Magneto-optical conversion structure, push-pull optical fiber magnetic field measurement probe and geomagnetic measurement device

Abstract

The invention relates to a magneto-optical conversion structure, a push-pull optical fiber magnetic field measurement probe and a geomagnetic measurement device, a first support member sleeves a magnetostrictive rod, a first sensing optical fiber is wound around the first support member in the circumferential direction, and two end portions of the magnetostrictive rod are connected with the first support member through first transmission units. When the magneto-optical conversion structure receives a magnetic field signal, the length of the magnetostriction rod is changed, so that the first transmission unit is pulled, the diameter of the first supporting piece is changed between a first state and a second state, and the deformation quantity of the first sensing optical fiber wound on the first supporting piece is changed. The purpose of converting an external magnetic field signal into an optical signal is achieved. As the first sensing optical fiber is wound outside the first supporting piece, the first sensing optical fiber can obtain larger deformation quantity when the diameter of the first supporting piece is slightly changed, the length of an interference arm can be greatly reduced, and the influence of environmental noise on magnetic field signal detection is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of optoelectronic measuring devices, and in particular to a magneto-optical conversion structure, a push-pull optical fiber magnetic field measuring probe and a geomagnetic measuring device. Background Art

[0002] The geomagnetic field is one of the basic physical fields of the earth. As an inherent physical property of the earth, it contains rich and important information about the internal and external space of the earth. As an ancient discipline, geomagnetism is widely used in many fields such as navigation and communication, resource exploration, near-earth space and deep earth research, and earthquake prediction and forecasting, serving the national economy and national defense construction. On the other hand, geomagnetism is of great significance to the understanding of the earth and human living environment. In the past two decades, with the development of optical information technology, the price of optical information products has gradually decreased, and optical fiber sensing technology has also been greatly developed. Compared with the traditional dynamic measurement technology based on electrical quantities, optical fiber sensors have the advantages of high sensitivity, anti-electromagnetic interference, corrosion resistance, light weight, and low power consumption.

[0003] In the prior art, a push-pull optical fiber geomagnetic measurement probe, device and method (CN118169770A) are disclosed, in which two interference arms are respectively pasted on the front and back sides of the strain gauge. However, the elongation of the interference arm of the strain gauge as the magnetostrictive rod changes is too small, so a very long interference arm needs to be pasted to amplify the change of the magnetostrictive rod. If the interference arm is too long, more environmental noise will be introduced, reducing the measurement accuracy of the system. Summary of the invention

[0004] In order to solve the defect that an interferometer arm that is too long will introduce more environmental noise and reduce the measurement accuracy of the system, the present invention proposes a magneto-optical conversion structure.

[0005] The technical solution adopted by the present invention is a magneto-optical conversion structure, comprising a first support member, the first support member is sleeved outside a magnetostrictive rod, a first sensing optical fiber is circumferentially wound around the first support member, both ends of the first support member and the magnetostrictive rod are connected through a first transmission unit, the first support member has a first state and a second state with different diameters, and when the magnetostrictive rod is extended or retracted, the first support member is changed between the first state and the second state through the first transmission unit.

[0006] Preferably, the first support member is a cylindrical structure, and the cylindrical structure is composed of a plurality of first mounting blocks distributed along the circumference of the magnetostrictive rod.

[0007] Preferably, the first transmission unit includes a first connecting member and a first elastic strain gauge, one end of the first strain gauge is connected to the first mounting block, and the other end extends in a direction away from the magnetostrictive rod and is connected to the end of the magnetostrictive rod through the first connecting member.

[0008] Preferably, the plurality of first mounting blocks are all identical, there are a plurality of first strain gauges, and the plurality of first strain gauges are evenly distributed at the same angle along the circumference of the magnetostrictive rod.

[0009] Preferably, the first support member is sleeved at a middle position of the magnetostrictive rod.

[0010] In order to solve the defects that an interferometer arm that is too long will introduce more environmental noise and a single probe is easily affected by temperature, thereby reducing the measurement accuracy of the system, the present invention proposes a push-pull optical fiber magnetic field measurement probe.

[0011] The present application also discloses a push-pull optical fiber magnetic field measurement probe, comprising the above-mentioned magneto-optical conversion structure, the magneto-optical conversion structure being connected to a control module;

[0012] The control module includes a second support member, which is sleeved outside the elastic unit, a second sensing optical fiber is wound around the circumference of the second support member, both ends of the second support member and the elastic unit are connected through a second transmission unit, the second support member has a third state and a fourth state with different diameters, and the elastic unit abuts against the magnetostrictive rod in the axial direction of the magnetostrictive rod;

[0013] When the magnetostrictive rod is extended / contracted, the elastic unit is shortened / extended by the same distance, and the second supporting member is changed between the third state and the fourth state through the second transmission unit.

[0014] Preferably, the elastic unit comprises an elastic gasket and a support rod, and the elastic gasket abuts against the support rod in the axial direction;

[0015] The second support member is a cylindrical structure, which is composed of a plurality of second mounting blocks distributed along the circumference of the magnetostrictive rod;

[0016] The second transmission unit includes a second strain gauge and a second connecting member, wherein one end of the second strain gauge is connected to the second mounting block, and the other end of the second strain gauge extends in a direction away from the support rod and is connected to the end of the support rod through the second connecting member;

[0017] The elastic gasket is arranged between the second connecting member and the second supporting member.

[0018] Preferably, it also includes a cylindrical shell, the magneto-optical conversion structure and the control module are both arranged in the cylindrical shell, the shape of the second connecting member and the shape of the inner wall of the cylindrical shell match each other, a limiting rod is connected inside the cylindrical shell, a limiting hole is provided on the second connecting member, and the second connecting member is sleeved on the outside of the limiting rod through the limiting hole.

[0019] Preferably, the first sensing optical fiber and the second sensing optical fiber are the same optical fiber, the first support member and the second support member have the same shape and size, the magnetostrictive rod and the elastic unit have the same length in the initial state, the position where the first support member is sleeved on the magnetostrictive rod corresponds to the position where the second support member is sleeved on the elastic unit, the first transmission unit and the second transmission unit have the same shape and size, the diameter in the first state is the same as the diameter in the third state, and the diameter in the third state is the same as the diameter in the fourth state.

[0020] In order to solve the defect of low measurement accuracy of the existing geomagnetic measurement device, the present invention proposes a geomagnetic measurement device.

[0021] The present application also discloses a geomagnetic measurement device, including the above-mentioned push-pull optical fiber magnetic field measurement probe, wherein three push-pull optical fiber magnetic field measurement probes are respectively arranged perpendicular to each other.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present application discloses a magneto-optical conversion structure, wherein a first support member is sleeved outside a magnetostrictive rod, a first sensing optical fiber is circumferentially wound around the first support member, and both ends of the magnetostrictive rod and the first support member are connected via a first transmission unit. When the magneto-optical conversion structure receives a magnetic field signal, the length of the magnetostrictive rod will change, thereby pulling the first transmission unit, causing the diameter of the first support member to change between a first state and a second state, thereby changing the deformation of the first sensing optical fiber wound on the first support member, thereby achieving the purpose of converting the external magnetic field signal into an optical signal. Since the first sensing optical fiber is wound outside the first support member, a small change in the diameter of the first support member can enable the first sensing optical fiber to obtain a large deformation, which can greatly reduce the length of the interference arm and effectively reduce the impact of environmental noise on the detection of magnetic field signals.

[0024] Compared with the prior art, the magneto-optical conversion structure disclosed in the present application can reduce the impact of environmental noise on the detection results.

[0025] The present application discloses a push-pull optical fiber magnetic field measurement probe, which is connected to a control module based on a magneto-optical conversion structure. The control module includes a second support member, which is sleeved on an elastic unit, and a second sensing optical fiber is wound around the circumference of the second support member. The two ends of the elastic unit are connected to the second support member through a second transmission unit. When the push-pull optical fiber magnetic field measurement probe receives a magnetic field signal, the length of the magnetostrictive rod will change, causing the elastic unit to change in length in the opposite direction and the same distance, thereby pulling the second transmission unit, causing the diameter of the second support member to change between the third state and the fourth state, thereby changing the deformation of the second sensing optical fiber wound on the second support member. In this way, the deformation of the first sensing optical fiber and the deformation of the second sensing optical fiber can be obtained respectively, and the influence of temperature on the test results can be eliminated after calculation.

[0026] Compared with the prior art, the push-pull optical fiber magnetic field measurement probe disclosed in the present application can avoid the influence of temperature on the detection result.

[0027] The present application discloses a geomagnetic measurement device, comprising three push-pull optical fiber magnetic field measurement probes which are perpendicular to each other, so as to realize the measurement of magnetic field in different directions.

[0028] Compared with the prior art, the geomagnetic measurement device disclosed in the present application can achieve the purpose of improving the measurement accuracy of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0030] Figure 1 A schematic structural diagram of a geomagnetic measurement device provided by an embodiment of the present invention is shown;

[0031] Figure 2 A diagram showing the relationship between geomagnetic elements is shown;

[0032] Figure 3 A schematic structural diagram of a push-pull optical fiber magnetic field measurement probe provided according to an embodiment of the present invention is shown;

[0033] Figure 4 Shown according to Figure 3 A cross-sectional view of a push-pull optical fiber magnetic field measurement probe provided;

[0034] Figure 5 Shown according to Figure 3 A schematic structural diagram of a second support member in a push-pull optical fiber magnetic field measurement probe is provided;

[0035] Figure 6 Shown according to Figure 3A schematic structural diagram of a first support member or a second support member in a push-pull optical fiber magnetic field measurement probe provided;

[0036] Figure 7 Shown according to Figure 1 A schematic structural diagram of a base in a geomagnetic measuring device provided;

[0037] Figure 8 Shown according to Figure 1 A schematic diagram of the connection between a geomagnetic measurement device and a fiber optic interferometer is provided.

[0038] Description of labels:

[0039] 1. 1X2 coupler; 2. reflector; 31. first strain gauge; 32. second strain gauge; 41. first support member; 42. second support member; 51. first sensing optical fiber; 52. second sensing optical fiber; 6. support rod; 7. magnetostrictive rod; 8. limit rod; 91. first connecting member; 92. second connecting member; 10. cylindrical shell; 11. elastic gasket; 12. base; 13. shell; 14. gland joint; 15. multi-core optical cable; 16. mounting groove; 17. optical fiber interferometer. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0041] The present invention discloses a magneto-optical conversion structure, comprising a first support member 41, the first support member 41 is sleeved outside a magnetostrictive rod, a first sensing optical fiber 51 is circumferentially wound around the first support member 41, the first support member 41 and both ends of the magnetostrictive rod are connected through a first transmission unit, the first support member 41 has a first state and a second state with different diameters, and when the magnetostrictive rod is extended or retracted, the first support member 41 is changed between the first state and the second state through the first transmission unit.

[0042] The first support member 41 is sleeved outside the magnetostrictive rod, and the first support member 41 is circumferentially wound with a first sensing optical fiber 51, and the two ends of the magnetostrictive rod and the first support member 41 are connected through a first transmission unit. When the magneto-optical conversion structure receives the magnetic field signal, the length of the magnetostrictive rod will change, thereby pulling the first transmission unit, causing the diameter of the first support member 41 to change between the first state and the second state, thereby changing the deformation of the first sensing optical fiber 51 wound on the first support member 41, and achieving the purpose of converting the external magnetic field signal into an optical signal. Since the first sensing optical fiber 51 is wound outside the first support member 41, a small change in the diameter of the first support member 41 can enable the first sensing optical fiber 51 to obtain a large deformation, which can greatly reduce the length of the interference arm and effectively reduce the impact of environmental noise on the detection of magnetic field signals. Compared with the prior art, the magneto-optical conversion structure disclosed in the present application can reduce the impact of environmental noise on the detection results.

[0043] Specifically, the reason why the first transmission unit is provided at both ends of the first support member 41 is to prevent the first sensing optical fiber 51 from being deformed drastically when the first support member 41 is pulled on one side, or even the first sensing optical fiber 51 cannot transmit light normally when it is pulled severely. This problem can be solved by providing the first transmission unit at both ends to pull simultaneously. At the same time, the signal amplification factor when pulling on one side is smaller than the amplification factor when pulling on both sides at the same time, so pulling on both sides at the same time is more conducive to improving the quality of signal transmission.

[0044] It should be noted that the end of the magnetostrictive rod refers to a section of the magnetostrictive rod located at the edges of both ends, and does not only refer to the most edge position. In addition, the first state and the second state in which the first support member 41 has different cross-sectional areas refer to that in the first state and the second state, the area of ​​the same cross section on the first support member 41 will change, thereby causing the first sensing optical fiber 51 wound on the first support member 41 to deform. The axial direction of the first support member 41 refers to the sleeve direction on the magnetostrictive rod, and the circumferential direction of the first support member 41 refers to the direction around the axis of the first support member 41. At this time, the first sensing optical fiber 51 can be selected to be completely wound on the surface of the first support member 41, that is, tightly attached to the circumferential surface of the first support member 41, or the first sensing optical fiber 51 can be selected to be incompletely wound on the surface of the first support member 41, that is, part of the first sensing optical fiber 51 is not attached to the circumferential surface of the first support member 41.

[0045] The change from the first state to the second state of the first support member 41 is caused by the change in length of the magnetostrictive rod under the action of the magnetic field. After the magnetostrictive rod is extended, the first transmission units at both ends will pull the first support member 41, thereby changing the cross-sectional area of ​​the first support member 41. The first support member 41 may be an elastic structure that can cause a change in cross-sectional area after being compressed, such as a rubber block; or a cylindrical structure that can be inserted and removed by the first transmission unit, and the cross-sectional area of ​​the cylindrical structure increases when the first transmission unit is inserted into the cylindrical structure.

[0046] It should be explained that the first support member 41 is adhered or interference fit with the magnetostrictive rod, so that the first support member 41 is more stable when changing from the first state to the second state, avoiding complete reliance on the connection of the first transmission unit. In other embodiments, it can also be suspended outside the magnetostrictive rod and kept suspended by the first transmission unit.

[0047] The magnetostrictive rod 7 is mainly used to connect the first carbon fiber support 41. The magnetostrictive rod 7 is glued to convert the size of the earth's magnetic field into the length of the magnetostrictive rod 7, so that the distance between the first carbon fiber support 41 increases or decreases with the expansion and contraction of the magnetostrictive rod 7. The specific connection diagram is as follows: Figure 1 , Figure 3 , Figure 4 The magnetostrictive rod 7 of the present invention is made of terbium-dysprosium-iron alloy, having a saturated large magnetostriction coefficient greater than 1500 ppm, and has a specific size of a cylinder with a diameter of 1 cm and a length of 18 cm.

[0048] In some embodiments, the first support member 41 is cylindrical. Since the optical fiber has a bending radius, a cylindrical structure is selected to minimize the bending radius of the optical fiber and ensure the passing loss. On the other hand, the cylindrical first support member 41 can be wound with more turns under the same length of optical fiber, achieving a greater magnification.

[0049] In some embodiments, the first support member 41 is a cylindrical structure, which is composed of a plurality of first mounting blocks distributed along the circumference of the magnetostrictive rod.

[0050] Specifically, the first support member 41 is a cylindrical structure, which may be a circular cylinder, a square cylinder, a polygonal cylinder or the like. A plurality of first mounting blocks are distributed circumferentially around the magnetostrictive rod to form a cylindrical structure. The first mounting blocks can move in a direction away from the magnetostrictive rod under the drive of the first transmission unit, thereby achieving a change in the cross-sectional area of ​​the cylindrical structure.

[0051] The shapes of the plurality of first mounting blocks may be the same or different, and their sizes may be the same or different. Preferably, the shapes and sizes of the plurality of first mounting blocks are the same, so as to facilitate the selection and determination of the position of the first transmission unit, so as to achieve the purpose of uniformly controlling the cylindrical structure.

[0052] In some specific embodiments, the first transmission unit includes a first connecting member 91 and a first elastic strain gauge 31, one end of the first strain gauge 31 is connected to the first mounting block, and the other end extends in a direction away from the magnetostrictive rod and is connected to the end of the magnetostrictive rod through the first connecting member 91.

[0053] Specifically, the first transmission unit includes a first strain gauge 31 and a first connecting member 91. The first connecting member 91 is connected to the end of the magnetostrictive rod. One end of the first strain gauge 31 is connected to the first mounting block, and the other end extends in a direction away from the magnetostrictive rod and is connected to the first connecting member 91. The first strain gauge 31 can be strained. When the magnetostrictive rod is extended, the first strain gauge 31 can generate a greater tensile stress. The tensile stress generated by the first strain gauge 31 has a component force perpendicular to the axial direction of the first support member 41 and a component force parallel to the axial direction of the first support member 41. The component force perpendicular to the axial direction of the first support member 41 can make the first mounting block move away from the magnetostrictive rod. When the magnetostrictive rod is shortened, the tensile stress on the first mounting block is reduced, resulting in a similar reduction in the component force perpendicular to the axial direction of the first support member 41. Furthermore, since the first strain gauges 31 are provided on both sides of the first support member 41 in the axial direction of the first support member 41, when the tensile stresses of the first strain gauges 31 on both sides are the same, the component force on the first strain gauge 31 parallel to the axial direction of the first support member 41 will be offset, so that the first mounting block can only move in the direction away from or close to the magnetostrictive rod.

[0054] By using the first strain gauge 31 capable of deformation as a transmission component, the magneto-optical conversion structure has higher controllability, and its smaller size, lighter weight, and simpler structure can meet the needs of miniaturizing magneto-optical conversion.

[0055] In some more specific embodiments, the plurality of first mounting blocks are all the same, there are a plurality of first strain gauges 31 , and the plurality of first strain gauges 31 are evenly distributed at the same angle along the circumference of the magnetostrictive rod.

[0056] Among them, making multiple first mounting blocks the same and multiple first strain gauges 31 uniformly distributed at the same angle along the circumference of the magnetostrictive rod will prevent the first support member 41 from tilting due to different tensile stresses, thereby improving the accuracy of the magnetic field measurement results and reducing the additional calculation amount due to uneven tension. It should be noted that it is not required to install the first strain gauge 31 on each mounting block at this time.

[0057] In some embodiments, the first support member 41 is sleeved at the middle position of the magnetostrictive rod.

[0058] It should be noted that the first support member 41 is sleeved in the middle of the magnetostrictive rod, and the first support member 41 is equidistant from both ends of the magnetostrictive rod, which is more conducive to maintaining the stability of the first support member 41, thereby obtaining a more accurate magnetic field measurement result.

[0059] The present invention also discloses a push-pull optical fiber magnetic field measurement probe, comprising the above-mentioned magneto-optical conversion structure, wherein the magneto-optical conversion structure is connected to a control module;

[0060] The control module includes a second support member 42, which is sleeved outside the elastic unit. A second sensing optical fiber 52 is wound around the circumference of the second support member 42. Both ends of the second support member 42 and the elastic unit are connected through a second transmission unit. The second support member 42 has a third state and a fourth state with different diameters. In the axial direction of the magnetostrictive rod, the elastic unit abuts against the magnetostrictive rod.

[0061] When the magnetostrictive rod is extended / contracted, the elastic unit is shortened / extended by the same distance, and the second supporting member 42 is changed between the third state and the fourth state through the second transmission unit.

[0062] A control module is connected on the basis of the magneto-optical conversion structure, and the control module includes a second support member 42, the second support member 42 is sleeved on the elastic unit, and the second support member 42 is circumferentially wound with a second sensing optical fiber 52, and the two ends of the elastic unit are connected to the second support member 42 through a second transmission unit. When the push-pull optical fiber magnetic field measurement probe receives the magnetic field signal, the length of the magnetostrictive rod will change, causing the elastic unit to produce a length change in the opposite direction and the same distance, thereby pulling the second transmission unit, causing the diameter of the second support member 42 to change between the third state and the fourth state, thereby changing the deformation of the second sensing optical fiber 52 wound on the second support member 42. In this way, the deformation of the first sensing optical fiber 51 and the deformation of the second sensing optical fiber 52 can be obtained respectively, and the influence of temperature on the test results can be eliminated after calculation. Compared with the prior art, the push-pull optical fiber magnetic field measurement probe disclosed in the present application can avoid the influence of temperature on the test results.

[0063] Specifically, the setting of the control module is to avoid the influence of environmental factors other than magnetic field on the test results, such as temperature, to obtain more accurate test results, and to avoid loading too long interference arms, so as to obtain a push-pull fiber optic magnetic field measurement probe with higher accuracy. In addition, the push-pull fiber optic magnetic field measurement probe can also double the amount of change in the optical fiber, because the amount of push is the same as the amount of pressure.

[0064] It should be explained that, for the convenience of description, the support members appearing in the present application include a first support member 41 and a second support member 42 , and the rest of the structure is similar. For example, when only the strain gauge is mentioned, the strain gauge includes a first strain gauge 31 and a second strain gauge 32 .

[0065] The support is mainly used to connect the strain gauge and the sensing optical fiber. The support is glued to the middle of the strain gauge with glue. When the connector drives the strain gauge to deform, the support will move inward or outward with the deformation, thereby changing the diameter of the circle of the sensing optical fiber on the support. The actual picture of the support is as follows: Figure 6 , the specific connection diagram is as follows Figure 1 , Figure 3 , Figure 4 The supporting member of the present invention is 8 trapezoidal mounting blocks, which, after being assembled, are wound around the sensing optical fiber with an outer diameter of 3 cm, an inner diameter of 1.5 cm and a thickness of 4 cm.

[0066] Strain gauges are mainly used to connect support parts and connectors. The connection between strain gauges, connectors and support parts is firmly bonded with glue. When the distance between the two connectors connected to the strain gauge changes, the strain gauge will drive the support part to move, thereby changing the diameter of the winding circle of the sensing optical fiber on the support part, which plays a role in amplifying the deformation. The specific connection diagram is as follows: Figure 1 , Figure 3 , Figure 4 ; The strain gauge of the present invention uses a carbon fiber sheet with a width of 6mm x length of 23cm x thickness of 0.25mm.

[0067] The connector is mainly used to connect the strain gauge, magnetostrictive rod 7, support rod 6, elastic gasket 11 and cylindrical shell 10. The connector is the main force-bearing support. The material of the connector is preferably a non-magnetic material with a relative magnetic permeability close to 1 to ensure that the geomagnetic field fully acts on the magnetostrictive rod 7. Otherwise, interference parameters need to be introduced. The actual picture of the connector is as follows: Figure 5 , the specific connection diagram is as follows Figure 1 , Figure 3 , Figure 4 The connecting piece of the present invention uses a carbon fiber plate with a diameter of 20 cm and a thickness of 1 cm.

[0068] In some embodiments, the elastic unit includes an elastic gasket 11 and a support rod 6, and the elastic gasket 11 abuts against the support rod 6 in the axial direction;

[0069] The second support member 42 is a cylindrical structure, which is composed of a plurality of second mounting blocks distributed along the circumference of the magnetostrictive rod;

[0070] The second transmission unit includes a second strain gauge 32 and a second connecting member 92, one end of the second strain gauge 32 is connected to the second mounting block, and the other end extends in a direction away from the support rod 6 and is connected to the end of the support rod 6 through the second connecting member 92;

[0071] The elastic gasket 11 is disposed between the second connecting member 92 and the second supporting member 42 .

[0072] Specifically, the elastic unit includes an elastic gasket 11 and a support rod 6. The elastic gasket 11 can undergo elastic deformation. When the magnetostrictive rod is extended, the elastic gasket 11 is shortened or thinned; when the magnetostrictive rod is shortened, the elastic gasket 11 can be extended or thickened. Only by deforming the elastic gasket 11, the comparison module and the magneto-optical conversion structure move in the same size and opposite directions, which increases the degree of coordination during the comparison process, allowing the comparison module to obtain higher stability and higher controllability.

[0073] The support rod 6 is mainly used to connect the elastic gasket 11 and the connecting piece. While supporting the two connecting pieces, there is also a certain displacement between the two connecting pieces. When the magnetostrictive rod 7 is extended or retracted, the connecting pieces on both sides of the support rod 6 also achieve relative reverse displacement. The specific connection diagram is as follows: Figure 1 , Figure 3 , Figure 4 The support rod 6 of the present invention uses a solid rod made of carbon fiber with a diameter of 1 cm and a length of 18 cm.

[0074] The elastic gasket 11 is mainly used to connect the support rod 6 and the connecting piece. When the connecting piece is squeezed by the magnetostrictive rod 7, the connecting piece will move and squeeze the elastic gasket 11, so that the distance between the connecting pieces on both sides of the support rod 6 changes, thereby affecting the telescopic state of the optical fiber wrapped around the support piece. The specific connection diagram is as follows: Figure 1 , Figure 3 , Figure 4 The elastic gasket 11 of the present invention uses a silicone gasket with a diameter of 8 mm and a thickness of 2 mm.

[0075] In other embodiments, the elastic unit is an elastic rod. By using the elastic rod, the structure of the control module can be simplified. The elastic rod itself can be shortened / extended when the magnetostrictive rod is extended / shortened, which is an implementation method that is more convenient to install and maintain.

[0076] The second support member 42 is a cylindrical structure, which may be a circular cylinder, a square cylinder, a polygonal cylinder or the like. A plurality of second mounting blocks are distributed circumferentially around the magnetostrictive rod to form a cylindrical structure. The second mounting blocks can move in a direction away from the magnetostrictive rod under the drive of the second transmission unit, thereby achieving a change in the cross-sectional area of ​​the cylindrical structure.

[0077] The shapes of the plurality of second mounting blocks may be the same or different, and their sizes may be the same or different. Preferably, the shapes and sizes of the plurality of second mounting blocks are the same, so as to facilitate the selection and determination of the position of the second transmission unit, so as to achieve the purpose of uniformly controlling the cylindrical structure.

[0078] It should be noted that the elastic gasket 11 is disposed between the second connecting member 92 and the second supporting member 42 so that the deformation generated by the elastic gasket 11 can be transmitted to the second strain gauge 32 , thereby achieving normal deformation of the second sensing optical fiber 52 .

[0079] In some embodiments, the second connecting member 92 has a groove, and the elastic gasket 11 is placed in the groove. The groove plus the gasket can greatly reduce the deformation other than the axial direction.

[0080] In some embodiments, the first connecting member 91 and the second connecting member 92 between the first supporting member 41 and the second supporting member 42 are of the same structure, so there is no need to set the first connecting member 91 and the second connecting member 92 separately, thereby optimizing the structure of the push-pull fiber optic magnetic field measurement probe, making its layout more compact and suitable for use in more miniaturized places.

[0081] In some embodiments, the middle parts of both sides of the first support member 41 and / or the second support member 42 are recessed inwards. The recessed parts make the swing length of the first strain gauge 31 and / or the second strain gauge 32 longer, and the magnification of the structure can be increased when the size is the same.

[0082] In some embodiments, the first support member 41 and the second support member 42 are preferably made of a material with a low thermal expansion coefficient, high strength, and no effect on the magnetic field, such as a carbon fiber material or a plastic steel material, to reduce the effect of temperature on the sensing optical fiber.

[0083] In some specific embodiments, a cylindrical shell 10 is also included, and the magneto-optical conversion structure and the control module are both arranged in the cylindrical shell 10. The shape of the second connecting member 92 and the shape of the inner wall of the cylindrical shell 10 match each other. A limiting rod 8 is connected inside the cylindrical shell 10, and a limiting hole is provided on the second connecting member 92. The second connecting member 92 is sleeved on the outside of the limiting rod 8 through the limiting hole.

[0084] It should be noted that in order to obtain a good comparison relationship between the magneto-optical conversion structure and the comparison module, both of them can move in the same direction to avoid interference with the detection result due to different directions. Therefore, through the setting of the cylindrical shell 10, the magneto-optical conversion structure and the comparison module are set in the cylindrical shell 10, and the second connecting member 92 and the cylindrical shell 10 are respectively connected by the limiting rod 8. On the one hand, the inner wall of the cylindrical shell 10 has a limiting effect on the second connecting member 92, and on the other hand, the limiting rod 8 also has a limiting effect on the second connecting member 92. Under the multiple limiting effects, the comparison module obtains better comparison accuracy.

[0085] The limit rod 8 is mainly used to connect the connecting piece and the cylindrical shell 10 to connect the two push-pull structures. The cylindrical shell 10 is used to fix the distance between the two connecting pieces outside the two sets of structures, and the two connecting pieces close to each other in the middle can be moved. The specific connection diagram is as follows: Figure 1 , Figure 3 , Figure 4 The limiting rod 8 of the present invention uses a solid rod made of carbon fiber with a diameter of 1 cm and a length of 40 cm.

[0086] The cylindrical shell 10 is mainly used to connect the connectors, and forms a relatively closed space with the connectors on both sides to protect the sensitive force-bearing components of the push-pull optical fiber magnetic field measurement probe. The material of the cylindrical shell 10 is preferably a non-magnetic material with a relative magnetic permeability close to 1 to ensure that the earth's magnetic field completely acts on the magnetostrictive rod 7, otherwise it is necessary to introduce interference parameters. The specific connection diagram is as follows Figure 1 , Figure 3 , Figure 4 The cylindrical shell 10 of the present invention uses a carbon fiber cylinder with an outer diameter of 21 cm, an inner diameter of 20 cm, and a length of 40 cm.

[0087] Both ends of the cylindrical shell 10 have mounting grooves 16, which are mainly used to connect the limit rod 8 and the connecting piece. The limit rod 8 and the mounting groove 16 are bonded with glue so that both ends of the limit rod 8 can clamp the connecting piece and apply a certain prestress to the connecting piece. The specific connection diagram is as shown in FIG. Figure 1 , Figure 3 , Figure 4 The mounting groove 16 used in the present invention is a carbon fiber cylinder with an outer diameter of 1.5 cm, an inner diameter of 1 cm, and a length of 1 cm.

[0088] In some more specific embodiments, the shape of the first connecting member 91 matches the shape of the inner wall of the cylindrical housing 10, and the first connecting member 91 also has a limiting hole, through which the first connecting member 91 is sleeved outside the limiting rod 8. On the one hand, the inner wall of the cylindrical housing 10 has a limiting effect on the first connecting member 91, and on the other hand, the limiting rod 8 also has a limiting effect on the first connecting member 91. Under the multiple limiting effects, the magneto-optical conversion structure can be extended or shortened in a limited direction, and can be better used with the control module.

[0089] In some embodiments, the first sensing optical fiber 51 and the second sensing optical fiber 52 are the same optical fiber, the first support member 41 and the second support member 42 have the same shape and size, the magnetostrictive rod and the elastic unit have the same length in the initial state, the position where the first support member 41 is sleeved on the magnetostrictive rod corresponds to the position where the second support member 42 is sleeved on the elastic unit, the first transmission unit and the second transmission unit have the same shape and size, the diameter in the first state is the same as the diameter in the third state, and the diameter in the third state is the same as the diameter in the fourth state.

[0090] It should be noted that in order to obtain a more direct comparison result and avoid excessive calculation, the above parameters of the comparison module and the magneto-optical conversion structure are set to be the same. In addition, the first sensing optical fiber 51 and the second sensing optical fiber 52 are the same optical fiber to avoid occupying too many interfaces of the interferometer analyzer, and at the same time, it can also avoid the differences between different optical fibers, thereby achieving a more convenient and more accurate detection result.

[0091] In some embodiments, the first sensing optical fiber 51 and the second sensing optical fiber 52 are the same optical fiber, and a reflector 2 is provided at the tail end of the optical fiber. By setting the reflector 2, the reflected light will return along the original path, which can double the optical path change, thereby obtaining a better detection result. The reflector 2 is mainly used to connect the sensing optical fiber and reflect the sensing light signal in the sensing optical fiber back. The specific optical path connection is as follows: Figure 1 , Figure 3 The reflectivity of the reflector 2 of the present invention is 99.9%, and the specific size is a cylinder with a diameter of 3 mm and a length of 1.5 cm.

[0092] The present invention also discloses a geomagnetic measurement device, comprising the above-mentioned push-pull optical fiber magnetic field measurement probe, wherein three push-pull optical fiber magnetic field measurement probes are respectively arranged perpendicular to each other.

[0093] It includes three push-pull optical fiber magnetic field measurement probes that are perpendicular to each other, so as to measure the magnetic field in different directions. Compared with the prior art, the geomagnetic measurement device disclosed in the present application can achieve the purpose of improving the measurement accuracy of the system.

[0094] The geomagnetic measurement device also includes a 1X2 coupler 1, which is mainly used to connect the sensing optical fiber and the optical cable to split the sensing optical signal into two interference arms and combine the reflected optical signal to generate an interference signal for demodulation by the optical fiber interferometer 17. The specific optical path connection diagram is shown in FIG. Figure 1 , Figure 3 and Figure 8 The splitting ratio of the 1X2 coupler 1 of the present invention is 50:50, and the specific size is a cylinder with a diameter of 3mm and a length of 6cm.

[0095] The sensing optical fiber is mainly used to connect the 1X2 coupler 1, the reflector 2 and the support. The sensing optical fiber is the two interference arms of the Michelson interferometer. The two ends of the sensing optical fiber are glued to the support so that it has a certain prestress and is wound on the support. The specific connection diagram is as follows: Figure 1 , Figure 3 The sensing optical fiber of the present invention uses Corning's bend-resistant optical fiber with a minimum bending diameter of 3 cm.

[0096] The geomagnetic measurement device also includes a base 12, which is used to fix three push-pull optical fiber magnetic field measurement probes. The base 12 is mainly used to connect the push-pull optical fiber magnetic field measurement probes, the 1X2 coupler 1, the reflector 2 and the housing 13, so that the three push-pull optical fiber magnetic field measurement probes are fixed in a state perpendicular to each other. The 1X2 coupler 1 and the reflector 2 also need to be firmly fixed on the base 12 to prevent the optical device from loosening and affecting the measurement results. The housing 13 is fixed to the base 12 by screws. The actual picture of the base 12 is as shown in Figure 7 , the specific connection diagram is as follows Figure 1 , Figure 3 , Figure 4 The material of the base 12 must be a non-magnetic material with a relative magnetic permeability close to 1 to ensure that the earth's magnetic field acts completely on the magnetostrictive rod 7. The present invention uses a plastic steel material with a length of 60 cm, a width of 60 cm and a height of 25 cm. The three holes on the base 12 that are perpendicular to each other are 21 cm in diameter and 5 cm in depth. The push-pull optical fiber magnetic field measurement probe can be directly placed in and fixed.

[0097] There is also a shell 13 outside the three push-pull optical fiber magnetic field measurement probes, which is mainly used to connect the base 12 and the gland connector 14, so that the three push-pull optical fiber magnetic field measurement probes are isolated from the external space to ensure the stability of the magnetic field measurement environment. The material of the shell 13 is preferably a non-magnetic material with a relative magnetic permeability close to 1 to ensure that the earth's magnetic field completely acts on the magnetostrictive rod 7, otherwise it is necessary to introduce interference parameters. The specific connection diagram is as follows Figure 1 The outer shell 13 of the present invention uses a plastic steel material with an outer size of 60cm in length, 60cm in width, 60cm in height and a thickness of 2mm.

[0098] The gland connector 14 is mainly used to connect the multi-core optical cable 15 and the housing 13, so that the optical fiber in the multi-core optical cable 15 enters the interior of the sealed geomagnetic detection device and is connected to the 1X2 coupler 1. The specific connection diagram is as follows: Figure 1 The material of the gland joint 14 of the present invention is all PVC plastic, the thread specification of the gland joint 14 is M20x1.5, the opening size is 12mm, and the length is 22.7mm.

[0099] The multi-core optical cable 15 is mainly used to connect the Gland connector 14 and the optical fiber interferometer 17, so that the optical signal between the optical fiber interferometer 17 and the geomagnetic detection device can be stably transmitted. The specific connection diagram is as follows: Figure 1 , Figure 8 The multi-core optical cable 15 of the present invention has a diameter of 8 mm and contains three-core single-mode optical fibers, which conform to the ITU-T G.652 standard.

[0100] The fiber interferometer 17 is mainly used to connect the multi-core optical cable, output the sensing light signal to the geomagnetic detection device through the multi-core optical cable, and demodulate the phase difference of the reflected light interference signal, and calculate the seven elements of geomagnetism through the relevant formula to achieve geomagnetic measurement; the specific connection diagram is as follows Figure 8 The minimum recognizable phase change of the fiber interferometer of the present invention is 1X10 -5 rad,; sensitivity is greater than 50dB, the chassis size is 45cm long, 43cm wide and 18cm high.

[0101] The following is a further description of the geomagnetic detection device, which is used to measure the horizontal component (H), north component (X), east component (Y), vertical component (Z), magnetic declination (D), magnetic inclination (I) and total field strength (F) of the geomagnetic field. It is mainly used in earth magnetic field measurement, mineral resource exploration, engineering and environmental exploration, underground buried object detection and high-precision measurement of material magnetism.

[0102] The geomagnetic field is a vector field, which has both magnitude and direction, and is generally represented by the vector F (Jerzy Jankowski, 1999). The description of F is generally expressed by its various components, which are called geomagnetic elements. The geomagnetic elements mainly include 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 strength (F). The relationship between the components can be seen in Figure 2 Among them, X, Y, and Z are commonly used in theoretical research, H, Z, and D are commonly used in geomagnetic relative records, and F, D, and I are commonly used in absolute observations. F, H, X, Y, and Z are called intensity components, and D and I are called angle components. The relationship between the components is as follows:

[0103] Z=FsinI............(1-1)

[0104] Y=HsinD............(1-2)

[0105] F=H 2 +Z 2 =X 2 +Y 2 +Z 2 ......(1-3)

[0106] When a magnetic field acts on a magnetostrictive material, the magnetic nuclei inside it will be orderly arranged along the direction of the magnetic field, causing the magnetostrictive material to expand and contract in volume along the direction of the magnetic field. This is the magnetostrictive effect. However, due to the different materials that the magnetostrictive material itself is composed of (mainly including metal alloy materials such as iron-nickel alloy, iron-aluminum alloy, iron-cobalt alloy and rare earth metal alloy materials such as terbium-dysprosium-iron alloy), the volume deformation and the trend of change in the direction or size of the magnetic field are different, and the degree of expansion and contraction caused by the magnetostrictive effect of different materials is also different. In the linear working area, the relationship between the magnetostrictive coefficient and the axial strain ε can be expressed as:

[0107] C(E0+ΔE)=Δd / d=ε.............(1-4)

[0108] In the above formula, C is the magnetostriction coefficient, E0 is the initial magnetic field intensity, ΔE is the change in magnetic field intensity, Δd is the change in material length caused in the direction of the magnetic field, and d is the initial length of the telescopic material.

[0109] When the external magnetic field changes, the length of the magnetostrictive material changes, thereby changing the spacing of the connectors and the outer diameter of the support, and then causing the two sensing optical fibers wound on the support to produce an optical path difference (i.e., the interference arm length difference). The relationship between the length change of the magnetostrictive material and the interference arm length difference Δr can be expressed as:

[0110] Δr=KNlΔd.............(1-5)

[0111] In the above formula, K is the conversion coefficient between the magnetostrictive material and the sensing optical fiber change, N is the number of windings of the sensing optical fiber on the support, and l is the strain distance of one circle of the sensing optical fiber on the support.

[0112] The difference in the interference arm length of the fiber optic interferometer system causes a phase difference in the fiber optic interference signal. The arm length difference Δr is related to the phase change signal. The relationship can be expressed as:

[0113]

[0114] In the above formula, n is the refractive index of the optical fiber, υ0 is the central wavelength of the interference light signal, and c0 is the speed of light in a vacuum.

[0115] When the fiber interference signal is transmitted back to the fiber interferometer, the fiber interference signal I detected by the photodetector (PD) PD (t) in the following form:

[0116]

[0117] In the above formula, I0 is the laser radiation intensity, k v (0≤k v ≤1) is the interference fringe contrast, is the initial phase difference of the fiber interferometer.

[0118] Combining formulas (1-4), (1-5), (1-6), and (1-7) we can get

[0119]

[0120] Where I0, k v , π, n, K, N, l, C, d, c0, When E0 is a known quantity, the phase change can be demodulated by the interferometer and the magnetic field intensity in the measuring direction can be calculated.

[0121] By measuring the magnetic field strength on the three components of the X-axis, Y-axis and Z-axis, the seven elements of geomagnetism can be calculated using formulas (1-1), (1-2) and (1-3): horizontal component (H), north component (X), east component (Y), vertical component (Z), magnetic declination (D), magnetic inclination (I) and total field strength (F).

[0122] Based on the above device, the following method is used for geomagnetic measurement:

[0123] Step 1: Connect the geomagnetic measurement device and the fiber optic interferometer through a multi-core optical cable, and run the fiber optic interferometer to measure the magnetic field change ΔE in real time.

[0124] Step 2: After placing the geomagnetic measuring device at the point to be measured, strictly align the three measuring axes of the geomagnetic measuring device with the north component (X component), east component (Y component) and vertical component (Z component) and fix them.

[0125] Step 3: Calibrate E0; Method 1: Align another geomagnetic measuring device with the three-axis direction of the geomagnetic measuring device to be calibrated, and then measure the initial magnetic field strength E0 in three directions; Method 2: Place the magnetostrictive material in a zero magnetic space through a magnetic field shielding device to make E0=0 for calibration.

[0126] Step 4: Substitute the calibration value E0 of each axis into formula (1-8) to calculate the magnitude of the geomagnetic field intensity components on the north component (X component), east component (Y component) and vertical component (Z component).

[0127] Step 5: The horizontal component (H), magnetic declination (D), magnetic inclination (I) and total field strength (F) can be calculated using formulas (1-1), (1-2) and (1-3).

[0128] The present invention achieves more than 30 times amplification of the magnetostriction of each dimensional magnetostrictive material through a magneto-optical conversion structure, and acts on the actual length of a circle of sensing optical fiber, and also achieves the effect of temperature compensation, thereby increasing the measurement accuracy and sensitivity of the geomagnetic measurement device.

[0129] The present invention uses a support to control the diameter of the winding circle of the sensing optical fiber, and uses a bending-resistant optical fiber to achieve the maximum number of winding circles under the premise of a certain length of the sensing optical fiber; the design of the magneto-optical conversion structure can amplify the magnetostriction of the magnetostrictive material by 3-4 orders of magnitude and effectively transfer it to the expansion and contraction of the sensing optical fiber, greatly increasing the measurement accuracy and sensitivity of the geomagnetic measurement device.

[0130] In the description of this specification, if the terms "embodiment one", "this embodiment", "in an embodiment" and the like appear, it means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in the invention or at least one embodiment or example of the invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in an appropriate manner.

[0131] In the description of this specification, the terms "connect", "install", "fix", "set", "have", etc. are all understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0132] In the description of this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0133] The above description of the embodiments is to facilitate ordinary technicians in the technical field to understand and apply the technology of this case. People familiar with the technology in this field can obviously easily make various modifications to these examples and apply the general principles described here to other embodiments without creative work. Therefore, this case is not limited to the above embodiments. Modifications to the following situations should all be within the scope of protection of this case: ① A new technical solution implemented based on the technical solution of the present invention and combined with existing common knowledge, the technical effect produced by the new technical solution does not exceed the technical effect of the present invention; ② The equivalent replacement of some features of the technical solution of the present invention by using known technology, the technical effect produced is the same as the technical effect of the present invention; ③ The technical solution of the present invention can be expanded, and the substantive content of the expanded technical solution does not exceed the technical solution of the present invention; ④ The equivalent transformation made by using the contents of the description and drawings of the present invention is directly or indirectly applied to other related technical fields.

Claims

1. A magneto-optical conversion structure, characterized in that: The invention comprises a first support member, wherein the first support member is sleeved outside a magnetostrictive rod, a first sensing optical fiber is wound around the circumference of the first support member, the first support member and both ends of the magnetostrictive rod are connected through a first transmission unit, the first support member has a first state and a second state with different diameters, and when the magnetostrictive rod is extended or retracted, the first support member is changed between the first state and the second state through the first transmission unit.

2. A magneto-optical conversion structure according to claim 1, characterized in that: The first support member is a cylindrical structure, and the cylindrical structure is composed of a plurality of first mounting blocks distributed along the circumference of the magnetostrictive rod.

3. A magneto-optical conversion structure according to claim 2, characterized in that: The first transmission unit includes a first connecting member and a first elastic strain gauge, one end of the first strain gauge is connected to the first mounting block, and the other end extends in a direction away from the magnetostrictive rod and is connected to the end of the magnetostrictive rod through the first connecting member.

4. A magneto-optical conversion structure according to claim 3, characterized in that: The first mounting blocks are all the same, there are a plurality of first strain gauges, and the first strain gauges are evenly distributed at the same angle along the circumference of the magnetostrictive rod.

5. A magneto-optical conversion structure according to any one of claims 1 to 4, characterized in that: The first support member is sleeved at the middle position of the magnetostrictive rod.

6. A push-pull optical fiber magnetic field measurement probe, characterized in that: A magneto-optical conversion structure comprising any one of claims 1 to 5, wherein the magneto-optical conversion structure is connected to a control module; The control module includes a second support member, the second support member is sleeved outside the elastic unit, a second sensing optical fiber is wound around the circumference of the second support member, both ends of the second support member and the elastic unit are connected through a second transmission unit, the second support member has a third state and a fourth state with different diameters, and in the axial direction of the magnetostrictive rod, the elastic unit abuts against the magnetostrictive rod; When the magnetostrictive rod is extended / contracted, the elastic unit is shortened / extended by the same distance, and the second supporting member is changed between the third state and the fourth state through the second transmission unit.

7. A push-pull optical fiber magnetic field measurement probe according to claim 6, characterized in that: The elastic unit comprises an elastic gasket and a support rod, and the elastic gasket abuts against the support rod in the axial direction; The second support member is a cylindrical structure, and the cylindrical structure is composed of a plurality of second mounting blocks distributed along the circumference of the magnetostrictive rod; The second transmission unit includes a second strain gauge and a second connecting member, wherein one end of the second strain gauge is connected to the second mounting block, and the other end of the second strain gauge extends in a direction away from the support rod and is connected to the end of the support rod through the second connecting member; The elastic gasket is arranged between the second connecting member and the second supporting member.

8. The push-pull optical fiber magnetic field measurement probe according to claim 7, characterized in that: It also includes a cylindrical shell, the magneto-optical conversion structure and the control module are both arranged in the cylindrical shell, the shape of the second connecting piece and the shape of the inner wall of the cylindrical shell match each other, a limiting rod is connected inside the cylindrical shell, a limiting hole is provided on the second connecting piece, and the second connecting piece is sleeved outside the limiting rod through the limiting hole.

9. The push-pull optical fiber magnetic field measurement probe according to claim 6, characterized in that: The first sensing optical fiber and the second sensing optical fiber are the same optical fiber, the first supporting member and the second supporting member have the same shape and size, the magnetostrictive rod and the elastic unit have the same length in the initial state, the position where the first supporting member is sleeved on the magnetostrictive rod corresponds to the position where the second supporting member is sleeved on the elastic unit, the first transmission unit and the second transmission unit have the same shape and size, the diameter in the first state is the same as the diameter in the third state, and the diameter in the third state is the same as the diameter in the fourth state.

10. A geomagnetic measuring device, characterized in that: It comprises a push-pull optical fiber magnetic field measurement probe as claimed in any one of claims 6 to 9, wherein three push-pull optical fiber magnetic field measurement probes are respectively perpendicular to each other.

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