Optical fiber sound wave positioning instrument
By using small-module field, thin-diameter fibers with sensitive elastomers in deep-sea high-frequency beacon locator, a small-size and high-density fiber acoustic locator array is constructed, which solves the problem of difficult array gain in the prior art. , realizes high sensitivity and precise positioning of the acoustic target signal.
Patent Information
- Application Number
- CN202411436224.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-14
- Publication Date
- 2025-02-14
AI Technical Summary
In existing deep-sea high-frequency beacon positioners, the size of the sensitive device is larger than half the wavelength of the ultrasonic signal, making it difficult to form array gain, resulting in the inability to accurately locate.
A small-scale and dense array of optical fibers with small-module field and thin-diameter optical fibers is used to combine with sensitive elastomers to build a small-sized and dense fiber acoustic wave locator array. The deformation of the optical fibers detects the acoustic wave signals and form an interference pattern to determine the direction and intensity of the acoustic waves.
By building a small-size and high-density acoustic positioner array, high sensitivity and precise positioning of the acoustic target signal is achieved, and the problem of difficulty in forming array gain in the prior art is solved.
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Figure CN119439057A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of underwater target search and positioning, and in particular to a fiber optic acoustic wave locator. Background Art
[0002] With the country's high attention and huge investment in marine development and coastal defense construction, marine economic activities are becoming increasingly frequent. In order to ensure the safety of personnel in maritime activities, deep-sea search and rescue related hydroacoustic positioning technology has ushered in new challenges and development opportunities. Deep-sea search and rescue is the search and positioning of acoustic beacons configured for search and rescue targets in deep sea areas, so as to determine the depth and position of the target under the sea.
[0003] In the related art, the commonly used instrument for searching and locating underwater beacons is a towed sonar locator. For example, the towed sonar locator TPL-25 is widely used in deep-sea searches to locate aircraft wreckage or black boxes. The operating frequency of the underwater beacon is 37.5kHz. When facing a deep sea with a water depth of 6km to 7km, the detector needs to be placed at least 4km underwater to perform effective underwater acoustic detection. Moreover, in order to achieve good pressure resistance and high sound pressure sensitivity, the size of the sensitive devices in the deep-sea high-frequency beacon locator in the related art is generally larger than the half-wavelength of the ultrasonic signal. Large-sized devices are difficult to form an array gain, resulting in an inability to accurately locate. Summary of the invention
[0004] Based on this, it is necessary to provide a fiber optic sonic locator to address the above technical problems, which can construct a small-sized, dense fiber optic sonic locator array to form array gain and improve the sensitivity and accuracy of target signal positioning.
[0005] The present application provides a fiber optic acoustic wave locator, which includes a laser and a photoelectric detector. The fiber optic acoustic wave locator also includes a cabin, a plurality of sensitive units and an interference unit. The cabin forms a accommodating cavity; the sensitive unit is arranged on the surface of the cabin, and the pigtail of the sensitive unit extends into the accommodating cavity; the interference unit is arranged in the accommodating cavity, and the interference unit includes a coupler and a Faraday reflector, the first end of the coupler is coupled to the laser through a transmission optical cable, and is used to receive a first light signal emitted by the laser, the second end of the coupler is coupled to a photodetector through the transmission optical cable, and is used to output a second light signal containing sound wave information, the third end of the coupler is coupled to the Faraday reflector through the pigtail of the sensitive unit to form a sensing arm, and the fourth end of the coupler is coupled to the Faraday reflector to form a reference arm; wherein, each of the sensitive units is arranged at equal intervals on the surface of the cabin with a half wavelength corresponding to the target signal as the array element spacing, and any of the sensitive units includes a sensitive elastomer and a fine optical fiber wound on the sensitive elastomer, and the fine optical fiber is a small mode field and thin diameter optical fiber.
[0006] In one of the embodiments, when the micro-optical fiber is wound on the surface of the sensitive elastomer, the loss of the micro-optical fiber is less than 0.5 dB / km.
[0007] In one of the embodiments, the mode field diameter of the micro-optical fiber is less than or equal to 7 microns, and the fiber bending radius of the micro-optical fiber wound on the surface of the sensitive elastomer is not less than 5 millimeters.
[0008] In one embodiment, a coating layer is disposed on the surface of the fine optical fiber, and an outer diameter of the coating layer is less than or equal to 130 microns.
[0009] In one embodiment, the micro-optical fiber includes a core, a cladding, a carbon layer and a coating layer; the cladding covers the core, the carbon layer is arranged on the periphery of the cladding, and the coating layer is arranged on the periphery of the carbon layer.
[0010] In one embodiment, the coating layer includes an inner coating layer and an outer coating layer.
[0011] In one embodiment, the transmission optical cable has twice the number of optical fibers as the number of sensitive units.
[0012] In one of the embodiments, when the frequency of the target signal is 37.5 kHz, the array element spacing of the sensitive unit is 2 cm.
[0013] In one embodiment, the cabin is made of titanium alloy.
[0014] In one of the embodiments, the fiber optic acoustic wave locator is fully wrapped and watertightly packaged with polyurethane material, and the internal gap of the cabin is filled with the polyurethane material.
[0015] The above-mentioned fiber optic sonic locator constructs a sonic locator array by arranging a plurality of sensitive units on the surface of the cabin at equal intervals with the half wavelength corresponding to the target signal as the array element spacing. The sensitive unit includes a sensitive elastomer and a fine optical fiber wound on the sensitive elastomer. The fine optical fiber is a small mode field and thin diameter optical fiber to construct a small-sized and dense sonic locator array to form an array gain. Furthermore, when the sound wave acts on the sensitive unit, the fine optical fiber on the sensitive elastomer will deform due to the pressure change of the sound wave, thereby causing the phase of the optical signal in the sensing arm to change. This phase change of the optical signal interferes with the optical signal of the reference arm in the interference unit to generate an interference pattern. The interference pattern on each sensitive unit is analyzed to determine the direction and intensity of the sound wave. The spatial gain is improved by high-density arraying of units, thereby improving the sensitivity and accuracy of positioning the acoustic target signal. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 A schematic diagram of the structure of a fiber optic acoustic wave locator provided according to an embodiment of the present application;
[0017] Figure 2 A schematic diagram of the structure of a sensitive unit provided according to an embodiment of the present application;
[0018] Figure 3 A cross-sectional schematic diagram of a sensitive unit provided according to an embodiment of the present application;
[0019] Figure 4 It is a structural schematic diagram of an interference unit provided according to an embodiment of the present application;
[0020] Figure 5 A schematic cross-sectional view of a micro-optical fiber provided according to an embodiment of the present application;
[0021] Figure 6 A schematic cross-sectional view of another fine optical fiber provided according to an embodiment of the present application;
[0022] Figure 7 A cloud diagram of radial displacement of the optical fiber layer of a micro optical fiber under a pressure of 1 MPa provided in an embodiment of the present application;
[0023] Figure 8 A test data chart of the sound pressure sensitivity of 1KHz-40KHz provided in an embodiment of the present application;
[0024] Fig. 9A schematic diagram of setting the hydrostatic pressure resistance boundary conditions for a simulation test of the hydrostatic pressure resistance capability of a cabin provided in an embodiment of the present application;
[0025] Fig.10 Equivalent stress cloud diagram of a titanium alloy structural part provided in an embodiment of the present application;
[0026] Fig.11 This is a cloud diagram of the safety factor of the titanium alloy structural parts provided in the embodiment of the present application.
[0027] Explanation of the reference numerals: 100, fiber optic sonic locator; 11, cabin; 12, sensitive unit; 121, sensitive elastomer; 122, fine optical fiber; 1221, fiber core; 1222, cladding; 1223, carbon layer; 1224, coating; 13, interference unit; 131, coupler; 132, Faraday reflector; 14, transmission optical cable; 15, sensor arm; 16, reference arm. DETAILED DESCRIPTION
[0028] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0029] It should be noted that, in the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way. The terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, "multiple" means two or more.
[0030] An optical fiber acoustic wave locator 100 provided in one embodiment of the present application is as follows Figure 1 As shown, the fiber optic sonic locator 100 includes a laser (not shown in the figure), a photodetector (not shown in the figure), a cabin 11, a plurality of sensitive units 12 and an interference unit 13. The laser is used to generate an optical signal, and the photodetector is used to detect the optical signal modulated by the acoustic wave and convert the optical signal into an electrical signal to analyze the information in the acoustic wave. It should be noted that the laser and the photodetector can also be connected to the fiber optic sonic locator 100 in an external manner.
[0031] The cabin body 11 forms a containing cavity, and the cabin body 11 is used to place and isolate the protection elements.
[0032] The sensitive unit 12 is arranged on the surface of the cabin 11, and the pigtail of the sensitive unit 12 extends into the accommodating cavity. The sensitive unit 12 is used to detect sound waves. Specifically, each sensitive unit 12 is arranged on the surface of the cabin 11 at equal intervals with the half wavelength corresponding to the target signal as the array element spacing to form a sonar array. Figure 2 and Figure 3 As shown, any sensitive unit 12 includes a sensitive elastic body 121 and a fine optical fiber 122 wound on the sensitive elastic body 121. When the sound wave acts on the sensitive elastic body 121, the deformation of the sensitive elastic body 121 will change the length of the fine optical fiber 122, thereby affecting the phase of the optical signal passing through the fine optical fiber 122. The fine optical fiber 122 is a small mode field and thin diameter optical fiber.
[0033] The interference unit 13 is arranged in the accommodating cavity. The interference unit 13 is used to form an interference pattern between the optical signal containing the acoustic wave information and the original optical signal. By analyzing the intensity and phase changes of these interference patterns, the pressure, temperature and other information of the acoustic wave can be analyzed to realize the detection and positioning of the underwater acoustic wave target signal. Figure 1 and Figure 4 As shown, the interference unit 13 includes a coupler 131 and a Faraday reflector 132. The first end of the coupler 131 is coupled to the laser through the transmission optical cable 14, and the first end of the coupler 131 is used to receive the first optical signal emitted by the laser, that is, the original optical signal. The second end of the coupler 131 is coupled to the photodetector through the transmission optical cable 14, and the second end of the coupler 131 is used to output the second optical signal containing the acoustic wave information. The third end of the coupler 131 is coupled to the Faraday reflector 132 through the pigtail of the sensitive unit 12 to form a sensing arm 15, and the fourth end of the coupler 131 is coupled to the Faraday reflector 132 to form a reference arm 16.
[0034] Specifically, the fiber optic acoustic wave locator 100 is usually placed underwater or in an environment where sound waves need to be detected. The first optical signal emitted by the laser is divided into two paths through the first end of the coupler 131, one of which is transmitted in the sensor arm 15. Along its transmission path, the optical signal will be directly affected by the sound wave. When the sound wave acts on the sensitive unit 12, the fine optical fiber 122 on the sensitive elastic body 121 will be deformed due to the pressure change of the sound wave. The pressure change of the sound wave will cause the length, refractive index, etc. of the fine optical fiber 122 to change, thereby causing the phase of the optical signal to change, forming a first signal containing sound wave information. The other optical signal is transmitted in the reference arm 16, which is not modulated by the sound wave to keep the original phase of the optical signal unchanged. The optical signal is defined as the second optical signal as a reference standard during interference. When the first optical signal and the second optical signal return to the coupler 131 and merge, interference is generated to form an interference pattern, thereby generating a second optical signal containing sound wave information. The second end of the coupler 131 outputs the second optical signal to the photodetector. By analyzing the intensity and phase changes of the interference pattern on each sensitive unit 12, the pressure, temperature and other information of the sound wave can be analyzed to realize the detection and positioning of the sound wave target signal.
[0035] According to the above description, the fiber optic sonar locator 100 of this embodiment constructs a sonar array by arranging a plurality of sensitive units 12 at equal intervals on the surface of the cabin 11 with a half wavelength corresponding to the target signal as the array element spacing, and by winding a fine optical fiber 122 of a small mode field and a thin diameter optical fiber on a sensitive elastic body 121 to reduce the size of the sensitive unit 12, thereby constructing a small-sized and dense sonar array to form an array gain, thereby solving the problem that the size of the sensitive device of the deep-sea high-frequency beacon locator in the related art is larger than the half wavelength of the ultrasonic signal and is difficult to form an array. Furthermore, when the sound wave acts on the small-sized sensitive unit 12, the fine optical fiber 122 of the small mode field and thin diameter optical fiber is significantly deformed due to the pressure change of the sound wave, resulting in a significant change in the phase of the optical signal in the sensing arm 15. This phase change of the optical signal interferes with the optical signal of the reference arm 16 in the interference unit 13, generating a clear interference pattern. By analyzing the interference pattern on each sensitive unit 12, the direction and intensity of the sound wave can be determined, and the spatial gain can be improved by high-density arraying of the units, thereby improving the sensitivity and accuracy of locating the target signal of the sound wave.
[0036] In order to make the fiber optic sonic locator 100 have high transmission efficiency and high sensitivity in an underwater environment, in one embodiment, when the fine optical fiber 122 is wound on the surface of the sensitive elastic body 121, the loss of the fine optical fiber 122 is less than 0.5 dB / km (decibel per kilometer).
[0037] Among them, optical fiber loss, also known as optical attenuation, refers to the energy loss of the optical signal during the transmission process of the fine optical fiber 122, measured in decibels per kilometer. When the fine optical fiber 122 is wound on the surface of the sensitive elastic body 121, the loss of the fine optical fiber 122 is less than 0.5dB / km, ensuring that the optical signal emitted from the laser can maintain a high intensity during the process of being transmitted through the fine optical fiber 122 to the sensitive unit 12 and then returning to the photodetector, thereby ensuring the long-distance transmission of the optical signal without significantly reducing the intensity of the optical signal and affecting the detection signal-to-noise ratio, so as to ensure the accuracy and reliability of the detection results, thereby ensuring the detection sensitivity of the optical fiber sonic locator 100 in an underwater environment.
[0038] Furthermore, in one embodiment, the mode field diameter of the fine optical fiber 122 is less than or equal to 7 microns, and the fiber bending radius of the fine optical fiber 122 wound around the surface of the sensitive elastomer 121 is not less than 5 millimeters.
[0039] Among them, the mode field diameter of the fine optical fiber 122 describes the distribution state of the fundamental mode light in the single-mode optical fiber. A small mode field diameter means that the light energy is more concentrated, and the optical fiber bending radius can be reduced without changing the transmission loss, and the optical fiber can be wound with a small bending radius, which helps the optical fiber sonic locator 100 to reduce the size of the sensitive unit while ensuring the detection sensitivity, meet the half-wavelength production of the high-frequency short-wavelength signal sensitive unit, realize half-wavelength array, improve spatial gain, and thus improve detection accuracy.
[0040] In addition, the bending radius of the fine optical fiber 122 refers to the radius of curvature of the curved portion of the optical fiber. A small bending radius will cause excessive loss of light energy in the curved portion. A small mode field diameter (i.e., less than or equal to 7 microns) can maintain the light transmission characteristics inside the fine optical fiber 122 under a matching small bending radius (as small as 5 mm), avoiding signal distortion caused by additional loss due to bending, and enabling the fiber optic acoustic wave locator 100 to work stably in complex or irregular environments.
[0041] In this embodiment, the mode field diameter of the fine optical fiber 122 is set to be less than or equal to 7 microns, and the bending radius of the fine optical fiber 122 wound on the surface of the sensitive elastic body 121 is not less than 5 mm, thereby reducing the overall size of the sensitive unit 12, so as to construct a sonar array with a half-wavelength array element spacing. In addition, the sensitivity of the acoustic wave detection of the sensitive unit 12 can be improved by adjusting the winding length of the fine optical fiber 122.
[0042] In order to reduce the size of the sensitive unit 12 and improve the sensitivity without increasing the transmission loss, in one embodiment, Figure 5 As shown, the surface of the fine optical fiber 122 is provided with a coating layer 1224, and the outer diameter of the coating layer 1224 is less than or equal to 130 microns, which is much smaller than the outer diameter of 250 microns of the conventional optical fiber coating layer.
[0043] The coating layer 1224 is a material coated on the surface of the micro-optical fiber 122. The coating layer 1224 has the function of protecting the micro-optical fiber 122 from physical damage and environmental factors, such as temperature, humidity, and chemical corrosion. In the micro-optical fiber 122, the outer diameter of the coating layer 1224 is less than or equal to 130 microns, which helps to reduce the size of the sensitive unit 12 while maintaining the flexibility and lightness of the optical fiber, so that the micro-optical fiber 122 can be wound and installed on the surface of the sensitive elastic body 121, so as to construct a small-sized sonar locator array.
[0044] In order to improve the stability and durability of the fine optical fiber 122, in one embodiment, as Figure 5 As shown, the fine optical fiber 122 includes a core 1221 , a cladding 1222 , a carbon layer 1223 and a coating layer 1224 . The cladding 1222 covers the core 1221 , the carbon layer 1223 is arranged on the periphery of the cladding 1222 , and the coating layer 1224 is arranged on the periphery of the carbon layer 1223 .
[0045] The core 1221 is the central part of the optical fiber. The core 1221 is used to transmit optical signals. The core 1221 can be made of high-purity silica or other high-refractive index materials. The refractive index of the core 1221 is higher than that of the cladding 1222, which enables the optical signal to be effectively transmitted in the core 1221 through total internal reflection. The cladding 1222 is tightly wrapped around the core 1221. The cladding 1222 is used to form a refractive index difference with the core 1221, and the optical signal is confined to propagate in the core 1221 through the total internal reflection mechanism, preventing the optical signal from leaking to the outside of the fine optical fiber 122. The cladding 1222 can be made of low-refractive-index silicon glass. A carbon layer 1223 is disposed on the periphery of the cladding 1222. The carbon layer 1223 is a high-strength, low-expansion-coefficient material. The carbon layer 1223 can protect the micro-optical fiber 122 from mechanical pressure and environmental factors. The carbon layer 1223 enhances the tensile strength and durability of the micro-optical fiber 122, and improves the thermal stability and corrosion resistance of the micro-optical fiber 122. The outermost layer of the micro-optical fiber 122 is a coating layer 1224. The coating layer 1224 can be made of a polymer material. The coating layer 1224 is disposed on the periphery of the carbon layer 1223 to prevent the micro-optical fiber 122 from being damaged by scratches, compression, etc. The coating layer 1224 also makes the micro-optical fiber 122 easy to handle and install when it is bent and wound. Moreover, the outer diameter of the coating layer 1224 is less than or equal to 130 microns, which improves the flexibility and handleability of the micro-optical fiber 122.
[0046] Further, in one embodiment, if Figure 6 As shown, coating layer 1224 includes inner coating layer 1224a and outer coating layer 1224b.
[0047] Among them, the inner coating layer 1224a provides the first layer of protection for the micro-optical fiber 122. The inner coating layer 1224a can be closely attached to the outer periphery of the cladding 1222 or carbon layer 1223 of the micro-optical fiber 122. The inner coating layer 1224a protects the cladding 1222 or carbon layer 1223 from physical damage and environmental factors, improves the mechanical lightness of the micro-optical fiber 122, and makes the micro-optical fiber 122 more resistant to stretching and compression. The outer coating layer 1224b provides the second layer of protection for the micro-optical fiber 122. The outer coating layer 1224b covers the outside of the inner coating layer 1224a. The outer coating layer 1224b adds additional buffering to the inner coating layer 1224a. The outer coating layer 1224b can provide better thermal stability and resistance to chemical corrosion.
[0048] At the same time, this double-layer coating method can also select different materials according to different application environments, such as special materials such as high temperature resistance and UV resistance, to adapt to specific or complex environmental conditions, providing more comprehensive protection for the micro-optical fiber 122 and improving the stability and durability of the micro-optical fiber 122.
[0049] In one embodiment, the sensitive elastomer 121 adopts an air-backed mandrel structure, which includes a central mandrel, an air cavity around the mandrel, and a sensitive elastic material on the outermost layer. The air cavity can provide a low-rigidity backing, which helps to improve the flexibility and responsiveness of the sensitive elastomer 121. In different sensitive units 12, the sensitive elastomer 121 can be made of different materials, and the inner diameter of the sensitive elastomer 121 can be adjusted, thereby improving the sensitivity and frequency response range of the acoustic wave detection.
[0050] In order to improve the reliability of the optical signal transmission in the fiber optic sonar locator 100 and reduce the loss of the optical signal, in one embodiment, the number of optical fibers in the transmission optical cable 14 is twice that of the plurality of sensitive units 12 .
[0051] Specifically, in the fiber optic sonic locator 100, the function of each sensitive unit 12 is to sense the external sound wave signal and convert it into the change of the light signal to detect the sound wave information. Since the first end of the coupler 131 is coupled to the laser through the transmission optical cable 14, and the second end of the coupler 131 is coupled to the photodetector through the transmission optical cable 14, the transmission optical cable 14 is used to input the first light signal emitted by the laser and output the second light signal containing the sound wave information, therefore, the number of optical fibers of the transmission optical cable 14 is twice the number of the plurality of sensitive units 12, that is, for the fiber optic sonic locator 100 containing one sensitive unit 12, the transmission optical cable 14 of the fiber optic locator contains two optical fibers, one optical fiber is used to transmit the first light signal to the sensitive unit 12, and the other optical fiber is used to transmit the second light signal containing the sound wave information back. Based on this, for the fiber optic sonic locator containing a plurality of sensitive units 12, the number of optical fibers of the transmission optical cable 14 is equal to the plurality multiplied by 2. This bidirectional transmission design ensures the high efficiency and stability of optical signal transmission, improves the transmission efficiency and reliability of the fiber optic acoustic wave locator 100, and reduces the transmission loss of the optical signal.
[0052] In one embodiment, the optical fiber of the transmission optical cable 14 may be any of the above-mentioned fine optical fibers 122 , thereby improving the reliability and stability of the transmission optical cable 14 .
[0053] In order to improve the spatial resolution and accuracy of the fiber optic sonar locator 100, in one embodiment, when the frequency of the target signal is 37.5 kHz, the array element spacing of the sensitive unit 12 is 2 cm.
[0054] Among them, the array element spacing is the distance between adjacent sensitive units 12 in the array, and the array element spacing will affect the resolution and directionality of the fiber optic sonic locator 100. When the frequency of the target signal is a higher 37.5 kHz, the array element spacing uses a smaller 2 cm, which helps to improve the spatial resolution of the fiber optic sonic locator 100. At the same time, under high-frequency signals, the small spacing can capture the spatial changes of the sound wave signal more finely, thereby providing a clearer interference image. Moreover, the compact array element spacing enhances the directionality of the array, allowing the fiber optic sonic locator 100 to more accurately determine the source direction of the sound wave, thereby improving the overall performance and reliability of the fiber optic sonic locator 100.
[0055] In order to improve the performance of the fiber optic sonic locator 100 and adapt to the needs of the complex underwater environment of the deep sea, in one embodiment, the cabin 11 is made of titanium alloy. Among them, titanium alloy has the characteristics of high strength and low density. Titanium alloy has better stability and pressure resistance when subjected to high hydrostatic pressure environment, and the low density of titanium alloy reduces the overall weight of the fiber optic sonic locator 100, which is convenient for deployment and recovery. At the same time, titanium alloy also has excellent corrosion resistance and can resist a variety of corrosive media in seawater, including chlorides, sulfides, etc., which enables the fiber optic sonic locator 100 made of titanium alloy to work stably for a long time in the deep sea environment and is not easily affected by corrosion, thereby extending the service life of the fiber optic sonic locator 100. In addition, the change in material size caused by temperature change may have a negative impact on the sensitivity and accuracy of the fiber optic sonic locator 100. The titanium alloy has a low thermal expansion coefficient and can maintain the dimensional stability of the fiber optic sonic locator 100 at different temperatures. The low thermal expansion coefficient ensures that the fiber optic sonic locator 100 can maintain high accuracy and stability from normal temperature to extreme temperature environment.
[0056] In this embodiment, by using titanium alloy as the material of the cabin 11 of the fiber optic sonic locator 100, not only the mechanical properties and corrosion resistance of the fiber optic sonic locator 100 are improved, but also the stability and reliability of the fiber optic sonic locator 100 in complex marine environments are enhanced, and the efficiency and durability of underwater sound wave detection and positioning are improved.
[0057] In order to improve the pressure resistance and corrosion resistance of the fiber optic sonic locator 100, in one embodiment, the fiber optic sonic locator 100 is fully wrapped in a watertight package with polyurethane material, and the internal gap of the cabin 11 is filled with polyurethane material. Among them, the polyurethane material not only has good waterproof performance, but also can effectively prevent water penetration, which enables the fiber optic sonic locator 100 to work stably in deep water. Moreover, the polyurethane material has good corrosion resistance. In underwater environments, especially in seawater, there are a large number of corrosive media such as salt and other chemicals. Polyurethane can resist the erosion of these corrosive media, thereby extending the service life of the equipment and improving the high sensitivity and stability of the fiber optic sonic locator 100 in underwater environments.
[0058] In order to more clearly illustrate the effect of the above embodiment, the present application provides a detection method for calculating the sound pressure sensitivity of the sensitive unit 12 using a finite element simulation analysis method. Specifically, the sensitive elastic body 121 has a length of 10 mm and a diameter of 8 mm, and a 25-meter fine optical fiber 122 is wound around the sensitive elastic body 121, and the outer diameter of the coating layer 1224 of the fine optical fiber 122 is 130 microns.
[0059] According to the principle of Michelson interference optical path, the calculation formula of sound pressure sensitivity can be expressed as follows:
[0060]
[0061] In the formula, S P represents the sound pressure sensitivity, n represents the refractive index of the fine optical fiber 122, ΔL represents the deformation amount of the fine optical fiber 122, λ represents the wavelength of the optical signal, and ΔP represents the unit sound pressure.
[0062] like Figure 7 As shown, it is a cloud diagram of radial displacement of the fiber layer of the micro-optical fiber 122 under a pressure of 1 MPa. The radial displacement of the fiber layer node of the micro-optical fiber 122 under a pressure of 1 MPa and the elongation of the micro-optical fiber 122 can be calculated. Substituting the parameters into the above formula (1) for simulation calculation, the simulation calculation value of the sound pressure sensitivity can be obtained as -152.54 dB.
[0063] like Figure 8 As shown in the figure, it is a test data chart of the sound pressure sensitivity of 1KHz-40KHz. Among them, the fiber optic sonar locator 100 includes 5 sensitive units 12. In the deep sea area, the sound pressure sensitivity of the fiber optic sonar locator 100 is measured according to Chapter 5 of GB / T3223-1994. It can be seen from the figure that all sound pressure sensitivity data are better than 157.1dB. Among them, Chapter 5 of GB / T3223-1994 is a public document and will not be repeated here.
[0064] Exemplarily, the finite element simulation analysis method is used to conduct a simulation test on the hydrostatic pressure resistance of the cabin 11. The cabin 11 and the cover plate covering the cabin 11 are imported into the ANSYS software as an assembly for simulation. The cabin 11 is made of titanium alloy. The hydrostatic pressure resistance boundary conditions include the setting of the fixed end and the application of the load. The fixed ends are the two end faces of the cabin 11, and a pressure of 46MPa is applied to the entire outer surface (according to GJB23B, 46MPa can meet the use of 4000 meters in the deep sea). Among them, GJB23B is a public document and will not be repeated here. Furthermore, as Fig. 9 As shown in the figure, the hydrostatic pressure resistance boundary condition is set, where the blue surface is the fixed end and the red surface is the applied load. Fig.10 As shown in the figure, it is the equivalent stress cloud diagram of titanium alloy structural parts. The central stress of the cabin and cover is about 570MPa. Fig.11 As shown, it is a cloud diagram of the safety factor of titanium alloy structural parts, and the safety factor of the cabin 11 and the center of the cover plate is about 1.46. From the simulation results, it can be seen that the cabin 11 made of titanium alloy can meet the use of the fiber optic sonic locator 100 under a water pressure of 46MPa.
[0065] Exemplarily, a fiber optic sonic locator array including 8 sensitive units 12 is used as a sample to carry out a 46MPa hydrostatic pressure test. The sample is placed in a water pressure tank for a 12-hour pressure test at 46MPa. After the test, the sample is taken out and it is observed that there is no obvious deformation or damage on the surface of the sample. The optical path loss changes of the 8 sensitive units 12 before and after the test are less than 1.5dB, indicating that the fiber optic sonic locator array can meet the 46MPa pressure requirement. It can be seen that the test results show that the fiber optic sonic locator array formed in this application can achieve small size, high pressure resistance, high frequency response and centimeter-level array, which improves the sensitivity and accuracy of locating acoustic target signals.
[0066] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0067] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.
Claims
1. A fiber optic acoustic wave locator, comprising a laser and a photoelectric detector, characterized in that: The optical fiber acoustic wave locator also includes: A cabin body, wherein the cabin body forms a receiving cavity; A plurality of sensitive units, wherein the sensitive units are arranged on the surface of the cabin, and the pigtails of the sensitive units extend into the accommodating cavity; An interference unit, the interference unit is arranged in the accommodating cavity, the interference unit comprises a coupler and a Faraday reflector, the first end of the coupler is coupled to the laser through a transmission optical cable, and is used to receive a first optical signal emitted by the laser, the second end of the coupler is coupled to a photodetector through the transmission optical cable, and is used to output a second optical signal containing acoustic wave information, the third end of the coupler is coupled to the Faraday reflector through the pigtail of the sensitive unit to form a sensing arm, and the fourth end of the coupler is coupled to the Faraday reflector to form a reference arm; Among them, each of the sensitive units is arranged at equal intervals on the surface of the cabin with half the wavelength corresponding to the target signal as the array element spacing, and any of the sensitive units includes a sensitive elastomer and a fine optical fiber wound on the sensitive elastomer, and the fine optical fiber is a small mode field, thin diameter optical fiber.
2. The optical fiber acoustic wave locator according to claim 1, characterized in that: When the fine optical fiber is wound on the surface of the sensitive elastomer, the loss of the fine optical fiber is lower than 0.5 dB / km.
3. The fiber optic acoustic wave locator according to claim 2, characterized in that: The mode field diameter of the micro-optical fiber is less than or equal to 7 microns, and the fiber bending radius of the micro-optical fiber wound on the surface of the sensitive elastomer is not less than 5 millimeters.
4. The fiber optic acoustic wave locator according to claim 1, characterized in that: The surface of the fine optical fiber is provided with a coating layer, and the outer diameter of the coating layer is less than or equal to 130 microns.
5. The fiber optic acoustic wave locator according to claim 1, characterized in that: The micro-optical fiber comprises a core, a cladding, a carbon layer and a coating layer; The cladding covers the core, the carbon layer is arranged on the periphery of the cladding, and the coating layer is arranged on the periphery of the carbon layer.
6. The fiber optic acoustic wave locator according to claim 5, characterized in that: The coating layer includes an inner coating layer and an outer coating layer.
7. The fiber optic acoustic wave locator according to claim 1, characterized in that: The transmission optical cable has twice the number of optical fibers as the number of the plurality of sensitive units.
8. The fiber optic acoustic wave locator according to claim 1, characterized in that: When the frequency of the target signal is 37.5 kHz, the array element spacing of the sensitive unit is 2 cm.
9. The fiber optic acoustic wave locator according to claim 1, characterized in that: The cabin body is made of titanium alloy.
10. The fiber optic acoustic wave locator according to claim 1, characterized in that: The optical fiber acoustic wave locator is fully wrapped and watertightly packaged with polyurethane material, and the internal gap of the cabin is filled with the polyurethane material.