Double-cavity isolated optical hydrophone

Abstract

The invention provides a double-cavity isolated optical hydrophone. The double-cavity isolated optical hydrophone comprises an optical interference module, a spatial light path system, a waterproof inclined window, a diaphragm assembly and a packaging layer, the waterproof inclined window is arranged in the packaging layer and divides the interior of the packaging layer into a matching cavity and a protection cavity which are isolated from each other; the optical interference module and the spatial light path system are arranged in the packaging layer and are positioned in the matching cavity; the vibrating diaphragm assembly is arranged in the packaging layer and is located in the protection cavity; the matching cavity faces an external water environment and can be coupled with an external underwater sound signal; and one surface of the vibrating diaphragm assembly is in contact with a water medium in an external water environment. By adopting a double-cavity packaging structure in which the optical interference area is physically isolated from the underwater sensing film area, the problems that an interference cavity in a traditional optical hydrophone cannot be encapsulated, the stability of an optical path is difficult to maintain, the interference cavity needs to directly touch a water body with a film surface, and acoustic impedance matching is difficult to consider are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber measurement, and in particular to a dual-cavity isolated optical hydrophone. Background Art

[0002] An optical hydrophone is a device that uses optics to detect underwater sound waves. It converts acoustic signals into optical signals for measurement, offering advantages such as high sensitivity and resistance to electromagnetic interference. The operating principle of an optical hydrophone is based on the acousto-optic effect, whereby underwater sound wave vibrations modulate certain characteristics of the optical signal (such as phase, intensity, or wavelength) to detect the acoustic signal. Its core principle is to convert changes in sound pressure into measurable changes in the optical signal through optical sensing technology.

[0003] Reference 1, Zhang Guojun's team from North University of China: Liu Mengran, Jian Zeming, Zhang Guojun & Zhang Wendong. Design of a MEMS bionic hydrophone based on nitrile rubber cap packaging. Journal of Sensor Technology, 21-25 (2014). Although this reference is effective in improving the acoustic impedance matching and low-frequency sensitivity of MEMS chips, it is only applicable to electrical signal acquisition structures and cannot meet the requirements of optical interferometry for optical cavity stability and a dry environment.

[0004] Document 2, patent publication number CN109397617B, discloses a packaging method for fiber-optic hydrophones using an integrally encapsulated acoustically transparent material. While this patent enhances structural stability and watertightness through encapsulation, the inclusion of the encapsulating material in the optical path can easily cause moisture, scattering, and reflection interference, leading to degradation or even failure of the interference signal.

[0005] The above-mentioned existing technologies fail to take into account the structural coordination requirements of "acoustic transparency" and "optical interference cavity closure", and are particularly difficult to apply to the packaging scenarios of thin-film optical hydrophones. Summary of the Invention

[0006] In view of the defects in the prior art, an object of the present invention is to provide a dual-cavity isolated optical hydrophone.

[0007] According to the present invention, a dual-cavity isolated optical hydrophone is provided, comprising: an optical interference module, a spatial optical path system, a waterproof tilt window, a diaphragm assembly, and a packaging layer;

[0008] The waterproof inclined window is arranged in the packaging layer, and divides the interior of the packaging layer into a matching cavity and a protection cavity that are isolated from each other;

[0009] The optical interference module and the spatial optical path system are arranged in the packaging layer and located in the matching cavity; the diaphragm assembly is arranged in the packaging layer and located in the protection cavity;

[0010] The matching cavity faces the external water environment and is capable of coupling external water acoustic signals; one side of the diaphragm assembly is in contact with the water medium of the external water environment.

[0011] Preferably, the laser light emitted by the light source of the optical interference module is divided into reference light and measurement light;

[0012] The reference light propagates inside the optical interference module;

[0013] The measuring light is emitted through the spatial optical path system, irradiates the surface of the diaphragm assembly, and then returns to the optical interference module after reflection, forming an interference signal with the reference light to extract the vibration information of the diaphragm assembly caused by the underwater sound.

[0014] Preferably, the matching cavity is filled with a first medium, and the acoustic impedance of the first medium matches the acoustic impedance of the external water environment medium;

[0015] The protection cavity is filled with a second medium, and the second medium can keep the optical interference module and the optical path dry and stable.

[0016] Preferably, the first medium is any one of the following: water, saline;

[0017] The second medium is any one of the following: air, inert gas, and electrical insulating liquid.

[0018] Preferably, the diaphragm assembly is a metal film or a microstructured film processed by MEMS technology;

[0019] The side of the diaphragm assembly close to the external water environment is in contact with the water medium, and the side of the diaphragm assembly close to the waterproof tilt window is coated with a reflective material.

[0020] Preferably, the spatial optical path system is capable of modulating the divergent light beam into a focused or collimated state, irradiating the center of the diaphragm assembly, and guiding the reflected light back to the spatial optical path system.

[0021] Preferably, the spatial optical path system is any one of the following: a pair of plano-convex lenses, a collimating focusing lens, and a micro lens array.

[0022] Preferably, the waterproof inclined window can achieve a transparent light path and suppress the formation of Fabry-Perot type multiple interference.

[0023] Preferably, the waterproof tilted window is made of quartz or optical glass.

[0024] Preferably, the encapsulation layer is polyurethane or silicone rubber.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention provides an optical hydrophone that achieves physical isolation between the optical interference path and the underwater sensing diaphragm through a dual-cavity structure. While ensuring the stability of the optical cavity, the diaphragm is directly coupled to the water environment, effectively solving the acoustic impedance mismatch problem caused by traditional cavity structures, and significantly improving low-frequency response performance and overall structural reliability.

[0027] 2. The present invention adopts a dual-cavity packaging structure that physically isolates the optical interference area from the underwater sensing membrane area. This effectively solves the problems in traditional optical hydrophones, such as the inability to seal the interference cavity and maintain optical path stability, and the difficulty in balancing the need for the membrane surface to directly contact the water body and achieve acoustic impedance matching.

[0028] 3. The present invention realizes photoacoustic decoupling by tilting the optical window, which ensures the long-term stability of the interference signal while achieving efficient coupling of the underwater acoustic signal to the diaphragm, significantly improving the sensitivity, reliability and applicability of the sensor in low-frequency environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0030] Figure 1 This is a schematic diagram of the structural principle of a dual-cavity isolated optical hydrophone;

[0031] Figure 2 Schematic diagram of the principle of the optical interference module;

[0032] Figure 3 Schematic diagram of the principle of matching cavity sound transmission;

[0033] Figure 4 Schematic diagram of the structure of the dual-cavity isolated optical hydrophone in Example 1;

[0034] Figure 5 Schematic diagram of the structure of the dual-cavity isolated optical hydrophone in Example 2;

[0035] Figure 6A 、 6B 6C is a schematic structural diagram of the dual-cavity isolated optical hydrophone in Example 3.

[0036] The figure shows:

[0037] DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0039] Example 1

[0040] like Figures 1 to 3 As shown, this embodiment provides a dual-cavity isolated optical hydrophone, comprising: an optical interference module 1, a spatial optical path system 2, a waterproof tilt window 3, a diaphragm assembly 4, and an encapsulation layer 5. The waterproof tilt window 3 is disposed within the encapsulation layer 5, dividing the interior of the encapsulation layer 5 into a matching cavity 501 and a protective cavity 502, which are isolated from each other. The optical interference module 1 and the spatial optical path system 2 are disposed within the encapsulation layer 5 and located within the matching cavity 501. The diaphragm assembly 4 is disposed within the encapsulation layer 5 and located within the protective cavity 502. The matching cavity 501 faces the external water environment and is capable of coupling external underwater acoustic signals. One side of the diaphragm assembly 4 contacts the aqueous medium of the external water environment.

[0041] Matching cavity 501 is filled with a first medium whose acoustic impedance matches that of the external aqueous environment. Protective cavity 502 is filled with a second medium that maintains the dryness and stability of optical interference module 1 and the optical path. The first medium can be any of the following: water or salt water; the second medium can be any of the following: air, an inert gas, or an electrically insulating liquid.

[0042] The laser emitted by the light source 101 of the optical interference module 1 is divided into reference light 102 and measurement light 103; the reference light 102 propagates inside the optical interference module 1; the measurement light 103 is emitted through the spatial optical path system 2, irradiates the surface of the diaphragm assembly 4, and then returns to the optical interference module 1 after reflection, forming an interference signal with the reference light 102, and extracting the vibration information of the diaphragm assembly 4 caused by the underwater sound.

[0043] The diaphragm assembly 4 is a metal film or a microstructured film processed by MEMS technology; the side of the diaphragm assembly 4 close to the external water environment is in contact with the water medium, and the side of the diaphragm assembly 4 close to the waterproof tilt window 3 is plated with a reflective material.

[0044] Spatial optical system 2 modulates the divergent light beam into a focused or collimated state, irradiating it to the center of diaphragm assembly 4 and guiding the reflected light back to spatial optical system 2. Spatial optical system 2 can be any of the following: a pair of plano-convex lenses, a collimating focusing lens, or a microlens array. Waterproof tilted window 3 ensures optical transparency and suppresses the formation of Fabry-Perot-type multiple interference. Waterproof tilted window 3 is made of quartz or optical glass. Encapsulation layer 5 is made of polyurethane or silicone rubber.

[0045] Example 2

[0046] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1.

[0047] This embodiment proposes a dual-cavity isolated optical hydrophone packaging structure, which aims to achieve high-sensitivity, wide-bandwidth, and structurally stable underwater acoustic detection. It mainly includes an optical interference module 1, a spatial optical path system 2, a waterproof tilt window 3, a diaphragm assembly 4, and a packaging layer 5. Figure 1 shown.

[0048] The optical interference module 1 can be a fiber interferometer or an on-chip optical waveguide interferometer, etc., which can detect the micro displacement of the diaphragm through the interference principle of the reference light and the measurement light path difference. Figure 2 As shown in the figure, the laser light emitted by the light source 101 is divided into reference light 102 and measurement light 103. The reference light 102 propagates within the interference module, while the measurement light 103 is emitted through the spatial optical path system 2, irradiates the surface of the diaphragm assembly 4, and then returns to the optical interference module 1 through reflection, forming an interference signal with the reference light 102, thereby extracting the vibration information of the diaphragm assembly 4 caused by the underwater sound.

[0049] The output end of the measuring light 103 is provided with a spatial optical path system 2 for improving the light beam coupling efficiency, wherein the spatial optical path system 2 may include a pair of plano-convex lenses, a collimating focusing lens or a micro-lens array for modulating the divergent light beam into a focused or collimated state, accurately irradiating the center of the diaphragm assembly 4, and at the same time efficiently guiding the reflected light back to the spatial optical path system 2.

[0050] A waterproof tilted window 3 is provided between the diaphragm assembly 4 and the optical interference module 1. The window is made of a high optical transmittance material (such as quartz or optical glass) and is used to achieve optical transparency while suppressing the formation of Fabry-Perot type multiple interference and maintaining the stability of the interference signal.

[0051] The above components are supported and covered by the encapsulation layer 5. The material of the encapsulation layer 5 is preferably an elastic material with an acoustic impedance close to that of water, such as polyurethane or silicone rubber, to ensure that the sound energy is efficiently transmitted to the membrane surface, while improving the pressure resistance and waterproof performance of the system.

[0052] The waterproof inclined window 3 divides the interior of the packaging layer 5 into two functional areas: a matching cavity and a protection cavity.

[0053] The matching cavity 501 is located on the side of the window containing the diaphragm assembly, directly facing the external water environment, and is used to couple external underwater acoustic signals; the protection cavity 502 is located on the optical path side, and is used to keep the optical assembly dry and stable.

[0054] The matching cavity 501 is filled with a medium 1, including water, salt water, etc., which matches the acoustic impedance of the external water environment medium 2, thereby achieving efficient penetration of sound waves. The principle is as follows Figure 3 shown.

[0055] The protective cavity 502 can be filled with a medium 3, including air, an inert gas, or an electrically insulating liquid, to maintain the dryness and stability of the optical path. Preferably, the protective cavity can further integrate a spatial optical path system, or the spatial optical path system and the optical interference module can be packaged together to improve structural compactness and environmental adaptability.

[0056] The diaphragm assembly 4 is located in the matching cavity. The diaphragm assembly 4 is preferably a metal film or a microstructured film processed using MEMS technology. Its front side is in direct contact with the water medium, and the back side (facing the light path) is coated with a highly reflective material (such as silver) to increase the intensity of the reflected light signal.

[0057] This embodiment proposes a packaging method for an optical hydrophone, using a dual-cavity structure to physically isolate the optical interference path from the underwater sensing diaphragm. While maintaining the stability of the optical cavity, the diaphragm is directly coupled to the water environment, effectively resolving the acoustic impedance mismatch associated with traditional cavity structures and significantly improving low-frequency response and overall structural reliability.

[0058] This embodiment adopts a dual-cavity packaging structure that physically isolates the optical interference area from the underwater sensing membrane area. This effectively solves the problems in traditional optical hydrophones where the interference cavity cannot be sealed, making it difficult to maintain optical path stability, while the membrane surface needs to directly contact the water body and achieve acoustic impedance matching.

[0059] This embodiment achieves photoacoustic decoupling by tilting the optical window, ensuring the long-term stability of the interference signal while achieving efficient coupling of the underwater acoustic signal to the diaphragm, significantly improving the sensitivity, reliability and applicability of the sensor in low-frequency environments.

[0060] Example 3

[0061] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1.

[0062] like Figure 4 As shown, this embodiment employs a fiber-optic Mach-Zehnder interferometer. The measuring arm light is guided to the spatial optical path system via an optical fiber and a circulator. A biplano-convex lens focuses the light onto the surface of the diaphragm in the water. The matching cavity on one side of the waterproof window is filled with pure water to match the acoustic impedance of the lake water; the protective cavity on the other side is filled with air. The optical interferometer module is located outside the sensing cavity and connected to the optical path system via optical fiber.

[0063] In this embodiment, the optical interference module 1 includes an oscilloscope 6 , a photodetector 7 , a 3×3 coupler 8 , a laser diode 9 , a 1×2 coupler 10 and a circulator 11 .

[0064] The light emitted by the laser diode 9 is divided into reference light and measurement light by a 1×2 coupler 10. The reference light passes through a 3×3 coupler 8 and enters the photodetector 7. After exiting the photodetector 7, it enters the oscilloscope 6. The measurement light is reflected by the diaphragm assembly 6, passes through a circulator 11, enters the 3×3 coupler 8, exits the 3×3 coupler 8, enters the photodetector 7, and then enters the oscilloscope 6.

[0065] In this embodiment, the material of the encapsulation layer 5 is polyurethane, the first medium is pure water, the second medium is air, and the spatial optical path system 2 is a focusing lens group 12.

[0066] Example 4

[0067] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1.

[0068] like Figure 5 As shown, this embodiment employs an on-chip interferometer structure, encapsulating the interference module and spatial optical system within a protective cavity. Measurement light is output from the chip and focused by a focusing lens system onto the underwater diaphragm. The reflected light is then received by the on-chip optical circuit for interferometric detection. This more compact structure is suitable for applications requiring small size and high integration. The matching cavity is filled with saline, while the protective cavity is preferably filled with fluorinated liquid, achieving both electrical insulation and pressure resistance.

[0069] In this embodiment, the optical interference module 1 includes a laser diode 9 , a fiber coupler 13 , a photodetector 7 , and an optical waveguide chip 16 .

[0070] Optical waveguide chip 16 is equipped with two on-chip 1×2 couplers 14 and one on-chip 4×4 coupler 15. The two on-chip 1×2 couplers 14 are connected to each other, and both on-chip 1×2 couplers 14 are connected to the on-chip 4×4 coupler 15. Light emitted by laser diode 9 reaches one on-chip 1×2 coupler 14 through a fiber coupler 13. Light is then transmitted between the other on-chip 1×2 coupler 14 and collimating lens 11 via a fiber coupler 13. Photodetector 7 is connected to the on-chip 4×4 coupler 15 via four fiber couplers 13.

[0071] In this embodiment, the material of the encapsulation layer 5 is polyurethane, the first medium is salt water, the second medium is fluorinated liquid, and the spatial optical path system 2 is a collimating lens 12.

[0072] Example 5

[0073] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1.

[0074] As shown in FIG6 , the Mach-Zehnder interferometers in Examples 3 and 4 may be replaced with Fabry-Perot interferometers, or with interferometers with laser stabilization control, or with interferometers with both the light source and the detector integrated on a chip.

[0075] In this embodiment, the optical interference module 1 includes an oscilloscope 6 , a photodetector 7 , a circulator 11 , a laser diode 9 and an isolator 18 .

[0076] Light from laser diode 9 passes through isolator 18 and enters circulator 11. A portion of the light from circulator 11 enters photodetector 7, and the light emitted from photodetector 7 enters oscilloscope 6. Another portion of the light from circulator 11 exits, reaches diaphragm assembly 4, and is reflected. Circulator 11 receives the reflected light, and the light emitted from circulator 11 enters oscilloscope 6.

[0077] In other embodiments, the optical interference module 1 may further include: an oscilloscope 6, a photodetector 7, a feedback control unit 19, a 3×3 coupler 8, a circulator 11, a 1×2 coupler 10, and a laser diode 9. The light emitted by the laser diode 9 passes through the 1×2 coupler 10, with part of the light entering the 3×3 coupler 8, and the other part exiting through the circulator 11 to the diaphragm assembly 4. The light entering the 3×3 coupler 8 enters the photodetector 7 after exiting, and then enters the oscilloscope 6 after exiting from the photodetector 7. The light exiting the diaphragm assembly 4 enters the 3×3 coupler 8 after reflection through the circulator 11, then exits from the 3×3 coupler 8 and enters the photodetector 7, and then exits from the photodetector 7 and enters the oscilloscope 6. The light exiting the diaphragm assembly 4 enters the 3×3 coupler 8 after reflection through the circulator 11, then exits from the 3×3 coupler 8 and enters the photodetector 7, and then exits from the photodetector 7 and enters the oscilloscope 6.

[0078] In other embodiments, the optical interference module 1 may further include: an optical waveguide chip 16 and a fiber coupler 13. The optical waveguide chip 16 is provided with an on-chip laser 20, two on-chip 1×2 couplers 14, an on-chip 4×4 coupler 15, and an on-chip photodetector 21. The two on-chip 1×2 couplers 14 are connected to each other, and both on-chip 1×2 couplers 14 are connected to the on-chip 4×4 coupler 15. The on-chip 4×4 coupler 15 is connected to the on-chip photodetector 21. The light emitted by the on-chip laser 20 reaches one on-chip 1×2 coupler 14, and the other on-chip 1×2 coupler 14 transmits the light through the fiber coupler 13.

[0079] The present invention adopts a dual-cavity packaging structure that physically isolates the optical interference area from the underwater sensing membrane area, effectively solving the problems in traditional optical hydrophones, such as the inability to seal the interference cavity and maintain optical path stability, and the difficulty in balancing the need for the membrane surface to directly contact the water body and achieve acoustic impedance matching.

[0080] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply 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 on this application.

[0081] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A dual-cavity isolated optical hydrophone, characterized in that: include: Optical interference module (1), spatial optical path system (2), waterproof tilt window (3), diaphragm assembly (4) and packaging layer (5); The waterproof inclined window (3) is arranged in the packaging layer (5), and divides the interior of the packaging layer (5) into a matching cavity (501) and a protection cavity (502) that are isolated from each other; The optical interference module (1) and the spatial optical path system (2) are arranged in the packaging layer (5) and located in the matching cavity (501); the diaphragm assembly (4) is arranged in the packaging layer (5) and located in the protection cavity (502); The matching cavity (501) faces the external water environment and is capable of coupling external water acoustic signals; one side of the diaphragm assembly (4) is in contact with the water medium of the external water environment.

2. The dual-cavity isolated optical hydrophone according to claim 1, characterized in that: The laser light emitted by the light source (101) of the optical interference module (1) is divided into reference light (102) and measurement light (103); The reference light (102) propagates inside the optical interference module (1); The measuring light (103) is emitted through the spatial optical path system (2), irradiated onto the surface of the diaphragm assembly (4), and then reflected back to the optical interference module (1), forming an interference signal with the reference light (102), thereby extracting vibration information of the diaphragm assembly (4) caused by underwater sound.

3. The dual-cavity isolated optical hydrophone according to claim 1, characterized in that: The matching cavity (501) is filled with a first medium, the acoustic impedance of the first medium being matched with the acoustic impedance of the external water environment medium; The protective cavity (502) is filled with a second medium, and the second medium is capable of keeping the optical interference module (1) and the optical path dry and stable.

4. The dual-cavity isolated optical hydrophone according to claim 3, characterized in that: The first medium is any one of the following: water, saline; The second medium is any one of the following: air, inert gas, and electrical insulating liquid.

5. The dual-cavity isolated optical hydrophone according to claim 1, characterized in that: The diaphragm assembly (4) is a metal film or a microstructured film processed using a MEMS process; The side of the diaphragm assembly (4) close to the external water environment is in contact with the water medium, and the side of the diaphragm assembly (4) close to the waterproof tilted window (3) is coated with a reflective material.

6. The dual-cavity isolated optical hydrophone according to claim 1, characterized in that: The spatial optical path system (2) is capable of modulating a divergent light beam into a focused or collimated state, irradiating the center of the diaphragm assembly (4), and guiding the reflected light back to the spatial optical path system (2).

7. The dual-cavity isolated optical hydrophone according to claim 6, characterized in that: The spatial optical path system (2) is any one of the following: a pair of plano-convex lenses, a collimating and focusing lens, and a micro lens array.

8. The dual-cavity isolated optical hydrophone according to claim 1, characterized in that: The waterproof inclined window (3) can achieve a transparent light path and suppress the formation of Fabry-Perot type multiple interference.

9. The dual-cavity isolated optical hydrophone according to claim 8, characterized in that: The waterproof tilted window (3) is made of quartz or optical glass.

10. The dual-cavity isolated optical hydrophone according to claim 1, characterized in that: The encapsulation layer (5) is polyurethane or silicone rubber.

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