A sensing optical cable

Abstract

The present invention relates to the technical field of cables, and provides a sensing optical cable, which includes a core shaft, a sensing layer, and an outer protective layer arranged in sequence from inside to outside; the core shaft includes a tensile element and a transducer layer arranged in sequence from inside to outside, and the core shaft is divided into a plurality of first core shafts and second core shafts that are alternately connected. A sensitizing layer is provided outside the transducer layer in the first core shaft. The sensing layer includes a first braided section and a second braided section. The first braided section is arranged on the outer surface of the sensitizing layer in the first core shaft, and the second braided section is arranged on the outer surface of the transducer layer in the second core shaft. The length of the first braided section is different from the length of the second braided section. The sensing optical cable provided by the present invention can capture and amplify acoustic vibration signals by designing a structure in which the first core shaft containing the sensitizing layer and the second core shaft without the sensitizing layer are alternately connected, and arranging the sensing layer in a braided form on the outer surfaces of these two core shafts respectively. The sensitizing layer enhances the response ability of the optical cable to acoustic signals and improves the overall sensing sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, and in particular to a sensing optical cable. Background Art

[0002] Distributed Acoustic Sensing (DAS) technology, as an important branch of Distributed Optical Fiber Sensing System (DOFS), has shown great application potential in multiple fields in recent years. This technology uses optical fiber as the sensing and transmission medium, and can realize the comprehensive monitoring of acoustic and vibration signals, so as to extract rich characteristic information of the object to be measured. Especially in special fields such as oil exploration, seismic wave monitoring, and marine security detection, DAS technology has attracted much attention due to its unique advantages.

[0003] In a DAS system, the sensing optical cable plays a crucial role. It is not only the transmission medium of the signal, but also the sensing element that directly senses the external environmental disturbance signal. However, the optical cables widely used in the market at present are mainly traditional commercial communication optical cables. These optical cables mainly consider communication performance in design, and do not specifically optimize the vibration / acoustic wave sensing function. Therefore, in practical applications, these optical cables often have problems such as serious signal strength attenuation and weak ability to pick up external sound / vibration signals.

[0004] Specifically, when acoustic or vibration signals are transmitted through the optical cable, due to the limitations of the optical cable structure and production process, the signal strength will be greatly attenuated. This not only reduces the signal transmission efficiency, but also greatly reduces the sensing ability of the optical cable to external disturbance signals. Therefore, when traditional communication optical cables are applied to DAS technology, they often cannot meet the detection requirements of high precision and high sensitivity. Summary of the Invention

[0005] The present invention provides a sensing optical cable to solve the problem that existing optical cables are difficult to meet the detection requirements of high precision and high sensitivity when applied to DAS technology.

[0006] The present invention provides a sensing optical cable, including: a core shaft, a sensing layer, and an outer protective layer arranged in sequence from inside to outside;

[0007] The core shaft includes a tensile element and a transducer layer arranged in sequence from inside to outside. The core shaft is divided into a plurality of first core shafts and second core shafts that are alternately connected. A sensitization layer is provided outside the transducer layer in the first core shaft;

[0008] The sensing layer includes a first braided section and a second braided section. The first braided section is disposed on the outer surface of the sensitizing layer in the first mandrel, and the second braided section is disposed on the outer surface of the transducer layer in the second mandrel. The length of the first braided section is different from the length of the second braided section, so that the detection sensitivity of the optical cable changes in a gradient manner.

[0009] The present invention also provides a sensing optical cable, which further includes: a strengthening layer disposed between the sensing layer and the outer sheath layer.

[0010] The present invention also provides a sensing optical cable, and a plurality of signal transmission holes spaced apart and all arranged along the extending direction of the strengthening layer are provided in the strengthening layer.

[0011] The present invention also provides a sensing optical cable, wherein the length of the first braided section is the same as the length of the sensitizing layer in the first mandrel, and the length of the second braided section is the same as the length of the transducer layer in the second mandrel.

[0012] The present invention also provides a sensing optical cable, and the first braided section and the second braided section include: a plurality of optical units. The plurality of optical units of the first braided section are woven in a net shape on the outer surface of the sensitizing layer in the first mandrel, and the plurality of optical units of the second braided section are woven in a net shape on the outer surface of the transducer layer in the second mandrel.

[0013] The present invention also provides a sensing optical cable, and a plurality of the optical units in the first braided section and / or the second braided section are provided with multiple layers. The optical units of each layer in the first braided section are sequentially stacked and woven in a net shape on the outer surface of the sensitizing layer in the first mandrel, and the optical units of each layer in the second braided section are sequentially stacked and woven in a net shape on the outer surface of the transducer layer in the second mandrel.

[0014] The present invention also provides a sensing optical cable, and the weaving density of the plurality of optical units in the first braided section is greater than the weaving density of the plurality of optical units in the second braided section.

[0015] The present invention also provides a sensing optical cable, which further includes:

[0016] a coating layer, which is coated on the outer surfaces of the plurality of optical units of the first braided section and the second braided section and is located between the plurality of optical units and the outer sheath layer.

[0017] The present invention also provides a sensing optical cable, and the length of the first braided section is less than the length of the second braided section.

[0018] The present invention also provides a sensing optical cable, wherein the sound transmission coefficients of the outer protective layer, the sensitizing layer, and the transducer layer decrease in sequence, and / or the Young's moduli of the sensitizing layer, the outer protective layer, and the transducer layer increase in sequence.

[0019] The sensing optical cable provided by the present invention, through designing a structure in which a first mandrel including a sensitizing layer and a second mandrel without a sensitizing layer are alternately connected, and disposing the sensing layer in a woven form on the outer surfaces of these two mandrels respectively, enables the optical cable to more effectively capture and amplify acoustic vibration signals. The design of the sensitizing layer further enhances the response ability of the optical cable to acoustic signals, thereby improving the overall sensing sensitivity. The tensile element inside the mandrel and the transducer layer work together, not only providing the mechanical strength required for the optical cable, but also ensuring the effective transmission of acoustic vibration signals inside the optical cable. By disposing the sensing layer in a woven form on the outer surface of the mandrel, the optical cable can better adapt to the surfaces of objects with different shapes and sizes, increasing the applicability and flexibility of the optical cable in complex environments. In addition, the design of the outer protective layer not only provides additional protection for the optical cable, but also can prevent damage to the internal structure of the optical cable caused by external environmental factors. This structural design helps to improve the reliability and durability of the optical cable and extend its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 It is one of the schematic structural diagrams of the sensing optical cable provided by the present invention.

[0022] Figure 2 It is the schematic diagram of the woven form of the optical unit provided by the present invention.

[0023] Figure 3 It is the schematic diagram of the mandrel provided by the present invention.

[0024] Figure 4 It is the schematic diagram of the reinforcing layer provided by the present invention.

[0025] Figure 5 It is the second schematic structural diagram of the sensing optical cable provided by the present invention.

[0026] Reference Signs:

[0027] 100, mandrel; 1010, tensile element; 1020, transducer layer; 1030, sensitivity enhancement layer; 200, sensing layer; 2010, first braided section; 2020, second braided section; 2030, optical unit; 300, outer protective layer; 400, reinforcing layer; 4010, signal transmission hole; 500, coating layer. Detailed implementation manners

[0028] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0029] The following combines Figures 1 to 5 to describe the sensing optical cable of the present invention. This sensing optical cable is applied to DAS technology to meet the detection requirements of high precision and high sensitivity.

[0030] In some embodiments, as Figures 1 to 3 shown, the sensing optical cable includes a mandrel 100, a sensing layer 200, and an outer protective layer 300 that are sequentially arranged from the inside to the outside. The mandrel 100 includes a tensile element 1010 and a transducer layer 1020 that are sequentially arranged from the inside to the outside. The mandrel 100 is divided into a plurality of alternately connected first mandrels and second mandrels. An sensitivity enhancement layer 1030 is provided outside the transducer layer 1020 in the first mandrel. The sensing layer 200 includes a first braided section 2010 and a second braided section 2020. The first braided section 2010 is arranged on the outer surface of the sensitivity enhancement layer 1030 in the first mandrel, and the second braided section 2020 is arranged on the outer surface of the transducer layer 1020 in the second mandrel. The length of the first braided section 2010 is different from the length of the second braided section 2020, so that the detection sensitivity of the optical cable changes in a gradient manner, and it can more easily receive the acoustic vibration signals transmitted in different angular directions.

[0031] In this embodiment, the outer protective layer 300 is the outermost layer of the optical cable. The main function of the outer protective layer 300 is to protect the optical cable from damage by the external environment, such as abrasion, corrosion, etc. It is usually made of tough and durable materials to ensure the durability and reliability of the optical cable. The sensing layer 200 is the component in the optical cable responsible for capturing acoustic vibration signals. It is composed of a first braided section 2010 and a second braided section 2020, and these braided sections are respectively arranged on the peripheries of the first mandrel and the second mandrel. The braided structure not only provides additional strength but also optimizes the acoustic signal reception ability of the optical cable. The mandrel 100 supports the entire structure of the optical cable and cooperates with the sensing layer 200 to improve the acoustic sensitivity performance of the optical cable. The mandrel 100 is divided into a plurality of alternately connected first mandrels and second mandrels.

[0032] Specifically, the mandrel 100 is an integral cylinder with a constant diameter structure as a whole. Its function is to support the sensing layer 200 and, at the same time, cooperate with the sensing layer 200 to improve the acoustic sensitivity performance of the optical cable. It has a relatively large cross-sectional area, and the outer diameter of the cross-section is not less than 10 mm, aiming to increase the sensing area of the optical cable and reduce the macro-bending loss of the optical fiber.

[0033] The tensile element 1010 uses a metal wire rope, which has both flexibility and can ensure that the optical cable has a relatively high tensile strength. For example, the structure of the metal wire rope is "1 7" or "1 19". If 1.0 mm steel wires are used, a 1 7 structure is adopted, and the outer diameter of the metal wire rope is 3.0 mm; if 0.8 mm steel wires are used, a 1 19 structure is adopted, and the outer diameter of the metal wire rope is 4.0 mm. The transducer layer 1020 is continuously coated with a polymer material around the tensile element 1010 and extends longitudinally along the tensile element 1010. The sensitizing layer 1030 is coated with a polymer material in a spaced and embedded manner around the transducer layer 1020 and extends longitudinally along the periphery of the transducer layer 1020.

[0034] When the external acoustic wave vibration signal is transmitted to the sensing layer 200, a part of the signal will be directly captured by the sensing layer 200, and a part of the signal will be absorbed by the sensitizing layer 1030 with a large sound transmission coefficient, thereby generating a certain micro-deformation and resonating with the sensing layer 200 to amplify the acoustic wave vibration signal; after the remaining part of the signal passes through the sensitizing layer 1030, it will be reflected on the surface of the transducer layer 1020 with a small sound transmission coefficient, and then continue to enter the sensitizing layer 1030. The three cooperate with each other, which can promote the acoustic wave vibration signal to be received by the sensing layer 200 as much as possible, and then improve the detection sensitivity of the optical fiber.

[0035] The sensing optical cable provided by the present invention, by designing a structure in which the first mandrel including the sensitizing layer 1030 and the second mandrel without the sensitizing layer 1030 are alternately connected, and arranging the sensing layer 200 in a woven form on the outer surfaces of these two mandrels 100 respectively, enables the optical cable to capture and amplify the acoustic wave vibration signal more effectively. The design of the sensitizing layer 1030 further enhances the response ability of the optical cable to the acoustic wave signal, thereby improving the overall sensing sensitivity. The tensile element 1010 and the transducer layer 1020 inside the mandrel 100 work together, not only providing the mechanical strength required by the optical cable, but also ensuring the effective transmission of the acoustic wave vibration signal inside the optical cable. By arranging the sensing layer 200 in a woven form on the outer surface of the mandrel 100, the optical cable can better adapt to the surfaces of objects with different shapes and sizes, increasing the applicability and flexibility of the optical cable in complex environments. In addition, the design of the outer sheath 300 not only provides additional protection for the optical cable, but also can prevent the damage of the internal structure of the optical cable by external environmental factors. This structural design helps to improve the reliability and durability of the optical cable and extend the service life of the optical cable.

[0036] It should be noted that in order to reduce the obstruction of the outer sheath 300 plastic to the transmission of external signals and improve the transmission efficiency of signals such as sound waves and vibrations, the outer sheath 300 also needs to adopt a polymer material with a high sound transmission coefficient, so that a large amount of reflection does not occur on the surface of the material for the incident sound wave, reducing the loss of sound wave energy and promoting as much sound wave energy as possible to enter the sensing layer 200 position.

[0037] In some embodiments, such as Figures 1 to 4 shown, the sensing optical cable further includes: a reinforcing layer 400 disposed between the sensing layer 200 and the outer sheath 300. The reinforcing layer 400 may be made of materials with high strength and high modulus, such as aramid fibers, glass fibers or other similar synthetic materials. These materials not only have excellent tensile strength, but also can provide the necessary toughness when subjected to external forces, preventing the optical cable from being damaged due to excessive bending or stretching.

[0038] Specifically, when the laying environment of the optical cable is harsh and the optical cable needs to have a certain compressive strength, a reinforcing layer 400 can be added outside the sensing layer 200, generally by covering with a metal strip / tube. Since the acoustic impedance of the metal material is high, that is, the sound transmission coefficient is small, the sound wave and vibration signals transmitted through the outer sheath 300 will be reflected at the metal interface, resulting in signal attenuation.

[0039] In one example, such as Figure 4 shown, the reinforcing layer 400 is provided with a plurality of signal transmission holes 4010 that are spaced apart and all arranged along the extending direction of the reinforcing layer 400.

[0040] The presence of the signal transmission holes 4010 allows the sound wave vibration signals to be transmitted more smoothly inside the optical cable. These channels can serve as "fast channels" for sound wave signals, reducing the attenuation and interference of signals when propagating inside the optical cable, thereby improving the clarity and accuracy of the signals.

[0041] And by providing spaced signal transmission holes 4010 in the reinforcing layer 400, the weight of the optical cable can be effectively reduced without affecting the overall strength of the optical cable. This is particularly important for optical cables that need to be laid over long distances or used in environments such as high altitudes and deep seas, which can reduce the burden of transportation and installation.

[0042] In addition, the signal transmission holes 4010 can also increase the flexibility of the optical cable, making it easier to adapt to various complex environments and terrains. This is particularly useful for installing optical cables on curved or irregular surfaces, ensuring that the optical cable can meet the actual application requirements while maintaining high performance. The shape of the signal transmission holes 4010 can be circular, oval, or other shapes suitable for sound wave transmission. The size and spacing of the holes also need to be optimized according to the specific application and requirements of the optical cable. The reinforcement layer 400 itself needs to be made of high-strength and high-modulus materials to ensure the mechanical strength of the optical cable. The material around the signal transmission holes 4010 needs to have good sound wave transmission performance to reduce signal attenuation around the holes.

[0043] In some embodiments, as Figures 1 to 3 shown, the length of the first braided section 2010 is the same as the length of the sensitizing layer 1030 in the first mandrel, and the length of the second braided section 2020 is the same as the length of the transducer layer 1020 in the second mandrel.

[0044] In this embodiment, the first braided section 2010 is tightly wrapped around the outer surface of the sensitizing layer 1030 of the first mandrel, and its length is the same as that of the sensitizing layer 1030. This design ensures that the sensitizing layer 1030 can fully play its role in amplifying acoustic signals, while the braided section provides additional mechanical support and protection. Since the length of the braided section is the same as that of the sensitizing layer 1030, acoustic signals will not be attenuated or interfered due to the gap between the braided section and the mandrel 100 during transmission. Similarly, the second braided section 2020 is tightly wrapped around the outer surface of the transducer layer 1020 of the second mandrel, and its length is the same as that of the transducer layer 1020. This design ensures that the transducer layer 1020 can effectively transmit the acoustic vibration signal to the braided section and then to other parts of the optical cable. Since the length of the braided section is the same as that of the transducer layer 1020, acoustic signals can also remain clear and accurate during transmission.

[0045] Specifically, the sensitizing layer 1030 is in direct contact with the first braided section 2010 of the optical unit 2030 in the sensing layer 200, and its longitudinal extension length is the same as that of the first braided section 2010; the transducer layer 1020 is in direct contact with the second braided section 2020 of the optical unit 2030 in the sensing layer 200, and its longitudinal extension length is the same as that of the second braided section 2020. That is, in the first braided section 2010 of the optical unit 2030, the cross-section of the mandrel 100 includes the tensile element 1010, the transducer layer 1020, and the sensitizing layer 1030, and the thickness of the sensitizing layer 1030 is 0.5 mm to 2 mm. In the second braided section 2020 of the optical unit 2030, the cross-section of the mandrel 100 only includes the tensile element 1010 and the transducer layer 1020, that is, the thickness of the transducer layer 1020 in the second braided section 2020 is 0.5 mm to 2 mm larger than that of the transducer layer 1020 in the first braided section 2010.

[0046] In addition, the sensitizing layer 1030 can be continuously coated around the transducer layer 1020; correspondingly, multiple optical units 2030 can be continuously braided with equal pitch. At the same time, the optical units 2030 can be compounded and reinforced with optical fibers, high-performance fiber yarns, and flexible resins. First, it improves the tensile strength of the optical units 2030; second, the optical units 2030 are softer, which is beneficial to braiding; its size can be controlled within 0.28 - 0.36 mm, which is more suitable for the braiding of thin-diameter optical units 2030.

[0047] In some embodiments, as Figures 1 to 3 shown, the first braided section 2010 and the second braided section 2020 include: multiple optical units 2030. The multiple optical units 2030 of the first braided section 2010 are braided in a net-like form on the outer surface of the sensitizing layer 1030 in the first mandrel, and the multiple optical units 2030 of the second braided section 2020 are braided in a net-like form on the outer surface of the transducer layer 1020 in the second mandrel.

[0048] Specifically, as Figure 3 shown, the multiple optical units 2030 of the first braided section 2010 are tightly braided in a net-like form on the outer surface of the sensitizing layer 1030 of the first mandrel. This braiding method ensures close contact between the optical units 2030 and the sensitizing layer 1030, thereby enabling effective capture and transmission of acoustic vibration signals. The net-like braiding also provides additional mechanical support, enhancing the tensile and bending resistance of the optical cable. Similar to the first braided section 2010, the multiple optical units 2030 of the second braided section 2020 are also tightly braided in a net-like form on the outer surface of the transducer layer 1020 of the second mandrel. This design ensures good contact between the optical units 2030 and the transducer layer 1020, enabling the acoustic vibration signals to be smoothly transmitted to other parts of the optical cable.

[0049] The first braided section 2010 and the second braided section 2020 have different lengths (pitches). For example, the length of the first braided section 2010 is less than the length (pitch) of the second braided section 2020. The braiding pitch L of the optical unit 2030, that is, the distance that the optical unit 2030 moves along the axial direction of the coating when it goes around the mandrel 100 once. During the braiding process of every two optical units 2030, there will be intersections, forming overlapping points. Record the overlapping points of the optical units 2030 along a 1-inch (25.4 mm) length of the mandrel 100, which is the braiding count N. The larger N is, the denser the braiding. The relationship between the braiding pitch L and the braiding count N is: P = 25.4 F / 2N = 12.7F / N, where F is the number of cores of the optical unit 2030, generally an even number and at least 4 cores. Because each optical unit 2030 will be twisted into a mesh structure during the braiding process, and its twisting direction will change along with the core shaft 100, enabling the sensing layer 200 to sense external signals omnidirectionally at 360°. Compared with the optical unit 2030 simply wound on the surface of the core shaft 100, the braided optical unit 2030 is more likely to receive acoustic vibration signals transmitted from different angular directions outside, making the detection more sensitive.

[0050] In this embodiment, the optical unit 2030 has a size of 0.25 - 0.9 mm. Its structure is that a plastic layer with a high sound transmission coefficient is tightly sleeved outside the optical fiber, such as the thermoplastic elastomer similar to the sensitizing layer 1030 of the core shaft 100; the optical fiber in the optical unit 2030 uses grating optical fiber, that is, multiple continuous grating arrays are arranged on each optical fiber. Through the writing technology of fiber gratings, the grating length, spacing and wavelength can be controlled; compared with ordinary optical fibers, grating optical fibers are more likely to achieve vibration, stress and strain monitoring at the microstrain level.

[0051] Furthermore, by controlling the braiding pitch and braiding length of the optical unit 2030, it is ensured that two adjacent grating points are exactly located at the starting point and the ending point of each first pitch / second braiding section 2020. In this way, by demodulating the changes of the grating points, the specific position of the external acoustic vibration signal can be traced, which is more conducive to the precise positioning of the optical cable to sense external signals.

[0052] In an example, for the sensing layer 200 formed by braiding the optical unit 2030, the sensing optical cable further includes: a coating layer 500. The coating layer 500 covers the outer surfaces of multiple optical units 2030 in the first braiding section 2010 and the second braiding section 2020, and is located between the multiple optical units 2030 and the outer sheath 300.

[0053] The coating layer 500 can be coated with a composite tape of a foamed plastic layer and a polyester film. In this way, firstly, it plays a role of fixing and protecting; secondly, by using the softness of the foamed composite tape, it can be filled in the gaps formed by the braiding of adjacent optical units 2030 during the coating process, reducing the obstruction of the acoustic vibration signals transmitted by the air to the outside; thirdly, by using the porous characteristics of the foamed composite tape, a sound-containing cavity can be formed in the sensing layer 200, which can easily absorb the acoustic vibration signals.

[0054] In some embodiments, as Figures 1 to 5 shown, multiple optical units 2030 in the first braiding section 2010 and / or the second braiding section 2020 are provided with multiple layers. The optical units 2030 in each layer of the first braiding section 2010 are sequentially stacked and braided in a mesh shape on the outer surface of the sensitizing layer 1030 in the first core shaft, and the optical units 2030 in each layer of the second braiding section 2020 are sequentially stacked and braided in a mesh shape on the outer surface of the transducer layer 1020 in the second core shaft.

[0055] Among them, in the first braided section 2010, the optical unit layers 2030 are stacked in sequence and woven in a net shape on the outer surface of the sensitization layer 1030 of the first mandrel. This design ensures close contact between the optical unit layer 2030 and the sensitization layer 1030. And due to the existence of the multi-layer structure, acoustic vibration signals can be effectively transmitted and amplified between the optical unit layers 2030 of different layers. In addition, the multi-layer braiding also provides additional mechanical support, enhancing the tensile and bending resistance of the optical cable. Similar to the first braided section 2010, the optical unit layers 2030 in the second braided section 2020 are also stacked in sequence and woven in a net shape on the outer surface of the transducer layer 1020 of the second mandrel. This design enables acoustic vibration signals to be smoothly transmitted to other parts of the optical cable and be amplified and processed by the multi-layer optical unit layers 2030, thereby improving the detection accuracy and sensitivity of the acoustic signals.

[0056] The number of layers can be further adjusted as needed. As the number of layers set increases, the formed braided net will be denser, and the range covered by its braiding angle will be wider, which is more conducive to sensing acoustic vibration signals transmitted from different angular directions outside.

[0057] Generally, the braiding density of multiple optical unit layers 2030 in the first braided section 2010 is greater than that of multiple optical unit layers 2030 in the second braided section 2020.

[0058] Since the length L1 of the first braided section 2010 is less than the length L2 of the second braided section 2020, and L1 < (0.2 - 0.5) L2; the optical unit layers 2030 will be denser in the first braided section 2010 and sparser in the second braided section 2020, thus forming an obvious dense and sparse braided section.

[0059] By setting the dense and sparse braided section, on the one-dimensional continuous detection path of the optical cable, according to the needs of the detection scenario, the limited length of the optical cable resources can be maximally utilized, and the manufacturing cost of the optical cable can be reduced. At the same time, the dense and sparse braided section exactly corresponds to the transducer layer 1020 and the sensitization layer 1030 of the mandrel 100, making the detection sensitivity of the optical cable change in a gradient manner, which can better fit the application scenario of the optical cable.

[0060] For example, due to the high density within the first braided section 2010, the signal acquisition density of the sensing optical unit layers 2030 within the first braided section 2010 increases, and in cooperation with the sensitization layer 1030, the detection sensitivity of the optical cable will be significantly improved.

[0061] In some embodiments, such as Figure 1As shown, a plurality of tensile elements 1010 are provided, and a transducer layer 1020 is wrapped around the plurality of tensile elements 1010. The parallel use of the plurality of tensile elements 1010 significantly enhances the tensile strength of the optical cable, enabling it to withstand greater external forces and more complex environmental conditions. The transducer layer 1020 is tightly wrapped around the outside of the tensile elements 1010, ensuring that acoustic vibration signals can effectively be transmitted from the outside to the inside of the optical cable. This structural design not only enhances the mechanical properties of the optical cable but also improves the reliability and stability of the optical cable in acoustic monitoring applications by optimizing the transmission path and efficiency of acoustic signals.

[0062] In some embodiments, as Figures 1 to 4 shown, the transducer layer 1020 and the sensitizing layer 1030 are made of polymer materials with different sound transmission coefficients, and the sound transmission coefficient of the sensitizing layer 1030 is significantly higher than that of the transducer layer 1020. (The sound transmission coefficient is the ratio of the internal sound field intensity to the external sound field intensity under a specific external sound pressure at a specific frequency; the larger the sound transmission coefficient, the less reflection of sound waves occurs on the material surface, reducing the loss of sound wave energy; the smaller the sound transmission coefficient, the easier it is for sound waves to be reflected on the material surface).

[0063] On the test surface, at a sound pressure frequency of 20 Hz to 2000 Hz, the smaller the Young's modulus of the plastic layer, the larger its sound transmission coefficient. Therefore, in the sensing optical cable provided in this embodiment, the Young's modulus of the transducer layer 1020 is greater than that of the sensitizing layer 1030, generally at least 5 times higher. Generally, the transducer layer 1020 uses a polymer plastic with a Young's modulus of 2000 - 4000 MPa, and a typical material is polyvinyl chloride. The sensitizing layer 1030 uses a polymer plastic with a Young's modulus of 400 - 600 MPa, and a typical material is thermoplastic elastomer.

[0064] In addition, a plastic layer with a small Young's modulus can generate a higher micro - deformation under external acoustic vibration excitation, resonate with the sensing layer 200 together, amplify the acoustic vibration signal, and improve the acoustic sensitivity of the optical cable.

[0065] Generally, the outer protective layer 300, as the outermost layer of the optical cable, mainly provides mechanical protection and durability. It uses a thermoplastic elastomer material similar to that of the sensitizing layer 1030 of the core shaft 100 but with a higher Young's modulus to ensure that the optical cable can withstand external pressure and abrasion in complex environments (such as underwater, underground, etc.). The material with a high Young's modulus can provide better structural support and prevent the optical cable from being damaged by external forces. The outer protective layer 300 can use materials such as hollow glass microspheres, vermiculite powder, montmorillonite, etc. These fillers can form a porous structure inside the material, which helps to increase the sound transmission coefficient while maintaining a certain mechanical strength.

[0066] In this embodiment, the relationship between the sound transmission coefficient and Young's modulus of the outer protective layer 300, the sensitizing layer 1030, and the transducer layer 1020:

[0067] Sound transmission coefficient: Outer protective layer 300 > Sensitizing layer 1030 > Transducing layer 1020. When the sound wave propagates in the outer protective layer 300, the obstacle encountered is the smallest, which is beneficial to the capture and transmission of the sound wave signal.

[0068] Young's modulus: Sensitizing layer 1030 < Outer protective layer 300 < Transducing layer 1020. While maintaining sufficient flexibility, the optical cable can also provide necessary structural support and stability.

[0069] Furthermore, when the sensing optical cable is used for underwater monitoring, it is necessary to reduce the influence of water flow noise. The surface of the outer protective layer 300 can have a hydrophobic and low-friction coating. Common coating materials include silane-modified polymers, co-built polymers on the polymer surface, and nanoparticles.

[0070] In a specific embodiment, the sensing layer 200 can be coated and fixed with a composite tape of resin replacing the foamed plastic layer and composite polyester film; that is, a layer of resin with a thickness of 0.15 - 0.35 mm is coated on the surface of the woven sensing layer 200. Typical characteristics of the resin: viscosity (25°C), 3000 - 4000 mPa·s, after curing: tensile strength (25°C) is 8 - 15 MPa, elongation at break (25°C) is 5% - 12%, elastic modulus (25°C) is 150 - 250 MPa, and hardness (HD) is 30 - 50. The resin has a small tensile strength and elongation at break, and a small elastic modulus, is softer, deformable, and is more conducive to the optical unit 2030 fitting on the surface of the mandrel 100, and can also undergo micro-deformation with the mandrel 100.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sensing optical cable, characterized in that, Comprising: A mandrel (100), a sensing layer (200), and an outer protective layer (300) arranged in sequence from the inside to the outside; The mandrel (100) includes a tensile element (1010) and a transducer layer (1020) arranged in sequence from the inside to the outside. The mandrel (100) is divided into a plurality of first mandrels and second mandrels that are alternately connected. A sensitizing layer (1030) is provided outside the transducer layer (1020) in the first mandrel; The sensing layer (200) includes a first braided section (2010) and a second braided section (2020); the first braided section (2010) is disposed on the outer surface of the sensitizing layer (1030) in the first mandrel, and the second braided section (2020) is disposed on the outer surface of the transducer layer (1020) in the second mandrel. The length of the first braided section (2010) is different from the length of the second braided section (2020) so that the detection sensitivity of the optical cable changes in a gradient manner.

2. The sensing optical cable according to claim 1, wherein The sensing optical cable further includes: a reinforcing layer (400) disposed between the sensing layer (200) and the outer protective layer (300).

3. The sensing optical cable according to claim 2, wherein A plurality of signal transmission holes (4010) are provided in the reinforcing layer (400) at intervals and all arranged along the extending direction of the reinforcing layer (400).

4. The sensing optical cable according to claim 1, wherein The length of the first braided section (2010) is the same as the length of the sensitizing layer (1030) in the first mandrel, and the length of the second braided section (2020) is the same as the length of the transducer layer (1020) in the second mandrel.

5. The sensing optical cable according to claim 1, characterized in that, The first braided section (2010) and the second braided section (2020) include: a plurality of optical units (2030). The plurality of optical units (2030) of the first braided section (2010) are woven in a net shape on the outer surface of the sensitizing layer (1030) in the first mandrel, and the plurality of optical units (2030) of the second braided section (2020) are woven in a net shape on the outer surface of the transducer layer (1020) in the second mandrel.

6. The sensing optical cable according to claim 5, wherein, A plurality of the optical units (2030) in the first braided section (2010) and / or the second braided section (2020) are provided with multiple layers. The optical units (2030) of each layer in the first braided section (2010) are sequentially stacked and woven in a net shape on the outer surface of the sensitizing layer (1030) in the first mandrel, and the optical units (2030) of each layer in the second braided section (2020) are sequentially stacked and woven in a net shape on the outer surface of the transducer layer (1020) in the second mandrel.

7. The sensing optical cable according to claim 5, characterized in that, The weaving density of the plurality of optical units (2030) in the first braided section (2010) is greater than the weaving density of the plurality of optical units (2030) in the second braided section (2020).

8. The sensing optical cable according to claim 5, wherein The sensing optical cable further includes: A coating layer (500) covering the outer surfaces of the plurality of optical units (2030) of the first braided section (2010) and the second braided section (2020), located between the plurality of optical units (2030) and the outer protective layer (300).

9. The sensing optical cable according to claim 1, characterized in that, The length of the first braided section (2010) is less than the length of the second braided section (2020).

10. The sensing optical cable according to any one of claims 1-9, characterized in that, The sound transmission coefficients of the outer protective layer (300), the sensitivity enhancement layer (1030), and the transducer layer (1020) decrease in sequence, and / or the Young's moduli of the sensitivity enhancement layer (1030), the outer protective layer (300), and the transducer layer (1020) increase in sequence.

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