Flame-retardant optical cable with online early warning function

Abstract

The application belongs to the field of optical communication transmission technology, and discloses a flame-retardant optical cable with online early warning function, which comprises, from inside to outside, a cable core, a flame-retardant band and an outer sheath layer which are concentrically matched, wherein the cable core comprises a central reinforcing core and a water-blocking band arranged outside the central reinforcing core, and an annular cavity is formed between the central reinforcing core and the water-blocking band; a plurality of optical fiber units and at least one temperature sensitive element are circumferentially distributed in the annular cavity. In addition, the flame-retardant band and the temperature sensitive element are designed by using crystalline porous materials, expanded graphite and the like respectively. Through the application, not only good effects of flame retardation, water blocking and rat prevention can be obtained, but also functions such as early fire warning can be realized, so that the application is especially suitable for application occasions such as communication systems of subway and high-speed rail track transportation.

Description

Technical Field

[0001] This invention belongs to the field of optical communication transmission technology, and more specifically, relates to a flame-retardant optical cable with online early warning function. Background Technology

[0002] Optical fiber cables are optical communication components consisting of a cable core made of several optical fibers and an outer sheath. Due to their characteristics such as large transmission capacity, long transmission distance, small size, light weight, and no electromagnetic interference, they are currently the most promising communication transmission media and have been increasingly widely used in telecommunications, power, broadcasting and other fields.

[0003] Flame retardancy and water resistance are among the key performance characteristics that must be considered for flame-retardant optical cables. In existing technologies, the common approach is to fill the gaps inside the cable core with water-blocking filler and then install a flame-retardant polyolefin sheath on the outside.

[0004] However, further research has shown that the aforementioned existing technologies still have the following defects or steps:

[0005] First, current flame-retardant optical cables mostly use a single flame-retardant raw material, resulting in poor flame-retardant and protective effects, shortening the lifespan of communication devices. Furthermore, traditional flame retardants have poor compatibility with polymers, affecting the polymer's mechanical properties, making them difficult to degrade, and polluting the environment. Considering that flame-retardant optical cables are mainly used in communication systems of subways, high-speed railways, and other rail transit systems with high passenger flow, higher requirements are placed on their flame-retardant performance. Second, traditional optical cables mostly use water-blocking grease for water blocking. Because the grease is difficult to clean, heavy, and causes inconvenience in production, testing, and wiring, it also increases costs. Finally, existing flame-retardant optical cables are easily damaged by rodents, leading to shortened service life and communication interruptions. Such communication cable failures cause incalculable losses to social activities and the national economy, greatly impacting the user experience.

[0006] Accordingly, it is necessary to make further improvements in this area to better meet the comprehensive protection needs of various optical cables. Summary of the Invention

[0007] To address one or more of the above-mentioned deficiencies or needs of existing technologies, this invention provides a flame-retardant optical cable with online early warning function. By re-studying and redesigning the internal structure and its arrangement, and by making targeted improvements to key components such as flame-retardant strips and temperature-sensitive elements in terms of their specific materials and working mechanisms, this invention not only ensures that the optical cable achieves good results in flame retardancy, water resistance, and rodent prevention, but also enables functions such as early fire warning. Therefore, it is particularly suitable for applications such as communication systems in rail transit systems such as subways and high-speed railways.

[0008] To achieve the above objectives, according to the present invention, a flame-retardant optical cable with online early warning function is provided, characterized in that the optical cable comprises, from the inside out, a concentrically nested cable core, a flame-retardant tape, and an outer sheath layer, characterized in that:

[0009] The cable core includes a central reinforcing core and a water-blocking strip disposed on its outer side, and an annular cavity is formed between the central reinforcing core and the water-blocking strip; in the annular cavity, a plurality of optical fiber units and at least one temperature-sensitive element are distributed circumferentially.

[0010] The flame-retardant strip is composed of a composite filling of crystalline porous material and flame-retardant polymer, wherein the crystalline porous material is formed by the self-assembly of transition metal elements and organic ligands through coordination bonds.

[0011] As a further preferred embodiment of the present invention, an armor plating may also be provided between the flame-retardant strip and the outer sheath layer of the optical cable.

[0012] As a further preferred embodiment of the present invention, the temperature-sensitive element includes a loose tube and expanded graphite and sensing optical fiber filled in the loose tube. When the surface temperature of the optical cable rises to a critical value, the volume of the expanded graphite in the loose tube expands to compress the sensing optical fiber, causing the attenuation state of the sensing optical fiber to change or the fiber to break, thereby realizing high temperature alarm and fault location.

[0013] As a further preferred embodiment of the present invention, the temperature-sensitive element may further include water-blocking yarn disposed within the loose sleeve.

[0014] As a further preferred embodiment of the present invention, for the temperature-sensitive element, it is preferable to use gas delivery to blow expanded graphite into the loose tube during the secondary molding process.

[0015] As a further preferred embodiment of the present invention, the flame-retardant tape preferably uses thermoplastic polyurethane or similar materials as its flame-retardant polymer matrix, and the transition metal element in its crystalline porous material is preferably Zn or Co, etc.

[0016] As a further preferred embodiment of the present invention, each of the optical fiber units includes an optical fiber sleeve and multiple optical fibers centrally placed in the optical fiber sleeve, and water-blocking yarn can be used to fill the sleeve to block water.

[0017] As a further preferred embodiment of the present invention, a plurality of filler ropes may also be provided in the annular cavity of the optical cable.

[0018] As a further preferred embodiment of the present invention, the armor of the optical cable is preferably made of high-strength glass fiber yarn.

[0019] As a further preferred embodiment of the present invention, the outer sheath of the optical cable is preferably made of a low-smoke, halogen-free flame-retardant material.

[0020] In summary, the technical solutions conceived by this invention have the following main technical advantages compared with the prior art:

[0021] (1) This invention redesigns the internal structure and configuration of the multifunctional optical cable, and makes targeted improvements to the specific material composition and working mechanism of the key component, the flame-retardant strip: the flame-retardant elements and transition metals contained in the composite material can exhibit characteristics such as high specific area and microporous structure, which enable it to more effectively adsorb smoke, release non-combustible gases, and isolate oxygen from the contact between the polymer matrix, thereby avoiding various problems caused by traditional flame-retardant materials; in particular, when the optical cable fire spreads to the flame-retardant strip isolation layer, the metal sites in the above-mentioned materials can generate metal oxides, promote the formation of a continuous and dense carbon layer, thereby playing the role of a thermal barrier to isolate some combustible gases and heat, while the released non-combustible gases will reduce the oxygen concentration, further achieving the purpose of flame retardancy;

[0022] (2) The present invention also focuses on making targeted improvements to the specific structure and working mechanism of the important component of temperature-sensitive element: when the surface temperature of the optical cable is within the normal operating temperature range, the sensing optical fiber in the temperature-sensitive element works normally, and the optical fiber attenuation is small; when a fire occurs and the surface temperature of the optical cable rises, the expanded graphite expands in volume when exposed to high temperature, causing it to squeeze the optical fiber in the sleeve, at which point the optical fiber attenuation is abnormal or even breaks. Thus, the working status of the optical cable (including steps, attenuation exceeding the standard parameters) can be known and environmental anomalies can be detected in time to avoid major accidents. Furthermore, the location of the fault can be accurately known through the abnormal attenuation of the optical fiber.

[0023] (3) The temperature sensing method in this invention makes full use of the intrinsic characteristics of optical fiber transmission, namely that the attenuation will deviate from the normal value when subjected to force. In practical applications, there is no need to use high-precision equipment, and the optical fiber attenuation data does not need to be processed. The attenuation value can be directly read by testing equipment (such as optical time domain reflectometer), and the optical fiber fault point can be accurately located. It can be directly integrated into the fire alarm intelligent monitoring system. In addition, this temperature sensing method has high sensitivity, utilizes the physical properties of the material itself, has good operational stability, is not easily affected by external interference leading to functional failure, and is conducive to reducing maintenance costs.

[0024] (4) The multifunctional optical cable of the present invention has a compact overall structure, is easy to process and manufacture, and can achieve good results in many aspects such as flame retardancy, water blocking and rodent prevention. At the same time, it can realize functions such as early warning of fire. Therefore, it is particularly suitable for applications such as communication systems of rail transit such as subways and high-speed railways, and has good practical value and application prospects. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view of the structure of a flame-retardant optical cable with online early warning function according to a preferred embodiment of the present invention;

[0026] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, specifically:

[0027] 1-Central reinforcing core; 2-Optical fiber; 3-Optical fiber sheath; 4-Expanded graphite; 5-Water-blocking yarn; 6-Filling rope; 7-Water-blocking tape; 8-Flame-retardant tape; 9-Armor; 10-Outer sheath. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0031] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to 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 invention according to the specific circumstances.

[0032] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0033] Figure 1 This is a cross-sectional view of a flame-retardant optical cable with online early warning function according to a preferred embodiment of the present invention. The following will refer to... Figure 1 To explain the invention in more detail.

[0034] See Figure 1 The multifunctional optical cable of the present invention comprises, from the inside out, a concentrically nested cable core, a flame-retardant strip 8, and an outer sheath layer 10. The cable core includes a central reinforcing core 1 and a water-blocking strip 7 disposed on its outer side, with an annular cavity formed between the central reinforcing core 1 and the water-blocking strip 7. Within this annular cavity, multiple optical fiber units and at least one temperature-sensitive element are circumferentially distributed, and multiple filler ropes 6 may also be provided. Furthermore, an armor 9 may be provided between the flame-retardant strip 8 and the outer sheath layer 10 of the aforementioned optical cable.

[0035] More specifically, each optical fiber unit, as a conventional structure, may include an optical fiber sheath 3 and multiple optical fibers 2 centrally placed within the sheath 3, and may be filled with water-blocking yarn. The armor 9 of the aforementioned optical cable is preferably made of high-strength glass fiber yarn, thereby providing excellent tensile strength, preventing damage from rodents, and resulting in a compact, lightweight, and small-diameter all-dry optical cable structure. The outer sheath 10 is preferably made of a low-smoke, halogen-free flame-retardant material.

[0036] As one of the key improvements of this invention, the flame-retardant band 8 is composed of a composite filling of a crystalline porous material and a flame-retardant polymer. The crystalline porous material is formed by the self-assembly of a transition metal element and an organic ligand through coordination bonds. More specifically, its flame-retardant polymer matrix is ​​preferably thermoplastic polyurethane or a similar material, and the transition metal element in its crystalline porous material additive is preferably Zn or Co, etc.

[0037] The reason for this design is that the flame-retardant elements and transition metals contained in the composite material exhibit characteristics such as high specific area and microporous structure, which enable it to more effectively adsorb flue gas, release non-combustible gases, and isolate oxygen from contact with the polymer matrix, thereby avoiding various problems caused by traditional flame-retardant materials. In particular, when the optical cable fire spreads to the flame-retardant isolation layer, the metal sites in the above-mentioned material can generate metal oxides, promoting the formation of a continuous and dense carbon layer, thereby acting as a thermal barrier to isolate some combustible gases and heat. At the same time, the released non-combustible substances will reduce the oxygen concentration, further achieving the purpose of flame retardancy.

[0038] As another key improvement of the present invention, the temperature-sensitive element includes a loose tube and expanded graphite 4 and sensing optical fiber filled in the loose tube. It may also include water-blocking yarn 5, etc. When the surface temperature of the optical cable rises to a critical value, the volume of the expanded graphite in the loose tube expands to squeeze the sensing optical fiber, causing the attenuation state of the sensing optical fiber to change or the fiber to break, thereby realizing high temperature alarm and fault location.

[0039] This design is based on the fact that expanded graphite, as a functional carbon material, is obtained from natural graphite flakes through intercalation, washing, drying, and high-temperature expansion, resulting in a loose, porous, worm-like morphology. In addition to possessing the excellent properties of natural graphite, such as resistance to heat and cold, corrosion resistance, and self-lubrication, it also exhibits characteristics not found in natural graphite, including softness, compression resilience, adsorption, environmental compatibility, biocompatibility, and radiation resistance.

[0040] In this application, expanded graphite can instantly expand 150 to 300 times its original volume when exposed to high temperatures, changing from a sheet-like structure to a worm-like structure. This results in a loose, porous, and tortuous structure, increased surface area, enhanced surface energy, and stronger adsorption of flake graphite. The worm-like graphite particles can self-interlock, thus increasing its flexibility, resilience, and plasticity. When the surface temperature of the optical cable is within the normal operating temperature range, the fiber optic unit of the temperature sensing device operates normally, and the fiber attenuation is minimal. However, when a fire causes the surface temperature of the optical cable to rise, the expanded graphite expands due to the high temperature, causing it to compress the optical fiber inside the sheath. This results in abnormal fiber attenuation or even fiber breakage. This allows for the determination of the optical cable's operating status (including steps and excessive attenuation parameters) and timely detection of environmental anomalies, preventing major accidents. Furthermore, the location of the fault can be identified through abnormal fiber attenuation.

[0041] The above design fully utilizes the intrinsic characteristics of optical fiber transmission, namely, its attenuation deviates from normal values ​​under stress. On one hand, in practical applications, high-precision equipment is unnecessary, and the fiber attenuation data requires no additional processing; the attenuation value can be directly read using testing equipment (such as an optical time-domain reflectometer), allowing for the location of fiber optic faults and direct integration into intelligent fire alarm monitoring systems. On the other hand, this temperature sensing method offers high sensitivity, utilizes the inherent physical properties of the material, exhibits good operational stability, and is not easily affected by external interference leading to functional failure. Furthermore, flame-retardant optical cables are frequently used in fire-prevention scenarios. In the event of a fire, the above design can reduce maintenance costs, and the temperature-sensing material is unaffected by electromagnetic interference, enabling this temperature sensing system to operate stably even in high-pressure and strong electromagnetic field environments.

[0042] According to a preferred embodiment of this application, the temperature-sensitive element is preferably injected into the loose tube via gas delivery during the secondary molding process, where expanded graphite is blown in. For example, a powder feeding device can be provided, with its airflow path connected to the extruder head, to blow expanded graphite powder into the loose tube via gas delivery. In this way, a stable and dry airflow is not only used to transport the powder, but the addition ratio is also controllable, without affecting the transmission performance of the optical fiber itself. It also ensures the roundness of the loose tube and prevents the optical fiber from sticking to the inner wall of the loose tube.

[0043] In summary, the optical cable according to the present invention, through re-study and redesign of its internal structure and its arrangement, and with targeted improvements to key components such as flame-retardant strips and temperature-sensitive elements in terms of specific materials and working mechanisms, can achieve good results in multiple aspects such as flame retardancy, water resistance, and rodent prevention. At the same time, it can realize functions such as early fire warning. Therefore, it is particularly suitable for applications such as communication systems of rail transit such as subways and high-speed railways, and has good practical value and application prospects.

[0044] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flame-retardant optical cable with online early warning function, characterized in that, The optical cable comprises, from the inside out, a concentrically nested cable core, a flame-retardant tape (8), and an outer sheath layer (10), characterized in that: The cable core includes a central reinforcing core (1) and a water-blocking strip (7) disposed on its outer side, and an annular cavity is formed between the central reinforcing core (1) and the water-blocking strip (7); in the annular cavity, a plurality of optical fiber units and at least one temperature-sensitive element are distributed circumferentially. The temperature-sensitive element includes a loose tube and expanded graphite (4) and sensing optical fiber filled in the loose tube. When the surface temperature of the optical cable rises to a critical value, the volume of the expanded graphite in the loose tube expands to squeeze the sensing optical fiber, causing the attenuation state of the sensing optical fiber to change or the fiber to break, thereby realizing high temperature alarm and fault location. The flame-retardant strip (8) is composed of a crystalline porous material and a flame-retardant polymer composite, wherein the crystalline porous material is formed by the self-assembly of transition metal elements and organic ligands through coordination bonds.

2. The flame-retardant optical cable as described in claim 1, characterized in that, An armor (9) is also provided between the flame-retardant strip (8) and the outer sheath layer (10) of the above-mentioned optical cable.

3. The flame-retardant optical cable as described in claim 1, characterized in that, The temperature-sensitive element also includes a water-blocking yarn (5) arranged inside the loose tube.

4. The flame-retardant optical cable as described in claim 1, characterized in that, For the temperature-sensitive element, in the secondary molding process, the expanded graphite (4) is blown into the loose tube by gas delivery.

5. The flame-retardant optical cable as described in any one of claims 1 to 4, characterized in that, For the flame-retardant tape (8), its flame-retardant polymer matrix is ​​thermoplastic polyurethane, and the transition metal element in its crystalline porous material is Zn or Co.

6. The flame-retardant optical cable as described in claim 1, characterized in that, Each of the optical fiber units includes an optical fiber sleeve (3) and multiple optical fibers (2) centrally placed in the optical fiber sleeve (3), and is filled with water-blocking yarn to block water.

7. The flame-retardant optical cable as described in claim 1, characterized in that, In the annular cavity of the aforementioned optical cable, multiple filler ropes (6) are also provided.

8. The flame-retardant optical cable as described in claim 2, characterized in that, The armor (9) of the aforementioned optical cable is made of high-strength glass fiber yarn.

9. The flame-retardant optical cable as described in claim 1, characterized in that, The outer sheath (10) of the aforementioned optical cable is made of low-smoke halogen-free flame-retardant material.

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