CN105629185B - A method of based on ultrasonic pulse induction grating deformation for measuring magnetic field - Google Patents

Abstract

The invention provides a method for measuring a magnetic field based on ultrasonic pulse-induced grating deformation, the method for measuring a magnetic field includes the following steps: a) lapping an optical fiber sensor magnetic field measurement system, the system includes a section with a continuous uniform grating optical fiber, ultrasonic generator and demodulator, the optical fiber with continuous uniform grating has a multi-section grating, each section of grating grid is evenly distributed, and the interval between the gratings is the same; b) placing the optical fiber sensor magnetic field measurement system In the magnetic field to be measured, record the distance from the peak that the demodulator collects and deviate from the main peak; c) the distance from the peak that deviates from the main peak described in step b) and the distance from the peak that deviates from the main peak as the magnetic field strength changes Compare the relationship curves to get the magnitude of the magnetic field strength.

Description

A Method for Measuring Magnetic Fields Based on Ultrasonic Pulse-Induced Grating Deformation

technical field

The present invention relates to the field of fiber grating technology, in particular to a method for measuring magnetic field based on ultrasonic pulse induced grating deformation

Background technique

Usually, the purpose of measurement is to obtain the relevant information of the research object, and perform corresponding processing, and then control the object. The completion of this functional operation is the sensing technology. The basic working principle of the optical fiber sensor is to send the light from the light source to the modulator through the optical fiber, and after the parameter to be measured interacts with the light entering the modulation area, the optical properties of the light (such as light intensity, wavelength, frequency, phase, Normal state, etc.) changes, called the modulated signal light, which is sent to the photodetector through the optical fiber, and after demodulation, the measured parameters are obtained. In recent years, sensors are developing in the direction of sensitivity, precision, adaptability, compactness and intelligence. In this process, fiber optic sensors, a new member of the sensor family, are favored. Optical fiber has many excellent properties, such as: anti-electromagnetic interference and atomic radiation performance, thin diameter, soft and light mechanical properties; electrical properties of insulation and non-induction; chemical properties of water resistance, high temperature resistance and corrosion resistance, etc. It can act as the eyes and ears of people in places that people can't reach (such as high temperature areas) or areas that are harmful to people (such as nuclear radiation areas), and it can also go beyond human physiological boundaries and receive human sensory information. Insensible external information. With the development and maturity of dense wavelength division multiplexing DWDM technology, erbium-doped fiber amplifier EDFA technology and optical time division multiplexing OTDR technology, optical fiber communication technology is developing in the direction of ultra-high-speed and large-capacity communication systems, and is gradually evolving into an all-optical network. . Driven by the rapid development of optical communication, optical fiber sensors play an important role in the measurement of material strain, magnetic field, temperature field, and solution refractive index.

However, the traditional optical fiber sensor only improves the accuracy of the sensor by changing the light source and the material of the optical fiber itself, which is greatly limited.

Therefore, there is a need for a method that can effectively couple ultrasonic waves in an optical fiber to cause grating deformation and measure a magnetic field.

Contents of the invention

The object of the present invention is to provide a method for measuring a magnetic field based on ultrasonic pulse-induced grating deformation. In one aspect, the method for measuring a magnetic field includes the following steps:

a) Lap fiber optic sensor magnetic field measurement system, the system includes a pump source, a first optical fiber, a wavelength division multiplexer, a section of optical fiber with a continuous uniform grating, an ultrasonic generator and a demodulator, the described One end of the optical fiber with a continuous uniform grating is a spherical end, the ultrasonic generator is provided with a transmitting probe, the transmitting probe is fixed to the spherical end, and the demodulator is connected to the other end of the optical fiber with a continuous uniform grating connection; the optical fiber with a continuous uniform grating has multiple gratings, each grating grid is evenly distributed, and the intervals between the gratings are the same;

b) placing the optical fiber sensor magnetic field measurement system in the magnetic field to be measured, and recording the distance from the peak to the main peak collected by the demodulator;

c) Comparing the distance between the off-peak and the main peak described in step b) and the relationship curve of the distance between the off-peak and the main peak as a function of the magnetic field strength, to obtain the magnitude of the magnetic field strength.

In one aspect, in the method for measuring the magnetic field, the relationship curve of the distance from the peak to the main peak in the step c) varies with the magnetic field strength through calibration, and the calibration includes the following steps:

(1) bonding the optical fiber with the continuous uniform grating to the controllable magnetostrictive material;

(2) The pump source emits light waves into the first optical fiber, and the ultrasonic generator emits ultrasonic waves into the optical fiber with a continuous uniform grating;

(3) Record the distance from the peak that the demodulator time t gathers and deviates from the main peak;

(4) gradually increase the size of the magnetic field strength, repeat the process from the step (2) to the step (3), and record the separation caused by the different magnetic field strengths collected by the demodulator at the same time t as the step (3). The distance between the peak and the main peak;

(5) Fit the relationship curve of the distance from the main peak to the variation of the magnetic field strength.

In one aspect, in the method for measuring a magnetic field, the spherical end is a small ball sintered at the end of an optical fiber, and the small ball and the ultrasonic probe are fixed by silica gel.

In one aspect, in the method for measuring a magnetic field, an acoustic paste is coated between the ball and the ultrasonic probe, and the acoustic paste is a photoacoustic matching material for coupling acoustic waves into the optical fiber.

In one aspect, in the method for measuring a magnetic field, the ultrasonic waves in step (2) propagate in the form of longitudinal waves, and the wavelength of the ultrasonic waves is longer than the grating length of the grating.

In one aspect, in the method for measuring a magnetic field, the ultrasonic wavelength is 1cm-2cm.

In one aspect, in the method for measuring a magnetic field, in the step (4), increasing the magnitude of the magnetic field causes the magnetostrictive material to stretch, bend, vibrate or squeeze.

In one aspect, in the method for measuring the magnetic field, the curve of the relationship between the distance from the peak and the main peak versus the change of the magnetic field is fitted by linear fitting or least square method.

In another aspect, the present invention provides the optical fiber sensor measurement system of the method for measuring the magnetic field, the measurement system includes a pump source, a first optical fiber, a wavelength division multiplexer, a section of optical fiber with a continuous uniform grating, Ultrasonic generator and demodulator;

One end of the optical fiber with a continuous uniform grating is a spherical end;

The ultrasonic generator is provided with a supersonic probe, the transmitting probe is fixed to the spherical end, the demodulator is connected to the other end of the optical fiber with a continuous uniform grating, and the optical fiber with a continuous uniform grating The optical fiber has multiple sections of gratings, each section of gratings is evenly distributed, and the intervals between the gratings are the same.

The invention provides a method for measuring the magnetic field based on ultrasonic pulse-induced grating deformation. By thinly coupling the ultrasonic wave into the grating fiber, the grating grid is deformed, thereby forming off-peaks on both sides of the main peak of the light wave. Peak monitoring and magnetic field measurement make the accuracy of magnetic field measurement more accurate.

It should be understood that both the foregoing general description and the following detailed description are exemplary illustrations and explanations, and should not be used as limitations on the claimed content of the present invention.

Description of drawings

With reference to the accompanying drawings, more objects, functions and advantages of the present invention will be clarified through the following description of the embodiments of the present invention, wherein:

Fig. 1 schematically shows an optical fiber sensor measurement system for measuring a magnetic field according to an embodiment of the present invention;

Fig. 2 shows the schematic diagram of the present invention with continuous uniform grating optical fiber;

Fig. 3 shows the schematic diagram of the fiber-coupled ultrasonic front grid of the present invention;

Fig. 4 shows the reflection spectrum of the fiber-coupled ultrasonic pre-pulse of the present invention;

Fig. 5 shows the schematic diagram of the fiber-coupled ultrasonic back grid of the present invention;

Fig. 6 shows the off-peak of the optical fiber of the present invention under the action of ultrasonic pulse;

Fig. 7 shows the schematic diagram of the off-peak deviation from the main peak when the present invention is in different magnetic fields;

Fig. 8 shows the curve that the distance from the peak of the present invention deviates from the main peak varies with the magnetic field;

Fig. 9 shows another embodiment of the present invention, a fiber optic sensor measuring system for measuring magnetic field.

Detailed ways

The objects and functions of the present invention and methods for achieving the objects and functions will be clarified by referring to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below; it can be implemented in various forms. The essence of the description is only to help those skilled in the relevant art comprehensively understand the specific details of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

Embodiment one:

The present invention provides a method for measuring a magnetic field based on ultrasonic pulse-induced grating deformation. In this embodiment, as shown in FIG. , a first optical fiber 102, a wavelength division multiplexer 103, a section of optical fiber 106 with a continuous uniform grating 108, an ultrasonic generator 105 and a demodulator 104; one end of the optical fiber with a continuous uniform grating is a spherical end; the spherical end It is a small ball 107 formed by sintering the end of the optical fiber; the ultrasonic generator is provided with an ultrasonic probe, and the ultrasonic probe and the small ball 107 at the end of the optical fiber are fixed by silica gel. An acoustic paste is coated between the ultrasonic probe and the small ball 107, and the acoustic paste is used as an acoustic matching material to couple sound waves into the optical fiber. The demodulator 104 is connected to the other end of the optical fiber 106 with a continuous uniform grating 108 for collecting the reflection spectrum of the optical fiber.

The principle of ultrasonic-induced grating deformation is described in detail below:

As shown in Figure 2, the present invention has a schematic diagram of a continuous uniform grating optical fiber. The optical fiber with a continuous uniform grating is composed of multiple fiber gratings 108 with the same parameters in series or directly distributed continuous uniform gratings. In this embodiment, the distributed continuous uniform grating is preferably used. The grating fiber made by the method has multiple gratings, each grating is evenly distributed, and the distance between the gratings is the same.

When the light emitted by the pumping source 101 passes through the grid of distributed continuous uniform grating optical fiber in the embodiment of the present invention, the grid 108a of the optical fiber will not be mechanically deformed, as shown in Figure 3. . The light wave completely passes through the grating fiber, and the reflection spectrum of the grating fiber is collected by the demodulator 104. A main peak appears in the reflection spectrum, as shown in FIG.

When the ultrasonic waves emitted by the ultrasonic generator 105 pass through the acoustic paste between the ultrasonic probe and the sintered ball 107 at the end of the optical fiber to couple the ultrasonic waves into the optical fiber, at the same time, the light emitted by the pump source 101 enters the first optical fiber 102 and passes through the wave division A multiplexer 103 couples the light waves into an optical fiber with a continuous uniform grating. The ultrasonic wave propagates forward in the optical fiber in the form of longitudinal waves. When the ultrasonic wave propagates to the nth section of the grating, it will induce mechanical deformation of the optical fiber grid 108b. When the ultrasonic wave leaves the nth section of the grating, the mechanical deformation recovers, as shown in Figure 5 A schematic diagram showing the fiber-coupled ultrasonic grid of the present invention. In the present invention, the wavelength of the emitted ultrasonic wave is greater than the grating length of the grating fiber, and when the ultrasonic wave completely passes through the nth section of the grating, the reflection spectrum collected by the demodulator 104 will appear at both ends of the main peak. Two off-peaks, such as Figure 6 shows the off-peak of the optical fiber of the present invention under the action of ultrasonic pulses.

The method for measuring the magnetic field by off-peak in this embodiment is described in detail below:

Lap fiber optic sensor magnetic field measurement system:

Build an optical fiber sensor system for measuring the magnetic field, the system includes a pump source 101, a first optical fiber 102, a wavelength division multiplexer 103, a section of optical fiber 106 with a continuous uniform grating, an ultrasonic generator 105 and a demodulator 104 One end of the optical fiber with a continuous uniform grating is a spherical end; the spherical end is a small ball 107 formed by sintering the end of the optical fiber; the ultrasonic generator is provided with an ultrasonic probe, and the ultrasonic probe and the small ball 107 at the end of the optical fiber Fix by silicone. The acoustic paste is coated between the ultrasonic probe and the ball, and the acoustic paste is used as an acoustic matching material to couple the sound wave into the optical fiber. The demodulator 104 is connected to the other end of the optical fiber 106 with a continuous uniform grating for collecting the reflection spectrum of the optical fiber.

Perform magnetic field calibration on the fiber optic sensor magnetic field measurement system:

Bond the optical fiber 106 with a continuous uniform grating to the controllable magnetostrictive material 109, select epoxy resin (EpoxyResin) or acrylate as an adhesive, and fix the grid area of the grating optical fiber on the surface of the material by pasting. The material is placed in a magnetic field environment. The pumping source 101 emits light waves into the first optical fiber 102, and the ultrasonic generator 105 emits ultrasonic waves through the acoustic paste between the ultrasonic probe and the sintered ball 107 at the end of the optical fiber to couple the ultrasonic waves into the optical fiber 106 with a continuous uniform grating. The ultrasonic waves propagate forward in the form of longitudinal waves, and the wavelength of the ultrasonic wave is longer than the grating length of the grating fiber. Preferably, in this embodiment, the ultrasonic wave emitted by the ultrasonic generator 105 has a wavelength of 1 cm-2 cm. The light wave in the first optical fiber 102 is coupled to an optical fiber 106 with a continuous uniform grating through a wavelength division multiplexer 103 . Record the distance between the off-peak and the main peak collected by the demodulator at time t.

The magnetic field intensity value H ₁ of the magnetic field 110 is changed by the magnetic field controller, thereby causing the change of the magnetostrictive material 109, the distance s ₁ from the peak to the main peak caused by the magnetic field collected by the recorder and demodulator at the same time t, and the change of the magnetostrictive material 109 The method can stretch, compress or bend the material through the strength change of the magnetic field 110, and the stretching method is preferred in this embodiment. Repeat the above process, and record the _distances s _{2 ,} , s 3 ...s _n from the peak and the main peak collected by the demodulator corresponding to different magnetic fields H ₂ , H _{3 ,} ... H _n at the same time t, as shown in Figure 7 Schematic diagram of the off-peak deviation from the main peak when the invention is in different magnetic fields. Fit the relationship curve of the distance from the main peak to the distance from the main peak with the change of the magnetic field, and the curve fitting can be linearly fitted by the least square method, as shown in formula 1.

y=ax+b (1)

The curve fitting can also adopt the least squares fitting, and the fitting curve can be deduced from the following equations (2) and (3).

By solving the equations and finding a ₀ and a ₁ , an approximation function that satisfies the square approximation condition can be constructed.

f(x)＝a ₀ +a ₁ x (4)

FIG. 8 shows the curve of the off-peak deviation from the main peak distance as a function of the magnetic field obtained through fitting in the embodiment of the present invention.

To measure the magnetic field to be measured:

Lay the optical fiber sensor magnetic field measurement system with the magnetostrictive material, place it in the magnetic field to be measured, record the distance s from the main peak at the time t, and compare the distance s from the main peak to the calibrated optical fiber sensor magnetic field measurement system Comparing the relationship curves of the distance from the peak to the main peak with the change of the magnetic field intensity, the strain of the material can be obtained.

Embodiment two:

Compared with the first embodiment, this embodiment measures the magnetic field strength of the non-uniform magnetic field.

Lap fiber optic sensor magnetic field measurement system:

The optical fiber sensor measurement system for measuring magnetic field in the embodiment shown in Fig. 9 is set up the optical fiber sensor system for measuring magnetic field, and described system comprises pumping source 201, the first optical fiber 202, a wavelength division multiplexer 203, a section with Optical fiber 206 with continuous uniform grating, ultrasonic generator 205 and demodulator 204; one end of the optical fiber with continuous uniform grating is a spherical end; the spherical end is a small ball 207 formed by sintering the end of the optical fiber; with continuous uniform grating The optical fiber is composed of multiple sections of fiber gratings 208 with the same parameters in series or directly distributed with continuous uniform gratings. In this embodiment, the grating optical fiber made by preferably adopting the method of distributing continuous uniform gratings has multiple sections of gratings, and each section of the grating grid is evenly distributed. The spacing between the gratings is the same. The ultrasonic generator is provided with an ultrasonic probe, and the ultrasonic probe and the ball 207 at the end of the optical fiber are fixed by silica gel. The acoustic paste is coated between the ultrasonic probe and the ball, and the acoustic paste is used as an acoustic matching material to couple the sound wave into the optical fiber. The demodulator 204 is connected to the other end of the optical fiber 206 with a continuous uniform grating for collecting the reflection spectrum of the optical fiber.

Perform magnetic field calibration on the fiber optic sensor magnetic field measurement system:

Bond the optical fiber 206 with a continuous uniform grating to the controllable magnetostrictive material 209, select epoxy resin (EpoxyResin) or acrylate as an adhesive, and fix the grid area of the grating optical fiber on the surface of the material by pasting. The material is placed in a magnetic field environment. The pumping source 201 emits light waves into the first optical fiber 202, and the ultrasonic generator 205 emits ultrasonic waves through the acoustic paste between the ultrasonic probe and the sintered ball 207 at the end of the optical fiber to couple the ultrasonic waves into the optical fiber 206 with a continuous uniform grating. The ultrasonic waves propagate forward in the form of longitudinal waves, and the wavelength of the ultrasonic wave is longer than the grating length of the grating fiber. Preferably, in this embodiment, the ultrasonic wave emitted by the ultrasonic generator 205 has a wavelength of 1 cm-2 cm. The light wave in the first optical fiber 202 is coupled to an optical fiber 206 with a continuous uniform grating through a wavelength division multiplexer 203 . Record the distance between the off-peak and the main peak collected by the demodulator at time t.

The magnetic field intensity value H ₁ of the magnetic field is changed by the magnetic field controller 210, thereby causing the change of the magnetostrictive material 209, the distance s ₁ from the peak deviated from the main peak caused by the magnetic field collected by the recorder and demodulator at the same time t, and the change of the magnetostrictive material 209 The method can stretch, compress or bend the material by changing the intensity of the magnetic field, and the stretching method is preferred in this embodiment. Repeat the above process, record the distances s ₂ , , s ₃ ... _{s n} from the peak and the main peak collected by the demodulator corresponding to different magnetic fields H _{2 ,} H ₃ , ... H n at the same time t, and complete the measurement of the optical fiber sensor magnetic field The calibration of the system, as shown in Figure 7, is a schematic diagram of the off-peak deviation from the main peak of the present invention at different magnetic fields. Fit the relationship curve of the distance from the main peak to the distance from the main peak with the change of the magnetic field, and the curve fitting can be linearly fitted by the least square method, as shown in formula 1.

y=ax+b (1)

The curve fitting can also adopt the least squares fitting, and the fitting curve can be deduced from the following equations (2) and (3).

By solving the equations and finding a ₀ and a ₁ , an approximation function that satisfies the square approximation condition can be constructed.

f(x)＝a ₀ +a ₁ x (4)

FIG. 8 shows the curve of the off-peak deviation from the main peak distance as a function of the magnetic field obtained through fitting in the embodiment of the present invention.

To measure the magnetic field to be measured:

Lay the optical fiber sensor magnetic field measurement system with the magnetostrictive material, place it in the magnetic field to be measured, record the distance s from the main peak at the time t, and compare the distance s from the main peak to the calibrated optical fiber sensor magnetic field measurement system Comparing the relationship curves of the distance from the peak to the main peak with the change of the magnetic field intensity, the strain of the material can be obtained.

Other embodiments of the invention will be apparent to and understood by those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The description and examples are considered exemplary only, with the true scope and spirit of the invention defined by the claims.

Claims (8)

1. a kind of method for measuring magnetic field inducing grating deformation based on ultrasonic pulse, which is characterized in that the measurement magnetic The method of field includes the following steps：

A) overlap fibre optical sensor magnetic field measurement system, the system comprises pumping source, the first optical fiber, a wavelength division multiplexer, One section of optical fiber, supersonic generator and (FBG) demodulator for carrying continuous uniform grating, the optical fiber with continuous uniform grating One end is bulbous end, and the supersonic generator is equipped with transmitting probe, and the transmitting probe is fixed with the bulbous end, institute (FBG) demodulator is stated to connect with the optical fiber other end with continuous uniform grating；The optical fiber tool with continuous uniform grating There are multistage grating, every section of raster grid to be uniformly distributed, is spaced between the grating identical；

Wherein, the bulbous end is bead made of optical fiber connector sintering, is passed through between the bead and the transmitting probe Silica gel is fixed；

B) the fibre optical sensor magnetic field measurement system is placed in magnetic field to be measured, it is collected inclined from peak records the (FBG) demodulator Spacing from main peak；

C) by the spacing from peak deviation main peak described in step b) and the spacing from peak deviation main peak with change of magnetic field strength Relation curve compares, and obtains the size of magnetic field intensity.

2. the method according to claim 1 for measuring magnetic field, which is characterized in that deviate main peak from peak in the step c) Spacing with change of magnetic field strength relation curve by calibration obtain, the calibration includes the following steps：

(1) optical fiber with continuous uniform grating is bonded with controllable magnetic telescopic material；

(2) the pumping source transmitting light wave enters first optical fiber, and the supersonic generator emits described in ultrasonic wave entrance Optical fiber with continuous uniform grating；

(3) the collected spacing for deviateing main peak from peak of record (FBG) demodulator moment t；

(4) gradually increase the size of magnetic field intensity, the process of repeating said steps (2) to step (3), record (FBG) demodulator with it is described The collected different magnetic field intensity of the t caused spacing for deviateing main peak from peak at the time of identical in step (3)；

(5) it is fitted and deviates the spacing of main peak with the relation curve of change of magnetic field strength from peak.

3. the method according to claim 1 for measuring magnetic field, which is characterized in that between the bead and the transmitting probe It is coated with and leads sound paste, the sound paste of leading is optoacoustic matching materials, enters optical fiber for coupled acoustic wave.

4. the method according to claim 2 for measuring magnetic field, which is characterized in that the ultrasonic wave described in step (2) is with vertical Waveshape is propagated, and the wavelength of the ultrasonic wave is more than the grid length of the grating.

5. the method according to claim 2 or 4 for measuring magnetic field, which is characterized in that the ultrasonic wavelength is 1cm- 2cm。

6. the method according to claim 2 for measuring magnetic field, which is characterized in that increase the big of magnetic field in the step (4) It is small so that magnetic telescopic material is stretched, bending, vibrate or squeeze.

7. it is according to claim 2 measure magnetic field method, which is characterized in that it is described from peak deviate main peak spacing with The relation curve of changes of magnetic field is fitted by linear fit or least square method.

8. measuring the Optical Fiber Sensor Measurement System of methods of magnetic field described in a kind of claim 1, which is characterized in that the measurement system System includes pumping source, the first optical fiber, a wavelength division multiplexer, one section of optical fiber, supersonic generator for carrying continuous uniform grating And (FBG) demodulator；

Described optical fiber one end with continuous uniform grating is bulbous end；

The supersonic generator is equipped with transmitting probe, and the transmitting probe fixes with the bulbous end, the (FBG) demodulator and The optical fiber other end connection with continuous uniform grating, the optical fiber with continuous uniform grating have multistage light Grid, every section of raster grid are uniformly distributed, and are spaced between the grating identical, wherein the bulbous end is optical fiber connector sintering Made of bead, fixed by silica gel between the bead and the transmitting probe.