CN118169770A - Push-pull type optical fiber geomagnetic measurement probe, device and method - Google Patents
Push-pull type optical fiber geomagnetic measurement probe, device and method Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention relates to the technical field of optical fiber sensing, in particular to a push-pull optical fiber geomagnetic measurement probe, a device and a method. By the arrangement, the defects of high manufacturing cost, large measurement error and small precision of the conventional optical fiber geomagnetic measurement device are overcome.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to a push-pull optical fiber geomagnetic measurement probe, a device and a method.
Background
Geomagnetism is widely applied to a plurality of fields such as navigation communication, resource detection, near-earth space, earth deep research, earthquake prediction and forecast, and the like, and has important significance for knowing the earth and human living environment.
Compared with the traditional measurement technology based on electric quantity, the optical fiber sensor has the advantages of high sensitivity, electromagnetic interference resistance, corrosion resistance, light weight, easy distribution and the like, and therefore, the optical fiber sensor is commonly used for measuring and acquiring the magnetic field intensity at present. However, the existing optical fiber geomagnetic measurement device is high in manufacturing cost, large in measurement error and small in precision.
Disclosure of Invention
In order to solve the defects of high manufacturing cost, large measurement error and small precision of the conventional optical fiber geomagnetic measurement device, the invention provides a push-pull optical fiber geomagnetic measurement probe, a device and a method.
The technical scheme includes that the push-pull type optical fiber geomagnetic measurement probe comprises a base, a magnetostriction unit and a strain gauge, wherein two ends of the magnetostriction unit are respectively connected with one end of the base and one end of the strain gauge, the other end of the strain gauge is connected with the other end of the base, and the strain gauge comprises a bottom plate and two first optical fibers respectively adhered to two side surfaces of the bottom plate.
Preferably, the first optical fibers are respectively stuck to the two side surfaces of the bottom plate in a reciprocating way for a plurality of times.
Preferably, the magnetostrictive element and the strain gauge are fixedly connected along a straight line.
Preferably, the magnetostrictive element has a rod-like structure, and the strain gauge has a long plate-like structure.
Preferably, the device further comprises a connecting piece with two side surfaces respectively connected with the magnetostriction unit and the strain gauge, wherein the two side surfaces of the connecting piece are respectively larger than/equal to the end surface size of the magnetostriction unit/the strain gauge connected with the connecting piece.
Preferably, the optical fiber further comprises a second optical fiber and a reflecting mirror connected with the first optical fiber through the second optical fiber in a signal mode.
The invention also provides a push-pull type optical fiber geomagnetic measurement device, which comprises three push-pull type optical fiber geomagnetic measurement probes, wherein the strain center axes of the three magnetostrictive units are mutually 90-degree orthogonal.
Preferably, the device further comprises a demodulation unit, a multi-core optical cable, a coupler, a third optical fiber and a fourth optical fiber, wherein one end of the coupler is connected with the first optical fiber through a third optical fiber signal, the other end of the coupler is connected with one end of the multi-core optical cable through a fourth optical fiber signal, and the other end of the multi-core optical cable is connected with the demodulation unit through a signal.
Preferably, the optical fiber geomagnetic sensor further comprises a housing and a gram connector, wherein the housing and the base enclose a containing cavity, the gram connector is arranged on the housing, the push-pull optical fiber geomagnetic measurement probe, the coupler, the third optical fiber and the fourth optical fiber are all arranged in the containing cavity, and the multicore optical cable and the fourth optical fiber are in signal connection through the gram connector.
The invention also provides a geomagnetic measurement method based on the push-pull optical fiber geomagnetic measurement device, which is characterized by comprising the following steps:
Placing the push-pull optical fiber geomagnetic measurement device at a position to be measured, and enabling strain center axes of the three magnetostriction units to be aligned to the geographic north, geographic east and vertical downward directions respectively;
acquiring an optical fiber interference signal according to the push-pull optical fiber geomagnetic measurement device;
acquiring measuring magnetic field components in the three directions of geographic north, geographic east and vertical downward of the position to be measured;
calculating and obtaining actual magnetic field components of the position to be detected in the geographic north, the geographic east and the vertical downward direction according to the measured magnetic field components of the position to be detected in the geographic north, the geographic east and the vertical downward direction and the optical fiber interference signal;
And calculating and obtaining the actual total field intensity of the position to be measured, the actual magnetic field component in the horizontal direction, the magnetic dip angle and the magnetic declination angle according to the actual magnetic field components in the geographic north, geographic east and vertical downward directions of the position to be measured.
Preferably, the acquiring the measured magnetic field components in the three directions of geographic north, geographic east and vertical downward of the position to be measured specifically includes: and placing the push-pull type optical fiber geomagnetic measurement device in a zero magnetic space, and calculating and acquiring measurement magnetic field components in the geographic north, the geographic east and the vertical downward directions of the position to be measured according to the optical fiber interference signals.
Compared with the prior art, the invention has the following beneficial effects:
1. According to the invention, the remote real-time measurement of the horizontal component (H), the north component (X), the east component (Y), the vertical component (Z), the magnetic declination (D), the magnetic inclination (I) and the total field intensity (F) of the earth magnetic field is realized through the push-pull optical fiber geomagnetic measurement device, the remote accurate measurement of seven elements of the geomagnetic field under the all-optical fiber interference principle is realized, the production cost and difficulty of the geomagnetic measurement device are reduced, the stability of the device is increased, and the later maintenance cost is reduced;
2. According to the geomagnetic sensor, the length of the sensing section of the optical fiber interference arm is greatly increased by repeatedly pasting the first optical fibers on the upper surface and the lower surface of the strain gauge in a reciprocating manner, the optical fiber interference arm is of a push-pull structure when the strain gauge is deformed, the sensitivity is improved while the arm length difference is increased, meanwhile, the magnetic field gradient noise is greatly reduced, the temperature compensation is realized, and the measurement precision of the geomagnetic sensor is increased;
3. According to the geomagnetic sensor, three magnetostrictive units with compact structures are used for measuring three components of geomagnetism, so that the measurement space is reduced, the use cost of magnetostrictive materials is reduced, and the magnetic field gradient interference suffered during geomagnetism measurement is offset greatly, so that geomagnetism measurement with high precision is realized.
Drawings
The invention is described in detail below with reference to examples and figures, wherein:
FIG. 1 is a geomagnetic element relationship diagram;
FIG. 2 is a schematic diagram of a push-pull optical fiber geomagnetic measurement apparatus in one embodiment;
FIG. 3 is a front view of FIG. 2;
FIG. 4 is a schematic view of a portion of the structure of FIG. 2;
FIG. 5 is a schematic diagram of three internal Michelson interference optical paths of a push-pull fiber geomagnetic measurement apparatus;
FIG. 6 is a schematic structural view of the base;
FIG. 7 is a front view of FIG. 6;
FIG. 8 is a schematic structural view of a connector;
FIG. 9 is a front view of FIG. 8;
FIG. 10 is a schematic diagram of a push-pull optical fiber geomagnetic measurement apparatus in another embodiment;
fig. 11 is a flowchart of the geomagnetic measurement method.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in further detail with reference to the accompanying drawings. Examples of the embodiments are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements throughout, or elements having like or similar functionality. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.
In one embodiment, as shown in fig. 2-3, a push-pull optical fiber geomagnetic measurement probe comprises a base 1, a magnetostrictive unit 3 and a strain gauge 4, wherein two ends of the magnetostrictive unit 3 are respectively connected with one end of the base 1 and one end of the strain gauge 4, the other end of the strain gauge 4 is connected with the other end of the base 1, the strain gauge 4 comprises a bottom plate and two first optical fibers, and the two first optical fibers are respectively adhered to two side surfaces of the bottom plate.
The base 1 is a supporting structure of a geomagnetic measurement probe, one end of the magnetostrictive unit 3 and one end of the strain gauge 4 are both fixed on the base 1, and the other end of the magnetostrictive unit 3 is fixedly connected with the other end of the strain gauge 4. When a magnetic field acts on the magnetostrictive unit 3, the magnetic nuclei inside the magnetostrictive unit 3 are orderly combined and arranged along the direction of the magnetic field, which causes the magnetostrictive unit 3 to expand and contract in volume along the direction of the magnetic field, which is a magnetostrictive effect, so that the magnetostrictive unit 3 can convert the magnetic field into a change in length thereof. The base 1 does not deform, so that the length change of the magnetostrictive unit 3 is transmitted to the strain gauge 4 and converted into the deformation of the strain gauge 4, and one end of the strain gauge 4 away from the magnetostrictive unit 3 is limited by the base 1, so that the strain gauge 4 can bend or relax, and the two first optical fibers have a length difference. The arm length difference is detected to calculate and obtain the magnetic field intensity.
The weak magnetic field measurement sensor based on an atomic spin system and on the non-spin-exchange relaxation effect requires special materials such as NV color center diamond, an alkali metal air chamber and the like, so that the manufacturing cost of the sensor is increased, and the use environment of the sensor is limited. The geomagnetic measurement probe in the embodiment does not need to use special materials, has low manufacturing cost and is suitable for various use environments. The first optical fibers are stuck on the upper surface and the lower surface of the bottom plate to form a push-pull structure, so that the sensitivity is improved, the temperature compensation is realized, and the measurement accuracy of the geomagnetic measurement probe is improved.
In one embodiment, the first optical fibers are respectively stuck back and forth on two sides of the bottom plate for multiple times, so that the length of the first optical fibers can be increased, the length difference of the two first optical fibers is further increased, and the sensitivity of the geomagnetic measurement probe is improved.
In one embodiment, the magnetostrictive unit 3 and the strain gauge 4 are fixedly connected along a straight line, the connection mode is direct and clear, a complex structure or a connecting piece 2 is not needed, assembly and maintenance are simplified, the response speed of a system can be improved through the straight line fixed connection, deformation of the magnetostrictive unit 3 can be accurately and directly transmitted to the strain gauge 4, the process of calculating the magnetic field intensity is simpler, and the error rate is low.
In one embodiment, the magnetostrictive unit 3 has a rod-shaped structure, and two ends of the rod-shaped magnetostrictive unit 3 are respectively connected with the base 1 and the strain gauge 4; the strain gauge 4 is of a long plate-shaped structure, the magnetostriction unit 3 and the base 1 are respectively connected to two ends of the long plate-shaped strain gauge 4, and the magnetostriction unit 3 and the strain gauge 4 are both arranged in a shape with long length, so that the deformation of the magnetostriction unit 3 and the first optical fiber on the strain gauge 4 is more obvious, and the sensitivity of the geomagnetic measurement probe is improved.
In one embodiment, the push-pull optical fiber geomagnetic measurement probe further comprises a connecting piece 2, wherein two side surfaces of the connecting piece 2 are respectively connected with the magnetostrictive unit 3 and the strain gauge 4, and the sizes of the two side surfaces of the connecting piece 2 are respectively larger than/equal to the end surface sizes of the magnetostrictive unit 3/the strain gauge 4 connected with the connecting piece. The magnetostrictive element 3 and the strain gage 4 with the difference in end face sizes are directly connected, so that the unconnected part of the end face with the larger size is wasted, and the actual connection area of the magnetostrictive element and the strain gage is smaller. The end surfaces of the magnetostrictive element 3 and the strain gauge 4 in the embodiment can be completely connected with the two side surfaces of the connecting piece 2, so that a larger contact area and tight connection can be provided, the strength and stability of the connection are enhanced, the possibility of loosening and displacement is reduced, and the firm connection between the magnetostrictive element 3 and the strain gauge 4 is ensured. By increasing the contact area, the connecting piece 2 can more effectively transfer the deformation of the magnetostrictive unit 3 to the strain gauge 4, so that the sensitivity and the measurement accuracy of the strain gauge 4 can be improved, and the accuracy of the measurement result can be ensured.
In one embodiment, the optical fiber further comprises a second optical fiber and a reflecting mirror 6, and two ends of the second optical fiber are respectively connected with the first optical fiber and the reflecting mirror 6 in a signal mode. When the geomagnetic field changes, the two first optical fibers have a length difference, so that the first optical fibers generate phase change signals, the second optical fibers are used for transmitting the signals from the first optical fibers to the reflector 6, the reflector 6 reflects the signals to the second optical fibers and then transmits the signals back to the optical detection system for signal analysis and processing, and the reflector 6 enables the signals to be transmitted and detected, so that geomagnetic measurement and monitoring are achieved.
In one embodiment, as shown in fig. 2-3, a push-pull optical fiber geomagnetic measurement device includes three push-pull optical fiber geomagnetic measurement probes in the above embodiment, strain axes of the three magnetostrictive units 3 are orthogonal to each other by 90 degrees, so that the push-pull optical fiber geomagnetic measurement device is placed at a position to be measured, and the strain axes of the three magnetostrictive units 3 are aligned to three directions of geographic north, geographic east and vertical down respectively, so that cross interference can be reduced, accurate measurement of three components of a north component (X component), an east component (Y component) and a vertical component (Z component) of a geomagnetic field by the measurement device is ensured, accurate geomagnetic field strength and direction information are further provided, and fine geomagnetic field analysis and research are facilitated.
The base 1 of the three geomagnetic measurement probes can be fixedly connected into a whole and used for structural support of the whole geomagnetic measurement device, so that stability of the whole geomagnetic measurement device can be improved, relative movement and mutual interference between the probes are reduced, the probes are always positioned at the correct positions and at the correct relative angles, and measurement accuracy and consistency are maintained.
In one embodiment, the push-pull optical fiber geomagnetic measurement apparatus further includes a demodulation unit, a multi-core optical cable 11, a coupler 7, a third optical fiber 10 and a fourth optical fiber, as shown in fig. 5, one end of the coupler 7 is connected with the first optical fiber through the third optical fiber 10 signal, and the other end is connected with one end of the multi-core optical cable 11 through the fourth optical fiber signal, so as to realize beam splitting and coupling of optical signals. The other end of the multi-core optical cable 11 is connected with a demodulation unit in a signal way, so that the optical fiber interference signal can be effectively transmitted from the geomagnetic measurement probe to the demodulation unit.
The demodulation unit is used for demodulating the mixed signal with a plurality of groups of optical signals received from the multi-core optical cable 11, and extracting information in each optical signal. As shown in fig. 10, the optical fiber interferometer 12 is used for demodulating the phase difference of each path of optical fiber interference signal in real time, and calculating to obtain geomagnetic seven elements through a correlation formula, so as to realize geomagnetic measurement. The minimum distinguishable phase variation of the fiber interferometer 12 in this embodiment is 1X10 -5 rad; the sensitivity is greater than 50dB, and the case has the dimensions of 45cm long, 43cm wide and 18cm high. In other embodiments, the specific parameters of the optical fiber interferometer 12 may be adjusted according to the actual situation, and the demodulation unit may also be configured as an opto-electromechanical modulator, a photodetector array, etc.
In one embodiment, the push-pull optical fiber geomagnetic measurement device further comprises a housing 9 and a gram connector 8, the housing 9 and the base 1 enclose a containing cavity, so that an inner space on the base 1 is isolated from an outer space, and the push-pull optical fiber geomagnetic measurement probe, the coupler 7, the third optical fiber 10 and the fourth optical fiber are all arranged in the containing cavity, so that the push-pull optical fiber geomagnetic measurement probe is prevented from being polluted by external dirt, and each component on the base 1 is ensured to stably and normally run. The connection between the base 1 and the shell 9 can be fixed by using a fixing screw 5, a buckle and the like, the fixing screw 5 is made of plastic steel, aluminum oxide and the like, the relative magnetic permeability is close to 1, the thermal expansion coefficient is small, the magnetic field measurement is not easily affected by temperature noise, and the specific size can be a hexagon screw 5 with the length of M5 being 20mm and the like. The material of the casing 9 is a non-magnetic material with a relative magnetic permeability close to 1, such as carbon fiber board, ceramic, or twist stone, so as to ensure that the geomagnetic field acts on the magnetostrictive unit 3 completely, and specific parameters of the casing 9 can be adjusted according to practical situations, such as an inner dimension of 50cm long, 50cm wide, 40cm high, and a thickness of 0.5 cm.
The gram joint 8 is arranged on the shell 9, the multi-core optical cable 11 and the fourth optical fiber are in signal connection through the gram joint 8, so that the multi-core optical cable can be fixed on the shell 9, and meanwhile, the multi-core optical cable 11 is in signal connection with the coupler 7 through the fourth optical fiber. The material of the gram joint 8 must be a non-magnetic material with a relative magnetic permeability close to 1, such as all PVC (polyvinyl chloride) plastic, all PTFE (polytetrafluoroethylene) plastic, etc., so as to ensure that the geomagnetic field acts on the magnetostrictive unit 3 completely, and specific parameters of the gram joint 8 can be adjusted according to practical situations, such as the screw specification of the gram joint 8 is m20x1.5, the opening size is 12mm, and the length is 22.7mm, etc.
As shown in fig. 6 to 7, the base 1 may be a carbon fiber module, and has a relative magnetic permeability close to 1 and a small thermal expansion coefficient, so that the magnetic field measurement is not easily affected by temperature noise, and it is ensured that the geomagnetic field acts on the magnetostrictive unit 3 completely, and the dimensions of the base 1 may be 50cm long, 50cm wide, and 40cm high. In other embodiments, the base 1 may also be made of a material with a relative magnetic permeability close to 1 and a smaller thermal expansion coefficient, such as glass ceramic, and the dimensions of the material may also be set according to practical needs, so as to connect and fix the casing 9, the magnetostrictive unit 3 and the strain gauge 4 with different sizes and shapes.
The connection between the base 1 and the magnetostrictive unit 3 and the strain gauge 4, and the connection between the magnetostrictive unit 3 and the strain gauge 4 may be glued by glue to ensure stable and firm connection, and the second optical fiber and the reflecting mirror 6 may be firmly fixed on the base 1 by glue to maintain the stability of the entire geomagnetic measurement apparatus. In other embodiments, the components may also be connected by a snap fit, interference fit, or the like. The specific parameters of the reflector 6 can be adjusted according to practical situations, such as a cylinder with a reflectivity of 99.9% and a specific dimension of 3mm in diameter and 1.5cm in length.
As shown in fig. 4, the strain central axes of the three magnetostrictive units 3 must strictly conform to that the triaxial directions are 90 degrees, the magnetostrictive units 3 are made of terbium dysprosium iron alloy, and have a saturation giant magnetostriction coefficient of more than 1500ppm, and the specific dimensions are cylinders with diameters of 1cm and lengths of 6 cm. In other embodiments, the magnetostrictive unit 3 may also be made of ferrous iron, iron platinum alloy, or other materials, and may also be configured as a rod-like structure such as a cuboid, and the specific size may be set according to actual requirements.
The material of the base plate of the strain gauge 4 is a carbon fiber plate material made of a non-magnetic material with relative magnetic conductivity close to 1, then two first optical fibers are respectively stuck on two side surfaces, the first optical fibers and the carbon fiber plate are stuck into a whole through DP420 and other glues special for sticking the optical fibers, the first optical fibers are stuck on the base plate to form an optical fiber interference arm of the demodulation unit, and the length difference of the two first optical fibers is the arm length difference of the optical fiber interference arm. The specific dimensions of the strain gauge 4 may be set according to practical requirements, such as a length of 32cm, a width of 10cm, a thickness of 0.5mm, etc.
As shown in fig. 8-9, the connecting piece 2 is mainly used for connecting the strain gauge 4 and the magnetostrictive unit 3, and transmitting the length change of the magnetostrictive unit 3 to the deformation of the strain gauge 4; the connecting piece 2 can be respectively adhered with the strain gauge 4 and the magnetostriction unit 3 by using glue, so that stable and reliable connection is ensured. The connecting piece 2 is made of carbon fiber modules, glass ceramics and the like, has relative magnetic permeability close to 1 and small thermal expansion coefficient, so that magnetic field measurement is not easily affected by temperature noise, and the specific size of the connecting piece 2 can be set according to the sizes of the strain gauge 4 and the magnetostriction unit 3, such as 11cm long, 1cm wide, 3cm high and the like.
The multi-core optical cable 11 is an optical cable containing a plurality of optical fibers, and is mainly used for connecting a geomagnetic measurement device and an optical fiber interferometer 12, so that optical fiber interference signals can be effectively transmitted; the specific parameters of the multi-core optical cable 11 can be adjusted according to practical conditions, such as the diameter is 8mm, the inside is a three-core single-mode optical fiber, and the multi-core optical cable meets the ITU-T G.652 standard.
The specific parameters of the coupler 7 can be adjusted according to practical situations, for example, a 1X2 coupler 7 is adopted, the spectral ratio is 50:50, and the specific size is a cylinder with the diameter of 3mm and the length of 6 cm.
The specific parameters of the first optical fiber, the second optical fiber, the third optical fiber 10 and the fourth optical fiber can be adjusted according to practical situations, such as using corning single-mode optical fiber, and conforming to ITU-T G.652 standard.
The geomagnetic field is a vector field, both in magnitude and direction, generally denoted by vector F. The description of F is generally described in terms of its individual components, which are referred to as geomagnetic elements. The geomagnetic elements mainly comprise a horizontal component (H), a north component (X), an east component (Y), a vertical component (Z), a declination angle (D), a magnetic dip angle (I) and a total field intensity (F), and the relation of the components is shown in figure 1. Wherein X, Y, Z is more common in theoretical studies, H, Z, D is more common in geomagnetic relative recordings, and F, D, I is more common in absolute observations. F. H, X, Y, Z as intensity component and D, I as angle component. The relationship between the components is as follows:
Z＝FsinI......................(1-1)
Y＝HsinD......................(1-2)
F＝H2+Z2＝X2+Y2+Z2......(1-3)
In one embodiment, as shown in fig. 11, a geomagnetic measurement method, based on the push-pull optical fiber geomagnetic measurement apparatus according to the above, includes:
S1, placing the push-pull optical fiber geomagnetic measurement device at a position to be measured, and enabling strain center axes of the three magnetostriction units to be aligned to the geographic north, the geographic east and the vertical downward directions respectively. The geomagnetic measurement probe is connected with the optical fiber interferometer through a multi-core optical cable, the push-pull optical fiber geomagnetic measurement device is placed at a position to be measured, and the strain center axes of the three magnetostriction units are aligned to the geographic north, the geographic east and the vertical downward directions respectively.
S2, obtaining an optical fiber interference signal, namely a magnetic field variation delta E, according to the push-pull optical fiber geomagnetic measurement device.
S3, acquiring measured magnetic field components in the three directions of geographic north, geographic east and vertical downward of the position to be measured, namely initial magnetic field strength E 0, wherein the step is used for calibrating E 0.
S4, calculating and obtaining actual magnetic field components of the position to be detected in the geographic north, the geographic east and the vertical downward direction according to the measured magnetic field components of the position to be detected in the geographic north, the geographic east and the vertical downward direction and the optical fiber interference signals. Specifically, when a magnetic field acts on the magnetostrictive material, the magnetic nuclei inside the magnetostrictive material are orderly combined and arranged along the direction of the magnetic field, so that the magnetostrictive material expands and contracts in volume along the direction of the magnetic field, which is the magnetostrictive effect. However, the deformation and the direction or magnitude of the magnetic field in the volume have different trend, and the magnetostrictive effect causes different degrees of expansion and contraction because the magnetostrictive materials are different in material and mainly comprise metal alloy materials such as iron-nickel alloy, iron-aluminum alloy, iron-cobalt alloy and the like and rare earth metal alloy materials such as terbium-dysprosium-iron alloy and the like. In the linear operating region, the magnetostriction coefficient versus axial strain ε can be expressed as:
C(E0+ΔE)＝Δd/d＝ε.................(1-4)
in the above formula, C is the magnetostriction coefficient, E 0 is the initial magnetic field strength, ΔE is the magnetic field strength variation, Δd is the material length variation caused in the magnetic field direction, and d is the initial length of the telescopic material.
When the external magnetic field changes to cause the length of the magnetostrictive material to change, the strain gauge is driven to bend or relax, and then the two optical fiber interference arms stuck on the upper surface and the lower surface of the strain gauge generate arm length difference, and the relation between the length change quantity of the magnetostrictive material and the interference arm length difference deltar can be expressed as:
Δr＝KNlΔd.................(1-5)
in the above description, K is the conversion coefficient of the distance between the strain gauge and the change amount of the optical fiber, N is the number of the optical fibers on the strain gauge, and l is the strain distance between the optical fibers on the strain gauge.
The optical fiber interference system interferes the arm length difference to cause the optical fiber interference signal to produce the phase difference, arm length difference Deltar and phase change signalThe relationship of (2) can be expressed as:
In the above formula, n is the refractive index of the optical fiber, v 0 is the central wavelength of the interference optical signal, and c 0 is the speed of light in vacuum.
When the optical fiber interference signal is transmitted back to the optical fiber interferometer, the optical fiber interference signal I PD (t) detected by the Photodetector (PD) is in the form as follows:
In the above, I 0 is the laser radiation intensity, k v(0≤kv is less than or equal to 1) is the interference fringe contrast, An initial phase difference for the fiber optic interferometer.
The combination of formulas (1-4), (1-5), (1-6) and (1-7) can be obtained
Wherein I 0、kv,π、n、/>K、N、l、C、d、c0、/>When E 0 is the known quantity, the phase change quantity demodulated by the interferometer and the initial magnetic field strength E 0 of each axis can be substituted into the formula (1-8) to calculate the magnetic field strength in the measuring direction.
S5, calculating and obtaining the actual total field intensity of the position to be measured, the actual magnetic field component in the horizontal direction, the magnetic dip angle and the magnetic declination angle according to the actual magnetic field components in the geographic north, geographic east and vertical downward directions of the position to be measured.
Specifically, by measuring the magnetic field strengths on three components of the X axis Y axis Z axis, the horizontal component (H), the declination angle (D), the inclination angle (I) and the total field strength (F) can be calculated by the formulas (1-1), (1-2) and (1-3).
In one embodiment, S3, acquiring measured magnetic field components in three directions, namely, geographic north, geographic east and vertical downward, of a position to be measured specifically includes: the push-pull type optical fiber geomagnetic measurement device is placed in a zero magnetic space, and measured magnetic field components in the geographic north, the geographic east and the vertical downward directions of a position to be measured are obtained through calculation according to optical fiber interference signals, namely E 0 =0 is brought into calibration to obtain each axis calibration value E 0 in the non-zero magnetic space.
In other embodiments, another three-component magnetometer may be aligned with the three axes of the geomagnetic measurement apparatus to be calibrated, and then the initial magnetic field strengths E 0 in the three directions may be measured.
According to the invention, the remote real-time measurement of the horizontal component (H), the north component (X), the east component (Y), the vertical component (Z), the magnetic declination (D), the magnetic inclination angle (I) and the total field intensity (F) of the earth magnetic field is realized through the push-pull optical fiber geomagnetic measurement device, the remote accurate measurement of seven elements of the geomagnetic field under the all-optical fiber interference principle is realized, the production cost and difficulty of the geomagnetic measurement device are reduced, the stability of the device is increased, and the later maintenance cost is reduced.
According to the geomagnetic sensor, the length of the sensing section of the optical fiber interference arm is greatly increased by repeatedly pasting the first optical fibers on the upper surface and the lower surface of the strain gauge in a reciprocating manner, the optical fiber interference arm is of a push-pull structure when the strain gauge is deformed, the sensitivity is improved while the arm length difference is increased, meanwhile, the magnetic field gradient noise is greatly reduced, the temperature compensation is realized, and the measurement precision of the geomagnetic sensor is increased.
According to the geomagnetic sensor, three magnetostrictive units with compact structures are used for measuring three components of geomagnetism, so that the measurement space is reduced, the use cost of magnetostrictive materials is reduced, and the magnetic field gradient interference suffered during geomagnetism measurement is offset greatly, so that geomagnetism measurement with high precision is realized.
In the description of the present specification, the terms "embodiment," "present embodiment," "in one embodiment," and the like, if used, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples; furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
In the description of the present specification, the terms "connected," "mounted," "secured," "disposed," "having," and the like are to be construed broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
In the description of this specification, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The embodiments have been described so as to facilitate a person of ordinary skill in the art in order to understand and apply the present technology, it will be apparent to those skilled in the art that various modifications may be made to these examples and that the general principles described herein may be applied to other embodiments without undue burden. Therefore, the present application is not limited to the above embodiments, and modifications to the following cases should be within the scope of protection of the present application: ① The technical scheme of the invention is taken as the basis and combined with the new technical scheme implemented by the prior common general knowledge, and the technical effect produced by the new technical scheme is not beyond that of the invention; ② Equivalent replacement of part of the characteristics of the technical scheme of the invention by adopting the known technology produces the technical effect the same as that of the invention; ③ The technical scheme of the invention is taken as a basis for expanding, and the essence of the expanded technical scheme is not beyond the technical scheme of the invention; ④ Equivalent transformation made by the content of the specification and the drawings of the invention is directly or indirectly applied to other related technical fields.
Claims (11)
1. The push-pull type optical fiber geomagnetic measurement probe is characterized by comprising a base, a magnetostriction unit and a strain gauge, wherein two ends of the magnetostriction unit are respectively connected with one end of the base and one end of the strain gauge, the other end of the strain gauge is connected with the other end of the base, and the strain gauge comprises a bottom plate and two first optical fibers respectively adhered to two side surfaces of the bottom plate.
2. The push-pull type optical fiber geomagnetic measurement probe of claim 1, wherein the first optical fibers are attached to both side surfaces of the base plate back and forth a plurality of times, respectively.
3. The push-pull optical fiber geomagnetic measurement probe of claim 2, wherein the magnetostrictive unit and the strain gauge are fixedly connected along a straight line.
4. A push-pull optical fiber geomagnetic measurement probe according to claim 3, wherein the magnetostrictive unit is a rod-like structure, and the strain gauge is a long plate-like structure.
5. The push-pull optical fiber geomagnetic measurement probe of claim 4, further comprising a connecting piece with two side surfaces respectively connected with the magnetostrictive unit and the strain gauge, wherein the two side surfaces of the connecting piece have a size respectively larger than/equal to the end surface size of the magnetostrictive unit/the strain gauge connected with the connecting piece.
6. The push-pull fiber geomagnetic measurement probe of any of claims 1 to 5, further comprising a second optical fiber, and a mirror in signal connection with the first optical fiber through the second optical fiber.
7. A push-pull optical fiber geomagnetic measurement apparatus, comprising three push-pull optical fiber geomagnetic measurement probes according to claim 6, wherein strain center axes of the three magnetostrictive units are orthogonal to each other by 90 degrees.
8. The push-pull optical fiber geomagnetic measurement apparatus of claim 7, further comprising a demodulation unit, a multicore optical cable, a coupler, a third optical fiber and a fourth optical fiber, wherein one end of the coupler is connected to the first optical fiber through the third optical fiber signal, the other end is connected to one end of the multicore optical cable through the fourth optical fiber signal, and the other end of the multicore optical cable is connected to the demodulation unit.
9. The push-pull optical fiber geomagnetic measurement apparatus of claim 8, further comprising a housing enclosing a receiving cavity with the base and a gram joint provided on the housing, wherein the push-pull optical fiber geomagnetic measurement probe, the coupler, the third optical fiber and the fourth optical fiber are all provided in the receiving cavity, and the multicore optical cable and the fourth optical fiber are connected by the gram joint signal.
10. A geomagnetic measurement method based on the push-pull optical fiber geomagnetic measurement apparatus according to claim 8 or 9, characterized in that the method comprises:
Placing the push-pull optical fiber geomagnetic measurement device at a position to be measured, and enabling strain center axes of the three magnetostriction units to be aligned to the geographic north, geographic east and vertical downward directions respectively;
acquiring an optical fiber interference signal according to the push-pull optical fiber geomagnetic measurement device;
acquiring measuring magnetic field components in the three directions of geographic north, geographic east and vertical downward of the position to be measured;
calculating and obtaining actual magnetic field components of the position to be detected in the geographic north, the geographic east and the vertical downward direction according to the measured magnetic field components of the position to be detected in the geographic north, the geographic east and the vertical downward direction and the optical fiber interference signal;
And calculating and obtaining the actual total field intensity of the position to be measured, the actual magnetic field component in the horizontal direction, the magnetic dip angle and the magnetic declination angle according to the actual magnetic field components in the geographic north, geographic east and vertical downward directions of the position to be measured.
11. The geomagnetic measurement method of claim 10, wherein the acquiring measured magnetic field components in three directions, that is, geographic north, geographic east, and vertical downward, of the position to be measured, specifically includes: and placing the push-pull type optical fiber geomagnetic measurement device in a zero magnetic space, and calculating and acquiring measurement magnetic field components in the geographic north, the geographic east and the vertical downward directions of the position to be measured according to the optical fiber interference signals.
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