity optical force magnetic field sensor (4) is located in the AC solenoid (13), the optical fiber circulator (2) is connected to the optical fiber beam splitter (8), the balanced optical detector (10) and the optical fiber cavity optical force magnetic field sensor (4) through an optical fiber connector, the two ends of the optical attenuator (9) are respectively connected to the continuously tunable light source (7) and the balanced optical detector (10), the oscilloscope (11) and the spectrometer (12) are both connected to the balanced optical detector (10) through a coaxial cable, the continuously tunable light source (7) is used to provide an optical signal, the optical fiber beam splitter (13) is connected to the balanced optical detector (10) through a coaxial cable, the continuously tunable light source (7) is used to provide an optical signal, and the optical fiber beam splitter (13) is connected to the balanced optical detector (10) through a coaxial cable. The device (8) is used to divide the optical signal emitted by the continuously tunable light source (7) into two beams, one of which enters the optical fiber circulator (2) and the other enters the optical attenuator (9). The optical fiber circulator (2) is used for inputting the optical signal of the continuously tunable light source (7) and outputting the optical signal reflected by the optical fiber grating (401). The optical attenuator (9) is used to adjust the optical power of one of the beams entering the balanced optical detector (10) so as to perform effective balanced detection. The balanced optical detector (10) is used to convert the optical signal into an electrical signal. The oscilloscope (11) is used to record the reflection spectrum of the optical fiber grating (401) output by the balanced optical detector (10) or to monitor the level values ​​of the two electrical signals output by the monitoring end of the balanced optical detector (10). The spectrum analyzer (12) is used to perform spectrum analysis on the AC component electrical signal output by the radio frequency end of the balanced optical detector (10) to obtain the frequency domain response of the optical fiber cavity optical force magnetic field sensor (4) with the change of the external AC magnetic field.

7. An AC magnetic field measurement system according to claim 6, characterized in that: The relationship between the frequency of the low-noise signal generator (14) and the characteristic mechanical resonant frequency of the magnetic field response component (404) in the optical fiber cavity optical force magnetic field sensor (4) is as follows: the resonant frequency corresponding to the strongest vibration mode of the magnetic field response component (404) is within the frequency range of the sinusoidal signal output by the low-noise signal generator (14).

8. A DC magnetic field measurement method based on the DC magnetic field measurement system of claim 5, characterized in that: The following steps are involved: A broadband light signal is outputted through a broadband light source (1), and the broadband light signal enters a fiber cavity optical force magnetic field sensor (4) through a fiber optic circulator (2). The reflected light of the fiber cavity optical force magnetic field sensor (4) is detected by a spectrometer (3) after passing through the fiber optic circulator (2). By changing the magnitude of the DC current outputted by the DC power supply (6), the DC solenoid (5) generates magnetic fields of different intensities in the axial direction. The spectrometer (3) detects the reflection spectrum under different magnetic fields, and the DC magnetic field test sensitivity of the fiber cavity optical force magnetic field sensor (4) is obtained by dividing the drift of the central wavelength of the reflection spectrum by the change in the magnetic field intensity.

9. An AC magnetic field measurement method based on the AC magnetic field measurement system of claim 6, characterized in that: It includes the following two stages: In the first stage, the reflection spectrum of the fiber Bragg grating (401) under the action of an uncalibrated AC magnetic field is obtained by testing: A continuously changing optical signal is outputted through a continuously tunable light source (7), wherein the spectral bandwidth range of the optical signal needs to cover the reflection spectrum of the optical fiber cavity optical force and magnetic field sensor (4); the optical signal enters the optical fiber cavity optical force and magnetic field sensor (4) through an optical fiber circulator (2); after being reflected by the optical fiber grating (401) in the optical fiber cavity optical force and magnetic field sensor (4), the optical signal enters the balanced optical detector (10) through the optical fiber circulator (2) again; the balanced optical detector (10) converts the optical signal into an electrical signal and outputs the electrical signal to an oscilloscope (11); the oscilloscope (11) records the reflection spectrum level value of the optical fiber grating (401); In the second stage, the AC magnetic field test sensitivity of the optical fiber cavity optical force magnetic field sensor (4) is obtained by testing: A light signal of a specific single wavelength is outputted through a continuously tunable light source (7), and the level values ​​of two electrical signals outputted from the monitoring end of the balanced light detector (10) displayed on an oscilloscope (11) are referred to, and the optical attenuator (9) is adjusted to adjust the optical power of one of the paths of the balanced light detector (10) through the optical fiber beam splitter (8) so as to perform effective balanced detection; the balanced light detector (10) performs balanced detection through two optical signal channels, subtracting the background optical noise of the continuously tunable light source (7), and the two monitoring ends are used to output the electrical signals converted from the two optical signals, and the radio frequency end is used to output the AC component electrical signal after the balanced detection, which is used for the optical fiber cavity optical force and magnetic field transmission. The method comprises the steps of: analyzing the frequency domain response of the optical fiber cavity optical force magnetic field sensor (4); changing the magnitude of the AC current with a continuously changing frequency output by the low noise signal generator (14), thereby changing the intensity of the AC magnetic field generated by the AC solenoid (13); performing spectrum analysis on the AC component electrical signal output by the radio frequency end of the balanced light detector (10) by a spectrum analyzer (12), thereby obtaining the frequency domain response of the optical fiber cavity optical force magnetic field sensor (4) as the external AC magnetic field changes; and performing mathematical operations on the spectrum curve of the optical fiber cavity optical force magnetic field sensor (4) when the AC magnetic field is applied and the spectrum curve of the device when the AC magnetic field is not applied, thereby obtaining the AC magnetic field test sensitivity of the optical fiber cavity optical force magnetic field sensor (4).

10. The DC magnetic field measurement method according to claim 9, characterized in that: The specific wavelength output by the continuously tunable light source (7) in the second stage refers to one of the two wavelength values ​​corresponding to one quarter power intensity of the reflection spectrum of the fiber grating (401) under the linearized power intensity.

Images