Sensitization tunable optical fiber sound wave sensing structure
By adopting a sensitive and tunable optical fiber acoustic sensing structure in optical fiber acoustic wave sensors, using the bending design of metal arc sheets and the winding of weak gratings, the problems of limited performance of traditional acoustic instruments in high temperature and high pressure environments and low measurement accuracy of distributed optical fiber sensors are solved, and efficient acoustic wave detection and long-distance detection are achieved.
Patent Information
- Application Number
- CN202311552537.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-20
- Publication Date
- 2025-05-20
AI Technical Summary
Traditional electronic acoustic instruments have limited performance in high temperature, high pressure or strong salinity environments, and their data processing efficiency is low; while the spatial resolution and measurement accuracy of distributed fiber sensors are already at a bottleneck state.
The sensitive-enhancing and tunable optical fiber acoustic wave sensing structure is adopted, including the first metal arc sheet, the second metal arc sheet, the cylinder and the weak grating. Through the bending design of the metal arc sheet and the winding method of the weak grating, the reception and propagation of the sound wave are enhanced, and the control of the acoustic wave sensitivity intensity is realized.
It significantly improves the audio response capability and acoustic wave sensitivity intensity of the sensor, maintains excellent detection performance in different environments, and converts the acoustic waveform into high-sensitivity optical signals through weak gratings, solving the problem of traditional fiber detectors in long-distance detection.
Smart Images
Figure CN120020498A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of cased - hole logging, and relates to a sensitivity - enhanced tunable fiber optic acoustic sensing structure. Background Technique
[0002] In the oil logging industry, most traditional acoustic instruments are based on electronic technology, mainly collecting and processing acoustic data through electrical signals. Although such electronic instruments have achieved remarkable results in many applications, their performance is limited in special environments such as high temperature, high pressure or high salinity, and the data - processing efficiency is low. In contrast, fiber - optic long - range detection devices can work stably in various environments, and the data is transmitted by optical fibers with high processing efficiency. However, the current mainstream distributed fiber - optic sensing systems use traditional optical cables laid near the oil pipe. Due to the limitations of the basic principles of backscattering such as Raman and Brillouin, the spatial resolution and measurement accuracy have reached a bottleneck state. Therefore, it is urgent to solve the problems of the limitations of traditional electronic acoustic instruments and existing distributed fiber - optic sensors in the oil - logging industry. Summary of the Invention
[0003] The purpose of the present invention is to solve the problems that in the prior art, the performance of traditional electronic acoustic instruments is limited in high - temperature, high - pressure or high - salinity environments during logging, and the data - processing efficiency is low; while the spatial resolution and measurement accuracy of distributed fiber - optic sensors have reached a bottleneck state, and to provide a sensitivity - enhanced tunable fiber optic acoustic sensing structure.
[0004] To achieve the above - mentioned purpose, the present invention adopts the following technical solutions:
[0005] A sensitivity - enhanced tunable fiber optic acoustic sensing structure includes: a first metal arc - shaped thin sheet, a second metal arc - shaped thin sheet, a cylinder, and a weak grating;
[0006] The first metal arc - shaped thin sheet and the second metal arc - shaped thin sheet form a cylindrical space; the cylinder is arranged in the cylindrical space; one end of the first metal arc - shaped thin sheet is fixed to the cylinder; at the same time, one end of the first metal arc - shaped thin sheet is in contact with one end of the second metal arc - shaped thin sheet; the other end of the second metal arc - shaped thin sheet is fixed to the cylinder; at the same time, the other end of the second metal arc - shaped thin sheet is in contact with the other end of the first metal arc - shaped thin sheet; the weak grating is wound around the outer sides of the first metal arc - shaped thin sheet and the second metal arc - shaped thin sheet.
[0007] A further improvement of the present invention lies in:
[0008] Further, one end of the first metal arc-shaped thin sheet has a first flap and a second flap; the other end of the first metal arc-shaped thin sheet has a third flap and a fourth flap; one end of the second metal arc-shaped thin sheet has a fifth flap and a sixth flap; the other end of the second metal arc-shaped thin sheet has a seventh flap and an eighth flap; the first flap and the third flap are formed by folding inwards once at the two ends of the first metal arc-shaped thin sheet respectively, and the second flap and the fourth flap are formed by folding inwards again at the creases at the two ends of the first metal arc-shaped thin sheet respectively; the fifth flap and the seventh flap are formed by folding inwards once at the two ends of the second metal arc-shaped thin sheet respectively, and the sixth flap and the eighth flap are formed by folding inwards again at the creases at the two ends of the second metal arc-shaped thin sheet respectively.
[0009] Further, one end of the first metal arc-shaped thin sheet is fixed to the cylinder; at the same time, one end of the first metal arc-shaped thin sheet is in contact with one end of the second metal arc-shaped thin sheet. Specifically: the first flap is fixed to the cylinder through a second bolt; the second flap is in contact with the sixth flap through a first bolt; the sixth flap moves freely along the direction of the first bolt; the fifth flap is close to the cylinder.
[0010] Further, the second flap is in contact with the sixth flap through a first bolt. Specifically: corresponding through holes are provided on the second flap and the sixth flap; when the first bolt passes through the through holes of the second flap and the sixth flap, the first bolt is fixed to the second flap through a first nut; the sixth flap slides freely on the first bolt.
[0011] Further, the other end of the second metal arc-shaped thin sheet is fixed to the cylinder; at the same time, the other end of the second metal arc-shaped thin sheet is in contact with the other end of the first metal arc-shaped thin sheet. Specifically: the seventh flap is fixed to the cylinder through a third bolt; the eighth flap is in contact with the fourth flap through a fourth bolt; the fourth flap moves freely along the direction of the fourth bolt; the third flap is close to the cylinder.
[0012] Further, the eighth flap is in contact with the fourth flap through a fourth bolt. Specifically: corresponding through holes are provided on the eighth flap and the fourth flap; when the fourth bolt passes through the through holes of the eighth flap and the fourth flap; the fourth bolt is fixed to the eighth flap through a second nut; the fourth flap slides freely on the fourth bolt.
[0013] Further, springs are provided on both the second bolt and the third bolt; when the first metal arc-shaped thin sheet and the second metal arc-shaped thin sheet are extruded by an external force, the springs can quickly restore the original shapes of the first metal arc-shaped thin sheet and the second metal arc-shaped thin sheet.
[0014] Further, the first flap, the second flap, the third flap, the fourth flap, the fifth flap, the sixth flap, the seventh flap and the eighth flap have the same width.
[0015] Further, the cylinder is made of PVC material.
[0016] Further, the angle between the first flap and the second flap can be customarily adjusted; the angle between the third flap and the fourth flap can be customarily adjusted; the angle between the fifth flap and the sixth flap can be customarily adjusted; the angle between the seventh flap and the eighth flap can be customarily adjusted.
[0017] Compared with the prior art, the present invention has the following beneficial effects:
[0018] In the present invention, the first metal arc thin sheet, the second metal arc thin sheet and the cylinder form an outer metal cylinder shell, and the metal cylinder shell can enhance the reception and propagation of sound waves, thereby significantly improving the audio response ability and sound wave sensitization intensity of the sensor. At the same time, the unique bending design of the present invention enables the vertical displacement of the first metal arc thin sheet and the second metal arc thin sheet under external pressure, realizing the regulation of the sound wave sensitization intensity. The sensor can maintain excellent detection performance in different working environments.
[0019] Further, the present invention uses a weak grating winding method to convert the deformation generated by the transmission of sound waves in the sensitization structure into an ultra-high-sensitivity optical signal. At the same time, based on the weak reflection characteristics of the weak grating, multiple sensitization devices can be cascaded to achieve distributed measurement, which can be widely used in cross-well acoustic dynamic measurement, injection-production profile monitoring, fracturing monitoring, etc., effectively solving the long-distance detection problem of traditional fiber optic geophones in these applications, thereby further expanding its application fields. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.
[0021] Figure 1 It is a three-dimensional view of the sensitization tunable fiber optic acoustic sensing structure of the present invention;
[0022] Figure 2 It is a top view of the sensitization tunable fiber optic acoustic sensing structure of the present invention;
[0023] Figure 3 It is a spectrogram collected under different conditions.
[0024] Among them, 1 - the first bolt; 2 - the second bolt; 3 - the cylinder; 4 - the first metal arc-shaped sheet; 5 - the weak grating; 6 - the fourth bolt; 7 - the third bolt; 8 - the first nut; 9 - the second metal arc-shaped sheet; 10 - the first flap; 11 - the second flap; 12 - the third flap; 13 - the fourth flap; 14 - the fifth flap; 15 - the sixth flap; 16 - the seventh flap; 17 - the eighth flap; 18 - the second nut. Specific implementation mode
[0025] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.
[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.
[0027] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.
[0028] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, terms such as "first", "second", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.
[0029] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.
[0030] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "arranged", "installed", "connected", and "coupled" should be understood in a broad sense. For example, it 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 directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0031] The present invention will be further described in detail below with reference to the accompanying drawings:
[0032] See Figure 1 and Figure 2 The present invention discloses a sensitivity-enhanced tunable fiber optic acoustic sensing structure, including: a first metal arc-shaped thin sheet 4, a second metal arc-shaped thin sheet 9, a cylinder 3, and a weak grating 5;
[0033] The first metal arc-shaped thin sheet 4 and the second metal arc-shaped thin sheet 9 form a cylindrical space; the cylinder 3 is arranged in the cylindrical space; one end of the first metal arc-shaped thin sheet 4 is fixed to the cylinder 3; at the same time, one end of the first metal arc-shaped thin sheet 4 is in contact with one end of the second metal arc-shaped thin sheet 9; the other end of the second metal arc-shaped thin sheet 9 is fixed to the cylinder 3; at the same time, the other end of the second metal arc-shaped thin sheet 9 is in contact with the other end of the first metal arc-shaped thin sheet 4; the weak grating 5 is wound around the outer sides of the first metal arc-shaped thin sheet 4 and the second metal arc-shaped thin sheet 9.
[0034] One end of the first metal arc-shaped thin sheet 4 has a first flap 10 and a second flap 11; the other end of the first metal arc-shaped thin sheet 4 has a third flap 12 and a fourth flap 13; one end of the second metal arc-shaped thin sheet 9 has a fifth flap 14 and a sixth flap 15; the other end of the second metal arc-shaped thin sheet 9 has a seventh flap 16 and an eighth flap 17; the first flap 10 and the third flap 12 are formed by folding inwards once at the two ends' edges of the first metal arc-shaped thin sheet 4 respectively, and the second flap 11 and the fourth flap 13 are formed by folding inwards again at the creases at the two ends of the first metal arc-shaped thin sheet 4; the fifth flap 14 and the seventh flap 16 are formed by folding inwards once at the two ends' edges of the second metal arc-shaped thin sheet 9 respectively, and the sixth flap 15 and the eighth flap 17 are formed by folding inwards again at the creases at the two ends of the second metal arc-shaped thin sheet 9.
[0035] One end of the first metal arc-shaped sheet 4 is fixed to the cylinder 3; at the same time, one end of the first metal arc-shaped sheet 4 is in contact with one end of the second metal arc-shaped sheet 9. Specifically: The first flap 10 and the cylinder 3 are fixed by the second bolt 2; the second flap 11 and the sixth flap 15 are in contact through the first bolt 1; the sixth flap 15 moves freely along the direction of the first bolt 1; the fifth flap 14 is closely attached to the cylinder 3.
[0036] The second flap 11 and the sixth flap 15 are in contact through the first bolt 1. Specifically: Corresponding through holes are provided on the second flap 11 and the sixth flap 15; when the first bolt 1 passes through the through holes of the second flap 11 and the sixth flap 15, the first bolt 1 is fixed to the second flap 11 by the first nut 8; the sixth flap 15 slides freely on the first bolt 1.
[0037] The other end of the second metal arc-shaped sheet 9 is fixed to the cylinder 3; at the same time, the other end of the second metal arc-shaped sheet 9 is in contact with the other end of the first metal arc-shaped sheet 4. Specifically: The seventh flap 16 and the cylinder 3 are fixed by the third bolt 7; the eighth flap 17 and the fourth flap 13 are in contact through the fourth bolt 6; the fourth flap 13 moves freely along the direction of the fourth bolt 6; the third flap 12 is closely attached to the cylinder 3.
[0038] The eighth flap 17 and the fourth flap 13 are in contact through the fourth bolt 6. Specifically: Corresponding through holes are provided on the eighth flap 17 and the fourth flap 13; when the fourth bolt 6 passes through the through holes of the eighth flap 17 and the fourth flap 13; the fourth bolt 6 is fixed to the eighth flap 17 by the second nut 18; the fourth flap 13 slides freely on the fourth bolt 6.
[0039] Springs are provided on both the second bolt 2 and the third bolt 7; when the first metal arc-shaped sheet 4 and the second metal arc-shaped sheet 9 are subjected to external extrusion, the springs can quickly restore the original shapes of the first metal arc-shaped sheet 4 and the second metal arc-shaped sheet 9.
[0040] The first flap 10, the second flap 11, the third flap 12, the fourth flap 13, the fifth flap 14, the sixth flap 15, the seventh flap 16, and the eighth flap 17 have the same width. The cylinder 3 is made of PVC material. The angle between the first flap 10 and the second flap 11 can be adjusted customarily; the angle between the third flap 12 and the fourth flap 13 can be adjusted customarily; the angle between the fifth flap 14 and the sixth flap 15 can be adjusted customarily; the angle between the seventh flap 16 and the eighth flap 17 can be adjusted customarily.
[0041] For the working requirements of different scenarios, the following are some preferred technical solution cases:
[0042] Preferred Solution 1: The cylinder 3 can be replaced with a polyimide (PI) material with higher performance. Due to the excellent heat resistance, chemical resistance, and good electrical insulation of polyimide (PI), it can exhibit more stable performance in extreme working environments, such as high-temperature, acid-base, and other environments. The length, width, and height of the cylinder 3 can be appropriately adjusted to a bottom circumference of 17 - 20 cm, a height of 9 - 11 cm, and a thickness of 2 - 2.5 mm to obtain a larger inner cavity space and better protection effect.
[0043] Preferred Solution 2: A rectangular metal sheet with super-strong bending elasticity can be selected to replace the existing first metal arc-shaped thin sheet 4 and second metal arc-shaped thin sheet 9. Compared with other materials, titanium alloy or high-strength steel has higher strength, better corrosion resistance, and lighter weight, which is beneficial to improving the overall performance of the device and its service life in special environments.
[0044] Preferred Solution 3: The bending angle can be enlarged to 100° according to the sensitization requirement. Increasing the bending angle can help adjust the distance between the first metal arc-shaped thin sheet 4 and the second metal arc-shaped thin sheet 9 and the cylinder 3, thereby changing the volume of the inner cavity space and optimizing the amplification effect of acoustic wave vibration.
[0045] Preferred Solution 4: The metal cylinder shell can choose to wind a longer weak grating optical fiber. Increasing the length of the weak grating can further improve the detection range to meet the requirements for the accuracy of acoustic wave detection in different scenarios. The metal cylinder shell is an outer shell formed by wrapping the first metal arc-shaped thin sheet 4 and the second metal arc-shaped thin sheet 9 on the cylinder 3.
[0046] Example:
[0047] Step 1: Bend the two ends of the first metal arc-shaped thin sheet 4 and the second metal arc-shaped thin sheet 9 at 1.5 cm from each end by 90° twice. After the first bend, a rectangular thin sheet with a length of 0.75 cm is obtained. Press the bent first metal arc-shaped thin sheet 4 and second metal arc-shaped thin sheet 9 tightly against the arc surface of the cylinder 3. Then drill two holes at symmetrical positions above for fixing the first metal arc-shaped thin sheet 4 and the second metal arc-shaped thin sheet 9 to the cylinder 3 with bolts and nuts. Among them, the length of the first metal arc-shaped thin sheet 4 and the second metal arc-shaped thin sheet 9 is 23 cm, the width is 7 cm, and the thickness is 1 mm. The bottom circumference of the PVC cylinder is 15.7 cm, the height is 8 cm, and the thickness is 2 mm.
[0048] Step 2: After the second bend, a vertical height space with a height of 0.75 cm will be formed between the first metal arc-shaped sheet 4 and the second metal arc-shaped sheet 9 and the cylinder 3. Drill holes at the adjacent positions of the first metal arc-shaped sheet 4 and the second metal arc-shaped sheet 9. Similarly, use bolts and nuts to fix one side of a single metal sheet unilaterally. The top of the bolt passes through the corresponding hole position of the other metal sheet, and no nut is fixed at the top of the bolt, so that the other metal sheet can move freely along the direction of the bolt.
[0049] Step 3: Wind an 8m long weak grating around the metal cylinder housing. When the external sound wave is transmitted to the sensitization structure, the cavity between the inner and outer cylinders can amplify the sound wave vibration effect, which can drive the metal sheet to generate a vertical displacement along the direction of the bolt stud, thereby increasing the deformation of the weak grating wound around the cylinder, increasing the optical path difference and improving the sensitivity. The sound wave signal sensitization effect is achieved. The role of the weak grating is to convert the deformation of the metal sheet into a measurable optical signal.
[0050] As Figure 3 shown, from top to bottom are the sound wave signals with the same frequency and amplitude measured by the weak grating under three conditions: without the sensitization structure, wound around the outer periphery of the cylinder, and wound around the sensitization structure. In Figure 3 , the left side is the time domain diagram; the right side is the single pulse signal; as Figure 3 can be seen, because of the ductility of the metal sheet and the telescopic property along the direction of the bolt, after the sound wave signal is transmitted to the sensitization structure, a large physical deformation occurs, the signal-to-noise ratio of the collected signal is greatly improved, and at the same time, the sampling accuracy of the instantaneous signal is gradually improved, indicating that this structure can effectively improve the vibration sensitivity of the weak grating acquisition system.
[0051] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A sensitivity-enhanced tunable optical fiber acoustic wave sensing structure, characterized in that: include: A first metal arc-shaped thin sheet (4), a second metal arc-shaped thin sheet (9), a cylinder (3) and a weak grating (5); The first metal arc-shaped thin sheet (4) and the second metal arc-shaped thin sheet (9) form a cylindrical space; the cylinder (3) is arranged in the cylindrical space; one end of the first metal arc-shaped thin sheet (4) is fixed to the cylinder (3); at the same time, one end of the first metal arc-shaped thin sheet (4) is in contact with one end of the second metal arc-shaped thin sheet (9); the other end of the second metal arc-shaped thin sheet (9) is fixed to the cylinder (3); at the same time, the other end of the second metal arc-shaped thin sheet (9) is in contact with the other end of the first metal arc-shaped thin sheet (4); the weak grating (5) is wound around the outside of the first metal arc-shaped thin sheet (4) and the second metal arc-shaped thin sheet (9).
2. The sensitivity-enhanced tunable optical fiber acoustic wave sensing structure according to claim 1, characterized in that: One end of the first metal arc-shaped thin sheet (4) has a first folding piece (10) and a second folding piece (11); the other end of the first metal arc-shaped thin sheet (4) has a third folding piece (12) and a fourth folding piece (13); one end of the second metal arc-shaped thin sheet (9) has a fifth folding piece (14) and a sixth folding piece (15); the other end of the second metal arc-shaped thin sheet (9) has a seventh folding piece (16) and an eighth folding piece (17); the first folding piece (10) and the third folding piece (12) are The edges of both ends of the first metal arc-shaped thin sheet (4) are respectively folded inward once, and the second folded sheet (11) and the fourth folded sheet (13) are respectively folded inward again at the fold marks at both ends of the first metal arc-shaped thin sheet (4); the fifth folded sheet (14) and the seventh folded sheet (16) are respectively folded inward once at the edges of both ends of the second metal arc-shaped thin sheet (9), and the sixth folded sheet (15) and the eighth folded sheet (17) are respectively folded inward again at the fold marks at both ends of the second metal arc-shaped thin sheet (9).
3. The sensitivity-enhanced tunable optical fiber acoustic wave sensing structure according to claim 2, characterized in that: One end of the first metal arc-shaped thin sheet (4) is fixed to the cylinder (3); at the same time, one end of the first metal arc-shaped thin sheet (4) is in contact with one end of the second metal arc-shaped thin sheet (9), specifically: the first folding sheet (10) is fixed to the cylinder (3) by a second bolt (2); the second folding sheet (11) is in contact with the sixth folding sheet (15) by a first bolt (1); the sixth folding sheet (15) is free to move along the direction of the first bolt (1); and the fifth folding sheet (14) is in close contact with the cylinder (3).
4. The sensitivity-enhanced tunable optical fiber acoustic wave sensing structure according to claim 3 is characterized in that: The second folding piece (11) and the sixth folding piece (15) are in contact with each other via a first bolt (1), specifically: corresponding through holes are provided on the second folding piece (11) and the sixth folding piece (15); when the first bolt (1) passes through the through holes of the second folding piece (11) and the sixth folding piece (15), the first bolt (1) is fixed to the second folding piece (11) via a first nut (8); and the sixth folding piece (15) slides freely on the first bolt (1).
5. The sensitivity-enhanced tunable optical fiber acoustic wave sensing structure according to claim 4, characterized in that: The other end of the second metal arc-shaped thin sheet (9) is fixed to the cylinder (3); at the same time, the other end of the second metal arc-shaped thin sheet (9) is in contact with the other end of the first metal arc-shaped thin sheet (4), specifically: the seventh folding sheet (16) is fixed to the cylinder (3) by a third bolt (7); the eighth folding sheet (17) is in contact with the fourth folding sheet (13) by a fourth bolt (6); the fourth folding sheet (13) is free to move along the direction of the fourth bolt (6); and the third folding sheet (12) is in close contact with the cylinder (3).
6. The sensitivity-enhanced tunable optical fiber acoustic wave sensing structure according to claim 5, characterized in that: The eighth folding piece (17) and the fourth folding piece (13) are in contact with each other through the fourth bolt (6), specifically: the eighth folding piece (17) and the fourth folding piece (13) are provided with corresponding through holes; when the fourth bolt (6) passes through the through holes of the eighth folding piece (17) and the fourth folding piece (13); the fourth bolt (6) is fixed to the eighth folding piece (17) through the second nut (18); and the fourth folding piece (13) slides freely on the fourth bolt (6).
7. The sensitivity-enhanced tunable optical fiber acoustic wave sensing structure according to claim 6, characterized in that: The second bolt (2) and the third bolt (7) are both provided with springs; when the first metal arc-shaped thin sheet (4) and the second metal arc-shaped thin sheet (9) are squeezed by external force, the springs can quickly restore the first metal arc-shaped thin sheet (4) and the second metal arc-shaped thin sheet (9) to their original shapes.
8. The sensitivity-enhanced tunable optical fiber acoustic wave sensing structure according to claim 7, characterized in that: The first folding piece (10), the second folding piece (11), the third folding piece (12), the fourth folding piece (13), the fifth folding piece (14), the sixth folding piece (15), the seventh folding piece (16) and the eighth folding piece (17) have the same width.
9. The sensitivity-enhanced tunable optical fiber acoustic wave sensing structure according to claim 8, characterized in that: The cylinder (3) is made of PVC material.
10. The sensitivity-enhanced tunable optical fiber acoustic wave sensing structure according to claim 9, characterized in that: The angle between the first folding piece (10) and the second folding piece (11) is customizable; the angle between the third folding piece (12) and the fourth folding piece (13) is customizable; the angle between the fifth folding piece (14) and the sixth folding piece (15) is customizable; and the angle between the seventh folding piece (16) and the eighth folding piece (17) is customizable.