Thin-walled cylindrical fiber hydrophone with internal acoustic wave diffraction structure

Abstract

The application discloses a thin-wall cylindrical fiber hydrophone with an internal acoustic wave diffraction structure and belongs to the technical field of acoustic wave detection, and solves the technical problem of low axial acoustic wave absorption utilization rate of an existing hydrophone. The fiber hydrophone comprises a thin-wall metal cylinder, a sensing optical fiber, a fixed end cover and a diffraction-negative Poisson ratio composite internal structure coaxially arranged in the cylinder, the composite internal structure comprises an acoustic wave diffraction unit and a negative Poisson ratio amplification unit. The acoustic wave diffraction unit guides and diffracts the axial incident acoustic wave to the negative Poisson ratio amplification unit; the negative Poisson ratio amplification unit generates axial deformation under the action of sound pressure and efficiently converts the axial deformation into radial force through the negative Poisson ratio structure, drives the thin-wall metal cylinder to generate radial deformation, and further drives the sensing optical fiber to generate strain. The application can significantly improve the absorption utilization rate and axial sensitivity of the axial acoustic wave, meanwhile, the original radial high sensitivity is maintained, and the omnidirectional detection performance of the hydrophone is improved.

Description

Technical Field

[0001] This invention relates to the field of acoustic wave detection technology, and specifically to a thin-walled cylindrical fiber optic hydrophone with an internal acoustic wave diffraction structure. Background Technology

[0002] Cylindrical fiber optic hydrophones are a common structure in the field of fiber optic underwater acoustic detection. Their core principle is to utilize the radial deformation of a thin-walled cylinder under the influence of sound waves, which causes phase modulation in the sensing fiber wound around its outer wall. This phase modulation is then used to detect the sound waves. Existing thin-walled cylindrical fiber optic hydrophones have high sensitivity to sound waves perpendicular to the cylinder's axis (radial direction). However, for sound waves incident along the cylinder's axis (axial direction), the radial deformation is weak because the sound wave propagation direction is inconsistent with the cylinder's deformation sensitivity direction. This results in low phase signal strength generated by the sensing fiber, ultimately leading to low axial sensitivity and poor axial sound wave absorption utilization.

[0003] Currently, existing technologies for optimizing the sensitivity of cylindrical fiber optic hydrophones mainly focus on the design of sensitizing structures on the outer wall, modification of cylindrical materials, and nesting of multiple cylinders. They rarely address the issue of low axial sound wave absorption utilization by considering the control of the acoustic field within the cylinder's interior. Axially incident sound waves often pass directly through the cylinder's interior without being effectively converted into strain that drives radial deformation. This not only wastes acoustic energy but also creates detection blind zones, affecting the hydrophone's omnidirectional detection performance and failing to meet the practical needs of underwater omnidirectional acoustic detection.

[0004] To address the shortcomings of the prior art, this invention introduces an acoustic wave diffraction structure inside a thin-walled metal cylinder to guide, reflect, diffract, and convert axially incident acoustic waves, thereby forcibly driving the cylinder wall to generate radial vibration. This efficiently converts the energy of the axial acoustic waves into effective strain, significantly improving the axial acoustic wave absorption utilization rate and the axial sensitivity of the hydrophone, thus overcoming the deficiencies of the prior art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a thin-walled cylindrical fiber optic hydrophone with an internal acoustic diffraction structure. This solves the defects of existing thin-walled cylindrical fiber optic hydrophones, such as low axial acoustic wave absorption utilization, poor axial sensitivity, and poor omnidirectional detection uniformity. This invention achieves efficient absorption and conversion of axial acoustic waves through the design of an internal cavity diffraction-negative Poisson's ratio composite internal structure, thereby improving axial sensitivity while maintaining the original high radial sensitivity. This improves the omnidirectional detection performance of the hydrophone and meets the practical application requirements of underwater omnidirectional acoustic detection.

[0006] This invention discloses a thin-walled cylindrical fiber optic hydrophone with an internal acoustic diffraction structure, comprising a thin-walled metal cylinder, a sensing fiber wound around the outer wall of the thin-walled metal cylinder, and fixed end caps fixed to both ends of the thin-walled metal cylinder.

[0007] The thin-walled metal cylinder has a diffraction-negative Poisson's ratio composite internal structure coaxially arranged inside. The diffraction-negative Poisson's ratio composite internal structure includes two sets of acoustic wave diffraction units and one set of negative Poisson's ratio amplification units arranged in series along the axial direction of the thin-walled metal cylinder.

[0008] The two sets of acoustic diffraction units are arranged at both ends of the negative Poisson's ratio amplification unit along the axial direction of the thin-walled metal cylinder;

[0009] The acoustic diffraction unit is an annular porous diffraction grating, which includes an annular disk and multiple conical grating holes penetrating the annular disk. The multiple conical grating holes are evenly distributed along the circumference of the annular disk, and the large-diameter end of the conical grating hole faces the incident end of the acoustic wave.

[0010] The negative Poisson's ratio amplification unit is a hollow cylinder with multiple axially symmetrically arranged hexagonal honeycomb grids on the cylinder wall.

[0011] Optionally, the outer diameter of the annular disk is smaller than the inner diameter of the thin-walled metal cylinder, so as to form an annular acoustic cavity between the outer wall of the annular disk and the inner wall of the thin-walled metal cylinder.

[0012] Optionally, the fixed end cap is made of a waterproof and sound-permeable material, and has a through hole in the center for allowing sound waves to enter the inner cavity of the thin-walled metal cylinder axially.

[0013] Optionally, the sensing fiber is uniformly and tightly wound around the outer wall of the thin-walled metal cylinder at a position corresponding to the internal structure of the diffraction-negative Poisson's ratio composite.

[0014] Optionally, the diffraction-negative Poisson's ratio composite internal structure is fixed to the thin-walled metal cylinder by pressing with a fixed end cap or by bonding with an adhesive, and the acoustic diffraction unit and the negative Poisson's ratio amplification unit are fixed by laser micro-welding.

[0015] Optionally, the ratio of the wall thickness to the inner diameter of the thin-walled metal cylinder is ≤1:50; the surface roughness Ra of the inner wall of the thin-walled metal cylinder is ≤0.2μm.

[0016] Optionally, the acoustic diffraction unit is made of polyetheretherketone (PEEK); the negative Poisson's ratio amplification unit is made of polyimide.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] (1) The thin-walled cylindrical fiber optic hydrophone of the present invention significantly improves the axial sound wave absorption utilization rate, efficiently converts the axial incident sound wave into effective radial strain, improves the axial sensitivity of the fiber optic hydrophone, and effectively makes up for the defect of weak axial response of existing hydrophones.

[0019] (2) The thin-walled cylindrical fiber optic hydrophone of the present invention improves the axial sensitivity while maintaining the original high radial sensitivity, making the omnidirectional response of the hydrophone more uniform, eliminating the axial detection blind zone, and improving the omnidirectional detection performance.

[0020] (3) The diffraction-negative Poisson's ratio composite internal structure of the thin-walled cylindrical fiber optic hydrophone of the present invention is built-in, which does not change the external size and overall structure of the hydrophone, is compatible with existing assembly processes, does not require modification of existing production equipment, and reduces production costs.

[0021] (4) The thin-walled cylindrical fiber optic hydrophone of the present invention has a compact structure, the acoustic diffraction unit is firmly connected to the thin-walled cylinder, and it has strong pressure resistance and anti-interference ability, and can adapt to the complex underwater working environment. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly introduced below. The features and advantages of the present invention can be more clearly understood by referring to the accompanying drawings. The accompanying drawings are schematic and should not be construed as limiting the present invention in any way. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a cross-sectional view of the thin-walled cylindrical fiber optic hydrophone of the present invention;

[0024] Figure 2 This is a schematic diagram of the cross-section of the annular porous diffraction grating of the thin-walled cylindrical fiber optic hydrophone of the present invention;

[0025] Figure 3 This is a schematic diagram of the negative Poisson's ratio amplification unit of the thin-walled cylindrical fiber optic hydrophone of the present invention.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1-Sound wave, 2-Thin-walled metal cylinder, 3-Sensing fiber, 4-Conical grating aperture, 5-Negative Poisson's ratio amplification unit. Detailed Implementation

[0028] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0029] A specific embodiment of the present invention, such as Figure 1 As shown, a thin-walled cylindrical fiber optic hydrophone with an internal acoustic diffraction structure is disclosed, including a thin-walled metal cylinder 2, a sensing fiber 3, a fixed end cap, and a diffraction-negative Poisson's ratio composite internal structure.

[0030] Furthermore, the thin-walled metal cylinder 2 adopts a thin-walled elastic structure, with a wall thickness much smaller than the inner diameter, and has high radial acoustic sensitivity. It can generate significant deformation under the action of radial sound waves, thereby causing the sensing optical fiber 3 wound on the outer wall of the thin-walled metal cylinder 2 to generate strain.

[0031] Furthermore, the thin-walled metal cylinder 2 is made of aluminum alloy, titanium alloy or stainless steel, with a wall thickness to inner diameter ratio of ≤1:50, taking into account both structural strength and deformation sensitivity; the inner wall of the cylinder is precision polished, with a surface roughness Ra≤0.2μm, which can adapt to the mechanical transmission of the diffraction-negative Poisson's ratio composite internal structure.

[0032] Furthermore, the sensing fiber 3 is selected as a single-mode sensing fiber or fiber grating, and is uniformly and tightly wound around the outer wall of the corresponding position of the diffraction-negative Poisson's ratio composite internal structure of the thin-walled metal cylinder 2. It is fixed with epoxy resin and is used to convert the radial deformation of the thin-walled metal cylinder into optical phase change, providing a signal carrier for acoustic wave detection. The number of turns of the fiber is set according to the actual detection requirements, usually 20 to 40 turns, to ensure sufficient phase modulation.

[0033] Furthermore, two fixed end caps are provided, which are respectively sealed and fixed to both ends of the thin-walled metal cylinder 2. They are made of waterproof and sound-permeable material, with a through hole in the center to ensure that the axial sound wave 1 can smoothly enter the inner cavity of the thin-walled metal cylinder 2. The function of the fixed end caps is to achieve the sealed support of the thin-walled metal cylinder, ensure the structural rigidity and water tightness of the hydrophone, and at the same time, to position and fix the internal structure of the diffraction-negative Poisson's ratio composite structure.

[0034] Furthermore, the internal structure of the diffraction-negative Poisson's ratio composite consists of acoustic diffraction units and negative Poisson's ratio amplification units 5 connected in series, arranged sequentially along the axial direction of the thin-walled metal cylinder 2. The length of the internal structure of the diffraction-negative Poisson's ratio composite is 20-25 mm. The internal structure of the diffraction-negative Poisson's ratio composite includes two sets of acoustic diffraction units and one set of negative Poisson's ratio amplification units 5. The two sets of acoustic diffraction units are set at both ends of one set of negative Poisson's ratio amplification units 5 along the axial direction of the thin-walled metal cylinder 2.

[0035] Furthermore, such as Figure 1-2As shown, the acoustic diffraction unit is an annular porous diffraction grating, including an annular disk and conical grating holes. The material is polyetheretherketone (PEEK), and the outer diameter is slightly smaller than the inner diameter of the thin-walled metal cylinder 2. An annular acoustic cavity is formed between the outer diameter of the annular disk and the wall of the thin-walled metal cylinder. Combining the inner diameter of the thin-walled metal cylinder and the outer and inner diameters of the annular disk, multiple conical grating holes 4 are evenly distributed along the circumference of the annular disk. Each conical grating hole penetrates the annular disk along the axial direction of the thin-walled metal cylinder 2, forming a circumferentially distributed porous structure. The large-diameter end of the conical grating hole faces the incident end of the acoustic wave 1, which can directionally diffract and split the axially incident acoustic wave 1, filtering out transverse clutter.

[0036] Furthermore, such as Figure 3 As shown, the negative Poisson's ratio amplification unit 5 is located between two sets of acoustic wave diffraction units and is made of polyimide (PI). The negative Poisson's ratio amplification unit 5 is a hollow cylinder, and the cylinder wall is provided with multiple axisymmetrically arranged hexagonal honeycomb grids. When the acoustic wave causes the negative Poisson's ratio amplification unit 5 to undergo axial stretching, the hexagonal honeycomb grids expand laterally outward and push outward against the inner wall of the thin-walled metal cylinder 2. When the acoustic wave causes the negative Poisson's ratio amplification unit 5 to undergo axial compression, the hexagonal honeycomb grids contract laterally inward, the pushing force on the inner wall of the thin-walled metal cylinder is released, and the cylinder wall rebounds inward and resets under its own elasticity. This can convert the axial deformation caused by the acoustic wave pressure into a radial force, so that the deformation amplification factor of the thin-walled metal cylinder 2 can reach 5-8 times.

[0037] Furthermore, the specific structure of the acoustic wave diffraction unit can be selected as follows:

[0038] Annular porous diffraction grating: The annular disk has an outer diameter of 14mm, an inner diameter of 8mm, and a thickness of 2mm. Twelve conical grating holes (large end diameter 2mm, small end diameter 1mm, hole depth 2mm) are evenly distributed along the circumference, which can be adapted to most thin-walled cylindrical sizes.

[0039] Furthermore, the hexagonal honeycomb grid has a side length of 0.8–1.2 mm and a wall thickness of 0.08–0.12 mm. The outer diameter of the negative Poisson ratio amplification unit 5 is consistent with that of the acoustic diffraction unit, and the length is 18–20 mm, ensuring a tight fit with the acoustic diffraction unit and no mechanical transmission loss.

[0040] Furthermore, the diffraction-negative Poisson's ratio composite internal structure is coaxially mounted with the thin-walled metal cylinder. The mounting method can be fixed by pressing with a fixed end cap or by bonding to the inner wall of the cylinder with a special adhesive. The acoustic diffraction unit and the negative Poisson's ratio amplification unit are fixed by laser micro-welding. Preferably, six weld points are evenly distributed around the circumference to ensure the installation is firm and coaxial, and to avoid affecting the acoustic wave conversion effect due to installation deviation.

[0041] The working principle of this invention is as follows: When an axially incident sound wave acts on the fiber optic hydrophone, the sound wave enters the inner cavity of the thin-walled metal cylinder through the central through-hole of the fixed end cap; the axial sound wave entering the inner cavity first acts on the sound wave diffraction unit, and under the guidance, reflection and diffraction of the sound wave diffraction unit, the sound wave propagates to the negative Poisson's ratio amplification unit; the sound wave pressure causes the negative Poisson's ratio unit to generate axial deformation, which is synchronously converted into lateral expansion or contraction deformation through its negative Poisson's ratio characteristics, applying a uniform radial force to the inner wall of the thin-walled metal cylinder, driving the thin-walled metal cylinder to generate radial deformation, and then causing the sensing fiber wound on the outer wall of the thin-walled metal cylinder to generate strain, causing the optical phase of the sensing fiber to change; by demodulating the phase change of the sensing fiber through an external interference optical path (such as a Michelson interference optical path or a Mach-Zehnder interference optical path), a high-sensitivity measurement of the axial sound wave can be achieved.

[0042] When radial incident sound waves act on the fiber optic hydrophone, the thin-walled metal cylinder directly undergoes radial deformation under the action of the radial sound waves, which drives the sensing fiber to produce a phase change, thereby realizing the detection of radial sound waves and maintaining the original advantage of high radial sensitivity.

[0043] Example 1

[0044] This embodiment provides a thin-walled cylindrical fiber optic hydrophone with an internal acoustic diffraction structure, the specific structure of which is as follows:

[0045] (1) Thin-walled metal cylinder: made of aluminum alloy, with an inner diameter of 16mm, a length of 40mm, a wall thickness of 0.2mm, and a wall thickness to inner diameter ratio of 1:80, which meets the requirements of high radial acoustic sensitivity. The inner wall is precision polished and the surface roughness Ra≤0.2μm.

[0046] (2) Sensing fiber: Single-mode sensing fiber is selected and uniformly and tightly wound around the outer wall of the thin-walled metal cylinder. The number of turns is 30, and it is fixed with epoxy glue to ensure that the fiber is tightly attached to the cylinder wall.

[0047] (3) Fixed end caps: Waterproof and sound-permeable material is selected. The two end caps are sealed and fixed at both ends of the thin-walled metal cylinder. A 5mm diameter through hole is opened in the center of the end cap to ensure that the axial sound wave can enter the inner cavity smoothly. The end caps are connected to the cylinder by bolts. A nitrile rubber sealing ring is set on the inner side. The waterproof sealing level reaches IP68.

[0048] (4) Internal structure of the diffraction-negative Poisson's ratio composite: The total length is 22mm, forming a 1mm wide annular acoustic cavity with the inner wall of the cylinder; the annular porous diffraction grating of the acoustic diffraction unit is made of PEEK material, with an outer diameter of 14mm, an inner diameter of 8mm, and a thickness of 2mm, and 12 fan-shaped grating holes are evenly distributed along the circumference (large end diameter 2mm, small end diameter 1mm, hole depth 2mm); the negative Poisson's ratio unit is a hexagonal honeycomb grid made of PI material, with a side length of 1mm, a wall thickness of 0.1mm, an outer diameter of 14mm, and a length of 18mm; the acoustic diffraction unit and the negative Poisson's ratio unit are fixed by laser micro-welding, and the whole is fixed by end cap pressing, with a coaxiality error ≤0.1mm. The assembly steps of the fiber optic hydrophone in this embodiment 1 are as follows:

[0049] First, pretreatment: The inner wall of the thin-walled metal cylinder is polished and cleaned to remove surface impurities and burrs; the apertures of the annular porous diffraction grating are cleaned to ensure unobstructed flow; the honeycomb structure of the negative Poisson's ratio unit is inspected to avoid damage; then, composite structure assembly: The two ends of the negative Poisson's ratio unit are aligned with the annular porous diffraction grating and fixed by laser micro-welding to form a composite module, ensuring that the module axes are aligned; next, composite structure installation: The assembled composite internal structure is placed into the inner cavity of the thin-walled metal cylinder, and the position is adjusted to ensure that the composite structure is coaxial with the cylinder, with an error not exceeding 0.1mm;

[0050] Next, the end caps are fixed: the two fixed end caps are installed at both ends of the cylinder and tightened with bolts. At the same time, the acoustic diffraction structure is tightened to ensure the sealing performance between the end caps and the cylinder and prevent underwater water leakage.

[0051] Then, fiber winding: the single-mode sensing fiber is evenly and tightly wound around the outer wall of the thin-walled metal cylinder at the negative Poisson's ratio unit. During the winding process, the fiber tension is kept uniform. After the winding is completed, the fiber is fixed with epoxy glue. After the epoxy glue has cured, the excess part of the fiber is trimmed.

[0052] Finally, encapsulation and debugging: a waterproof and acoustically transparent layer is encapsulated on the outer wall of the thin-walled metal cylinder and the surface of the optical fiber. Then, the fiber optic hydrophone is connected to the Michelson interferometer optical path for phase demodulation and debugging to ensure that the detection sensitivity of axial and radial sound waves meets the design requirements.

[0053] In this embodiment of the hydrophone, the axially incident sound wave is guided and reflected by the conical diffraction structure and successfully converted into a radially propagating sound wave, driving the thin-walled metal cylinder to produce a significant radial deformation. Compared with the traditional hydrophone without a diffraction structure, the axial sound wave absorption utilization rate is increased by more than 10%, the axial sensitivity is increased by 5dB, the radial sensitivity remains at the original level, and the omnidirectional response uniformity is significantly improved, which can meet the needs of underwater omnidirectional underwater acoustic detection.

[0054] All of the above-mentioned optional technical solutions can be combined in any way to form optional embodiments of the present invention, and will not be described in detail here.

[0055] In the description of this invention, it should be understood that if terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0056] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order and method of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0057] It should be understood that the foregoing only illustrates some embodiments, and changes, modifications, additions, and / or variations can be made without departing from the scope and spirit of the disclosed embodiments. These embodiments are illustrative and not restrictive. Furthermore, the described embodiments relate to those currently considered most practical and preferred, and should be understood as not being limited to the disclosed embodiments, but rather intended to cover different modifications and equivalent arrangements included within the spirit and scope of those embodiments. Moreover, the various embodiments described above can be used in conjunction with other embodiments; for example, an aspect of one embodiment can be combined with an aspect of another embodiment to achieve yet another embodiment. Additionally, individual features or components of any given component can constitute another embodiment.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A thin-walled cylindrical fiber optic hydrophone with an internal acoustic diffraction structure, comprising a thin-walled metal cylinder (2), a sensing fiber (3) wound around the outer wall of the thin-walled metal cylinder (2), and fixed end caps fixed to both ends of the thin-walled metal cylinder (2), characterized in that: The thin-walled metal cylinder (2) has a diffraction-negative Poisson's ratio composite internal structure coaxially arranged inside. The diffraction-negative Poisson's ratio composite internal structure includes two sets of acoustic wave diffraction units and one set of negative Poisson's ratio amplification units (5) arranged in series along the axial direction of the thin-walled metal cylinder (2). The two sets of acoustic diffraction units are arranged at both ends of the negative Poisson's ratio amplification unit (5) along the axial direction of the thin-walled metal cylinder (2); The acoustic wave diffraction unit is an annular porous diffraction grating, which includes an annular disk and multiple conical grating holes (4) penetrating the annular disk. The multiple conical grating holes (4) are evenly distributed along the circumference of the annular disk, and the large diameter end of the conical grating hole (4) faces the incident end of the acoustic wave (1). The negative Poisson ratio amplification unit (5) is a hollow cylinder with multiple axially symmetrically arranged hexagonal honeycomb grids on the cylinder wall.

2. The thin-walled cylindrical fiber optic hydrophone with an internal acoustic diffraction structure according to claim 1, characterized in that, The outer diameter of the annular disk is smaller than the inner diameter of the thin-walled metal cylinder (2) so as to form an annular acoustic cavity between the outer wall of the annular disk and the inner wall of the thin-walled metal cylinder (2).

3. The thin-walled cylindrical fiber optic hydrophone according to claim 1, characterized in that, The fixed end cap is made of waterproof and sound-permeable material, and has a through hole in the center for allowing sound waves (1) to enter the inner cavity of the thin-walled metal cylinder (2) axially.

4. The thin-walled cylindrical fiber optic hydrophone according to claim 1, characterized in that, The sensing fiber (3) is uniformly and tightly wound around the outer wall of the thin-walled metal cylinder (2) at a position corresponding to the internal structure of the diffraction-negative Poisson's ratio composite.

5. The thin-walled cylindrical fiber optic hydrophone according to claim 1, characterized in that, The internal structure of the diffraction-negative Poisson's ratio composite is fixed to the thin-walled metal cylinder (2) by pressing with a fixed end cap or by bonding with an adhesive, and the acoustic diffraction unit and the negative Poisson's ratio amplification unit (5) are fixed by laser micro-welding.

6. The thin-walled cylindrical fiber optic hydrophone according to claim 1, characterized in that, The ratio of the wall thickness to the inner diameter of the thin-walled metal cylinder (2) is ≤1:50; the surface roughness Ra of the inner wall of the thin-walled metal cylinder (2) is ≤0.2μm.

7. The thin-walled cylindrical fiber optic hydrophone according to claim 1, characterized in that, The acoustic diffraction unit is made of polyetheretherketone; the negative Poisson's ratio amplification unit (5) is made of polyimide.

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