Optical fiber ultrasonic sensor

Abstract

The invention belongs to the technical field of optical fiber ultrasonic sensors, and discloses an optical fiber ultrasonic sensor which comprises a sensor body, an installation groove is formed in the sensor body, and a coaxial packaging assembly is arranged in the installation groove; the diaphragm is arranged on one side of the coaxial packaging assembly; the mechanical fine adjustment assembly is arranged on one side of the sensor body and used for adjusting the cavity length; the dual-core structure is connected to the coaxial packaging assembly; and the two connectors are respectively connected to the double-core structure. In the sensor body assembling process through the coaxial packaging assembly and the mechanical fine tuning assembly, the F-P cavity length deviation caused by manual operation errors and the signal interference problem caused by vibration mismatching of the sensing arm and the reference arm are reduced, the cavity length is changed through the mechanical fine tuning assembly, and therefore the influence of interference is reduced, and the reliability of the sensor is improved. And vibration noise is suppressed by using a dual-fiber arm co-packaging design, so that high-precision and high-stability partial discharge ultrasonic detection is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fiber ultrasonic sensors, and particularly relates to an optical fiber ultrasonic sensor. BACKGROUND

[0002] The optical fiber ultrasonic sensor is a device for ultrasonic detection by using optical fiber technology. When partial discharge (PD) generates ultrasonic waves, the ultrasonic waves act on the diaphragm to make it vibrate, thereby changing the cavity length of the F-P cavity and causing the phase of reflected light to change. The phase change of the reflected light is converted into intensity change through an optical interference system. By demodulating the change of the light intensity, the information of the ultrasonic waves can be obtained, and then the occurrence of the partial discharge can be judged. In the field of optical fiber ultrasonic sensors, the traditional 3*3 phase demodulation system usually independently encapsulates the sensing arm and the reference arm in different structures, and this structure is easily disturbed by environmental noise and affects the demodulation result.

[0003] In the prior art, the assembly of the F-P cavity highly depends on manual operation, and the fibers at both ends of the cavity need to be fixed by adhesive bonding or mechanical crimping, and the target value needs to be approached by repeatedly disassembling or screening high-precision parts. However, in the use process, the F-P cavity length deviation is caused by hand shaking during manual assembly, adhesive shrinkage or processing error, it is inconvenient to actively adjust the cavity length, resulting in low production efficiency, high cost, and the vibration mismatch between the sensing arm and the reference arm will cause signal interference, and it is inconvenient to realize high-precision and high-stability partial discharge ultrasonic detection. SUMMARY

[0004] In view of the problems in the prior art, the technical scheme is proposed as follows: An optical fiber ultrasonic sensor comprises: A sensor body, an installation slot is formed in the inside of the sensor body, and a coaxial encapsulation assembly is arranged in the installation slot; A diaphragm is arranged on one side of the coaxial encapsulation assembly; A mechanical fine adjustment assembly is arranged on one side of the sensor body and is used for adjusting the cavity length; A double-core structure is connected to the coaxial encapsulation assembly; Two connectors are respectively connected to the double-core structure; A protective sleeve is connected to the sensor body and is used for protecting the mechanical fine adjustment assembly and the double-core structure; A first limiting assembly is arranged on the coaxial encapsulation assembly and is used for limiting the coaxial encapsulation assembly.

[0005] Further, the coaxial encapsulation assembly comprises: A sensing arm and a reference arm are arranged in the installation slot; A ceramic ferrule is connected to the sensing arm and the reference arm and is used for fixing and guiding the double-core structure; The ceramic ferrule outer structure is arranged on one side of the sensor body and is used for protecting the sensing arm, the reference arm and the ceramic ferrule.

[0006] Further, the double-core structure comprises: Two optical fibers are respectively connected to the ceramic ferrules, and one end of each of the two optical fibers penetrates through the middle part of the protective sleeve. The protective sleeve is connected to the outer side of the two optical fibers, and the protective sleeve is located between the protective sleeve and the two connectors.

[0007] Further, the mechanical fine-tuning assembly comprises: A nut is arranged on one side of the ceramic ferrule outer structure close to the sensing arm; A screw rod is connected to the nut, and the screw rod is threadedly connected to the ceramic ferrule outer structure close to the sensing arm, and the screw rod is located on one side of the first limiting assembly; A connecting groove is formed in the middle part of the nut and the screw rod, and is used for connecting the two optical fibers to the ceramic ferrule close to the sensing arm.

[0008] Further, the first limiting assembly comprises: A push plate and a movable plate are respectively arranged at two ends of the sensing arm; A connecting rod is connected between the push plate and the movable plate; A first elastic member is connected between the movable plate and the diaphragm.

[0009] Further, one side of the push plate is attached to one side of the ceramic ferrule, the push plate and the movable plate are movably arranged in the mounting groove, a piezoelectric ceramic driver in annular array is arranged between the screw rod and the ceramic ferrule, and is used for automatically adjusting the cavity length. Compared with manual cavity length adjustment, the step precision is further improved, and the automatic cavity length adjustment precision can reach 0.1 microns.

[0010] Further, a second limiting assembly is arranged on the nut and the ceramic ferrule outer structure, and the second limiting assembly comprises: A moving plate is arranged on one side of the nut, and the moving plate is connected to the nut through a second elastic member; A limiting rod is connected to the moving plate, and the limiting rod penetrates through the nut and is inserted into the ceramic ferrule outer structure close to the sensing arm.

[0011] Further, a fixing mechanism is arranged between the protective sleeve and the sensor body, and the fixing mechanism comprises: A moving rod and a circular convex are connected to the inner wall of the protective sleeve; A moving groove is formed on one side of the sensor body, and the moving groove is symmetrically arranged on both sides of the ceramic ferrule close to the sensing arm; A fixed plate is movably arranged in the moving groove, and one end of the fixed plate penetrates through the ceramic ferrule outer structure close to the sensing arm and is inserted into the nut; A third elastic member is connected to the fixed plate and the inner wall of the moving groove through a movable block.

[0012] Further, one end of the moving rod and the round convex are located in the moving groove, and the side of the fixed plate close to the third elastic member is a slope, and the round convex is located at the slope.

[0013] The present application has the following beneficial effects: (1) The present application reduces the F-P cavity length deviation caused by manual operation error and the signal interference problem caused by vibration mismatch of the sensing arm and the reference arm in the sensor body assembly process through the coaxial packaging assembly and the mechanical fine adjustment assembly, and proposes an optical sensing device integrating a co-packaged double optical fiber arm and an actively adjustable F-P cavity length, changes the cavity length through the mechanical fine adjustment assembly to reduce the influence of interference, and suppresses vibration noise through the double optical fiber arm co-packaging design, and realizes high-precision, high-stability partial discharge ultrasonic detection; (2) The first limiting assembly can prevent the screw rod from directly contacting the ceramic ferrule, thereby reducing the wear of the ceramic ferrule by the screw rod, and can also keep the sensing arm, the ceramic ferrule and the optical fiber stable during movement, prevent movement during movement, and affect the precision of F-P cavity length adjustment; (3) The second limiting assembly and the fixing mechanism limit the nut and the screw rod after rotation, improve the stability of the nut and the screw rod, ensure that the displacement adjustment of the ceramic ferrule and the optical fiber is more stable and accurate, and can also limit the connection between the protective cover and the sensor body, improve the stability and protection effect of the protective cover, and thus facilitate use. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The embodiment is shown as a whole structure schematic diagram; Figure 2 The embodiment is shown as a sensor body and a protective sleeve internal structure diagram; Figure 3 The embodiment is shown as a sensor body and a protective sleeve cross-sectional view; Figure 4 The embodiment is shown as Figure 3 The enlarged view of A of the embodiment is shown as; Figure 5 The embodiment is shown as a sensor body and a mechanical fine adjustment assembly structure diagram; Figure 6 The embodiment is shown as a mechanical fine adjustment assembly, a ceramic ferrule external structure and a second limiting assembly structure diagram; Figure 7 The embodiment is shown as a mechanical fine adjustment assembly and a first limiting assembly structure diagram; Figure 8 The embodiment is shown as a limiting assembly structure diagram; Figure 9 The embodiment is shown as a mechanical fine adjustment assembly and a ceramic ferrule external structure cross-sectional view; Figure 10 The diagram shown is a structural diagram of the mechanical fine-tuning component, the second limiting component, and the fixing mechanism of the embodiment.

[0015] In the diagram: 1. Sensor body; 2. Diaphragm; 3. Dual-core structure; 4. Connector; 5. Protective sleeve; 6. Sensing arm; 7. Reference arm; 8. Ceramic ferrule; 9. Ceramic ferrule outer structure; 10. Optical fiber; 11. Protective sleeve; 12. Nut; 13. Screw; 14. Push plate; 15. Movable plate; 16. Connecting rod; 17. First elastic element; 18. Piezoelectric ceramic actuator; 19. Moving plate; 20. Second elastic element; 21. Limiting rod; 22. Moving rod; 23. Round protrusion; 24. Fixed plate; 25. Third elastic element; 26. Movable block. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0017] Example 1: This invention provides a fiber optic ultrasonic sensor, such as... Figures 1 to 4 As shown, the sensor body 1 includes a coaxial encapsulation assembly, a diaphragm 2, a mechanical fine-tuning assembly, a dual-core structure 3, a connector 4, a protective sleeve 5, and a first limiting assembly. The sensor body 1 has an internal mounting slot containing the coaxial encapsulation assembly. The coaxial encapsulation assembly includes a sensing arm 6, a reference arm 7, a ceramic ferrule 8, and a ceramic ferrule outer structure 9. The sensing arm 6 and reference arm 7 are respectively located in two mounting slots. The ceramic ferrule 8 is fixedly connected to the sensing arm 6 and reference arm 7, respectively, for fixing and guiding the dual-core structure 3. The ceramic ferrule outer structure 9 is fixedly installed on one side of the sensor body 1, located on the same side as the sensing arm 6, reference arm 7, and ceramic ferrule 8, for protecting the sensing arm 6, reference arm 7, and ceramic ferrule 8. There are two mounting slots. The diaphragm 2 is located on one side of the coaxial encapsulation assembly. The diaphragm 2 is close to... The sensor arm 6 is fixedly installed on the inner wall of the mounting slot on one side. The mechanical fine-tuning component is set on one side of the sensor body 1 to adjust the cavity length, realizing the 1-micron-level step adjustment of the cavity length. The dual-core structure 3 is connected to the coaxial packaging assembly. Two connectors 4 are respectively connected to the dual-core structure 3. The dual-core structure 3 includes optical fiber 10 and protective sleeve 11. One end of the two optical fibers 10 is fixedly connected to the ceramic ferrule 8, and the other end of the two optical fibers 10 passes through the middle part of the protective sleeve 5 and is fixedly installed to the connector 4. The protective sleeve 11 is fixedly installed on the outside of the two optical fibers 10. The protective sleeve 11 is located between the protective sleeve 5 and the two connectors 4. The protective sleeve 5 is fixedly connected to one side of the sensor body 1. The mechanical fine-tuning component is located inside the protective sleeve 5 to protect the mechanical fine-tuning component and the dual-core structure 3. The first limiting component is set on the coaxial packaging assembly to limit the coaxial packaging assembly.

[0018] The sensing arm 6 and the reference arm 7 are collectively packaged in the sensor together with the ceramic ferrule 8, and the two optical fibers 10 in the protective sleeve 11 are in the same mechanical vibration environment through the coaxial packaging design, and the vibration deformation of the sensing arm 6 and the reference arm 7 is highly synchronized through the symmetrical layout and rigid fixation, so that the influence of external vibration on the optical paths of the sensing arm 6 and the reference arm 7 tends to change in the same direction, thereby forming common-mode noise in the interference signal, greatly reducing the phase difference introduced by vibration, and improving the signal-to-noise ratio of the demodulation signal.

[0019] The coaxial packaging of the double optical fiber 10 arm can effectively suppress vibration noise, and the mechanical fine adjustment assembly changes the cavity length to reduce the influence of unnecessary interference, and the reference arm fiber end face is coated with a high-reflection film, and the three are used in combination to greatly improve the signal-to-noise ratio of the signal, which is suitable for detecting weak local partial discharge inside high-voltage power equipment. In use, the reference arm 7 and the ceramic ferrule 8 are installed in one of the installation grooves, and the sensing arm 6 and the ceramic ferrule 8 are placed in the other installation groove, so that the sensing arm 6 is located in the middle of the first limiting component, and the ceramic ferrule 8 of the sensing arm 6 and one end of the optical fiber 10 pass through the middle of the ceramic ferrule outer structure 9, which prevents the ceramic ferrule 8 from being worn out, and the first limiting component is pushed by the mechanical fine adjustment assembly to move towards the diaphragm 2, thereby pushing the ceramic ferrule 8 and the optical fiber 10 of the sensing arm 6 to move, adjusting the distance between the ceramic ferrule 8, the optical fiber 10 and the diaphragm 2, adjusting the F-P cavity length, and moving the ceramic ferrule 8 and the optical fiber 10 along the inner wall of the installation groove through the first limiting component, preventing deviation during movement, which causes deviation of the F-P cavity length, and then the optical fiber 10 connected with the sensing arm 6 and the reference arm 7 passes through the protective sleeve 5, and then the optical fiber 10 is installed with the connector 4, and then the protective sleeve 5 is installed on one side of the sensor body 1, which protects the mechanical fine adjustment assembly and the optical fiber 10 connected with the ceramic ferrule 8 from being damaged due to collision, affecting the use effect of the sensor body 1, and the type of the connector 4 is FC-APC, which is directly connected with the fiber 10 interface of the sensing arm 6 and the reference arm 7 of the 3x3 local partial discharge ultrasonic detector through the FC-APC connector 4, and the laser emitted by the laser is modulated by the MEMS sensor and returned to the 3x3 coupler through the sensing arm 6 and the reference arm 7, and interference is generated at the coupler, and after collection and processing, the ultrasonic signal received by the MEMS sensor can be demodulated.

[0020] As Figure 2 , Figure 3 , Figure 6 , Figure 8 and Figure 9As shown, in order to improve the assembly fault tolerance, reduce the manual assembly error significantly, avoid the device scrap caused by too large error in the traditional scheme, and optimize the detection sensitivity, the mechanical fine adjustment assembly includes the nut 12, the screw rod 13 and the connecting groove. The nut 12 is arranged on one side of the ceramic plug core outer structure 9 close to the sensing arm 6. The screw rod 13 is fixedly connected to the nut 12. The middle part of the ceramic plug core outer structure 9 close to the sensing arm 6 is provided with a threaded groove. The screw rod 13 is threadedly connected with the threaded groove of the ceramic plug core outer structure 9 close to the sensing arm 6. The screw rod 13 is located on one side of the first limiting assembly. The connecting groove is arranged in the middle part of the nut 12 and the screw rod 13, and is used for connecting the two optical fibers 10 to the ceramic plug core 8.

[0021] A precision screw pair (pitch P = 0.15 mm) is arranged outside the sensor at the far end of the F-P cavity. The precision screw pair is composed of the nut 12 and the screw rod 13. When the sensing arm 6, the ceramic plug core 8 and the optical fiber 10 move into the mounting groove through the ceramic plug core outer structure 9, the first limiting assembly is located outside the sensing arm 6. One end of the first limiting assembly is located between the screw rod 13 and the sensing arm 6. By rotating the nut 12 to drive the screw rod 13 to rotate, the screw rod 13 rotates along the threaded groove and pushes the first limiting assembly to move, so that the first limiting assembly drives the sensing arm 6, the ceramic plug core 8 and the optical fiber 10 to move towards the diaphragm, adjusts the distance between the optical fiber 10 and the diaphragm 2, and then realizes the 1-micron-level step adjustment (step resolution ΔL = 0.42 μm / °) of the cavity length, so as to ensure the measurement accuracy and stability of the sensor body 1.

[0022] As shown in Figures 2 to 9 In order to improve the stability of the movement of the sensing arm 6, the ceramic plug core 8 and the optical fiber 10, prevent the screw rod 13 from pushing the sensing arm 6, the ceramic plug core 8 and the optical fiber 10 to move and produce deviation, increase the error during assembly, and prevent the screw rod 13 from directly contacting the ceramic plug core 8, which may cause wear of the ceramic plug core 8 after long-term use and affect the use effect, the first limiting assembly includes the pushing plate 14, the movable plate 15, the connecting rod 16 and the first elastic member 17. The pushing plate 14 and the movable plate 15 are arranged at both ends of the sensing arm 6 respectively. The connecting rod 16 is fixedly connected between the pushing plate 14 and the movable plate 15. The first elastic member 17 is fixedly connected between the movable plate 15 and the diaphragm 2. One side of the pushing plate 14 is attached to one side of the ceramic plug core 8. The outer sides of the pushing plate 14 and the movable plate 15 are movably connected with the inner wall of the mounting groove. The piezoelectric ceramic drivers 18 are arranged in an annular array between the screw rod 13 and the ceramic plug core 8. The screw rod 13 is provided with a plurality of fixing grooves close to one side of the pushing plate 14. The piezoelectric ceramic drivers 18 are fixedly installed in the fixing grooves. The piezoelectric ceramic drivers 18 are located in the middle part of the pushing plate 14. The piezoelectric ceramic drivers 18 arranged in an annular array can simultaneously push the ceramic plug core 8 of the sensing arm 6 to move, and are used for adjusting the cavity length.

[0023] When the sensing arm 6 and the ceramic ferrule 8, the optical fiber 10 are installed in the installation slot, the end of the optical fiber 10 is inserted through the connecting slot of the nut 12 and the screw rod 13, so that the screw rod 13 is inserted into the threaded groove of the outer structure 9 of the ceramic ferrule, the nut 12 is rotated to drive the screw rod 13 to rotate, so that the screw rod 13 drives the push plate 14 to move along the inner wall of the installation slot to the diaphragm 2, the push plate 14 drives the ceramic ferrule 8 and the sensing arm 6 to move to the diaphragm 2, the push plate 14 prevents the screw rod 13 from directly contacting the ceramic ferrule 8, prevents the ceramic ferrule 8 from being abraded, and further improves the service life of the ceramic ferrule 8, in this embodiment, the first elastic member 17 can be a compression spring, when the screw rod 13 drives the push plate 14 to drive the sensing arm 6, the ceramic ferrule 8 and the optical fiber 10 to move, the connecting rod 16 drives the movable plate 15 to press the compression spring, the position of the optical fiber 10 close to the movable plate 15 is limited by the action of the compression spring, and the F-P cavity length is limited, thereby improving the stability of the movement of the sensing arm 6, the ceramic ferrule 8 and the optical fiber 10, when the screw rod 13 is attached to the push plate 14, one side of the piezoelectric ceramic driver 18 is attached to the ceramic ferrule 8, and after coarse adjustment with the nut 12, different voltages are applied to the piezoelectric ceramic driver 18 to produce extremely small expansion and contraction deformation, and the piezoelectric ceramic driver 18 drives the ceramic ferrule 8 and the optical fiber 10 to finely adjust the 0.1 micrometer level displacement, thereby accurately controlling the cavity length of the F-P cavity.

[0024] As shown in Figure 3 , Figure 7 , Figure 8 and Figure 9 , in order to limit the nut 12 and the screw rod 13, prevent the nut 12 and the screw rod 13 from being affected by vibration, and further affect the cavity length of the adjusted F-P cavity, the second limiting assembly is arranged on the nut 12 and the outer structure 9 of the ceramic ferrule, the second limiting assembly includes a moving plate 19, a second elastic member 20 and a limiting rod 21, the moving plate 19 is arranged on one side of the nut 12, the side of the nut 12 close to the moving plate 19 is provided with a movable slot, one end of the second elastic member 20 is fixedly connected with the moving plate 19, and the other end is fixedly connected with the movable slot, the moving plate 19 is connected with the nut 12 through the second elastic member 20, the limiting rod 21 is fixedly connected with the moving plate 19, and a plurality of insertion slots are arranged on one side of the outer structure 9 of the ceramic ferrule, the plurality of insertion slots are arranged in a ring array, the limiting rod 21 is inserted through the insertion slots of the nut 12 and the outer structure 9 of the ceramic ferrule, and the insertion slots arranged in a ring array facilitate the rotation of the nut 12, the screw rod 13, the moving plate 19 and the limiting rod 21, so that the limiting rod 21 can be inserted into the corresponding insertion slot, thereby limiting the nut 12 and the screw rod 13, and improving the stability of the ceramic ferrule 8 limited by the nut 12 and the screw rod 13 to the sensing arm 6.

[0025] When the nut 12 drives the screw rod 13 to rotate and push the plate 14 to move, the sensing arm 6, the ceramic ferrule 8 and the optical fiber 10 are moved to the direction of the diaphragm 2 and to the appropriate position through the action of the connecting rod 16, the movable plate 15 and the first elastic element 17, and then the movable plate 19 is moved to the direction of the ceramic ferrule outer structure 9, so that the second elastic element 20 is compressed. The second elastic element 20 can be a compression spring. When the second elastic element 20 is compressed, the limiting rod 21 passes through the nut 12 and is inserted into the slot on one side of the ceramic ferrule outer structure 9, thereby limiting the nut 12, preventing the nut 12 from being driven to rotate by vibration, and then affecting the distance between the sensing arm 6, the ceramic ferrule 8, the optical fiber 10 and the diaphragm 2, and affecting the cavity length of the F-P cavity.

[0026] As Figure 2 , Figure 3 , Figure 5 , Figure 6 and Figure 10 shown, in order to improve the protective effect of the protective sleeve 5 on the optical fiber 10, the nut 12, the screw rod 13 and the ceramic ferrule outer structure 9 on one side of the sensor body 1, and to limit the screw rod 13 again, improve the stability of the screw rod 13, and then ensure the cavity length precision of the adjusted F-P cavity, a fixing mechanism is arranged between the protective sleeve 5 and the sensor body 1. The fixing mechanism includes a moving rod 22, a round convex 23, a fixed plate 24 and a third elastic element 25. One end of the moving rod 22 is fixedly connected with the round convex 23, and the other end of the moving rod 22 is fixedly connected to the inner wall of the protective sleeve 5. A moving groove is arranged on one side of the sensor body 1, and the moving groove is symmetrically arranged on both sides of the ceramic ferrule 8. The fixed plate 24 is movably arranged in the moving groove. One end of the fixed plate 24 passes through the ceramic ferrule outer structure 9 and is inserted into the nut 12. Limiting grooves are arranged in an annular array on the outside of the nut 12, so that the fixed plate 24 can be inserted into the limiting grooves after the nut 12 drives the screw rod 13 to rotate and adjusts the cavity length of the F-P cavity under the action of the first limiting assembly. An movable block 26 is fixedly installed on one side of the fixed plate 24. The movable block 26 is movably connected with the inner wall of the moving groove. The third elastic element 25 is connected with the fixed plate 24 and the inner wall of the moving groove through the movable block 26. One end of the moving rod 22 and the round convex 23 are located in the moving groove. The side of the fixed plate 24 close to the third elastic element 25 is a slope, and the round convex 23 is located at the slope.

[0027] When the position of the nut 12 and the screw rod 13 is limited, the protective sleeve 5 is connected with one side of the sensor body 1, at the same time, the moving rod 22 connected with the inner wall of the protective sleeve 5 drives the round convex 23 to move into the moving groove, so that the round convex 23 moves along the inclined surface of one side of the fixed plate 24 and extrudes the fixed plate 24, so that the third elastic member 25 is compressed, so that the fixed plate 24 is inserted through the outer structure 9 of the ceramic plug core and the insertion groove on the outer side of the screw rod 13, and the third elastic member 25 can be a compression spring, when the protective sleeve 5 drives the moving rod 22 and the round convex 23 no longer extrude the fixed plate 24, through the action of the compression spring, the fixed plate 24 moves to the original position, and then it is convenient to continue to adjust the cavity length of the F-P cavity through the nut 12, the screw rod 13 and the first limiting assembly, therefore, by limiting the position of the protective sleeve 5 and the screw rod 13, the stability of the protective sleeve 5 and the screw rod 13 can be improved at the same time, so as to protect the long-term stable high-precision adjustment.

[0028] Example 2 The 3x3 demodulation system also adopts the principle and structure of the Michelson interferometer, it is generally considered that the reflected light is only at the diaphragm 2 of the sensing arm 6 and the end surface of the ceramic plug core 8 of the reference arm 7, at this time, according to the 3x3 demodulation principle, a relatively perfect signal can be demodulated. The sensing arm 6 is not only the diaphragm 2 reflected light, but also the contact surface of the ceramic plug core 8 and the air cavity will reflect light, if the end surface of the ceramic plug core 8 is a plane structure, the light intensity of the reflected light is consistent with the light intensity of the reference arm 7, and cannot be directly ignored. In fact, the signal received by the 3x3 demodulation system is 3 paths of reflected light, including the diaphragm 2 (end surface 1) of the sensing arm 6, the end surface (end surface 2) of the ceramic plug core 8 of the sensing arm 6, and the end surface (end surface 3) of the ceramic plug core 8 of the reference arm 7, and the finally obtained signal after the reflected light interferes with each other. Assuming that the phase difference between the end surface 1 and the end surface 2 is , and the phase difference between the end surface 1 and the end surface 3 is . After simplification and direct current removal, the obtained signal can be represented as: Wherein, A1 and A2 are fixed proportional coefficients, which are proportional to the product of the reflection coefficients of the corresponding reflection end surfaces.

[0029] When the sensor body 1 receives the ultrasonic signal, the diaphragm 2 vibrates to cause and both change, and the change amount is , and this amount contains vibration information. In the 3x3 demodulation system, only the second term, i.e. is generally considered, and the influence of the first term needs to be eliminated. We can reduce or increase , that is, by changing the end surface of the ceramic plug core 8 into an inclined surface structure, so that is reduced, or by plating an enhanced film on the inner surface of the diaphragm 2, so that The first term is negligible. The resulting signal can be expressed as: The phase difference between the end face 1 and the end face 3 will be affected by the disturbance of the optical fiber 10, that is, it will change in real time with time, which affects the demodulation result. Therefore, a common packaging structure is designed, and the sensing arm 6 and the reference arm 7 optical fiber 10 are placed in the same sheath, which weakens the influence of the disturbance of the optical fiber 10 on the demodulation result.

[0030] Working principle: when in use, the reference arm 7 and the ceramic plug 8 are installed in one of the installation grooves, and the sensing arm 6 and the ceramic plug 8 are placed in the other installation groove, so that the sensing arm 6 is located in the middle of the push plate 14 and the movable plate 15, and the ceramic plug 8 of the sensing arm 6 and one end of the optical fiber 10 pass through the middle of the ceramic plug outer structure 9, and then the one end of the optical fiber 10 passes through the connecting groove of the nut 12 and the screw rod 13, so that the screw rod 13 is inserted into the threaded groove of the ceramic plug outer structure 9, and rotating the nut 12 drives the screw rod 13 to rotate, so that the screw rod 13 pushes the push plate 14 to move along the inner wall of the installation groove to the diaphragm 2 direction, and the push plate 14 pushes the ceramic plug 8 and the sensing arm 6 to move to the diaphragm 2 direction, adjusting the distance between the ceramic plug 8, the optical fiber 10 and the diaphragm 2, when the screw rod 13 pushes the push plate 14 to drive the sensing arm 6, the ceramic plug 8 and the optical fiber 10 to move to the appropriate position, through the connecting rod 16 drives the movable plate 15 to extrude the first elastic member 17, through the action of the first elastic member 17, the position of the optical fiber 10 close to the movable plate 15 is limited, and then the F-P cavity length is limited, when the screw rod 13 and the push plate 14 are attached, one side of the piezoelectric ceramic actuator 18 is attached to the ceramic plug 8, and is matched with the nut 12 for coarse adjustment, and then different voltages are applied to the piezoelectric ceramic actuator 18 to produce extremely small expansion and contraction deformation, and then the piezoelectric ceramic actuator 18 pushes the ceramic plug 8 and the optical fiber 10 to finely adjust the 0.1 micrometer level displacement, so as to accurately control the cavity length of the F-P cavity, and then move the moving plate 19 to the ceramic plug outer structure 9 direction, so that the second elastic member 20 is compressed, and the limiting rod 21 is inserted into the insertion slot on one side of the ceramic plug outer structure 9, and then the nut 12 is limited.

[0031] When the position of the nut 12 and the screw rod 13 is defined, the optical fiber 10 connecting the sensing arm 6 and the reference arm 7 is passed through the protective sleeve 5, and then the optical fiber 10 is installed with the connector 4, the protective sleeve 5 is connected with one side of the sensor body 1, the nut 12, the screw rod 13 and the outer side of the ceramic ferrule 8 are protected, the moving rod 22 connected with the inner wall of the protective sleeve 5 drives the round convex 23 to move into the moving groove, the round convex 23 moves along the inclined surface of one side of the fixed plate 24 and extrudes the fixed plate 24, the third elastic member 25 is compressed, the fixed plate 24 is inserted into the slot of the outer structure 9 of the ceramic ferrule and the outer side of the screw rod 13, the position of the protective sleeve 5 and the screw rod 13 is defined, the type of the connector 4 is FC-APC, the FC-APC connector 4 is directly connected with the optical fiber 10 interface of the sensing arm 6 and the reference arm 7 of the 3*3 partial discharge ultrasonic detector, the laser emitted by the laser is modulated by the MEMS sensor, and then returned to the 3*3 coupler by the sensing arm 6 and the reference arm 7, and the interference is generated at the coupler, and the ultrasonic signal received by the MEMS sensor can be demodulated after the interference signal is collected and processed.

[0032] The above examples are only used to illustrate the technical solutions of the present application, but not limit it.

Claims

1. An optical fiber ultrasound sensor, characterized by, The utility model relates to a sensor, including: Sensor body (1), internally open with installation groove, the installation groove is provided with coaxial package assembly in; Diaphragm (2), set up in coaxial package assembly one side; Mechanical fine adjustment assembly, set up in sensor body (1) one side, be used for adjusting cavity length; Double -core structure (3), be connected to coaxial package assembly; Two connectors (4) are connected to double -core structure (3) respectively; Protective sleeve (5) is connected in sensor body (1), be used for protecting mechanical fine adjustment assembly with double -core structure (3); First limit component, set up in coaxial package assembly, be used for limiting coaxial package assembly.

2. The optical fiber ultrasound sensor of claim 1, wherein, Coaxial package assembly includes: Sensing arm (6) with reference arm (7), set up in installation groove; Ceramic ferrule (8) is connected in sensing arm (6) with reference arm (7), be used for the action of fixed and guide double -core structure (3); Ceramic ferrule outer structure (9) is set up in sensor body (1) one side, be used for protecting sensing arm (6), reference arm (7) with ceramic ferrule (8).

3. The optical fiber ultrasound sensor of claim 2, wherein, Double -core structure (3) includes: Two optical fibers (10) are connected to ceramic ferrule (8) respectively, and one end of two optical fibers (10) penetrates the middle part of protective sleeve (5); Protective sleeve (11) is connected to the outer side of two optical fibers (10), and the protective sleeve (11) is located between the protective sleeve (5) and two connectors (4).

4. The optical fiber ultrasound sensor of claim 3, wherein, Mechanical fine adjustment assembly includes: Nut (12) is set up in ceramic ferrule outer structure (9) one side close to sensing arm (6); Screw rod (13) is connected to nut (12), and the screw rod (13) is threadedly connected with ceramic ferrule outer structure (9) close to sensing arm (6), and the screw rod (13) is located one side of first limit component; Connecting groove is set up in the middle part of nut (12) and screw rod (13), and is used for the connection of two optical fibers (10) close to ceramic ferrule (8) of sensing arm (6).

5. The optical fiber ultrasound sensor of claim 4, wherein, First limit component includes: Pushing plate (14) and movable plate (15) are set up in both ends of sensing arm (6) respectively; Connecting rod (16) is connected between pushing plate (14) and movable plate (15); First elastic member (17) is connected between movable plate (15) and diaphragm (2).

6. The optical fiber ultrasound sensor of claim 5, wherein, One side of pushing plate (14) is attached to one side of ceramic ferrule (8), and pushing plate (14) and movable plate (15) are movably arranged in installation groove, and piezoelectric ceramic driver (18) in annular array distribution is arranged between screw rod (13) and ceramic ferrule (8), for adjusting cavity length.

7. The optical fiber ultrasound sensor of claim 6, wherein, Second limit component is arranged on nut (12) and ceramic ferrule outer structure (9), and the second limit component includes: Moving plate (19) is set up in one side of nut (12), and the moving plate (19) is connected with nut (12) through second elastic member (20); A limiting rod (21) is connected to the moving plate (19), and the limiting rod (21) penetrates the nut (12) and is inserted into the ceramic ferrule outer structure (9) close to the sensing arm (6).

8. The optical fiber ultrasound sensor of claim 7, wherein, A fixing mechanism is arranged between the protective sleeve (5) and the sensor body (1), and the fixing mechanism comprises: A moving rod (22) and a round convex (23) are connected to the inner wall of the protective sleeve (5); A moving groove is arranged on one side of the sensor body (1), and the moving groove is symmetrically arranged on both sides of the ceramic ferrule (8) close to the sensing arm (6); A fixing plate (24) is movably arranged in the moving groove, and one end of the fixing plate (24) penetrates the ceramic ferrule outer structure (9) close to the sensing arm (6) and is inserted into the nut (12); A third elastic member (25) is connected to the fixing plate (24) and the inner wall of the moving groove through the movable block (26).

9. The optical fiber ultrasound sensor of claim 8, wherein, One end of the moving rod (22) and the round convex (23) are located in the moving groove, one side of the fixing plate (24) close to the third elastic member (25) is a slope, and the round convex (23) is located at the slope.

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