Asymmetric differential-cantilever beam composite sensibilization type optical fiber sonic sensor

Abstract

The invention relates to the technical field of partial discharge detection, and provides an asymmetric differential-cantilever beam composite sensibilization type optical fiber sonic sensor, which comprises a protective outer shell, an optical cable protection sleeve; the single-mode optical fiber is arranged in the protective outer shell and the optical cable protective sleeve; the asymmetric differential sensitization structure is arranged at the top of the protective outer shell, the top surface and the bottom surface of the asymmetric differential sensitization structure are both concave inwards, and a cavity is formed in the asymmetric differential sensitization structure; the sound-sensitive diaphragm is arranged on the top surface of the asymmetric differential sensitization structure and is integrated with the top surface of the asymmetric differential sensitization structure, a C-shaped hollow part is designed on the sound-sensitive diaphragm, the sound-sensitive diaphragm is divided to form a rectangular cantilever beam structure, bulges with different widths are designed on two sides of the sound-sensitive diaphragm, and an outer cavity is formed; and the distributed feedback fiber laser is arranged on the single-mode fiber. According to the technical scheme, the asymmetric differential sensitization structure and the rectangular cantilever beam structure are compounded and cooperate with the distributed feedback fiber laser, higher sensitivity is achieved, and the sensitivity is improved by several times to dozens of times.

Description

Technical Field

[0001] The present invention relates to the technical field of partial discharge detection, in particular to an asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor. Background Art

[0002] Transformers are core components of power systems. Deterioration in their insulation is a major cause of failure, and partial discharge (PD) is an early sign of insulation degradation. PD can lead to gradual carbonization of the insulation material and expansion of air gaps, ultimately causing breakdown and threatening the safe operation of the power grid. According to statistics, insulation defects account for over 60% of failures. Therefore, developing highly sensitive, real-time PD detection technology is of great significance.

[0003] Among the related technologies, the main methods for partial discharge detection are pulse current method, gas chromatography method and ultrasonic method. Although the pulse current method has high sensitivity, it is easily affected by electromagnetic interference and requires offline detection, which affects the continuity of power supply. Gas chromatography relies on gas analysis in oil and cannot monitor sudden discharges in real time, nor can it locate faults. The traditional ultrasonic method uses piezoelectric sensors to capture the ultrasonic signals generated by discharges. Although it can achieve non-invasive online detection, it has disadvantages such as low sensitivity, insufficient anti-electromagnetic interference ability, and susceptibility to interference from the strong electromagnetic environment of substations. Fiber optic acoustic wave sensors use optical fibers as sensitive or transmission elements. They have the advantages of being non-charged, strong anti-electromagnetic interference ability, high sensitivity, high temperature resistance, and corrosion resistance. They are gradually being used for partial discharge detection in power systems. Conventional fiber optic acoustic wave sensors generally use circular closed diaphragms as acoustic sensitive structures. Their sensitivity and measurement range need to be improved. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] To this end, the purpose of the present invention is to provide an asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor, in which the asymmetric differential sensitivity-enhancing structure is compounded with the rectangular cantilever beam structure and coordinated with the distributed feedback optical fiber laser to achieve higher sensitivity, with the sensitivity increased by several to dozens of times.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the present invention provides an asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor, comprising: a protective outer shell; an optical cable protection sleeve installed at the bottom of the protective outer shell; a single-mode optical fiber installed inside the protective outer shell and the optical cable protection sleeve, and one end of the optical fiber extends from the optical cable protection sleeve, and an adhesive fixing point is provided in the optical cable protection sleeve to fix the single-mode optical fiber; an asymmetric differential sensitivity-enhancing structure, which is provided on the top of the protective outer shell, and the top and bottom surfaces of the asymmetric differential sensitivity-enhancing structure are both concave inwards, forming a cavity inside; and an acoustically sensitive diaphragm, which is provided on the asymmetric differential sensitivity-enhancing structure. The top surface of the differential sensitivity enhancement structure is called the top surface, and is integrated with the top surface of the asymmetric differential sensitivity enhancement structure. As a part of the top surface, a C-shaped hollow is designed on the acoustically sensitive diaphragm, which is divided into a rectangular cantilever beam structure and a micro-through hole is opened. The micro-through hole is located at the geometric center position of the top surface of the asymmetric differential sensitivity enhancement structure when viewed from above. The top surfaces of the asymmetric differential sensitivity enhancement structures on both sides of the acoustically sensitive diaphragm are designed with protrusions of different widths to form an external cavity; a distributed feedback fiber laser is arranged on the single-mode optical fiber, one end of which passes through the micro-through hole on the acoustically sensitive diaphragm, is sintered into a sphere above the micro-through hole, and the other end is connected to the single-mode optical fiber.

[0007] Preferably, the width of the gap of the C-shaped hollow is 0.1 mm-0.7 mm; and the diameter of the micro through hole is 0.2 mm.

[0008] Preferably, according to the selected acoustic diaphragm material, the length, width and thickness of the rectangular cantilever beam structure are adjusted according to a formula model to achieve sensor sensitivity adjustment in different frequency bands. The formula model includes:

[0009]

[0010] in, f 1 represents the first-order resonance frequency of the rectangular cantilever beam structure; E Characterized by the Young's modulus of the acoustically sensitive diaphragm material; I Characterized as the moment of inertia in the cross-sectional direction of the rectangular cantilever beam structure; A Characterized by the cross-sectional area of the rectangular cantilever beam structure; ρ Characterized by the density of the sound-sensitive diaphragm material; a Characterized as the length from the fixed end to the micro-through hole in the rectangular cantilever beam structure; h Characterized as the thickness of the rectangular cantilever beam structure; W Characterized by the deflection of the micro-through hole in the rectangular cantilever beam structure; P Characterized by sound pressure value; S Characterized by sound pressure sensitivity; b Characterized by the width of the rectangular cantilever beam structure.

[0011] Preferably, the sensitivity enhancement factor is adjusted by adjusting the inclined surface structure from the outer edge of the asymmetric differential sensitivity enhancement structure to the outer edge of the middle protrusion, wherein the inclined surface structure is decomposed and the length perpendicular to the center line is n , the length along the center line is m , the sensitivity enhancement factor is n / m .

[0012] Preferably, the asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor further comprises: a quartz sleeve A, which is arranged inside the protective outer shell, and the top of the quartz sleeve A is connected to the connecting portion under the bottom surface of the asymmetric differential sensitivity-enhancing structure, the connecting portion under the bottom surface of the asymmetric differential sensitivity-enhancing structure is inserted into the interior of the protective outer shell and the narrower part of its end is inserted into the interior of the quartz sleeve A, and the bottom surface of the quartz sleeve A is spaced apart from the inner bottom surface of the protective outer shell; a quartz sleeve B, which is arranged inside the quartz sleeve A, and its bottom surface is flush with the bottom surface of the quartz sleeve A; and a quartz sleeve C, which is arranged inside the quartz sleeve B, and its top and bottom surfaces are both flush with the quartz sleeve B.

[0013] Preferably, a cavity is formed between the quartz sleeve A and the protective outer shell, the length of the cavity is 8-13 mm, and the single-mode optical fiber portion in the cavity is in a slightly bent free state.

[0014] Preferably, the protective outer shell is cylindrical, and its inner diameter is transitionally matched with the outer diameter of the quartz sleeve A, and epoxy glue is filled between the two for fixed sealing. The sealing end of the protective outer shell is provided with a threaded through hole matching the outer diameter of the optical cable protection sleeve, so as to fix the optical cable protection sleeve through an optical cable fixing buckle.

[0015] Preferably, the quartz sleeve A and the quartz sleeve B, and the quartz sleeve B and the quartz sleeve C are transitionally matched, and high-temperature melting point a and high-temperature melting point b are sequentially formed by high-temperature sintering; The top of the quartz sleeve C is provided with a circular hole with a diameter of 0.4-0.5 mm, and the bottom is provided with a tapered hole. The single-mode optical fiber passes through the circular hole and the tapered hole. The circular hole and the tapered hole are filled with epoxy glue to seal and fix the single-mode optical fiber.

[0016] Preferably, a preload force of 0.3-0.5N is applied to the distributed feedback fiber laser, and the long-term stability and effectiveness of the preload force are ensured by the sphere and the tapered hole; The material of the distributed feedback fiber laser is quartz, and its thermal expansion is the same as that of the quartz sleeve A at the same length and different temperatures, which is 5.5×10 -7 °C -1 .

[0017] Preferably, the cavity formed by the quartz sleeve A, the quartz sleeve B, and the quartz sleeve C is connected to the cavity formed inside the asymmetric differential sensitivity enhancement structure, and together form an inner cavity; The inner cavity and the outer cavity are connected through the C-shaped hollowing; The asymmetric differential sensitivity enhancement structure has a rectangular or cylindrical shape.

[0018] The asymmetric differential-cantilever beam composite enhanced sensitivity optical fiber acoustic wave sensor proposed in the present invention has the following beneficial technical effects: (1) The asymmetric differential-cantilever beam composite enhanced-sensitivity optical fiber acoustic wave sensor proposed in the present invention has the characteristics of high sensitivity, anti-electromagnetic interference, and real-time monitoring, and can be used for partial discharge detection of transformers in power systems.

[0019] (2) The asymmetric differential-cantilever beam composite enhanced sensitivity optical fiber acoustic wave sensor proposed in the present invention can monitor acoustic wave signals from the audible range to the ultrasonic frequency band. Compared with ordinary acoustic sensitive diaphragms of equivalent size, its sensitivity can be increased by several to dozens of times.

[0020] (3) The asymmetric differential-cantilever beam composite enhanced sensitivity optical fiber acoustic wave sensor proposed in the present invention can realize different sensitivities in different frequency bands according to the design and control of different parameters of the rectangular cantilever beam structure, and has high flexibility. When the working frequency band is in the ultrasonic frequency band (>20kHz), the diaphragm thickness is h When the diameter is greater than 0.5 mm, the sensitivity of the present invention can be improved by an order of magnitude compared with the pure circular acoustic diaphragm sensor.

[0021] (4) The asymmetric differential-cantilever beam composite enhanced-sensitivity optical fiber acoustic wave sensor proposed in the present invention can produce three-part deformation when in an external sound pressure environment, thereby increasing the deformation coefficient and increasing the sensitivity by several to dozens of times. The sensitivity enhancement factor can be adjusted by designing the inclined surface structure of the asymmetric differential enhanced-sensitivity structure.

[0022] (5) In the asymmetric differential-cantilever beam composite enhanced sensitivity fiber acoustic wave sensor proposed by the present invention, the quartz sleeve A, quartz sleeve B, and quartz sleeve C are transitionally matched and high-temperature welded. There is no additional material between the three. Through the glue-free packaging, the fixation is more sealed and reliable, which is conducive to ensuring the long-term stability of the preload force of the distributed feedback fiber laser.

[0023] (6) In the asymmetric differential-cantilever beam composite enhanced sensitivity fiber acoustic wave sensor proposed in the present invention, the single-mode optical fiber is sealed and fixed by filling the circular hole and the tapered hole with epoxy glue. The sphere at one end of the distributed feedback fiber laser and the tapered hole of the quartz sleeve C can further ensure the long-term stability and effectiveness of the preload force.

[0024] (7) The material of the distributed feedback fiber laser in the asymmetric differential-cantilever beam composite enhanced sensitivity fiber acoustic wave sensor proposed by the present invention is quartz, and the thermal expansion amount is the same as that of the quartz sleeve A at the same length and different temperatures, which can greatly reduce the temperature sensitivity of the sensor.

[0025] (8) The C-shaped hollow structure design of the acoustic sensitive diaphragm in the asymmetric differential-cantilever beam composite enhanced sensitivity optical fiber acoustic wave sensor proposed in the present invention can achieve conduction between the inner cavity and the outer cavity, thereby effectively avoiding the additional axial deformation of the distributed feedback optical fiber laser caused by the expansion and contraction of the gas due to temperature changes, further ensuring the detection accuracy.

[0026] (9) In the asymmetric differential-cantilever beam composite enhanced sensitivity optical fiber acoustic wave sensor proposed by the present invention, a cavity is formed between the quartz sleeve A and the protective outer shell. The length of the cavity is 8-13 mm. The single-mode optical fiber portion in the cavity is in a slightly bent free state, thereby further reducing the effects of shrinkage and straightening caused by temperature changes.

[0027] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which: Figure 1 A schematic structural diagram of an asymmetric differential-cantilever beam composite enhanced-sensitivity optical fiber acoustic wave sensor according to an embodiment of the present invention is shown; Figure 2 Shown Figure 1 Schematic diagram of the enlarged structure at point Ⅰ; Figure 3 Shown Figure 1 The schematic diagram of the enlarged structure from top view corresponding to position Ⅰ in the middle; Figure 4 Shown Figure 1 Schematic diagram of the enlarged structure at point II; Figure 5 The figure shows a schematic diagram of the principle of an asymmetric differential sensitivity enhancement structure in an asymmetric differential-cantilever beam composite sensitivity enhancement type optical fiber acoustic wave sensor according to an embodiment of the present invention. in, Figures 1 to 5 The corresponding relationship between the reference numerals and components is as follows: 102 Protective outer shell, 104 Optical cable protective sleeve, 106 Single-mode optical fiber, 108 Adhesive fixing point, 110 Asymmetric differential sensitivity enhancement structure, 1102 Inclined surface structure, 1104 Connector, 112 Acoustic diaphragm, 1122 C-shaped hollow, 1124 Rectangular cantilever beam structure, 1126 Micro-through hole, 114 External cavity, 116 Distributed feedback fiber laser, 118 Sphere, 120 Quartz sleeve A, 122 Quartz sleeve B, 124 Quartz sleeve C, 1242 Circular hole, 1244 Conical hole, 126 Cavity, 128 High-temperature fusion point a , 130 high temperature welding point b , 132 inner cavity, 134 equivalent circular acoustic diaphragm outer diameter, 136 epoxy adhesive. DETAILED DESCRIPTION

[0029] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0030] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0031] The following combination Figures 1 to 5 An asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor according to an embodiment of the present invention is described in detail.

[0032] like Figures 1 to 5As shown, an asymmetric differential-cantilever beam composite enhanced-sensitivity fiber acoustic wave sensor according to an embodiment of the present invention includes: a protective outer shell 102, an optical cable protection tube 104, a single-mode optical fiber 106, an asymmetric differential enhanced-sensitivity structure 110, an acoustically sensitive diaphragm 112, and a distributed feedback fiber laser 116. The optical cable protection tube is mounted at the bottom of the protective outer shell 102. The single-mode optical fiber 106 is mounted within the protective outer shell 102 and the optical cable protection tube 104, with one end extending from the optical cable protection tube 104. An adhesive fixing point 108 is provided within the optical cable protection tube 104 to secure the single-mode optical fiber 106. An asymmetric differential sensitivity enhancement structure 110 is provided on the top of the protective outer shell 102. The top and bottom surfaces of the asymmetric differential sensitivity enhancement structure 110 are both concave inward, forming a cavity inside. A sound-sensitive diaphragm 112 is provided on the top surface of the asymmetric differential sensitivity enhancement structure. The sound-sensitive diaphragm 112 is integrated with the top surface of the asymmetric differential sensitivity enhancement structure 110. As part of the top surface, a C-shaped hollow 1122 is designed on the sound-sensitive diaphragm 112, which is divided into a rectangular cantilever beam structure 1124 and has a micro-through hole 1126. The micro-through hole 1126 is located at the geometric center of the top surface of the asymmetric differential sensitivity enhancement structure when viewed from above. The top surface of the asymmetric differential sensitivity enhancement structure 110 on both sides of the sound-sensitive diaphragm 112 is designed with protrusions of different widths to form an outer cavity 114. Therefore, through the asymmetric differential-cantilever beam composite sensitivity enhancement, it is possible to achieve monitoring of sound wave signals from the audible range to the ultrasonic frequency band. Compared with an ordinary circular sound-sensitive diaphragm of equivalent size, its sensitivity can be increased by several to dozens of times. A distributed feedback fiber laser 116 is mounted on a single-mode optical fiber 106. One end passes through a micro-hole 1126 in the acoustically sensitive diaphragm 112 and is sintered into a sphere 118 above the micro-hole 1126. The other end is connected to the single-mode optical fiber 106. The preload force of the distributed feedback fiber laser 116 is stable and effective over a long period of time. The distributed feedback fiber laser 116 (DFB-FL) is a laser composed of fiber Bragg gratings (FBGs) directly inscribed on an erbium-doped optical fiber. It combines the advantages of FBGs with a very narrow linewidth of several kHz and a length of typically 30-40 mm. When packaged into an acoustic wave sensor using a sensitivity-enhancing structure, it exhibits very high sensitivity. The asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor proposed in this invention features high sensitivity, immunity to electromagnetic interference, and real-time monitoring capabilities, making it suitable for detecting partial discharge in transformers in power systems.

[0033] Further, if Figure 3As shown, the gap width of the C-shaped hollow 1122 is 0.1mm-0.7mm, that is, the gap width is designed to be any value between 0.1mm-0.7mm, which can form a relatively stable and controllable rectangular cantilever beam structure, among which it is better when it is designed to be 0.4mm. The diameter of the micro-through hole 1126 is 0.2mm. Thus, the distributed feedback fiber laser 116 can be accommodated so that it can pass through the micro-through hole 1126 and sintered into a sphere 118 above it, realizing the application of preload and long-term stable maintenance. At the same time, the rectangular cantilever beam structure 1124 is formed, and the rectangular cantilever beam structure 1124 is stable and controllable.

[0034] Furthermore, based on the selected acoustic diaphragm material, the length, width, and thickness of the rectangular cantilever beam structure 1124 are adjusted according to the formula model to achieve sensor sensitivity adjustment in different frequency bands. The formula model includes:

[0035]

[0036] in, f 1 represents the first-order resonance frequency of the rectangular cantilever beam structure 1124; E Characterized by the Young's modulus of the material of the acoustically sensitive diaphragm 112; I Characterized as the moment of inertia in the cross-sectional direction of the rectangular cantilever beam structure 1124; A Characterized by the cross-sectional area of a rectangular cantilever beam structure 1124; ρ Characterized by the density of the material of the acoustically sensitive diaphragm 112; a Characterized as the length from the fixed end to the micro-through hole in the rectangular cantilever beam structure; h Characterized as the thickness of the rectangular cantilever beam structure 1124; W Characterized as the deflection at the micro-through hole 1126 of the rectangular cantilever beam structure 1124; P Characterized by sound pressure value; S Characterized by sound pressure sensitivity; b Characterized as the width of the rectangular cantilever beam structure 1124.

[0037] The operating frequency of the asymmetric differential-cantilever beam composite enhanced sensitivity optical fiber acoustic wave sensor proposed by the present invention does not exceed the first-order resonance frequency of the acoustic sensitive diaphragm 112. f 1. When the material thickness of the acoustically sensitive diaphragm is selected, the length, width, and thickness of the rectangular cantilever beam structure 1124 can be adjusted by design, and the sensitivity of the sensor can be adjusted under different frequency bands according to the formula model, thereby making the sensor more widely applicable.

[0038] Conventional circular acoustic diaphragm, one end of the DFB-FL is fixed to the center of the circular acoustic diaphragm 112, and the other end is fixed to another substrate. At the same time, the DFB-FL is prestressed with 0.3-0.5N along the axial direction. When the circular acoustic diaphragm 112 receives the sound pressure P, it deforms, causing the DFB-FL to produce axial strain, which causes the wavelength of the DFB-FL to change. The acoustic wave signal is demodulated through the wavelength, intensity and phase demodulation algorithm. S r As shown below:

[0039]

[0040] in, W r is the deflection at the center of the circular sound-sensitive diaphragm; P is the sound pressure value; μ is the Poisson's ratio of the sound-sensitive diaphragm material; r is the effective radius of the circular sound-sensitive diaphragm.

[0041] like Figure 3 As shown, the length from the fixed end to the micro-through hole in the rectangular cantilever beam structure 1124 in the acoustic diaphragm 112 of the present invention is a Effective radius compared to conventional circular acoustic diaphragm (equivalent circular acoustic diaphragm outer diameter 134) r When they are equal, the sensitivity comparison between the two is as follows:

[0042] When the diaphragm is made of stainless steel, its Poisson's ratio μ Take 0.4, the width of the rectangular cantilever beam structure is 1124 b ,thickness h When both are set to 0.5mm, the sound pressure sensitivity of the sensor using the rectangular cantilever beam structure 1124 sound sensitive diaphragm 112 is about 20 times that of the sensor using the circular sound sensitive diaphragm 112. When the working frequency band of the sensor is in the ultrasonic frequency band (>20kHz), h When the pressure difference is greater than 0.5 mm, the acoustic pressure sensitivity of the sensor using the rectangular cantilever beam structure 1124 acoustic sensitive diaphragm 112 is two orders of magnitude higher than that of the sensor using the circular acoustic sensitive diaphragm 112. This shows that the sensitivity of the asymmetric differential-cantilever beam composite enhanced sensitivity optical fiber acoustic wave sensor proposed in the present invention has been greatly improved.

[0043] Further, if Figure 5As shown, by adjusting the outer edge of the asymmetric differential sensitivity enhancement structure 110 to the inclined surface structure 1102 at the outer edge of the middle protrusion, the sensitivity enhancement multiple is adjusted, wherein the inclined surface structure 1102 is decomposed, and the length perpendicular to the center line is n , the length along the center line is m , the sensitivity enhancement factor is n / m .

[0044] Specifically, through the asymmetric differential-cantilever beam composite, when in an external sound pressure environment, not only the upper and lower surfaces are deformed by the sound pressure, which significantly improves the sensitivity, but the sides are also deformed by the sound pressure, which significantly increases the deformation coefficient. The total sensitivity can be increased by several times to dozens of times. The sensitivity enhancement principle of the asymmetric differential sensitivity enhancement structure 110 is as follows: When it is in an external sound pressure environment, it will produce three parts of deformation. First, the side of the asymmetric differential sensitivity enhancement structure 110 is subjected to sound pressure. Due to the concave structure design of the upper and lower surfaces, the distance between the upper and lower surfaces is reduced, the pre-tension of the DFB-FL is reduced, and the wavelength of the emitted laser is reduced. The deformation coefficient is calculated as follows: K 1 ,like Figure 1 and Figure 5 As shown, the original length of the inclined surface structure 1102 from the outer edge of the asymmetric differential sensitivity enhancement structure 110 to the outer edge of the middle protrusion is L , decompose it, and the length perpendicular to the center line is n , the length along the center line is m , then L can be expressed as L= , where n>m. When the side is subjected to sound pressure P, the structure deforms. Let the deformation length perpendicular to the centerline be Δn, and the deformation length along the centerline be Δm. The length of the oblique structure remains unchanged, still L. In this case, L can be expressed as: , simplifying the above two formulas, we can get: Since n>m, the deformation Δn perpendicular to the axis is magnified to a deformation length Δm along the centerline direction, and the magnification factor is n / m. If n=10m, the deformation is magnified 10 times, and the sensor sensitivity is increased 10 times. Second, when the upper and lower surfaces of the asymmetric differential sensitivity enhancement structure 110 are subjected to sound pressure P, the distance between the upper and lower bottom surfaces decreases, the pre-tension of the DFB-FL decreases, and the wavelength of its emitted laser decreases. The deformation coefficient is calculated as follows: K 2. This part is similar to the case of using a conventional circular acoustic diaphragm 112. Third, when the upper and lower surfaces of the asymmetric differential sensitivity enhancement structure 110 are subjected to sound pressure P, the rectangular cantilever beam structure 1124 of the acoustic diaphragm 112 is deformed, the pre-tension of the DFB-FL is reduced, and the wavelength of the emitted laser is reduced. The deformation coefficient is calculated as K 3It can be seen that the asymmetric differential-cantilever beam composite enhanced sensitivity optical fiber acoustic wave sensor proposed in the present invention increases the deformation coefficient compared with the conventional circular acoustic sensitive diaphragm 112 sensor. K 1 、K 3 ， The overall sensitivity can be increased several to dozens of times.

[0045] Further, if Figure 1 and Figure 4 As shown, the asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor also includes: a quartz sleeve A120, which is arranged inside the protective outer shell 102, and the top of the quartz sleeve A120 is connected to the connecting portion 1104 under the bottom surface of the asymmetric differential sensitivity-enhancing structure 110, the connecting portion 1104 under the bottom surface of the asymmetric differential sensitivity-enhancing structure 110 is inserted into the interior of the protective outer shell 102 and the narrower part of its end is inserted into the interior of the quartz sleeve A120, and the bottom surface of the quartz sleeve A120 is spaced apart from the inner bottom surface of the protective outer shell 102; a quartz sleeve B122, which is arranged inside the quartz sleeve A120, and its bottom surface is flush with the bottom surface of the quartz sleeve A120; a quartz sleeve C124, which is arranged inside the quartz sleeve B122, and its top and bottom surfaces are both flush with the quartz sleeve B122.

[0046] A cavity 126 is formed between the quartz sleeve A120 and the protective outer shell 102. The length of cavity 126 is 8-13 mm. Any cavity length between 8 and 13 mm allows the portion of single-mode optical fiber 106 within cavity 126 to be slightly bend-free, with a length of 10 mm being particularly effective. This further reduces the effects of temperature fluctuations, such as stretching and straightening.

[0047] Further, if Figure 1 and Figure 4 As shown, the protective outer shell 102 is cylindrical, and its inner diameter is transitionally matched with the outer diameter of the quartz sleeve A120, and epoxy glue 136 is filled between the two for fixed sealing. The sealed end of the protective outer shell 102 is provided with a threaded through hole that matches the outer diameter of the optical cable protection sleeve 104 so as to fix the optical cable protection sleeve 104 through an optical cable fixing buckle.

[0048] The quartz sleeve A120 and the quartz sleeve B122, as well as the quartz sleeve B122 and the quartz sleeve C124 are transitionally matched, and a high-temperature melting point a128 and a high-temperature melting point b130 are sequentially formed by high-temperature sintering; A circular hole 1242 with a diameter of 0.4-0.5 mm, preferably 0.5 mm, is provided at the top of the quartz sleeve C124, and a tapered hole 1244 is provided at the bottom. The single-mode optical fiber 106 passes through the circular hole 1242 and the tapered hole 1244. The circular hole 1242 and the tapered hole 1244 are filled with epoxy glue 136 to seal and fix the single-mode optical fiber 106.

[0049] This achieves a transitional fit and high-temperature fusion bonding between quartz sleeve A120, quartz sleeve B122, and quartz sleeve C124, without the need for additional materials. The glue-free packaging provides a more reliable seal, facilitating the long-term stability of the preload force of distributed feedback fiber laser 116. Epoxy glue 136 is filled into circular hole 1242 and tapered hole 1244 to seal and secure single-mode fiber 106. The ball 118 at one end of distributed feedback fiber laser 116 and the tapered hole 1244 of quartz sleeve C124 further ensure the long-term stability and effectiveness of the preload force.

[0050] Furthermore, a preload force of 0.3-0.5 N is applied to the distributed feedback fiber laser 116 , preferably 0.4 N, and the long-term stability and effectiveness of the preload force are ensured by the sphere 118 and the tapered hole 1244 ; The material of the distributed feedback fiber laser 116 is quartz, and its thermal expansion is the same as that of the quartz sleeve A120 at the same length and different temperatures, which is 5.5×10 -7 °C -1 .

[0051] Thereby, the temperature sensitivity of the sensor can be greatly reduced.

[0052] Further, if Figures 1 to 3 As shown, the cavity formed by the quartz sleeve A120, the quartz sleeve B122, and the quartz sleeve C124 is connected to the cavity formed inside the asymmetric differential sensitivity enhancement structure 110, and together form an inner cavity 132; the inner cavity 132 and the outer cavity 114 are connected through the C-shaped hollow 1122; the outer shape of the asymmetric differential sensitivity enhancement structure 110 is a rectangular parallelepiped or a cylindrical shape.

[0053] Therefore, by connecting the inner cavity 132 and the outer cavity 114 , additional axial deformation of the distributed feedback fiber laser 116 caused by the expansion and contraction of the gas due to temperature changes can be effectively avoided, further ensuring the detection accuracy.

[0054] In the present invention, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "plurality" refers to two or more, unless expressly limited otherwise. Terms such as "installed," "connected," "connected," and "fixed" should be interpreted broadly. For example, "connected" can mean a fixed connection, a detachable connection, or an integral connection; "connected" can mean a direct connection or an indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0055] In the description of the present invention, it should be understood that the directions or positional relationships indicated by terms such as "up", "down", "left", "right", "front" and "back" are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0056] Throughout this specification, terms such as "one embodiment," "some embodiments," and "specific embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0057] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor, characterized in that: include: Protective outer shell; An optical cable protection sleeve installed at the bottom of the protective outer shell; a single-mode optical fiber installed inside the protective outer shell and the optical cable protection sleeve, with one end of the single-mode optical fiber extending from the optical cable protection sleeve, and an adhesive fixing point is provided in the optical cable protection sleeve to fix the single-mode optical fiber; an asymmetric differential sensitivity enhancement structure is provided on the top of the protective outer shell, and the top and bottom surfaces of the asymmetric differential sensitivity enhancement structure are both concave inward, forming a cavity inside; The acoustically sensitive diaphragm is arranged on the top surface of the asymmetric differential sensitivity enhancement structure and is integrated with the top surface of the asymmetric differential sensitivity enhancement structure. As part of the top surface, the acoustically sensitive diaphragm is designed with a C-shaped hollow, which is divided into a rectangular cantilever beam structure and has a micro-through hole. The micro-through hole is located at the geometric center position of the top surface of the asymmetric differential sensitivity enhancement structure when viewed from above. The top surfaces of the asymmetric differential sensitivity enhancement structures on both sides of the acoustically sensitive diaphragm are designed with protrusions of different widths to form an outer cavity. A distributed feedback fiber laser is arranged on the single-mode optical fiber, one end of which passes through the micro-through hole on the acoustically sensitive diaphragm and is sintered into a sphere above the micro-through hole, and the other end of which is connected to the single-mode optical fiber.

2. The asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor according to claim 1, characterized in that: The width of the gap of the C-shaped hollowing is 0.1mm-0.7mm; the diameter of the micro through hole is 0.2mm.

3. The asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor according to claim 2, characterized in that: According to the selected acoustic diaphragm material, the length, width and thickness of the rectangular cantilever beam structure are adjusted according to the formula model to achieve sensor sensitivity adjustment in different frequency bands. The formula model includes: in, f 1 represents the first-order resonance frequency of the rectangular cantilever beam structure; E Characterized by the Young's modulus of the acoustically sensitive diaphragm material; I Characterized as the moment of inertia in the cross-sectional direction of the rectangular cantilever beam structure; A Characterized by the cross-sectional area of the rectangular cantilever beam structure; ρ Characterized by the density of the sound-sensitive diaphragm material; a Characterized as the length from the fixed end to the micro-through hole in the rectangular cantilever beam structure; h Characterized as the thickness of the rectangular cantilever beam structure; W Characterized by the deflection of the micro-through hole in the rectangular cantilever beam structure; P Characterized by sound pressure value; S Characterized by sound pressure sensitivity; b Characterized by the width of the rectangular cantilever beam structure.

4. The asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor according to claim 3, characterized in that: The sensitivity enhancement factor is adjusted by adjusting the inclined surface structure from the outer edge of the asymmetric differential sensitivity enhancement structure to the outer edge of the middle protrusion, wherein the inclined surface structure is decomposed and the length perpendicular to the center line is n , the length along the center line is m , the sensitivity enhancement factor is n / m .

5. The asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor according to claim 4, characterized in that: Also includes: A quartz sleeve A is arranged inside the protective outer shell, and the top of the quartz sleeve A is connected to the connecting portion under the bottom surface of the asymmetric differential sensitivity enhancement structure, the connecting portion under the bottom surface of the asymmetric differential sensitivity enhancement structure is inserted into the interior of the protective outer shell, and the narrower portion of its end is inserted into the interior of the quartz sleeve A, and the bottom surface of the quartz sleeve A is spaced apart from the inner bottom surface of the protective outer shell; The quartz sleeve B is arranged inside the quartz sleeve A, and its bottom surface is flush with the bottom surface of the quartz sleeve A; The quartz sleeve C is arranged inside the quartz sleeve B, and its top surface and bottom surface are flush with the quartz sleeve B.

6. The asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor according to claim 5, characterized in that: A cavity is formed between the quartz sleeve A and the protective outer shell. The length of the cavity is 8-13 mm, and the single-mode optical fiber portion in the cavity is in a slightly bent free state.

7. The asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor according to claim 5, characterized in that: The protective outer shell is cylindrical, and its inner diameter is transitionally matched with the outer diameter of the quartz sleeve A, and epoxy glue is filled between the two for fixed sealing. The sealing end of the protective outer shell is provided with a threaded through hole matching the outer diameter of the optical cable protection sleeve, so as to fix the optical cable protection sleeve through an optical cable fixing buckle.

8. The asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor according to claim 5, characterized in that: The quartz sleeve A and the quartz sleeve B, and the quartz sleeve B and the quartz sleeve C are transitionally matched, and high-temperature welding points are formed in sequence by high-temperature sintering. a and high temperature welding point b ; The top of the quartz sleeve C is provided with a circular hole with a diameter of 0.4-0.5 mm, and the bottom is provided with a tapered hole. The single-mode optical fiber passes through the circular hole and the tapered hole. The circular hole and the tapered hole are filled with epoxy glue to seal and fix the single-mode optical fiber.

9. The asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor according to claim 8, characterized in that: A preload force of 0.3-0.5N is applied to the distributed feedback fiber laser, and the long-term stability and effectiveness of the preload force are ensured by the sphere and the tapered hole; The material of the distributed feedback fiber laser is quartz, and its thermal expansion is the same as that of the quartz sleeve A at the same length and different temperatures, which is 5.5×10 -7 °C -1 .

10. The asymmetric differential-cantilever beam composite sensitivity-enhanced optical fiber acoustic wave sensor according to claim 9, characterized in that: The cavity formed by the quartz sleeve A, the quartz sleeve B, and the quartz sleeve C is connected to the cavity formed inside the asymmetric differential sensitivity enhancement structure, and together form an inner cavity; The inner cavity and the outer cavity are connected through the C-shaped hollowing; The asymmetric differential sensitivity enhancement structure has a rectangular or cylindrical shape.

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