A distributed fiber land hearing unit and a distributed land hearing optical cable

Abstract

The utility model relates to the field of optical fiber sensing technology, more particularly, a kind of distributed optical fiber land listening unit and distributed land listening optical cable.The utility model aims at solving the problem of insufficient sound noise suppression force.Distributed optical fiber land listening unit includes shell, has the elasticity base element, sensitized optical fiber and noise reduction layer;Base element is located in the inside of shell, base element includes two end faces located in its length direction both ends and the circumferential surface connected end face, end face connects shell, circumferential surface is spaced apart with the inner wall of shell;Shell is equipped with two fiber guide holes and multiple sound guide holes, two fiber guide holes are set up before and after along the length direction of base element, sensitized optical fiber is passed into shell from one fiber guide hole, spiral is wound on base element, and is passed out from another fiber guide hole Shell;Noise reduction layer fills between base element and shell.Distributed land listening optical cable includes several distributed optical fiber land listening units and several connecting optical fibers, and the sensitized optical fiber between adjacent distributed optical fiber land listening units is connected by connecting optical fiber.

Description

Technical Field

[0001] This utility model relates to the field of fiber optic sensing technology, and more specifically, to a distributed fiber optic ground listening unit and a distributed ground listening optical cable. Background Technology

[0002] Currently, the main types of acoustic sensors used in land acoustic monitoring include distributed fiber optic acoustic sensors (DAS), fiber Bragg grating (FBG) sensors, and MEMS vibration sensor arrays. Among these, DAS, using bare fiber structures, is susceptible to wind-induced vibration interference; while FBG sensors are encapsulated for protection, their point-deployed nature makes them vulnerable to localized turbulence; and MEMS vibration sensor arrays require additional windproof shields. Therefore, current land acoustic sensors generally suffer from weak noise suppression capabilities. Furthermore, the aforementioned types of acoustic sensors have limited applicability and cannot fully cover common fiber optic cable incidents such as construction damage, cable theft, and ground subsidence. Utility Model Content

[0003] The present invention aims to overcome at least one of the defects of the prior art and provide a distributed optical fiber ground listening unit and a distributed ground listening optical cable to solve the problem of insufficient sound noise suppression.

[0004] The primary objective of this invention is to provide a distributed optical fiber listening unit, comprising a housing, a flexible element, a sensitivity-enhancing optical fiber, and a noise reduction layer.

[0005] The basic element is disposed inside the housing and has an extended length. The basic element includes two basic element end faces located at both ends in its length direction and a basic element peripheral surface connecting the two basic element end faces. The basic element end faces are connected to the housing, and the basic element peripheral surface is spaced apart from the inner wall of the housing.

[0006] The housing is provided with a first fiber guide hole, a second fiber guide hole and a plurality of sound guide holes. The first fiber guide hole and the second fiber guide hole are arranged one after the other along the length direction of the basic element. The sensitivity-enhancing fiber enters the housing from the first fiber guide hole, spirally winds around the basic element, and exits the housing from the second fiber guide hole.

[0007] The noise reduction layer is filled between the basic element and the inner wall of the housing.

[0008] In this scheme, the sensitive-enhancing optical fiber and the helical winding structure formed by the sensitive-enhancing optical fiber wound around the basic unit can synergistically enhance the response sensitivity to sound pressure signals. By filling the space between the basic unit and the inner wall of the shell with a noise reduction layer, wind noise interference can be effectively suppressed, improving the response sensitivity to sound waves / vibrations. The distributed ground listening cable obtained from the distributed optical fiber ground listening unit based on this scheme can achieve continuous, high-density monitoring of sound wave disturbances at various points along the line using a single communication optical cable based on the principle of phase-sensitive optical time-domain reflectometry (Φ-OTDR). It does not require the deployment of discrete sensing nodes or rely on active electronic components, possessing inherent passive characteristics and extremely strong electromagnetic interference immunity. Combined with high-frequency laser pulse and coherent demodulation technology, the distributed ground listening cable made from the distributed optical fiber ground listening unit based on this scheme can achieve continuous sound field sampling with meter-level spatial resolution over a cable length of tens of kilometers, significantly improving coverage and response accuracy.

[0009] In some embodiments, the noise reduction layer includes at least one of a sponge layer and a metal mesh layer.

[0010] In this design, both the sponge layer and the metal mesh layer can effectively suppress wind noise interference. Together with the shell with the sound guide hole, they can work synergistically to improve the response sensitivity of the distributed fiber optic ground listening unit to sound waves / vibrations.

[0011] In some embodiments, the noise reduction layer includes a sponge layer and a metal mesh layer, which are stacked sequentially from the element toward the housing.

[0012] In this design, the sponge layer, the metal mesh layer, and the shell with sound-guiding holes together form a triple protection design, which can effectively suppress wind noise interference while maintaining a high sensitivity response to sound waves / vibrations.

[0013] In some embodiments, the basic element is made of silicone or rubber.

[0014] The basic cost of this solution is controllable, and it can efficiently convert external acoustic pressure fluctuations into axial tensile / compressive strain of optical fibers, thereby improving response sensitivity.

[0015] In some embodiments, the primitive is detachably connected to the housing.

[0016] In some embodiments, the housing includes a first outer shell and a second outer shell, which are joined together by a detachable structure to form the housing.

[0017] This solution facilitates the spiral winding of the sensitive fiber onto the basic unit while separating the first and second outer shells, simplifying the process of fabricating the spiral winding structure.

[0018] In some embodiments, the housing includes two shell ends that are far apart and a cylindrical portion connecting the two shell ends. The two shell ends are arranged one after the other along the length of the element. The two ends of the element are respectively connected to one of the shell ends. The first fiber guide hole is provided at one of the shell ends, and the second fiber guide hole is provided at the other shell end.

[0019] In this design, the first and second fiber guide holes are positioned far apart, which helps to increase the wiring distance of the sensitivity-enhancing fiber inside the housing and facilitates the spiral winding of the sensitivity-enhancing fiber into the unit according to the target monitoring frequency band and sensitivity requirements.

[0020] Furthermore, the sound guide hole is located in the cylindrical portion.

[0021] The sound guide hole of this design is almost perpendicular to the radial direction of the sensitizing fiber, which helps the external sound pressure signal to be introduced along the radial direction of the sensitizing fiber, thereby increasing the strain of the sensitizing fiber and improving the response sensitivity.

[0022] The second objective of this invention is to provide a distributed terrestrial listening optical cable, which includes a plurality of distributed optical fiber terrestrial listening units and a plurality of connecting optical fibers, wherein the sensitizing optical fibers of adjacent distributed optical fiber terrestrial listening units are connected by the connecting optical fibers.

[0023] This distributed terrestrial listening optical cable solution is based on the principle of phase-sensitive optical time-domain reflectometry (Φ-OTDR). It utilizes a single ordinary communication optical cable to achieve continuous and high-density monitoring of acoustic disturbances at various points along the route. It does not require the deployment of discrete sensing nodes or rely on active electronic components, possessing inherent passive characteristics and extremely strong electromagnetic interference immunity. Combined with high-frequency laser pulse and coherent demodulation technology, this distributed terrestrial listening optical cable solution can achieve continuous sound field sampling with meter-level spatial resolution over a length of tens of kilometers of optical cable, significantly improving coverage and response accuracy.

[0024] In some embodiments, the distributed terrestrial listening cable is further provided with several tensile reinforcement members, and the shells of adjacent distributed optical fiber terrestrial listening units are connected by the tensile reinforcement members.

[0025] Compared with the prior art, the beneficial effects of this utility model are as follows: the sensitivity enhancement optical fiber and the spiral winding structure can synergistically enhance the response sensitivity to sound pressure signals. By filling the space between the basic element and the inner wall of the shell with a noise reduction layer, it can form a triple protection design together with the porous shell formed by opening the sound guide hole, effectively suppressing wind noise interference, while maintaining a high sensitivity response to sound waves / vibrations, thereby covering common optical cable accidents such as construction damage, optical cable theft, and ground subsidence. Attached Figure Description

[0026] Figure 1 This is a structural diagram of Example 1.

[0027] Figure 2 Partial structure of Example 1 Figure 1 .

[0028] Figure 3 Partial structure of Example 1 Figure 2 .

[0029] Figure 4 This is a structural diagram of Example 2.

[0030] Reference numerals in the figures: Distributed optical fiber listening unit 100, housing 110, first fiber guide hole 111, second fiber guide hole 112, sound guide hole 113, first outer shell 114, second outer shell 115, shell end 116, cylindrical part 117, element 120, sensitivity-enhancing optical fiber 130, sponge layer 140, metal mesh layer 150, connecting optical fiber 200. Detailed Implementation

[0031] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this invention. To better illustrate the following embodiments, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0032] Furthermore, in this utility model, unless otherwise explicitly specified and limited, the terms "connection," "fixing," etc., should be interpreted broadly. For example, "fixing" can mean a fixed connection, a detachable connection, or an integral part; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0033] Furthermore, in this utility model, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this utility model.

[0034] Example 1

[0035] like Figure 1-2As shown, this embodiment provides a distributed optical fiber listening unit, including a housing 110, a flexible element 120, a sensitivity-enhancing optical fiber 130, and a noise reduction layer;

[0036] The basic element 120 is disposed inside the housing 110 and has an extended length. The basic element 120 includes two basic element 120 end faces located at both ends in its length direction and a basic element 120 peripheral surface connecting the two basic element 120 end faces. The basic element 120 end faces are connected to the housing 110, and the basic element 120 peripheral surface is spaced apart from the inner wall of the housing 110.

[0037] The housing 110 is provided with a first fiber guide hole 111, a first fiber guide hole 112 and a plurality of sound guide holes 113. The first fiber guide hole 111, the first fiber guide hole 112 and the plurality of sound guide holes 113 are all provided through the housing. The first fiber guide hole 111 and the first fiber guide hole 112 are arranged back and forth along the length direction of the base 120. The sensitivity-enhancing fiber 130 enters the housing 110 from the first fiber guide hole 111, spirally winds around the base 120, and exits the housing 110 from the first fiber guide hole 112.

[0038] The noise reduction layer is filled between the inner wall of the base 120 and the housing 110.

[0039] In specific implementation, the noise reduction layer includes a sponge layer 140 and a metal mesh layer 150. The sponge layer 140 and the metal mesh layer 150 are sequentially stacked from the base unit 120 toward the housing 110. That is, the sponge layer 140 fills the space between the base unit 120 and the metal mesh layer 150, and the metal mesh layer 150 fills the space between the sponge layer 140 and the inner wall of the housing 110. In some other embodiments, the noise reduction layer may use only the sponge layer 140 or only the metal mesh layer 150. In this case, either the sponge layer 140 or the metal mesh layer 150 fills the space between the base unit 120 and the inner wall of the housing 110. Tests show that when only the sponge layer 140 or only the metal mesh layer 150 is used, the noise reduction effect is somewhat reduced, but it still meets the testing requirements of the distributed listening unit.

[0040] Among them, Core Element 120 is the mechanical transmission skeleton inside the optical cable that carries the spirally wound optical fiber. Its core function is to efficiently convert external sound pressure fluctuations into optical fiber axial strain.

[0041] Specifically, the enhanced fiber 130 significantly improves the phase response sensitivity of ordinary communication-grade optical fiber to external disturbances by introducing ultraviolet sensitization treatment or weak periodic fiber grating (Weak FBG) writing technology. This effectively amplifies the interference signal component of wind wave signals in Rayleigh scattering echoes, reducing the system's inherent noise level at the source and enhancing the detection capability of weak sound pressure events. Simultaneously, this sensitization structure does not affect the fiber's transmission performance, maintaining scalable communication functions and long-distance extension capabilities.

[0042] The spiral winding structure formed by the sensitive-enhancing fiber 130 wound around the basic element 120 enables a more uniform and controllable disturbance transmission path to be formed on the fiber surface when the sound wave is incident, thereby improving the strain response capability of the sound wave in the fiber axis and thus improving the overall sound pressure sensitivity of the distributed optical fiber listening unit.

[0043] In application, the sensitive-enhancing fiber 130 and the spiral winding structure formed by the sensitive-enhancing fiber 130 wound around the basic element 120 can synergistically enhance the response sensitivity to sound pressure signals. By filling the space between the basic element 120 and the inner wall of the housing 110 with a sponge layer 140 and a metal mesh layer 150, a triple protection design can be formed together with the housing 110 with the sound guide hole 113, which can significantly suppress wind noise interference and maintain a high sensitivity response to sound waves / vibrations. The distributed ground listening cable obtained by the distributed optical fiber ground listening unit of this utility model can realize continuous and high-density monitoring of sound wave disturbances at various points along the line based on the phase-sensitive optical time domain reflection (Φ-OTDR) principle and using communication optical fiber. It does not require the deployment of discrete sensing nodes and does not rely on active electronic components, and has natural passive characteristics and extremely strong electromagnetic interference resistance. Based on this, and in conjunction with high-frequency laser pulse and coherent demodulation technology, the distributed terrestrial listening cable made by the distributed optical fiber terrestrial listening unit in this embodiment can achieve continuous sound field sampling with meter-level spatial resolution over a cable length of tens of kilometers, significantly improving coverage and response accuracy.

[0044] In some implementations, the element 120 is made of silicone or rubber, which can efficiently convert external sound pressure fluctuations into axial tensile / compressive strain of the optical fiber, thereby improving response sensitivity.

[0045] refer to Figure 2-3 To facilitate the fabrication of the spiral wound structure, the housing 110 includes a first outer shell 114 and a second outer shell 115, which are joined together via a detachable structure to form the housing 110. In practice, the basic element can be housed within either the first outer shell 114 or the second outer shell 115, and the first fiber guide hole 111 and the second fiber guide hole 112 can both be located in the first outer shell 114, both in the second outer shell 115, or one of them respectively. Specifically, in fabricating the spiral wound structure, the first outer shell 114 and the second outer shell 115 are first separated. The sensitive-enhancing fiber 130 is introduced into the interior of the first outer shell 114 or the second outer shell 115 through the first fiber guide hole 111 and spirally wound onto the basic element 120, thus obtaining the spiral wound structure. Then, the sensitive-enhancing fiber 130 is led out of the first outer shell 114 or the second outer shell 115 through the second fiber guide hole 112. Finally, the first outer shell 114 and the second outer shell 115 are joined together to form the housing 110. This simplifies the fabrication process of the spiral wound structure.

[0046] refer to Figure 2-3In some embodiments, the housing 110 is a cylinder or a polygonal prism. The housing 110 includes two shell ends 116 that are far apart and a cylindrical portion 117 connecting the shell ends 116. The two shell ends 116 are arranged front and back along the length direction of the element 120. The two ends of the element 120 are respectively connected to one of the shell ends 116. A first fiber guide hole 111 is provided in one of the shell ends 116, a first fiber guide hole 112 is provided in the other shell end 116, and a sound guide hole 113 is provided in the cylindrical portion 117. It can be understood that the first fiber guide holes 111 and 112 are arranged far apart, thereby increasing the wiring distance of the sensitive fiber 130 inside the housing 110, which facilitates the spiral winding of the sensitive fiber 130 into the element 120 according to the target monitoring frequency band and sensitivity requirements. In addition, the sound guide hole 113 is almost perpendicular to the radial direction of the sensitive fiber 130, which helps to introduce external sound pressure signals into the spiral winding structure, increase the strain strength of the sensitive fiber 130, and thus improve the corresponding sensitivity. To facilitate processing, the sound guide hole 113 is specifically made into a circular through hole with a diameter of 5mm or more, and the sound guide hole 113 is evenly and densely distributed in the cylinder 117.

[0047] In other embodiments, the housing 110 may also be shaped like a sphere or an ellipsoid. In this case, there is no clear boundary between the shell end 116 and the cylindrical portion 117 of the housing 110. The first fiber guide hole 111 and the first fiber guide hole 112 can be arranged back and forth along the length direction of the base 120. Preferably, the first fiber guide hole 111 and the first fiber guide hole 112 are located at the two ends of the diameter of the sphere and the base 120 coaxially, or the first fiber guide hole 111 and the first fiber guide hole 112 are located at the two ends of the major axis of the ellipsoid and the base 120 coaxially, so that the sensitive fiber 130 has sufficient spiral winding space inside the housing 110.

[0048] In some implementations, the basic unit 120 and the housing 110 are detachably connected. For specific implementation details, refer to... Figure 3 The two ends of the basic element 120 abut against the two shell ends 116 of the housing 110 respectively, thereby limiting the basic element 120 inside the housing 110. Preferably, the two shell ends 116 have a certain thickness, and the inner surface of the shell ends 116 is provided with a limiting groove. By aligning the two ends of the basic element 120 inside the limiting groove respectively, the installation stability of the basic element 120 can be improved.

[0049] Example 2

[0050] refer to Figure 1 , 4 This embodiment provides a distributed ground listening optical cable, including several distributed optical fiber ground listening units 100 of Embodiment 1 and several connecting optical fibers 200. The sensitivity-enhancing optical fibers 130 of adjacent distributed optical fiber ground listening units 100 are connected by connecting optical fibers 200.

[0051] The distributed terrestrial listening optical cable of this embodiment has a simple structure and is easy to set up. Based on the principle of phase-sensitive optical time-domain reflectometry (Φ-OTDR), it can use ordinary communication optical cables to achieve continuous and high-density monitoring of acoustic disturbances at various points along the line. It does not require the deployment of discrete sensing nodes or rely on active electronic components, and has natural passive characteristics and extremely strong electromagnetic interference resistance. Combined with high-frequency laser pulse and coherent demodulation technology, the distributed terrestrial listening optical cable of this embodiment can achieve continuous sound field sampling with meter-level spatial resolution over a length of tens of kilometers of optical cable, significantly improving coverage and response accuracy.

[0052] In some embodiments, the distributed terrestrial listening cable is further provided with several tensile reinforcement members, and adjacent distributed optical fiber terrestrial listening units 100 are connected by tensile reinforcement members. In specific implementations, Kevlar rope can be used to implement the tensile reinforcement members to improve the physical and chemical properties such as tensile strength, temperature resistance, and abrasion resistance.

[0053] Preferably, the connecting optical fiber 200 and the tensile reinforcement are integrally manufactured. For example, both the connecting optical fiber 200 and the tensile reinforcement are located inside the optical cable protective sleeve. The tensile reinforcement is anchored to the optical cable protective sleeve. To better transmit axial tensile force, a connecting member can be provided at the shell end 116 of the housing, connecting the two ends of the tensile reinforcement to the connecting members of adjacent optical fiber listening units 100. In practical use, if the distributed listening optical cable is subjected to tension, the tension will first be transmitted to the outer protective sleeve. The outer protective sleeve then effectively transmits the tension to the Kevlar rope through its strong mechanical interlocking force with the Kevlar rope. The Kevlar rope, with its extremely high tensile strength, bears most of the tension, protecting the internal connecting optical fiber from only experiencing minimal strain, ensuring that the transmission performance of the optical fiber is not affected. It should be noted that the Kevlar rope is not fixed inside the optical cable by chemical bonding, but rather by the molten material penetrating into the fiber structure during the extrusion of the optical cable protective sleeve during the optical cable manufacturing process, which, after cooling and solidification, forms a strong physical and mechanical anchoring. Combined with the constraint of other structural layers inside the optical cable, the Kevlar rope is firmly integrated into the optical cable structure, becoming the core skeleton that bears the tensile force, thus reliably protecting the internal connecting optical fibers.

[0054] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the technical solution of this utility model, and are not intended to limit the specific implementation of this utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A distributed optical fiber ground listening unit, characterized in that, It includes a housing, a sensitivity-enhancing optical fiber, a noise reduction layer, and elastic basic components; The basic element is disposed inside the housing and has an extended length. The basic element includes two basic element end faces located at both ends in its length direction and a basic element peripheral surface connecting the two basic element end faces. The basic element end faces are connected to the housing, and the basic element peripheral surface is spaced apart from the inner wall of the housing. The housing is provided with a first fiber guide hole, a second fiber guide hole and a plurality of sound guide holes. The first fiber guide hole and the second fiber guide hole are arranged one after the other along the length direction of the basic element. The sensitivity-enhancing fiber enters the housing from the first fiber guide hole, spirally winds around the basic element, and exits the housing from the second fiber guide hole. The noise reduction layer is filled between the basic element and the inner wall of the housing.

2. The distributed optical fiber ground listening unit according to claim 1, characterized in that, The noise reduction layer includes at least one of a sponge layer and a metal mesh layer.

3. The distributed optical fiber ground listening unit according to claim 2, characterized in that, The noise reduction layer includes a sponge layer and a metal mesh layer, which are stacked sequentially from the basic element toward the housing.

4. The distributed optical fiber ground listening unit according to claim 1, characterized in that, The basic element is made of silicone or rubber.

5. The distributed optical fiber ground listening unit according to claim 1, characterized in that, The basic element is detachably connected to the housing.

6. The distributed optical fiber ground listening unit according to any one of claims 1 to 5, characterized in that, The housing includes a first outer shell and a second outer shell, which are joined together by a detachable structure to form the housing.

7. The distributed optical fiber ground listening unit according to any one of claims 1 to 5, characterized in that, The housing includes two shell ends that are far apart and a cylindrical portion that connects the two shell ends. The two shell ends are arranged one after the other along the length direction of the basic element. The two ends of the basic element are respectively connected to one of the shell ends. The first fiber guide hole is provided at one of the shell ends, and the second fiber guide hole is provided at the other shell end.

8. The distributed optical fiber ground listening unit according to claim 7, characterized in that, The sound guide hole is located in the cylindrical part.

9. A distributed terrestrial optical cable, characterized in that, The distributed ground listening optical cable includes several distributed optical fiber ground listening units as described in any one of claims 1-8 and several connecting optical fibers, wherein the sensitivity-enhancing optical fibers of adjacent distributed optical fiber ground listening units are connected by the connecting optical fibers.

10. The distributed terrestrial optical cable according to claim 9, characterized in that, It is also provided with several tensile reinforcement members, and adjacent distributed optical fiber ground listening units are connected through the tensile reinforcement members.

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