阅读说明：本技术 一种光纤矢量磁场传感器 (Optical fiber vector magnetic field sensor ) 是由 赵晨 冯丹平 曹亮 杨明明 高守勇 王升 江晨 谢辉 杨静 归朋飞 高海馨 于 2020-05-19 设计创作，主要内容包括：本发明公开了一种光纤矢量磁场传感器,目的是提供能同时进行磁场强度和方向测量的传感器。本发明由三维骨架、6个套管、单模光纤、6个3dB光纤耦合器、球型外壳组成；三维骨架由中心支撑块和6根支撑柱组成；套管由无磁钢套管和无磁钢套管表面镀层组成,无磁钢套管同轴套于支撑柱外侧；单模光纤分6组,每组包含参考臂光纤和传感臂光纤；参考臂光纤缠绕于细圆柱的外侧面；传感臂光纤缠绕于无磁钢套管表面镀层外侧面；球形外壳内容纳三维骨架、6个套管和6个3dB光纤耦合器。本发明可有效传感三维磁场强度和磁场方向,且磁场灵敏度可调、制作工艺简单,采用本发明的测试仪可实现无源探测,可同时进行磁场强度和磁场方向测量。(The invention discloses an optical fiber vector magnetic field sensor, and aims to provide a sensor capable of simultaneously measuring the magnetic field intensity and the direction. The invention is composed of a three-dimensional framework, 6 sleeves, a single-mode fiber, 6 3dB fiber couplers and a spherical shell; the three-dimensional framework consists of a central supporting block and 6 supporting columns; the sleeve consists of a non-magnetic steel sleeve and a non-magnetic steel sleeve surface coating, and the non-magnetic steel sleeve is coaxially sleeved outside the support pillar; the single mode fibers are divided into 6 groups, and each group comprises a reference arm fiber and a sensing arm fiber; the reference arm optical fiber is wound on the outer side surface of the thin cylinder; the optical fiber of the sensing arm is wound on the outer side surface of the surface coating of the non-magnetic steel sleeve; the spherical shell is internally provided with a three-dimensional framework, 6 sleeves and 6 3dB optical fiber couplers. The three-dimensional magnetic field strength and the magnetic field direction can be effectively sensed, the sensitivity of the magnetic field is adjustable, the manufacturing process is simple, passive detection can be realized by adopting the tester disclosed by the invention, and the measurement of the magnetic field strength and the magnetic field direction can be simultaneously carried out.)

1. An optical fiber vector magnetic field sensor is characterized in that the optical fiber vector magnetic field sensor consists of a three-dimensional framework (1), 6 sleeves (2), a single-mode optical fiber (3), 6 3dB optical fiber couplers (4) and a spherical shell (5);

the three-dimensional framework (1) comprises a central supporting block (1-1) and 6 supporting columns (1-2), wherein the central supporting block (1-1) is a cube with the side length of a, and is made of a non-magnetic steel material, the 6 supporting columns (1-2) are respectively welded on 6 faces of the central supporting block (1-1), the 6 supporting columns (1-2) are completely the same and are composed of 2 sections of cylinders with different diameters, namely a thick cylinder (1-2-1) and a thin cylinder (1-2-2), the total length of the supporting columns (1-2) is L, one end of the thick cylinder (1-2-1) is welded on one face of the central supporting block (1-1), the central axis of the thick cylinder (1-2-1) is vertical to the face of the central supporting block (1-1), the length of the thick cylinder (1-2-1) is L, the diameter of the thick cylinder is d1, d1< a, the side face of the thick cylinder (1-2-1) is carved with external thread, the thin cylinder (1-2-1) is connected with the external thread of the thick cylinder (3512, the external thread is 3612 < 7311, the external thread of the thick cylinder (3611, the external thread is carved, the external thread of the thin cylinder (;

the sleeve (2) consists of a non-magnetic steel sleeve (2-1) and a non-magnetic steel sleeve surface coating (2-2), wherein the non-magnetic steel sleeve (2-1) is a cylinder made of a non-magnetic steel material, the length of the non-magnetic steel sleeve (2-1) is L2, L is L, the inner diameter of the non-magnetic steel sleeve is d21, d21 is d1, the outer diameter of the non-magnetic steel sleeve is d22, d21 is d22, the outer side surface of the non-magnetic steel sleeve (2-1) is plated with the non-magnetic steel sleeve surface coating (2-2), the thickness of the non-magnetic steel sleeve surface coating (2-2) is h, the non-magnetic steel sleeve is made of a magnetostrictive material, an inner thread is carved on the inner side wall of one end, connected with a central supporting block (1-1), the inner thread is L, L is L11, an outer thread is carved on the outer side surface of the non-magnetic steel sleeve surface coating (2-2), the outer side surface coating (2) is L, L is L, the non-magnetic steel sleeve (2) is coaxially sleeved on the outer side surface of the supporting column (1) and is connected with a first section of a spherical shell (2) in a solidifying glue connection mode, and a first section of a cylindrical;

the single mode fibers (3) are anti-bending single mode fibers and are divided into 6 groups, each group comprises a reference arm fiber (3-1) and a sensing arm fiber (3-2), the initial length of the reference arm fiber (3-1) is L31, the initial length of the sensing arm fiber (3-2) is L32, L31 is L32, the reference arm fiber (3-1) and the sensing arm fiber (3-2) are both provided with an end face plated with an optical reflector film, the other end of the reference arm fiber is connected with a second port (4-2) and a third port (4-3) of a 3dB fiber coupler (4) in a melting mode through an optical fiber fusion splicer, the reference arm fiber (3-1) in each group of single mode fibers (3) is wound on the outer side face of a thin cylinder (1-2-2), and the sensing arm fiber (3-2) in each group of single mode fibers (3) is wound on the outer side face of a non-magnetic steel sleeve;

the 3dB optical fiber coupler (4) is prepared by adopting a single-mode anti-bending optical fiber, and the 3dB optical fiber coupler (4) comprises a first port (4-1), a second port (4-2), a third port (4-3) and a fourth port (4-4);

the spherical shell (5) consists of an upper hemispherical shell (5-1) and a lower hemispherical shell (5-2), the upper hemispherical shell (5-1) and the lower hemispherical shell (5-2) have the same shape, and the upper hemispherical shell (5-1) and the lower hemispherical shell (5-2) are screwed together in a threaded manner to form a sphere; the inner diameter of the upper hemispherical shell (5-1) is d5, the thickness of the wall of the spherical shell (5) is h5, and the spherical shell is prepared from a silicon dioxide material; a second round hole (5-3) is formed in the side surface of the upper hemispherical shell (5-1); the center of the central supporting block (1-1) is positioned in the spherical center of the spherical shell (5), the upper end surface of a supporting column (1-2) welded on the upper surface of the central supporting block (1-1) is connected with the inner surface of the upper hemispherical shell (5-1) by adopting curing glue, and the lower end surface of the supporting column (1-2) welded on the lower surface of the central supporting block (1-1) is connected with the inner surface of the lower hemispherical shell (5-2) by adopting curing glue; the front end face of a support column (1-2) welded on the front side face of the central support block (1-1) is connected with the inner surface of the spherical shell (5) by adopting curing glue, and the rear end face of the support column (1-2) welded on the rear side face of the central support block (1-1) is connected with the inner surface of the spherical shell (5) by adopting curing glue; the left end face of a support column (1-2) welded on the left side face of a central support block (1-1) is connected with the inner surface of a spherical shell (5) by adopting curing glue, and the right end face of the support column (1-2) welded on the right side face of the central support block (1-1) is connected with the inner surface of the spherical shell (5) by adopting curing glue;

after the three-dimensional framework (1) is installed in the spherical shell (5), the residual space is used for accommodating 6 3dB optical fiber couplers (4); the first port (4-1) and the fourth port (4-4) of each 3dB optical fiber coupler (4) extend out of a second round hole (5-3) on the side face of the upper hemispherical shell (5-1).

2. The optical fiber vector magnetic field sensor as claimed in claim 1, wherein the length of the side of the central supporting block (1-1) is a which satisfies 5mm ≤ a ≤ 100mm, the total length L1 of the supporting column (1-2) satisfies L1 ≤ 200mm, and the length L11 of the thick cylinder (1-2-1) satisfies 2mm ≤ L11 ≤ L1.

3. The optical fiber vector magnetic field sensor according to claim 1, wherein the thickness h of the non-magnetic steel sleeve surface coating (2-2) satisfies h < a-d 22.

4. A fiber optic vector magnetic field sensor according to claim 1, characterized in that the diameter d23 of the first circular hole (2-3) satisfies 1mm ≦ d23 ≦ d 21.

5. A fiber optic vector magnetic field sensor according to claim 1 wherein the initial length L32 of the sensing arm fiber (3-2) is such thats is the magnetic field sensitivity of the optical fiber vector magnetic field sensor, k is the sensitivity coefficient of the optical fiber vector magnetic field sensor, and is a constant related to the material of the non-magnetic steel sleeve surface coating (2-2) and the material of the single-mode optical fiber (3).

6. The optical fiber vector magnetic field sensor according to claim 1, wherein the end of the reference arm optical fiber (3-1) without the optical mirror film is extended from the first circular hole (2-3) of the ferrule (2) and then connected to the second port (4-2) of the 3dB optical fiber coupler (4).

7. The fiber vector magnetic field sensor according to claim 1, wherein the reference arm fiber (3-1) in each group of single mode fibers (3) is wound clockwise around the outer side of the thin cylinder (1-2-2) from the end near the central support block (1-1) along the thread direction of the thin cylinder (1-2-2) starting from the end coated with the optical mirror film; the sensing arm optical fiber (3-2) in each group of single mode optical fibers (3) is wound on the outer side surface of the non-magnetic steel sleeve surface coating (2-2) clockwise from one end close to the central supporting block (1-1) along the thread direction of the non-magnetic steel sleeve surface coating (2-2) by taking one end plated with an optical reflector film as a starting point.

8. The optical fiber vector magnetic field sensor according to claim 1, wherein two end points of the reference arm optical fiber (3-1) are fixedly connected to the outer side surface of the thin cylinder (1-2-2) by using a curing adhesive; two end points of the sensing arm optical fiber (3-2) are fixedly connected to the outer side surface of the non-magnetic steel sleeve surface coating (2-2) by adopting curing glue.

9. The optical fiber vector magnetic field sensor according to claim 1, wherein the first port (4-1) of the 3dB optical fiber coupler (4) is externally connected to the output port of the 1 × 6 optical fiber coupler (9) of the magnetic field tester by fusion splicing with an optical fiber fusion splicer, and the fourth port (4-4) is externally connected to the input port of the photodetector (10) of the magnetic field tester by fusion splicing with an optical fiber fusion splicer.

10. The optical fiber vector magnetic field sensor as claimed in claim 1, wherein the inner diameter d5 of the upper hemispherical shell (5-1) is satisfiedThe thickness h5 of the wall of the spherical shell (5) meets the requirement that h5 is more than or equal to 2mm and less than or equal to 30 mm; the diameter d51 of the second round hole (5-3) formed in the side surface of the upper hemispherical shell (5-1) meets the requirement that d51 is more than or equal to 1mm and less than or equal to 6 mm.

Technical Field

The invention relates to an optical fiber sensor, in particular to an optical fiber vector magnetic field sensor based on a magnetostrictive material optical fiber Michelson interferometer structure.

Background

When the magnetostrictive material is magnetized in an external magnetic field, the physical structure, such as length and volume, of the magnetostrictive material can change, and the magnetostrictive material is a functional material for magnetic field sensing. The magnetostrictive material is combined with the optical fiber sensor, so that the magnetic field sensitivity of the optical fiber sensor can be effectively improved.

The optical fiber Michelson interferometer structure is an optical structure which can be used for designing an optical sensor, the change of an external physical quantity causes the length change of a sensing arm of the optical fiber Michelson interferometer, further causes the phase change of output interference light, can effectively detect the change of the external physical quantity by detecting the phase change of the output interference light, and has higher sensitivity. Therefore, the optical fiber Michelson interferometer structure is widely applied to the structural design of optical sensors for various physical quantities.

Through the literature search of the prior art, Chen Guangfei et al have discovered that a vector magnetic field sensor based on side-polished fiber surface plasmon resonance is designed in a patent of 'a vector magnetic field sensor based on side-polished fiber surface plasmon resonance and a preparation and detection method thereof' with publication number CN 109541502A, and the sensor has a complex manufacturing process and higher condition requirements. Wan and admire in 2009 Shanghai university of transportation doctor's academic paper several key technical studies on the performance of the interference type optical fiber weak magnetic field sensor' have designed an improved interference type optical fiber weak magnetic field sensor, which adopts magnetostrictive material and an optical fiber Michelson interferometer structure to be combined, so that the sensor can measure the magnetic field intensity, but cannot measure the magnetic field direction, and is an optical fiber scalar magnetic field sensor. Kouzu et al, in patent "a magnetic field vector measurement device and method based on coherent particle number trapping effect" with publication number CN 105182257 a, propose a magnetic field vector measurement device and method based on coherent particle number trapping effect, although the device can measure the magnetic field direction, the structure is complex and the helmholtz coil included in the sensor needs to be energized to measure, and the passive detection at the sensor end cannot be realized.

At present, no published report exists on the fiber vector magnetic field sensor based on the fiber Michelson interferometer structure of magnetostrictive materials.

Disclosure of Invention

The technical problem to be solved by the invention is as follows:

based on the magnetic field sensing characteristic of a magnetostrictive material, the optical fiber vector magnetic field sensor based on the sensing principle of the optical fiber Michelson interferometer is provided, and under the condition of realizing passive detection of a sensor end, the measurement of the magnetic field intensity and the measurement of the magnetic field direction can be carried out.

The technical scheme of the invention is as follows:

the invention consists of a three-dimensional framework, 6 sleeves, a single-mode fiber, 6 3dB fiber couplers and a spherical shell.

The three-dimensional framework consists of a central supporting block and 6 supporting columns.

The central supporting block is a cube, the side length is a (a is more than or equal to 5mm and less than or equal to 100mm), and the central supporting block is made of a non-magnetic steel material.

The supporting column comprises 2 sections of cylinders with different diameters, namely a thick cylinder and a thin cylinder, wherein the total length of the supporting column is L1 (L1 is less than or equal to 200mm), one end of the thick cylinder is welded on one surface of the central supporting block, the central axis of the thick cylinder is perpendicular to the surface of the central supporting block, the length of the thick cylinder is L11, the length of the thick cylinder is less than or equal to 2mm, L11 is less than or equal to 2mm, L1 is less than or equal to 2mm, the diameter of the thick cylinder is d1, d1 is less than a, external threads are carved on the side surface of the thick cylinder, the thin cylinder is coaxially connected with the thick cylinder, the length of the thin cylinder is L12, L12 is L1-L11, the diameter of the thin cylinder is d2, and d2 is less than d1, and external threads.

The sleeve consists of a non-magnetic steel sleeve and a non-magnetic steel sleeve surface coating.

The nonmagnetic steel sleeve is a cylinder made of nonmagnetic steel materials, the length of the nonmagnetic steel sleeve is L, L is L, the inner diameter of the nonmagnetic steel sleeve is d21, d21 is d1, the outer diameter of the nonmagnetic steel sleeve is d22, d21 is d22< a, the outer side of the nonmagnetic steel sleeve is plated with a nonmagnetic steel sleeve surface plating layer, the thickness of the nonmagnetic steel sleeve surface plating layer is h, h < - (a-d22), the nonmagnetic steel sleeve is made of magnetostrictive materials, the inner side wall of one end, connected with the central supporting block, of the nonmagnetic steel sleeve is carved with internal threads, the length of the internal threads is L, L21 is L, the outer side of the nonmagnetic steel sleeve surface plating layer is carved with external threads, the length of the external threads is L, L is L, the nonmagnetic steel sleeve is coaxially sleeved on the outer side of the supporting column and is connected with a thick column in a threaded mode, the side of one end of the sleeve connected with a spherical shell is provided with a first round hole, the diameter of the first round hole is 58d 29, the diameter of the sleeve is not more than.

The single-mode optical fibers 3 are anti-bending single-mode optical fibers, and are divided into 6 groups, each group comprises a section of reference arm optical fiber and a section of sensing arm optical fiber, the initial length of the reference arm optical fiber is L31, the initial length of the sensing arm optical fiber is L32, L31 is L32, the reference arm optical fiber and the sensing arm optical fiber are both provided with an optical reflector film plated on one end surface, the other ends are respectively connected to a second port 4-2 and a third port 4-3 of a 3dB optical fiber coupler 4 in a melting mode through an optical fiber welding machine (wherein the other end of the reference arm optical fiber extends out of a first round hole of a sleeve pipe and then is connected to the second port of the 3dB optical fiber coupler in a melting mode through an optical fiber welding machine, the other end of the sensing arm optical fiber is directly connected to a third port of the 3dB optical fiber coupler in a melting mode through an optical fiber welding machine in a melting mode, the reference arm optical fiber in each group of single-mode optical fibers 3 is wound on the outer side surface of a thin cylinder along the thread direction of the thin cylinder from one end of the non-magnetic steel sleeve pipe with the non-magnetic reflector coating plated on the outer side of the non-magnetic steel sleeve pipe.

When the outer diameter d22 of the nonmagnetic steel sleeve and the thickness h of the surface coating of the nonmagnetic steel sleeve are fixed, the relation between the initial length L32 of the optical fiber of the sensing arm and the magnetic field sensitivity s of the sensor approximately satisfies the following conditions:

and k is a sensitivity coefficient of the optical fiber vector magnetic field sensor, is related to the material selection of the surface coating of the nonmagnetic steel sleeve and the material selection of the single-mode optical fiber, and is approximately a constant after the material of the surface coating of the nonmagnetic steel sleeve and the material of the single-mode optical fiber are determined.

The 3dB optical fiber coupler is prepared by adopting a single-mode anti-bending optical fiber, and comprises a first port, a second port, a third port and a fourth port, wherein the first port is externally connected with an output port of a 1 × 6 optical fiber coupler of a magnetic field tester in a fusion connection mode of an optical fiber splicer, the second port is connected with a reference arm optical fiber in a fusion connection mode of the optical fiber splicer, the third port is connected with a sensing arm optical fiber in a fusion connection mode of the optical fiber splicer, and the fourth port is externally connected with an input port of a photoelectric detector of the magnetic field tester in a fusion connection mode of an optical fiber splicer.

The spherical shell consists of an upper hemispherical shell and a lower hemispherical shell, the upper hemispherical shell and the lower hemispherical shell have the same shape, and the upper hemispherical shell and the lower hemispherical shell are screwed together in a thread mode to form a sphere. The upper hemispherical shell has an inner diameter d5,the wall of the spherical shell has the thickness of h5, (2mm ≤ h5 ≤ 30mm), and is made of silicon dioxide. The side surface of the upper hemispherical shell is provided with a second round hole, the diameter of the second round hole is d51, and d51 is more than or equal to 1mm and less than or equal to 6 mm. The center of the central supporting block is positioned in the center of the spherical shell 5, the upper end surface of the supporting column welded on the upper surface of the central supporting block is connected with the inner surface of the upper hemispherical shell by adopting curing glue, the lower end surface of the supporting column welded on the lower surface of the central supporting block is also connected with the inner surface of the lower hemispherical shell by adopting curing glue, the front end surface of the supporting column welded on the front side surface of the central supporting block is also connected with the inner surface of the spherical shell by adopting curing glue, the rear end surface of the supporting column welded on the rear side surface of the central supporting block is also connected with the inner surface of the spherical shell by adopting curing glue, the left end surface of the supporting column welded on the left side surface of the central supporting block is also connected with the inner surface of the spherical shell by adopting curing.

After a three-dimensional framework (6 sleeves are arranged on the three-dimensional framework) is installed in the spherical shell, the spherical shell is also provided with a residual space, and the residual space is used for accommodating 6 3dB optical fiber couplers. The first port and the fourth port of each 3dB fiber coupler extend out of a second round hole in the side face of the upper hemispherical shell.

The magnetic field tester comprises the optical fiber vector magnetic field sensor, the RIO laser, the optical isolator, the 1 × 6 optical fiber coupler, the photoelectric detector and the data receiving and signal processing device, wherein the optical fiber vector magnetic field sensor, the RIO laser, the optical isolator, the 1 × 6 optical fiber coupler and the photoelectric detector are connected by single-mode optical fibers, and the photoelectric detector and the data receiving and signal processing device are connected by a data connecting wire.

The process of testing the three-dimensional magnetic field intensity and the magnetic field direction by adopting the magnetic field tester of the invention is as follows:

firstly, an RIO laser outputs 1550nm laser;

secondly, protecting the RIO laser by an optical isolator to prevent the damage to the RIO laser caused by the fact that back scattered light in the optical fiber returns to the RIO laser;

thirdly, the 1 × 6 fiber coupler divides the transmission light output from the output end of the optical isolator into 6 paths, and correspondingly transmits the 6 paths of light to the first ports of 6 3dB fiber couplers in the fiber vector magnetic field sensor 6;

fourthly, the 6 3dB optical fiber couplers divide the received transmission light into two paths respectively, and the two paths are transmitted to the reference arm optical fiber and the sensing arm optical fiber respectively through the second port and the third port;

fifthly, under the influence of the change of the external magnetic field intensity, the physical form of the coating on the surface of the non-magnetic steel sleeve changes, so that the length of the optical fiber of the sensing arm changes, and the phase of an interference optical signal changes;

sixthly, each 3dB optical fiber coupler transmits the interference optical signal to the photoelectric detector from the fourth port through a connecting optical fiber;

seventhly, converting the interference optical signal into an electric signal by the photoelectric detector, and transmitting the electric signal to the data receiving and signal processing device through a connecting data line;

and eighthly, the data receiving and signal processing device (generally a computer) adopts MAT L AB software to process and analyze the transmitted electric signals, obtains the magnetic field intensity of the positions of the 6 supporting columns by analyzing the phase change of the 6 paths of interference optical signals, and further utilizes MAT L AB software to draw the isomagnetic line of the magnetic field of the position of the optical fiber vector sensor.

The invention can achieve the following technical effects:

1. the optical fiber vector magnetic field sensor can effectively sense the three-dimensional magnetic field intensity and the magnetic field direction, and has the unique advantages of adjustable magnetic field sensitivity, simple manufacturing process, small volume, low cost, good stability and the like;

2. the magnetic field tester can realize passive detection of a testing end;

3. the magnetic field tester mainly adopts the optical fiber sensing technology when testing the magnetic field intensity and the magnetic field direction, thereby being convenient for large-scale networking.

Drawings

Fig. 1 is a schematic structural diagram of an optical fiber vector magnetic field sensor according to the present invention.

Fig. 2 is a logical block diagram of a magnetic field tester to which the present invention is applied.

Fig. 3 is a schematic structural diagram of the three-dimensional skeleton 1.

Fig. 4 is a schematic structural view of the sleeve 2.

Fig. 5 is a schematic diagram of the structure of the 3dB optical fiber coupler 4.

Fig. 6 is a schematic structural view of the spherical shell 5.

The specific implementation mode is as follows:

embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 is a schematic structural diagram of the fiber vector magnetic field sensor of the present invention.

As shown in figure 1, the invention consists of a three-dimensional framework 1, 6 sleeves 2, a single-mode fiber 3, 6 3dB fiber couplers 4 and a spherical shell 5.

As shown in fig. 3, the three-dimensional skeleton 1 is composed of a center support block 1-1 and 6 support columns 1-2.

The central supporting block 1-1 is a cube, the side length is a (a is more than or equal to 5mm and less than or equal to 100mm), and the non-magnetic steel material is adopted for preparation.

6 support columns 1-2 are respectively welded on 6 surfaces of a central supporting block 1-1, the 6 support columns 1-2 are completely the same and are composed of 2 sections of cylinders with different diameters, namely a thick cylinder 1-2-1 and a thin cylinder 1-2-2, the total length of the support columns 1-2 is L (L is not more than 200mm), one end of the thick cylinder 1-2-1 is welded on one surface of the central supporting block 1-1, the central axis of the thick cylinder 1-2-1 is perpendicular to the surface of the central supporting block 1-1, the length of the thick cylinder 1-2-1 is L, 2mm is not more than 4611 < L, the diameter is d1, d1< a, the side surface of the thick cylinder 1-2-1 is provided with an external thread, the thin cylinder 1-2-2 is coaxially connected with the thick cylinder 1-2-1, the length is L, the length of L is L-L, the diameter is d2, the d2 is d, the side surface is not less than d1, and the side surface is also.

As shown in FIG. 4, the casing 2 is composed of a non-magnetic steel casing 2-1 and a non-magnetic steel casing surface coating 2-2.

The non-magnetic steel sleeve 2-1 is a cylinder made of a non-magnetic steel material, the length of the cylinder is L, L is L, the inner diameter of the cylinder is d21, d21 is d1, the outer diameter of the cylinder is d22, d21 is d22, the outer side of the non-magnetic steel sleeve 2-1 is plated with a non-magnetic steel sleeve surface plating layer 2-2, the thickness of the non-magnetic steel sleeve surface plating layer 2-2 is h, h is (a-d22), a magnetostrictive material is adopted to prepare, an inner thread is carved on the inner side wall of one end, connected with the central supporting block 1-1, of the non-magnetic steel sleeve 2-1, the length of the inner thread is L, L is L, an outer side of the non-magnetic steel sleeve surface plating layer 2-2 is carved with an external thread, the length of the external thread is L, L is L, the steel sleeve 2-1 is coaxially sleeved on the outer side of the supporting column 1-2, and is connected with the thick cylinder 1-2-1 in a threaded manner, the spherical shell is screwed with a first round hole 5, and a first round hole is connected with a first curing glue, the diameter of d 5mm or less, and the diameter of the first round hole is no more than 2.

The single mode optical fiber 3 is a bending-resistant single mode optical fiber, and is divided into 6 groups, each group comprises a section of reference arm optical fiber 3-1 and a section of sensing arm optical fiber 3-2, the initial length of the reference arm optical fiber 3-1 is L31, the initial length of the sensing arm optical fiber 3-2 is L32, L31 is L32, the reference arm optical fiber 3-1 and the sensing arm optical fiber 3-2 are both provided with an optical reflector film on one end face, the other end (i.e. the end without the optical reflector film) is respectively connected with a second port 4-2 and a third port 4-3 of a 3dB optical fiber coupler 4 by a fiber fusion splicer in a fusion mode (wherein the other end of the reference arm optical fiber 3-1 is firstly extended out of a first round hole 2-3 of a sleeve 2 and then is connected with a second port 4-2 of the 3dB optical fiber coupler 4 by the fiber fusion splicer after being fused with the fiber fusion splicer, the other end of the reference arm optical fiber 3-1 is directly connected with a third port 4-3 of the optical fiber coupler 4 by the fiber fusion splicer in a way that the fiber fusion splicer is connected with the third port 4-3 of the optical fiber coupler 4 of the single mode optical fiber coupler 4, the outer side face of the supporting block 3-2, the supporting block 3, the outer side face of the supporting block 2 of the thin optical fiber 3-2, the supporting block 2, the supporting block is fixed by adopting a thin cylindrical thin reflecting arm, the thin optical fiber is fixed with the thin reflecting arm, the thin reflecting arm optical fiber, and the thin reflecting arm optical fiber, the thin optical fiber-.

When the outer diameter d22 of the nonmagnetic steel sleeve 2-1 and the thickness h of the nonmagnetic steel sleeve surface coating 2-2 are fixed, the relation between the initial length L32 of the sensing arm optical fiber 3-2 and the magnetic field sensitivity s of the sensor approximately satisfies the following conditions:

and k is a sensitivity coefficient of the optical fiber vector magnetic field sensor, is related to the selection of the material of the non-magnetic steel sleeve surface coating 2-2 and the selection of the material of the single-mode optical fiber 3, and is approximately a constant after the material of the non-magnetic steel sleeve surface coating 2-2 and the material of the single-mode optical fiber 3 are determined.

As shown in fig. 5, the 3dB optical fiber coupler 4 is made of a single-mode bend-resistant optical fiber, and the 3dB optical fiber coupler 4 includes a first port 4-1, a second port 4-2, a third port 4-3, and a fourth port 4-4. as shown in fig. 2, the first port 4-1 is connected to an output port of a 1 × 6 optical fiber coupler 9 of the magnetic field tester by fusion splicing using an optical fiber fusion splicer, the second port 4-2 is connected to the reference arm optical fiber 3-1 by fusion splicing using an optical fiber fusion splicer (as shown in fig. 1), the third port 4-3 is connected to the sensing arm optical fiber 3-2 by fusion splicing using an optical fiber fusion splicer (as shown in fig. 1), and the fourth port 4-4 is connected to an input port of the photodetector 10 by fusion splicing using an optical fiber jumper.

As shown in figure 6, the spherical shell 5 consists of an upper hemispherical shell 5-1 and a lower hemispherical shell 5-2, the upper hemispherical shell 5-1 and the lower hemispherical shell 5-2 have the same shape, and the upper hemispherical shell 5-1 and the lower hemispherical shell 5-2 are screwed together in a threaded manner to form a sphere. The inner diameter of the upper hemispherical shell 5-1 is d5,the thickness of the wall of the spherical shell 5 is h5, h5 is more than or equal to 2mm and less than or equal to 30mm), and dioxide is adoptedAnd (4) preparing a silicon material. The side surface of the upper hemispherical shell 5-1 is provided with a second round hole 5-3, the diameter of the second round hole 5-3 is d51, and d51 is more than or equal to 1mm and less than or equal to 6 mm. The center of the central supporting block 1-1 is positioned in the spherical center of the spherical shell 5, the upper end surface of a supporting column 1-2 welded on the upper surface of the central supporting block 1-1 is connected with the inner surface of the upper hemispherical shell 5-1 by adopting curing adhesive, and the lower end surface of the supporting column 1-2 welded on the lower surface of the central supporting block 1-1 is also connected with the inner surface of the lower hemispherical shell 5-2 by adopting curing adhesive; the front end surface of a support column 1-2 welded on the front side surface of the central support block 1-1 is also connected with the inner surface of the spherical shell 5 by adopting curing glue, and the rear end surface of the support column 1-2 welded on the rear side surface of the central support block 1-1 is also connected with the inner surface of the spherical shell 5 by adopting curing glue; the left end face of the support column 1-2 welded on the left side face of the central support block 1-1 is also connected with the inner surface of the spherical shell 5 by adopting curing glue, and the right end face of the support column 1-2 welded on the right side face of the central support block 1-1 is also connected with the inner surface of the spherical shell 5 by adopting curing glue.

After the three-dimensional framework 1 is installed in the spherical shell 5, the residual space is used for accommodating 6 3dB optical fiber couplers 4. The first port 4-1 and fourth port 4-4 fibers of each 3dB fiber coupler 4 extend from the second circular hole 5-3 in the side of the upper hemispherical shell 5-1.

Fig. 2 is a schematic structural view of a magnetic field tester prepared based on the present invention.

The magnetic field tester shown in fig. 2 comprises an optical fiber vector magnetic field sensor 6, an RIO laser 7, an optical isolator 8, a 1 × 6 optical fiber coupler 9, a photoelectric detector 10 and a data receiving and signal processing device 11, wherein the optical fiber vector magnetic field sensor 6, the RIO laser 7, the optical isolator 8, the 1 × 6 optical fiber coupler 9 and the photoelectric detector 10 are all connected by single-mode optical fibers, and the photoelectric detector 10 is connected with the data receiving and signal processing device 11 by a data connecting wire.

The process of testing the three-dimensional magnetic field intensity and the magnetic field direction of the magnetic field tester shown in fig. 2 is as follows:

firstly, the RIO laser 7 outputs 1550nm laser;

secondly, the optical isolator 8 protects the RIO laser 7 and prevents the back scattering light in the optical fiber from returning to the RIO laser 7 to damage the RIO laser 7;

thirdly, the 1 × 6 optical fiber coupler 9 divides the transmission light output from the output end of the optical isolator 8 into 6 paths, and correspondingly transmits the 6 paths of light to the first ports 4-1 of 6 3dB optical fiber couplers 4 in the optical fiber vector magnetic field sensor 6;

fourthly, the 6 3dB optical fiber couplers 4 divide the received transmission light into two paths respectively, and the two paths are transmitted to the reference arm optical fiber 3-1 and the sensing arm optical fiber 3-2 through the second port 4-2 and the third port 4-3 respectively;

fifthly, under the influence of the change of the external magnetic field intensity, the physical form of the coating 2-2 on the surface of the non-magnetic steel sleeve changes, so that the length of the optical fiber 3-2 of the sensing arm changes, and the phase of an interference optical signal changes;

sixthly, each 3dB optical fiber coupler 4 transmits the interference optical signal from the fourth port 4-4 to the photoelectric detector 10 through a connecting optical fiber;

seventhly, the photoelectric detector 10 converts the interference light signal into an electric signal and transmits the electric signal to the data receiving and signal processing device 11 through a connecting data line;

eighthly, the data receiving and signal processing device 11 (generally, a computer) processes and analyzes the transmitted electric signal by using MAT L AB software, obtains the magnetic field intensity of the positions of the 6 supporting columns 1-2 by analyzing the phase change of the 6 interference optical signals, and further draws the isomagnetic line of the magnetic field of the position of the optical fiber vector sensor 6 by using MAT L AB software, wherein the magnetic induction line direction is perpendicular to the isomagnetic line, so that the magnetic induction line distribution is obtained, the magnetic field direction is obtained by analyzing the tangential direction of each point on the magnetic induction line, and further the magnetic field intensity and the information of the magnetic field direction of the position of the optical fiber vector magnetic sensor 6 are obtained and displayed.