Flame-retardant optical cable with online early warning function

Abstract

The invention belongs to the related field of optical communication transmission technology, and discloses a flame-retardant optical cable with an online early warning function, the optical cable comprises a cable core, a flame-retardant belt and an outer sheath layer which are concentrically sleeved from inside to outside, the cable core comprises a central reinforcing core and a water-blocking belt arranged on the outer side of the central reinforcing core, and an annular cavity is formed between the central reinforcing core and the water-blocking belt; a plurality of optical fiber units and at least one temperature sensitive element are distributed in the annular cavity in the circumferential direction. In addition, the flame-retardant belt and the temperature sensitive element are specifically designed by adopting a crystalline porous material, expanded graphite and the like. According to the invention, the optical cable can obtain good effects in multiple aspects of flame retardance, water resistance, rat prevention and the like, and can realize functions of early warning of fire and the like, so that the optical cable is especially suitable for application occasions such as communication systems of rail transit such as subways, high-speed rails and the like.

Description

Technical Field

[0001] The present invention belongs to the field related to optical communication transmission technology, and more specifically, relates to a flame-retardant optical cable with an online early warning function. Background Art

[0002] Communication optical cable is an optical communication component composed of a cable core made up of several optical fibers and an outer sheath layer. Due to its large transmission capacity, long transmission distance, small size, light weight, and no electromagnetic interference, it is currently the most promising communication transmission media and has been increasingly widely used in many fields such as telecommunications, electricity, and broadcasting.

[0003] Flame retardancy and water resistance are one of the key properties that must be considered for flame retardant optical cables. In the prior art, the commonly used method is to fill the gaps in the cable core with water-blocking fillers and then arrange a flame retardant polyolefin sheath on the outside.

[0004] However, further research shows that the above prior art still has the following defects or steps:

[0005] First, currently flame-retardant optical cables mostly use a single flame-retardant raw material, resulting in poor flame-retardant and protective effects, shortening the service life of communication devices; moreover, traditional flame retardants have poor compatibility with polymers, which will affect the mechanical properties of polymers, making them difficult to degrade and polluting the environment; considering that flame-retardant optical cables are mostly used in communication systems of subways, high-speed railways and other rail transit with large passenger flow, they face higher requirements in terms of flame-retardant effects; secondly, traditional optical cables mostly use water-blocking grease for water-blocking, and because the grease is not easy to clean and is heavy, it brings inconvenience to production testing and construction wiring, and increases costs; finally, existing flame-retardant optical cables are easily bitten by rodents, causing damage to the optical cables, resulting in shortened service life and communication interruptions. The resulting communication optical cable failures cause immeasurable losses to social activities and the national economy, greatly affecting the user experience.

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

[0007] In response to one or more of the above defects or needs in the prior art, the present invention provides a flame-retardant optical cable with an online early warning function, wherein the internal structure and configuration of the optical cable are re-studied and redesigned, and targeted improvements are made to the specific materials and working mechanisms of some key components such as flame-retardant tapes and temperature-sensitive elements. This not only ensures that the optical cable can achieve good results in flame retardancy, water resistance, rodent resistance and other aspects, but also can realize functions such as early warning of fire. Therefore, it is particularly suitable for application scenarios such as communication systems of rail transportation such as subways and high-speed railways.

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

[0009] The cable core includes a central reinforcing core and a water-blocking tape arranged on the outside thereof, and an annular cavity is formed between the central reinforcing core and the water-blocking tape; in the annular cavity, a plurality of optical fiber units and at least one temperature sensitive element are circumferentially distributed;

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

[0011] As a further preferred embodiment of the present invention, armor may be provided between the flame retardant tape 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 a sensing optical fiber filled in the loose tube, wherein 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 achieving high temperature alarm and fault location.

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

[0014] As a further preferred embodiment of the present invention, for the temperature sensitive element, it is preferred that in the secondary casing process, the expanded graphite is blown into the loose tube by gas conveying.

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

[0016] As a further preferred embodiment of the present invention, each of the optical fiber units includes an optical fiber sleeve and a plurality of optical fibers centrally placed in the optical fiber sleeve, and can be water-blocked by filling with water-blocking yarn.

[0017] As a further preferred embodiment of the present invention, a plurality of filling ropes may be arranged 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 layer of the optical cable is preferably made of low-smoke halogen-free flame-retardant material.

[0020] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0021] (1) The present invention redesigns the internal structure and configuration of the multifunctional optical cable, and focuses on improving the specific material composition and working mechanism of the key component of the flame retardant tape: the flame retardant elements and transition metals contained in the composite material can present characteristics such as high specific area and microporous structure, so that it can more effectively absorb smoke, release non-combustible gas, and isolate oxygen from the polymer matrix, thereby avoiding various problems caused by traditional flame retardant materials; in particular, when the combustion of the optical cable spreads to the flame retardant tape isolation layer, the metal sites in the above material can produce metal oxides, promote the formation of a continuous and dense carbon layer, thereby playing the role of a thermal barrier to isolate part of the combustible gas and heat, and at the same time, the released non-combustible gas will reduce the concentration of oxygen, 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 temperature sensitive element, which is an important component: 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 at this time; when a fire occurs and causes the surface temperature of the optical cable to rise, the expanded graphite expands in volume when exposed to high temperature, causing it to squeeze the optical fiber in the casing, and at this time the optical fiber attenuates abnormally or even breaks. This allows the working status of the optical cable (including steps, attenuation exceeding standard parameters) to be known and environmental abnormalities to be discovered in time to avoid major accidents, and the location of the fault can be accurately known through the abnormal attenuation of the optical fiber;

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

[0024] (4) The multifunctional optical cable of the present invention has a compact overall structure and is easy to process and manufacture. It can achieve good effects in flame retardancy, water resistance, and rodent resistance, and can also realize functions such as early warning of fire. Therefore, it is particularly suitable for application occasions such as communication systems of subways, high-speed railways, and other rail transportation, and has good practical value and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0026] In all 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 sleeve; 4-expanded graphite; 5-water-blocking yarn; 6-filling rope; 7-water-blocking tape; 8-flame-retardant tape; 9-armor; 10-outer sheath. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in each embodiment 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 the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0031] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0033] Figure 1 is a structural cross-sectional view of a flame-retardant optical cable with an online warning function according to a preferred embodiment of the present invention, which will be referred to below Figure 1 To explain the present invention in more detail.

[0034] See also Figure 1 The multifunctional optical cable of the present invention comprises a cable core, a flame retardant tape 8 and an outer sheath layer 10 which are concentrically sleeved from the inside to the outside, wherein the cable core comprises a central reinforcing core 1 and a water blocking tape 7 arranged on the outside thereof, and an annular cavity is formed between the central reinforcing core 1 and the water blocking tape 7; in the annular cavity, a plurality of optical fiber units and at least one temperature sensitive element are circumferentially distributed, and a plurality of filling ropes 6 may also be arranged. In addition, an armor 9 may also be arranged between the flame retardant tape 8 and the outer sheath layer 10 of the above-mentioned optical cable.

[0035] More specifically, each optical fiber unit may include an optical fiber sleeve 3 and a plurality of optical fibers 2 centrally placed in the optical fiber sleeve 3 as a conventional structure, and may be filled with water-blocking yarn to block water. The armor 9 of the above optical cable is preferably made of high-strength glass fiber yarn, which can provide excellent tensile strength and prevent damage by rodents, and the fully dry optical cable has a compact structure, light weight and small outer diameter. The outer sheath layer 10 is preferably made of low-smoke halogen-free flame-retardant material.

[0036] As one of the key improvements of the present invention, the flame retardant belt 8 is compositely filled with a crystalline porous material and a flame retardant high molecular polymer, and the crystalline porous material is self-assembled by transition metal elements and organic ligands through coordination bonds. More specifically, its flame retardant high molecular polymer matrix is ​​preferably thermoplastic polyurethane or similar materials, and the transition metal element in its crystalline porous material additive is preferably Zn or Co.

[0037] The reason for this design is that the flame retardant elements and transition metals contained in the composite material can present characteristics such as high specific area and microporous structure, which enables it to more effectively absorb smoke, release non-combustible gases, and isolate oxygen from the polymer matrix, thereby avoiding various problems caused by traditional flame retardant materials; in particular, when the combustion of the optical cable spreads to the flame retardant tape isolation layer, the metal sites in the above materials can produce metal oxides, promote the formation of a continuous and dense carbon layer, thereby acting as a thermal barrier to isolate part of the combustible gas and heat. At the same time, the released non-combustible gas will reduce the concentration of oxygen, 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 a sensing optical fiber filled in the loose tube, and may also include a 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 achieving high temperature alarm and fault location.

[0039] The reason for this design is that expanded graphite, as a functional carbon material, is obtained by intercalation, washing, drying, and high-temperature expansion of natural graphite flakes, and can present a loose and porous worm-like morphology. In addition to the excellent properties of natural graphite itself, such as resistance to cold and heat, corrosion resistance, and self-lubrication, it also has the characteristics of softness, compression resilience, adsorption, ecological environment coordination, biocompatibility, and radiation resistance that natural graphite does not have.

[0040] In the present application, when the expanded graphite is exposed to high temperature, its volume can instantly expand by 150 to 300 times, changing from flake to worm-like, so that the structure is loose, porous and curved, the surface area is enlarged, the surface energy is improved, the adsorption force of flake graphite is enhanced, and the worm-like graphite can be self-interlocked, thus increasing its softness, resilience and plasticity. When the surface temperature of the optical cable is within the normal operating temperature range, the optical fiber unit of the temperature sensing device works normally, and the optical fiber attenuation is small at this time; when a fire occurs and causes the surface temperature of the optical cable to rise, the expanded graphite expands in volume when exposed to high temperature, causing it to squeeze the optical fiber in the casing, and the optical fiber attenuation is abnormal or even broken. In this way, the working status of the optical cable (including steps, attenuation exceeding standard parameters) can be known, and the abnormality of the environment can be discovered in time to avoid major accidents, and the location of the fault can be known through the abnormal attenuation of the optical fiber.

[0041] Through the above design, the intrinsic characteristics of optical fiber transmission, that is, the characteristics that attenuation will deviate from the normal value when subjected to force, can be fully utilized. On the one hand, in actual applications, there is no need to use high-precision equipment, and the optical fiber attenuation data does not require additional processing. The attenuation value can be directly read through testing equipment (such as optical time domain reflectometer), and the optical fiber fault point can be located, which can be directly integrated into the intelligent fire alarm monitoring system; on the other hand, this temperature sensing method has high sensitivity, utilizes the physical properties of the material itself, has good operating stability, and is not easily affected by external interference and functional failure. In addition, flame-retardant optical cables are mostly used in fire prevention scenarios. If a fire actually occurs, the above design can reduce maintenance costs, and the temperature sensing material is not subject to electromagnetic interference, which allows this temperature sensing system to work stably in high voltage and strong electromagnetic field environments.

[0042] According to a preferred embodiment of the application, the temperature-sensitive element is preferably in the secondary sleeve molding process, and the expanded graphite is blown into the loose tube by the mode of gas delivery. For example, a powder feeding device can be set, and its airflow path is connected to the extruder head, and the expanded graphite powder is blown into the loose tube by the mode of gas delivery. In this way, stable and dry airflow is not only used to convey powder, and the addition ratio is controllable, and the transmission performance of the optical fiber itself is not affected. The roundness of the loose tube can also be guaranteed to prevent the optical fiber from sticking to the loose tube inner wall.

[0043] In summary, the optical cable according to the present invention has been re-studied and designed through its internal structure and its setting mode, and has made targeted improvements on the specific materials and working mechanisms of some key components such as flame retardant tapes and temperature sensitive elements. It can achieve good effects in flame retardancy, water resistance and rodent prevention, and can realize functions such as early warning of fire. Therefore, it is particularly suitable for application occasions such as communication systems of rail transportation such as subways and high-speed railways, and has good practical value and application prospects.

[0044] It will be easily understood by those skilled in the art that the above description is only 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 in the protection scope 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 to the outside, a cable core, a flame retardant tape (8) and an outer sheath layer (10) which are concentrically sleeved together, and is characterized in that: The cable core comprises a central reinforcing core (1) and a water-blocking tape (7) arranged on the outside thereof, and an annular cavity is formed between the central reinforcing core (1) and the water-blocking tape (7); in the annular cavity, a plurality of optical fiber units and at least one temperature sensitive element are circumferentially distributed; The flame retardant belt (8) is formed by composite filling of a crystalline porous material and a flame retardant high molecular polymer, wherein the crystalline porous material is formed by self-assembly of transition metal elements and organic ligands through coordination bonds.

2. The flame-retardant optical cable according to claim 1, characterized in that: An armor (9) may also be provided between the flame retardant tape (8) and the outer sheath layer (10) of the optical cable.

3. The flame-retardant optical cable according to claim 1 or 2, characterized in that: The temperature sensitive element comprises a loose tube and expanded graphite (4) and a 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 achieving high temperature alarm and fault location.

4. The flame-retardant optical cable according to claim 3, characterized in that: The temperature sensitive element may further include a water-blocking yarn (5) arranged in the loose tube.

5. The flame-retardant optical cable according to claim 3 or 4, characterized in that: For the temperature sensitive element, it is preferred that in the secondary casing process, the expanded graphite is blown into the loose tube by gas conveying.

6. The flame-retardant optical cable according to any one of claims 1 to 5, characterized in that: For the flame retardant belt (8), its flame retardant high molecular polymer matrix is ​​preferably thermoplastic polyurethane or similar materials, and the transition metal element in its crystalline porous material is preferably Zn or Co.

7. The flame-retardant optical cable according to any one of claims 1 to 6, characterized in that: Each of the optical fiber units comprises an optical fiber sleeve (3) and a plurality of optical fibers (2) centrally placed in the optical fiber sleeve (3), and can be water-blocked by filling with water-blocking yarn.

8. The flame-retardant optical cable according to any one of claims 1 to 7, characterized in that: A plurality of filling ropes (6) may also be arranged in the annular cavity of the optical cable.

9. The flame-retardant optical cable according to claim 2, characterized in that: The armor (9) of the above optical cable is preferably made of high-strength glass fiber yarn.

10. The flame-retardant optical cable according to any one of claims 1 to 9, characterized in that: The outer sheath layer (10) of the optical cable is preferably made of low-smoke halogen-free flame-retardant material.

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