Self-extinguishing fire resistant optical fiber cable

Abstract

The application belongs to the technical field of optical cables, and provides a self-extinguishing fire-retardant fire-resistant optical cable, a cladding sheath of which comprises, from inside to outside, a water-blocking layer, an inner protective layer, a fire-extinguishing layer, an expandable graphite layer, a non-metal braided layer and an outer protective layer, and a multi-layer cladding sheath layer structure design is adopted, so that the fire-retardant and fireproof performance is more excellent; the cable core comprises a center framework unit and an optical unit, the center framework unit is designed to have an arc-shaped groove on the surface, has a reinforcing element and a metal support inside, and the arc-shaped groove is provided with a metal strip and a flexible graphite paper inside, so that on the one hand, the optical unit can maintain a stable structure in a small space, and on the other hand, the metal strip and the flexible graphite paper form a fireproof belt, and further play a fire-retardant and fireproof role.

Description

Technical Field

[0001] This application relates to the field of optical cable technology, and in particular to a self-extinguishing flame-retardant and fire-resistant optical cable. Background Technology

[0002] Optical fiber cable is a communication cable assembly that uses one or more optical fibers encased in a sheath as the transmission medium and can be used individually or in groups. In recent years, due to the rapid development of my country's telecommunications services, the demand for optical fiber cable products has been continuously increasing, and safety issues have always been a concern for both manufacturers and users. Flame-retardant optical fiber cable is a new type of optical fiber cable that can delay ignition and slow the spread of fire. After the flame-retardant optical fiber cable is removed from the influence of an open flame, the flame will quickly and automatically extinguish, preventing further fire damage. Currently, flame-retardant optical fiber cable is widely used in building integrated wiring, power and telecommunications industries, aviation, shipping, mining, rail transportation, and various special communication applications prone to fire accidents.

[0003] Traditional flame-retardant optical cables typically improve their flammability by enhancing the flame-retardant properties of the cable sheath material. However, because optical cables contain other non-flame-retardant substances or components, even with relatively expensive flame-retardant materials, the spread of flames cannot be completely delayed in the event of a fire. Furthermore, the internal structure of the optical cable is easily damaged, causing signal transmission interruptions, thus affecting its application in high-safety-level applications. Summary of the Invention

[0004] In view of this, this application provides a self-extinguishing flame-retardant and fire-resistant optical cable.

[0005] In a first aspect, embodiments of this application provide a self-extinguishing flame-retardant and fire-resistant optical cable, comprising a cable core and a sheath covering the cable core. The sheath, from the inside out, comprises a water-blocking layer, an inner sheath, a fire-extinguishing layer, an expandable graphite layer, a non-metallic braided layer, and an outer sheath. The fire-extinguishing layer comprises a thermoplastic resin material bonded between the expandable graphite layer and the inner sheath. A fire-extinguishing capsule is disposed inside the thermoplastic resin material, and the fire-extinguishing capsule is filled with a fire-extinguishing agent. Both the outer and inner sheaths are made of low-smoke halogen-free flame-retardant materials. The cable core comprises a central skeleton unit and an optical unit. An arc-shaped groove is provided on the outer surface of the central skeleton unit along the extension direction of the optical cable. The optical unit is disposed within the arc-shaped groove. A reinforcing element is disposed at the center of the central skeleton unit along the extension direction of the optical cable. A metal support is embedded in the central skeleton unit along the extension direction of the optical cable, and the metal support is disposed around the reinforcing element.

[0006] In some embodiments, the maximum outer diameter of the metal support contacts the lowest point of the arcuate groove.

[0007] In some embodiments, the metal support is formed by spirally armoring a stainless steel wire along the periphery of the reinforcing element.

[0008] In some embodiments, a metal strip is attached to the inner surface of the arc-shaped groove, and flexible graphite paper is attached to the side of the metal strip facing the optical unit. The metal strip is a corrugated steel strip or a corrugated aluminum strip, and the thickness of the flexible graphite paper is 0.03 to 0.08 mm. The flexible graphite paper is completely attached to the surface of the metal strip.

[0009] In some embodiments, the expandable graphite layer is formed by bonding expandable graphite to the side of the non-metallic woven layer facing the fire extinguishing layer using a high-temperature resistant adhesive.

[0010] In some embodiments, the fire extinguishing capsules are uniformly disposed circumferentially within the thermoplastic resin material, and the fire extinguishing capsules are connected by capillary tubes to form a whole.

[0011] In some embodiments, the extinguishing agent is at least one of the following: a mixture of flame-retardant ultrafine solid powders with a particle size ≤0.5μm, a nano-substrate composite metal oxide, an inert gas, and a non-flammable gas.

[0012] In some embodiments, the optical unit comprises, from the outside to the inside, a first plastic layer, a fire-resistant layer, a second plastic layer, a water-blocking material, and an optical fiber. The heat distortion temperature, thermal decomposition temperature, and melting point of the first plastic layer are all greater than those of the second plastic layer. The fire-resistant layer is a polyimide composite tape coated with mica powder. The first plastic layer, the fire-resistant layer, and the second plastic layer are formed by three-layer co-extrusion. The water-blocking material is water-blocking yarn.

[0013] In some embodiments, the optical fibers within the optical unit are bound together by a binding element to form a single unit.

[0014] In some embodiments, the optical fiber has a plastic coating or a resin coating.

[0015] The beneficial effects that this application can achieve.

[0016] This application provides a self-extinguishing flame-retardant and fire-resistant optical cable with excellent flame-retardant and self-extinguishing properties. The sheath, from the inside out, consists of a water-blocking layer, an inner sheath, a fire-extinguishing layer, an expandable graphite layer, a non-metallic braided layer, and an outer sheath. The outer and inner sheaths use low-smoke halogen-free flame-retardant materials to inhibit the spread of flames and the generation of toxic fumes. The expandable graphite layer expands during combustion, thus suffocating the flames. Simultaneously, the generated expanded graphite material covers the surface of the inner sheath, isolating the internal materials from oxygen and delaying heat transfer inwards. The non-metallic braided layer, with its multi-mesh, loose fiber structure, provides space for graphite expansion. Furthermore, the fiberglass braid ensures that the expandable graphite does not detach during combustion, improving the structural stability of the fireproof layer. When the fire extinguishing layer is heated, the thermoplastic resin material softens and may even decompose, providing expansion space for the expandable graphite. Simultaneously, the fire extinguishing capsule, subjected to compression from the expandable graphite and high temperatures, experiences breakage in its thin-walled plastic layer, releasing the extinguishing agent inside. This agent lowers the temperature or isolates oxygen, further enhancing the flame-retardant effect and delaying or preventing the transfer of flames or heat to the inner sheath. The cable core includes a central skeleton unit and optical units. The central skeleton unit, with its arc-shaped grooves and internal reinforcing elements and metal supports, enhances the positional stability of the optical units within the cable core. Even if the internal thermoplastic material melts due to high temperatures, the metal supports confine the position of the optical units within a certain range, preventing them from shifting or twisting due to the melted thermoplastic material. This reduces the risk of fiber embrittlement and breakage caused by external environmental or mechanical stress. Therefore, this self-extinguishing flame-retardant and fire-resistant optical cable, with its multi-layered sheath and cable core structure design, exhibits superior flame-retardant and fire-resistant performance.

[0017] In addition, in some implementation examples, a metal strip and flexible graphite paper are provided inside the arc-shaped groove. The metal strip and flexible graphite paper form a fireproof strip. The metal strip improves the compressive strength of the groove and will not deform when exposed to high temperatures. The flexible graphite paper utilizes the fact that graphite expands when exposed to high temperatures or combustion, which can cover the light unit inside the groove and further play a role in flame retardancy and fire prevention.

[0018] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This invention provides a structural schematic diagram of a self-extinguishing flame-retardant and fire-resistant optical cable.

[0021] Figure 2 A schematic diagram of the structure of an optical unit according to this application is shown.

[0022] Among them: 1-outer sheath, 2-non-metallic braided layer, 3-expandable graphite layer, 4-fire extinguishing layer, 5-inner sheath, 6-water-blocking layer, 7-optical unit, 8-metal support component, 9-reinforcing element, 10-metal strip, 11-flexible graphite paper, 12-fireproof layer, 13-cable core, 14-fire extinguishing unit, 15-central skeleton unit, 16-arc groove, 17-first plastic layer, 18-fire resistant layer, 19-second plastic layer, 20-optical fiber, 21-water-blocking material. Detailed Implementation

[0023] The term "comprising" in the specification, claims, and accompanying drawings of this application is synonymous with "including," "containing," or "characterized in," and is inclusive of endpoints or open-ended, and does not exclude additional unstated elements or method steps. "Comprising" is a technical term used in the language of the claims, meaning that the stated element is present, but other elements may be added and still form a construction or method within the scope of the claims.

[0024] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. In this application, the term "about" means encompassing minute variations (at most + / - 10%) of the stated value.

[0025] With the rapid development of my country's telecommunications services, the demand for optical cable products is constantly increasing, and safety issues have always been a concern for both manufacturers and users. This application has identified that current flame-retardant optical cables have the following drawbacks: poor heat insulation between the sheath and the cable core, failing to effectively prevent external heat from transferring inwards during combustion, thus affecting the cable's flame-retardant performance; poor positional stability of the internal optical units, easily causing wear and even breakage of the optical fiber surface during a fire, affecting communication safety during a fire; and poor adhesion and tightness of the fire-resistant and flame-retardant materials, making them prone to detachment and rendering the fire-resistant materials ineffective in flame retardancy.

[0026] In view of this, some embodiments of this application provide a self-extinguishing flame-retardant and fire-resistant optical cable, including a cable core and a sheath covering the cable core. The sheath, from the inside out, consists of a water-blocking layer, an inner sheath, a fire-extinguishing layer, an expandable graphite layer, a non-metallic braided layer, and an outer sheath. The fire-extinguishing layer includes a thermoplastic resin material bonded between the expandable graphite layer and the inner sheath. A fire-extinguishing capsule is disposed inside the thermoplastic resin material. The fire-extinguishing capsule is covered by a thin-walled plastic layer and filled with a fire extinguishing agent. Both the outer and inner sheaths are made of low-smoke halogen-free materials. Flame-retardant material; the cable core includes a central skeleton unit and an optical unit. The outer surface of the central skeleton unit is provided with an arc-shaped groove along the extension direction of the optical cable. The optical unit is disposed in the arc-shaped groove. A metal strip is attached to the inner surface of the arc-shaped groove. Flexible graphite paper is attached to the side of the metal strip facing the optical unit. A reinforcing element is provided at the center of the central skeleton unit along the extension direction of the optical cable. A metal support is embedded in the central skeleton unit along the extension direction of the optical cable. The metal support is disposed around the reinforcing element.

[0027] The self-extinguishing flame-retardant and fire-resistant optical cable provided in this application has a sheath consisting of, from the inside out, a water-blocking layer, an inner sheath, a fire-extinguishing layer, an expandable graphite layer, a non-metallic braided layer, and an outer sheath. The outer and inner sheaths utilize low-smoke, halogen-free flame-retardant materials to inhibit the spread of flames and the generation of toxic fumes. The expandable graphite layer expands during combustion, thus suffocating the flames. Simultaneously, the resulting expanded graphite material covers the surface of the inner sheath, isolating the internal materials from oxygen and delaying heat transfer inwards. The non-metallic braided layer, with its multi-mesh, loose fiber structure, provides space for graphite expansion. Furthermore, the fiberglass braid ensures that the expandable graphite does not detach during combustion, improving the structural stability of the fireproof layer. When the temperature of the fire extinguishing layer rises due to heat, the thermoplastic resin material will slowly soften and even decompose, providing expansion space for the expandable graphite. At the same time, the fire extinguishing unit is subjected to the compression of the expandable graphite and the influence of high temperature, and its thin-walled plastic layer will break, thereby releasing the fire extinguishing agent filled inside. Through the function of the fire extinguishing agent to reduce temperature or isolate oxygen, it further plays a flame-retardant role, delaying or preventing the transfer of flames or heat to the inner protective layer. The cable core includes a central skeleton unit and optical units. The central skeleton unit features an arc-shaped groove on its surface, with reinforcing elements and metal supports inside. The arc-shaped groove contains a metal strip and flexible graphite paper. This design ensures the optical units maintain a stable structure within a small space, enhancing their positional stability and preventing internal displacement and twisting of the optical units due to melting of the internal plastic material. This reduces the risk of fiber embrittlement and breakage caused by external environmental or mechanical stress. Furthermore, the metal strip and flexible graphite paper form a fire-resistant layer. The metal strip improves the groove's compressive strength and prevents deformation at high temperatures. The flexible graphite paper, utilizing the expansion of graphite when exposed to high temperatures or combustion, can encapsulate the optical units within the groove, further enhancing flame retardancy and fire resistance. Therefore, this self-extinguishing flame-retardant and fire-resistant optical cable, with its multi-layered sheath and core structure design, exhibits superior flame-retardant and fire-resistant performance.

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0030] Traditional flame-retardant optical cables typically improve their combustion performance by enhancing the flame-retardant properties of the cable sheath material. However, because optical cables contain other non-flame-retardant substances or components, even with relatively expensive flame-retardant materials, the spread of flames cannot be completely delayed in the event of a fire. Furthermore, the internal structure of the optical cable is easily damaged, causing signal transmission interruptions and thus affecting its application in high-safety-level applications.

[0031] For example, this application has found that existing optical cables have poor heat insulation. When exposed to flames, the cables cannot prevent the external heat from being transferred to the loose tubes. The plastic loose tubes melt when heated, and the shrinkage of the tube material during cooling causes a sharp increase in optical fiber attenuation or even breakage. This application also finds that existing optical cables have poor positional stability of the internal optical units during combustion. The internal plastic material easily melts or carbonizes at high temperatures, causing the optical fibers inside the cable to move internally and become twisted. The fibers are easily compressed and bent, resulting in deformation and wear on the fiber surface, leading to breakage and affecting the normal use of the optical fiber. Furthermore, this application has found that the fire-resistant and flame-retardant materials in existing optical cables have poor adhesion and tightness, making them prone to detachment. For example, when ceramicized polyolefin materials are used as the sheath layer, the loose tube material of the optical unit continues to burn and carbonize at high temperatures during continuous combustion, causing the outer layer of the optical fiber to collapse inwards, affecting the optical fiber transmission performance and even causing fiber breakage.

[0032] In view of the above problems, this application provides a self-extinguishing flame-retardant and fire-resistant optical cable with excellent flame retardancy. In the event of a fire, it can delay the flame from burning into the optical cable, ensure that the optical fiber is not damaged by high temperature, and maintain the integrity of the optical cable communication line.

[0033] like Figure 1 As shown, a self-extinguishing flame-retardant and fire-resistant optical cable includes, from the outside in, an outer sheath 1, a fireproof layer 12, a fire-extinguishing layer 4, an inner sheath 5, a water-blocking layer 6, and a cable core 13. The fireproof layer 12 is composed of a non-metallic braided layer 2 combined with an expandable graphite layer 3. The water-blocking layer 6 is a water-blocking strip. Multiple fire-extinguishing units 14 are uniformly arranged circumferentially inside the fire-extinguishing layer 4. The cable core 13 includes a central skeleton unit 15, and the radial circumferential surface of the central skeleton unit 15 has at least one partially closed arc-shaped groove 16, such as... Figure 1 There are six arc-shaped grooves 16 shown. In other embodiments, the number of arc-shaped grooves 16 can be 1, 2, 3, 4, 5, 7, 8, etc. (natural numbers) depending on the number of optical units and the size of the optical cable. The inner surface of the arc-shaped groove 16 is sequentially bonded with a metal strip 10 and a flexible graphite paper 11. The arc-shaped groove 16 contains at least one optical unit 7. In this embodiment, one arc-shaped groove 16 accommodates one optical unit 7. In other embodiments, depending on the size of the arc-shaped groove 16 and the size of the optical unit 7, more than one optical unit 7 can be provided, such as 2, 3, 4, 5, 6, 7, 8, etc. (natural numbers). The central skeleton unit 15 contains a reinforcing element 9 and a metal support 8.

[0034] In this application, the fireproof layer 12 is composed of a non-metallic woven layer 2 and an expandable graphite layer 3. The non-metallic woven layer 2 can be, for example, made of fiberglass woven tape, mica tape, ceramizable silicone rubber fire-resistant tape, high flame-retardant, fire-resistant, and oxygen-barrier glass cloth wrapping tape, polyimide film tape, etc. Using the non-metallic woven layer 2 (e.g., fiberglass woven tape) as a carrier, expandable graphite is bonded to the non-metallic woven layer 2 with a high-temperature resistant adhesive, thereby forming a fireproof layer that covers the space between the outer protective layer 1 and the inner protective layer 5. The high-temperature resistant adhesive can be, for example, organic polyimide glue, phenolic resin glue, urea-formaldehyde resin glue, heat-resistant epoxy glue, silicone rubber, etc., or inorganic, such as the commonly used ZS-1071 high-temperature resistant inorganic adhesive, etc.

[0035] Graphite crystals possess a hexagonal, planar, layered structure composed of carbon atoms. Carbon atoms on the planes of the layers are bonded by strong covalent bonds, while the layers are bonded by van der Waals forces, which are very weak, and the interlayer distances are relatively large. Therefore, under suitable conditions, various chemical substances such as acids, alkali metals, and salts can intercalate between the graphite layers and combine with carbon atoms to form a new chemical phase—graphite intercalation on compounds (GICs). When heated to a suitable temperature, these GICs can rapidly decompose, producing a large amount of gas, causing the graphite to expand along its axis into a worm-like new substance—expanded graphite. The unexpanded graphite intercalation on compounds are expandable graphite.

[0036] During combustion, expandable graphite expands rapidly, suffocating the flames. Simultaneously, the resulting expanded graphite material covers the inner protective layer, isolating the internal materials from oxygen and slowing heat transfer inwards. The non-metallic woven layer 2, with its porous and loose fiber structure, provides space for graphite expansion. Furthermore, the fiberglass woven tape ensures that the expandable graphite does not detach during combustion, improving the structural stability of the fireproof layer.

[0037] In this application, the inner protective layer 5 and the outer protective layer 1 are made of highly flame-retardant, low-smoke polyolefin materials. For example, low-smoke halogen-free polyolefin materials, such as low-smoke halogen-free polyethylene materials, low-smoke halogen-free cross-linked polyethylene materials, low-smoke halogen-free irradiated cross-linked polyethylene materials, etc. Low-smoke halogen-free (LSZH) materials can control the spread of flames and the generation of toxic fumes.

[0038] In this application, the fire extinguishing layer 4 is made of thermoplastic resin material and is tightly bonded between the fireproof layer 12 and the inner protective layer 5. Multiple fire extinguishing units 14 are evenly spaced circumferentially within the thermoplastic resin material. These fire extinguishing units 14 are connected by tiny capillary tubes, forming a unified whole. Each fire extinguishing unit 14, for example, is shaped like a fire extinguishing capsule, covered by a thin-walled plastic layer and filled with a fire extinguishing agent. The wall thickness of the thin-walled plastic layer is less than 1 mm. When the fire extinguishing layer 4 is heated, the thermoplastic resin material slowly softens and may even gradually decompose, providing expansion space for the expandable graphite in the fireproof layer 12. Simultaneously, the fire extinguishing unit 14, under the pressure of the expandable graphite and the influence of high temperature, will have its thin-walled plastic layer break, releasing the fire extinguishing agent inside. Through the fire extinguishing agent's function of lowering the temperature or isolating oxygen, it further achieves a flame-retardant effect, delaying or preventing the transfer of flames or heat to the inner protective layer.

[0039] The extinguishing agent in this application is a mixture of flame-retardant ultrafine solid powders with a particle size ≤0.5μm. For example, it is a flame-retardant ultrafine solid powder with a particle size ≤0.5μm, including sodium bicarbonate or ammonium phosphate, magnesium stearate, silica powder, and talc. Its function is to decompose under high temperature, absorb heat, chemically inhibit flaming combustion, and suffocate flameless combustion.

[0040] In other embodiments, the extinguishing agent can be a nano-based composite metal oxide, such as nano-dihydroxy composite magnesium hydroxide material with a particle size ≤0.1μm. When heated, the composite metal oxide releases water of crystallization, evaporates, decomposes and releases water vapor, absorbing a large amount of combustion heat energy, thereby significantly reducing the surface temperature of the material, delaying or preventing the material from burning or thermally decomposing. At the same time, the huge specific surface area of ​​the nanoparticles can also suppress the material's smoke emission and reduce the smoke density.

[0041] In other embodiments, the extinguishing agent may also be an inert gas or a non-flammable gas, such as N2 or CO2, which reduces the oxygen content at the combustion site by releasing the gas, thereby preventing combustion.

[0042] The cable core 13 includes a central skeleton unit 15, optical units 7, a metal support 8, and reinforcing elements 9. The central skeleton unit 15 is a solid cylinder of a certain thickness, extruded from a thermoplastic elastomer material, with partially closed arc-shaped grooves 16 on its surface. The reinforcing element 9 fills the center of the central skeleton unit 15 to improve tensile strength. For example, the reinforcing element 9 can be a non-metallic fiber-reinforced plastic rod, such as a glass fiber-reinforced plastic rod, an aramid fiber-reinforced plastic rod, or a carbon fiber-reinforced plastic rod. The metal support 8 extends longitudinally along the periphery of the reinforcing element 9 and is embedded in the central skeleton unit 15 to improve lateral pressure resistance. The metal support 8 also serves to define the position of the optical units after the thermoplastic material within the cable core melts, preventing twisting or warping between the optical units. Among them, the reinforcing element 9 is a metal or non-metal rod with a certain tensile strength. Non-metallic fiber-reinforced plastic rods are preferred. The tensile strength is not less than 1450MPa, the elastic modulus is not less than 55GPa, the bending strength is not less than 1100MPa, the diameter deviation is ±0.02mm, and the density range is 2.05-2.15g / cm3. It should be a round rod with the required diameter, uniform color, and the surface should be free of cracks and burrs and have a smooth feel.

[0043] In some embodiments, the metal support 8 is made of a single stainless steel wire spirally armored, with its maximum outer diameter contacting the lowest point of the arc-shaped groove 16, providing a certain support to the groove. Especially under high temperature or fire conditions, the central skeleton unit 15, which is extruded from thermoplastic elastomer material, may soften or even suffer structural damage, while the metal support 8 will not deform, thus ensuring the stability of the arc-shaped groove 16 and improving the stability of the light unit 7 inside the arc-shaped groove 16.

[0044] In this application, the inner surface of the arc-shaped groove 16 is sequentially bonded with a metal strip 10 and flexible graphite paper 11, forming a fireproof strip with the metal strip 10 as the substrate and the flexible graphite paper 11 as the lining. The metal strip 10 is a corrugated steel strip or corrugated aluminum strip, which improves the compressive strength of the groove and will not deform under high temperatures. The flexible graphite paper 11 is completely bonded to the surface of the metal strip 10, with a thickness of 0.03 to 0.08 mm. Utilizing the fact that graphite expands when exposed to high temperatures or combustion, it can cover the light unit 7 inside the groove, further playing a role in flame retardancy and fire prevention. In some other embodiments of this application, a high-temperature resistant adhesive can be used to bond the flexible graphite paper 11 to the surface of the metal strip 10 to improve the bonding effect.

[0045] The optical unit 7 in this application, such as Figure 2As shown, from the outside in, it includes a first plastic layer 17, a fire-resistant layer 18, a second plastic layer 19, a water-blocking material 21, and an optical fiber 20. In terms of manufacturing process, the first plastic layer 17, the fire-resistant layer 18, and the second plastic layer 19 are co-extruded simultaneously, resulting in superior temperature resistance compared to conventional loose-sleeve tubing. Specifically, the heat distortion temperature, thermal decomposition temperature, and melting point of the first plastic layer 17 are all higher than those of the second plastic layer 19. For example, the material of the first plastic layer 17 is nylon, FEP, ETFE, PFA, LCP, etc. For example, the material of the second plastic layer 19 is PC, PE, PBT, LSZH, PVC, TPE, etc. The fire-resistant layer 18 is a polyimide composite tape coated with mica powder.

[0046] The optical fiber 20 has at least one core and is either single-mode or multimode. For example, it can be a bare fiber with a coating outer diameter of 200μm to 255μm, with common coating materials being acrylic resin or polyamide resin. Alternatively, it can be a coated optical fiber with a plastic coating and an outer diameter of 500μm to 1000μm, with common plastic layers being LSZH, PA, TPE, ETFE, PTFE, or FEP. Furthermore, in some other embodiments, the optical fiber 20 can be a heat-resistant optical fiber to accommodate the coating or plastic coating. For example, a heat-resistant optical fiber with a special polyester (polyimide coating) coating capable of withstanding temperatures up to 300°C.

[0047] Furthermore, in some embodiments, the multiple optical fibers 20 may be independent and dispersed within the optical unit 7. Alternatively, they may be arranged in a certain order and bound together by a suitable material to form a whole, the binding element including, but not limited to, an optical fiber bundle or an optical fiber ribbon.

[0048] Water-blocking material 21 is water-blocking yarn with a dry structure, which can reduce the use of grease and is clean and environmentally friendly.

[0049] It can be seen that the optical unit provided in this application has an overall thickness of 230μm to 600μm, which is similar to the thickness of the loose tube of conventional optical cable, but its heat resistance, flame retardancy, fire resistance and mechanical strength are significantly better than those of conventional loose tube.

[0050] This application discloses a self-extinguishing flame-retardant and fire-resistant optical cable with a multi-layered structure design, resulting in superior flame-retardant and fire-resistant performance. When the optical cable burns, flames and heat can easily penetrate the outer sheath. At this stage, the cable structure is not yet damaged, making fire prevention crucial. Therefore, designing a fire-resistant layer helps to prevent or delay the spread of flames inward, reducing the fire's intensity and providing flame retardancy, thus offering the first layer of protection for the internal cable core structure. Once the fire penetrates the fire-resistant layer, the presence of a fire-extinguishing layer helps the cable extinguish itself, providing the second layer of protection for the internal cable core structure. When the fire intensifies and the cable penetrates the fire-extinguishing layer, the cable structure is also damaged, and the cable's flame-retardant properties are essentially insufficient to prevent the spread of flames or heat. Therefore, maintaining the integrity of the communication line and ensuring uninterrupted fiber optic cable transmission is critical. By designing a cable core with grooved surfaces and internal metal supports, laying expandable fire-resistant tape within the grooves, and using heat-resistant optical units, the cable can further ensure that the optical units maintain a stable structure within a small space, reducing the risk of fiber optic embrittlement and breakage caused by external environmental or mechanical stress, thus providing the third layer of protection.

[0051] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A self-extinguishing flame-retardant and fire-resistant optical cable, comprising a cable core and a sheath covering the cable core, characterized in that, The protective sheath consists of, from the inside out, a water-blocking layer, an inner protective layer, a fire-extinguishing layer, an expandable graphite layer, a non-metallic woven layer, and an outer protective layer. The fire-extinguishing layer comprises a thermoplastic resin material bonded between the expandable graphite layer and the inner protective layer. A fire-extinguishing capsule is disposed inside the thermoplastic resin material, and the fire-extinguishing capsule is filled with a fire-extinguishing agent. Both the outer and inner protective layers are made of low-smoke halogen-free flame-retardant materials. The cable core includes a central skeleton unit and an optical unit. The outer surface of the central skeleton unit is provided with an arc-shaped groove along the extension direction of the optical cable. The optical unit is disposed in the arc-shaped groove. A reinforcing element is provided at the center of the central skeleton unit along the extension direction of the optical cable. A metal support is embedded in the central skeleton unit along the extension direction of the optical cable. The metal support is disposed around the reinforcing element. The maximum outer diameter of the metal support is in contact with the lowest point of the arc-shaped groove. The metal support is formed by spirally armoring a stainless steel wire along the periphery of the reinforcing element. The optical unit comprises, from the outside to the inside, a first plastic layer, a fire-resistant layer, a second plastic layer, a water-blocking material, and an optical fiber. The heat distortion temperature, thermal decomposition temperature, and melting point of the first plastic layer are all greater than those of the second plastic layer.

2. The self-extinguishing flame-retardant and fire-resistant optical cable according to claim 1, characterized in that, A metal strip is attached to the inner surface of the arc-shaped groove, and flexible graphite paper is attached to the side of the metal strip facing the optical unit; the metal strip is a corrugated steel strip or a corrugated aluminum strip, and the thickness of the flexible graphite paper is 0.03~0.08mm, and the flexible graphite paper is completely attached to the surface of the metal strip.

3. The self-extinguishing flame-retardant and fire-resistant optical cable according to claim 1, characterized in that, The expandable graphite layer is formed by bonding expandable graphite to the side of the non-metallic woven layer facing the fire extinguishing layer using a high-temperature resistant adhesive.

4. The self-extinguishing flame-retardant and fire-resistant optical cable according to claim 1, characterized in that, The fire extinguishing capsules are uniformly arranged circumferentially within the thermoplastic resin material, and the fire extinguishing capsules are connected by capillary tubes to form a whole.

5. A self-extinguishing flame-retardant and fire-resistant optical cable according to claim 1, characterized in that, The extinguishing agent is at least one of the following: a mixture of flame-retardant ultrafine solid powders with a particle size ≤0.5μm, a nano-substrate composite metal oxide, an inert gas, or a non-flammable gas.

6. A self-extinguishing flame-retardant and fire-resistant optical cable according to claim 1, characterized in that, The fire-resistant layer is a polyimide composite tape coated with mica powder, and the first plastic layer, the fire-resistant layer and the second plastic layer are three layers co-extruded and formed simultaneously; the water-blocking material is water-blocking yarn.

7. A self-extinguishing flame-retardant and fire-resistant optical cable according to claim 6, characterized in that, The optical fibers within the optical unit are bound together by a binding element to form a whole.

8. A self-extinguishing flame-retardant and fire-resistant optical cable according to claim 6, characterized in that, The optical fiber has a plastic coating or a resin coating.

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