Dual cavity isolated optical hydrophone

Abstract

The application provides a double-cavity isolated optical hydrophone, which comprises an optical interference module, a spatial optical 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 inside 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 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; the matching cavity faces the external water environment and can couple external underwater acoustic signals; one side of the diaphragm assembly is in contact with the water medium of the external water environment. By adopting the double-cavity packaging structure that the optical interference region is physically isolated from the underwater sensing film region, the application effectively solves the problem that the interference cavity in the traditional optical hydrophone cannot be filled and sealed, it is difficult to maintain the stability of the optical path, and the membrane surface needs to be directly in contact with the water body and the acoustic impedance matching cannot be achieved.

Description

Technical Field

[0001] This invention relates to the field of fiber optic measurement technology, and more specifically, to a dual-cavity isolated optical hydrophone. Background Technology

[0002] An optical hydrophone is a device that uses optical principles to detect underwater sound waves. It measures sound signals by converting them into light signals, offering advantages such as high sensitivity and resistance to electromagnetic interference. The working principle of an optical hydrophone is based on the acousto-optic effect, where underwater sound wave vibrations modulate certain characteristics of light signals (such as phase, intensity, or wavelength) to achieve sound signal detection. Its core is to convert changes in sound pressure into measurable changes in light signals through optical sensing technology.

[0003] Reference 1, Team of Zhang Guojun, North University of China: Liu Mengran, Jian Zeming, Zhang Guojun & Zhang Wendong. Design of MEMS bionic hydrophone based on nitrile rubber cap encapsulation. Journal of Sensor Technology, 21-25 (2014). Although this reference has significant effects on 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 dry environment.

[0004] Reference 2, patent document with publication number CN109397617B, discloses a method for encapsulating a fiber optic hydrophone using an integrally potted sound-transmitting material. However, while this patent document enhances structural stability and watertightness through potting, the potting material is prone to causing moisture, scattering, and reflection interference after it enters the optical path, leading to degradation or even failure of the interference signal.

[0005] The aforementioned existing technologies fail to meet the structural requirements of synergistic effect between "sound transmission performance" and "optical interference cavity sealing", and are particularly unsuitable for packaging scenarios of thin-film optical hydrophones. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a dual-cavity isolated optical hydrophone.

[0007] A dual-cavity isolated optical hydrophone according to the present invention includes: an optical interference module, a spatial optical path system, a waterproof tilting window, a diaphragm assembly, and an encapsulation layer;

[0008] The waterproof tilted window is disposed within the encapsulation layer, and the interior of the encapsulation layer is divided into a matching cavity and a protective cavity that are isolated from each other;

[0009] The optical interference module and the spatial optical path system are disposed within the encapsulation layer and located in the matching cavity; the diaphragm assembly is disposed within the encapsulation layer and located in the protective cavity;

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

[0011] Preferably, the laser 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 reflects back to the optical interference module, forming an interference signal with the reference light to extract the vibration information of the diaphragm assembly caused by underwater acoustics.

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

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

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

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

[0018] Preferably, the diaphragm assembly is a metal film or a microstructure thin film processed using MEMS technology;

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

[0020] Preferably, the spatial optical path system can modulate the diverging beam into a focused or collimated state, irradiate the center of the diaphragm assembly, and guide 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, or a microlens array.

[0022] Preferably, the waterproof tilted window enables light path transparency and suppresses the formation of Fabry-Perot type multiple interference.

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

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

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

[0026] 1. This 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, it enables the diaphragm to be 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. This invention effectively solves the problems in traditional optical hydrophones where the interference cavity cannot be encapsulated, it is difficult to maintain the stability of the optical path, and the membrane surface needs to be in direct contact with the water body to achieve acoustic impedance matching. By adopting a dual-cavity encapsulation structure that physically isolates the optical interference region and the underwater sensing membrane region, this invention effectively solves the problems of the interference cavity not being able to be encapsulated, the optical path not being able to be maintained, and the membrane surface not being able to be in direct contact with the water body.

[0028] 3. This invention achieves photoacoustic decoupling through a tilted optical window, ensuring long-term stability of the interference signal while realizing efficient coupling of the underwater acoustic signal to the diaphragm, significantly improving the sensor's sensitivity, reliability, and applicability in low-frequency environments. Attached Figure Description

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

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

[0031] Figure 2 This is a schematic diagram of the optical interference module.

[0032] Figure 3 A schematic diagram illustrating the principle of matching cavity sound transmission;

[0033] Figure 4 This is a schematic diagram of the dual-cavity isolated optical hydrophone in Embodiment 1;

[0034] Figure 5 This is a schematic diagram of the dual-cavity isolated optical hydrophone in Example 2;

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

[0036] The diagram shows:

[0037] Detailed Implementation

[0038] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0039] Example 1

[0040] like Figures 1 to 3 As shown, this embodiment provides a dual-cavity isolated optical hydrophone, including: an optical interference module 1, a spatial optical path system 2, a waterproof tilted window 3, a diaphragm assembly 4, and an encapsulation layer 5. The waterproof tilted window 3 is disposed within the encapsulation layer 5, dividing the interior of the encapsulation layer 5 into a mutually isolated matching cavity 501 and a protective cavity 502; the optical interference module 1 and the spatial optical path system 2 are disposed within the encapsulation layer 5 and located in the matching cavity 501; the diaphragm assembly 4 is disposed within the encapsulation layer 5 and located in 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 is in contact with the water medium of the external water environment.

[0041] The matching cavity 501 is filled with a first medium, the acoustic impedance of which matches the acoustic impedance of the external water environment medium; the protective cavity 502 is filled with a second medium, which can keep the optical interference module 1 and the optical path dry and stable. The first medium is any one of the following: water, salt water; the second medium is any one of the following: air, inert gas, electrically insulating liquid.

[0042] The laser emitted by the light source 101 of the optical interference module 1 is divided into a reference light 102 and a 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 to extract the vibration information of the diaphragm assembly 4 caused by water sound.

[0043] The diaphragm assembly 4 is a metal film or a microstructure film processed using MEMS technology; the side of the diaphragm assembly 4 closest to the external water environment is in contact with the water medium, and the side of the diaphragm assembly 4 closest to the waterproof tilted window 3 is coated with reflective material.

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

[0045] Example 2

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

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

[0048] The optical interference module 1 can be in the form of a fiber optic interferometer or an on-chip optical waveguide interferometer, etc. Both utilize the interference principle of the path difference between the reference light and the measurement light to detect minute displacements of the diaphragm. Figure 2 As shown. The laser emitted by the light source 101 is divided into a reference light 102 and a measurement light 103. The reference light 102 propagates inside 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 reflects back to the optical interference module 1 to form an interference signal with the reference light 102, thereby extracting the vibration information of the diaphragm assembly 4 caused by underwater acoustics.

[0049] The output end of the measuring light 103 is equipped with a spatial optical path system 2 to improve beam coupling efficiency. The spatial optical path system 2 may include a pair of plano-convex lenses, collimating focusing lenses or microlens arrays to modulate the diverging beam into a focused or collimated state, accurately illuminating the center of the diaphragm assembly 4, while efficiently guiding the reflected light back to the spatial optical path system 2.

[0050] A waterproof tilted window 3 is set 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) to achieve optical path transparency while suppressing the formation of Fabry-Perot type multiple interference and maintaining the stability of the interference signal.

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

[0052] The waterproof tilted window 3 divides the interior of the encapsulation layer 5 into two functional areas: a matching cavity and a protective 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 medium 1, including water, salt water, etc., which matches the acoustic impedance with the external water environment medium 2, thereby achieving efficient sound wave penetration. The principle is as follows: Figure 3 As shown.

[0055] The protective cavity 502 can be filled with a medium 3, including air, inert gas, or electrically insulating liquid, to maintain the dryness and stability of the optical path. Preferably, a spatial optical path system can be further integrated into the protective cavity, 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 microstructure thin film processed by MEMS technology. Its front side is in direct contact with the water medium, and its back side (the side facing the light path) is coated with a highly reflective material (such as silver) to improve the intensity of the reflected light signal.

[0057] This embodiment proposes a packaging method suitable for optical hydrophones, which 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, it allows the diaphragm to be 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.

[0058] This embodiment effectively solves the problems in traditional optical hydrophones where the interference cavity cannot be encapsulated, it is difficult to maintain the stability of the optical path, and it is difficult to balance the need for the membrane surface to directly contact the water body and achieve acoustic impedance matching by adopting a dual-cavity encapsulation structure that physically isolates the optical interference region and the underwater sensing membrane region.

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

[0060] Example 3

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

[0062] like Figure 4 As shown, in this embodiment, a fiber optic Mach-Zehnder interferometer is used. The measuring arm light is guided to the spatial optical path system via optical fiber and a circulator, and the light is focused onto the surface of the diaphragm in the water using a double plano-convex lens. 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 is 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 split 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, then exits the photodetector 7 and enters the oscilloscope 6. The measurement light is reflected by the diaphragm assembly 6 and passes through a circulator 11 and enters the 3×3 coupler 8, then exits the 3×3 coupler 8 and enters the photodetector 7, then exits the photodetector 7 and enters the oscilloscope 6.

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

[0066] Example 4

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

[0068] like Figure 5 As shown, in this embodiment, an on-chip interferometer structure is adopted, encapsulating the interferometer module and the spatial optical path system together in a protective cavity. Measurement light is output from the chip, focused onto the diaphragm in water by a focusing lens system, and the reflected light is received by the optical path within the chip to complete the interferometric detection. This structure is more compact and suitable for applications requiring small size and high integration. The matching cavity is filled with saline solution, 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, an optical fiber coupler 13, a photodetector 7, and an optical waveguide chip 16.

[0070] The optical waveguide chip 16 has 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. The light emitted by the laser diode 9 reaches one of the on-chip 1×2 couplers 14 through a fiber optic coupler 13. The other on-chip 1×2 coupler 14 and the collimating lens 11 transmit light through a fiber optic coupler 13. The photodetector 7 is connected to the on-chip 4×4 coupler 15 through four fiber optic couplers 13.

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

[0072] Example 5

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

[0074] As shown in Figure 6, the Mach-Zehnder interferometer in Embodiments 3 and 4 can also be replaced with a Fabry-Perot interferometer, or with an interferometer containing laser stabilization control, or with an interferometer where the light source and detector are all integrated on-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] The light emitted by the laser diode 9 enters the circulator 11 after passing through the isolator 18. A portion of the light emitted by the circulator 11 enters the photodetector 7, and the light emitted from the photodetector 7 enters the oscilloscope 6. Another portion of the light emitted by the circulator 11 exits, reaches the diaphragm assembly 4 and is reflected. The circulator 11 receives the reflected light, and the light emitted from the circulator 11 enters the 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. Light emitted from the laser diode 9 passes through the 1×2 coupler 10, with a portion entering the 3×3 coupler 8 and the other portion exiting through the circulator 11 to the diaphragm assembly 4. Light entering the 3×3 coupler 8 exits and enters the photodetector 7, then exits from the photodetector 7 and enters the oscilloscope 6. Light exiting the diaphragm assembly 4 is reflected and enters the 3×3 coupler 8 through the circulator 11, then exits from the 3×3 coupler 8 and enters the photodetector 7, and finally 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 an optical fiber coupler 13. The optical waveguide chip 16 is equipped with an on-chip laser 20, two on-chip 1×2 couplers 14, one on-chip 4×4 coupler 15, and an on-chip photodetector 21. The two on-chip 1×2 couplers 14 are connected together, 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. Light emitted from the on-chip laser 20 reaches one on-chip 1×2 coupler 14, and the other on-chip 1×2 coupler 14 transmits light through the optical fiber coupler 13.

[0079] This invention effectively solves the problems in traditional optical hydrophones where the interference cavity cannot be encapsulated, it is difficult to maintain the stability of the optical path, and the membrane surface needs to be in direct contact with the water to achieve acoustic impedance matching. By adopting a dual-cavity encapsulation structure that physically isolates the optical interference region from the underwater sensing membrane region, this invention effectively solves the problems of the interference cavity not being able to be encapsulated, the optical path not being able to be maintained, and the membrane surface needing to be in direct contact with the water to achieve acoustic impedance matching.

[0080] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., 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 application 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 limitations on this application.

[0081] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

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 encapsulation layer (5); The waterproof tilted window (3) is disposed inside the encapsulation layer (5) and divides the interior of the encapsulation layer (5) into a matching cavity (501) and a protective cavity (502) that 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 in the protective cavity (502); the diaphragm assembly (4) is disposed within the encapsulation layer (5) and located in the matching cavity (501); The matching cavity (501) faces the external water environment and can couple external underwater acoustic signals; one side of the diaphragm assembly (4) is in contact with the water medium of the external water environment; The matching cavity (501) is filled with a first medium, and the acoustic impedance of the first medium is matched with the acoustic impedance of the external water environment medium. The protective cavity (502) is filled with a second medium, which can keep the optical interference module (1) and the optical path dry and stable; The diaphragm assembly (4) is a metal film or a microstructure thin film processed using MEMS technology; The side of the diaphragm assembly (4) closest to the external water environment is in contact with the water medium, and the side of the diaphragm assembly (4) closest to the waterproof tilted window (3) is coated with a reflective material. The waterproof tilted window (3) enables light path transparency and suppresses the formation of Fabry-Perot type multiple interference.

2. The dual-cavity isolated optical hydrophone according to claim 1, characterized in that, 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 measuring light (103) is emitted through the spatial optical path system (2), irradiates the surface of the diaphragm assembly (4), and then reflects back to the optical interference module (1), forming an interference signal with the reference light (102) to extract the 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 first medium is any one of the following: water, salt water; The second medium is any one of the following: air, inert gas, or electrically insulating liquid.

4. The dual-cavity isolated optical hydrophone according to claim 1, characterized in that, The spatial optical path system (2) can modulate the diverging beam into a focused or collimated state, irradiate the center of the diaphragm assembly (4), and guide the reflected light back to the spatial optical path system (2).

5. The dual-cavity isolated optical hydrophone according to claim 4, characterized in that, The spatial optical path system (2) can be any of the following: a pair of plano-convex lenses, a collimating focusing lens, or a microlens array.

6. The dual-cavity isolated optical hydrophone according to claim 1, characterized in that, The waterproof tilting window (3) is made of quartz or optical glass.

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

Images