High-performance flame-retardant low-smoke optical cable for rail transit

Abstract

The application provides a high-performance low-smoke and low-flame optical cable for rail transit, which comprises a central reinforcing member, an optical unit layer, a flame-retardant and water-proof tape layer, an aluminum tape layer, an inner protective layer, a flame-retardant glass fiber yarn layer, a steel tape layer and an outer sheath arranged in sequence along the outer circumference of the central reinforcing member, so that the effect of isolating external open flames is achieved, the heat resistance of the optical cable is improved, the overall smoke emission of the optical cable during combustion is reduced, the light transmittance of the optical cable after ignition is significantly improved, the optical cable can be normally used in the case of external combustion or heating of the optical cable, and the safety performance of the optical cable during use is improved.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, specifically to a high-performance flame-retardant low-smoke optical cable for rail transit. Background Technology

[0002] With the rapid development of my country's rail transit industry, the demand for communication optical cables for rail transit is also constantly increasing. Statistics show that in the next few years, the total mileage of passenger dedicated lines and intercity railways under construction will reach 12,000 kilometers; more than 20 cities in my country plan to build subways and light rail systems, with a total mileage of 1,250 km. By 2020, the total length of urban rail transit lines in my country will reach approximately 2,200 km. High- and medium-capacity subway and light rail transit are already quite common. In rail transit systems, because the operating environment for optical cables is a closed environment, and to protect personnel safety during use, there are requirements for the light transmittance and smoke density of optical cables used in rail transit. Existing optical cables for rail transit have the following technical problems:

[0003] 1) Light transmittance is an important factor in evaluating the combustion characteristics of flame-retardant optical cables. Existing optical cables used in rail transit have low light transmittance, which makes it impossible for people to see the escape route and escape smoothly in a fire.

[0004] 2) The existing optical cables used in rail transit have a high smoke density, which results in a large amount of smoke and fumes generated when the optical cables burn, increasing the risk of asphyxiation.

[0005] 3) Existing optical cables for rail transit have poor flame self-extinguishing properties and poor shell-forming properties when burning, which cannot prevent the flame temperature from penetrating further. The penetration of external heat into the optical cable will accelerate the decomposition of the polymer inside the optical cable. When the optical cable is burned or heated from the outside, it will cause the optical cable to malfunction and make it impossible to establish the transmission and connection of optical signals between rail transit lines. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a high-performance flame-retardant low-smoke optical cable for rail transit, which can effectively isolate external open flames, improve the heat resistance of the optical cable, reduce the overall smoke emission of the optical cable during combustion, and significantly improve the light transmittance of the optical cable after ignition. The optical cable can also be used normally even when the external environment is burning or heated, thus improving the safety performance of the optical cable during use.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] This invention provides a high-performance flame-retardant and low-smoke optical cable for rail transit, comprising: a central reinforcing member, and along the outer circumference of the central reinforcing member are sequentially arranged an optical unit layer, a flame-retardant and water-blocking tape layer, an aluminum tape layer, an inner sheath, a flame-retardant fiberglass yarn layer, a steel tape layer, and an outer sheath.

[0009] The present invention provides a high-performance flame-retardant low-smoke optical cable for rail transit, which can isolate the optical cable from external open flames, improve the heat resistance of the optical cable, reduce the overall smoke emission of the optical cable when burning, and significantly improve the light transmittance of the optical cable after ignition. The optical cable can also be used normally when the optical cable is burned or heated in the outside, thus improving the safety performance of the optical cable during use.

[0010] As a preferred technical solution, the optical unit layer includes: multiple loose tubes, multiple optical fibers are disposed inside the loose tubes, fiber grease is filled between the optical fibers and the loose tubes, and the multiple loose tubes are disposed on the outer circumference of the central reinforcing member to form a cable core.

[0011] As a preferred technical solution, the flame-retardant and water-blocking tape layer comprises: a water-blocking tape base treated with a water-based flame retardant and a water-absorbing resin modified with flame-retardant filler, which are used to longitudinally wrap the cable core.

[0012] As a preferred technical solution, a first tear cord is provided on the flame-retardant fiberglass yarn layer, and a second tear cord is provided on the steel strip layer. The first tear cord and the second tear cord are arranged opposite to each other, and both the first tear cord and the second tear cord are longitudinally wrapped with the steel strip layer.

[0013] As a preferred technical solution, water-blocking yarn is provided between the flame-retardant fiberglass yarn layer and the steel strip layer in a relatively opposite manner.

[0014] As a preferred technical solution, the steel strip layer includes: a steel strip and a chromium plating layer, wherein the chromium plating layer covers the steel strip to form a steel strip layer.

[0015] As a preferred technical solution, the flame-retardant fiberglass yarn layer includes: multiple flame-retardant fiberglass yarns, which are uniformly arranged on the outer periphery of the inner protective layer, and the flame-retardant fiberglass yarn is prepared by treating the fiberglass yarns with a flame retardant agent.

[0016] As a preferred technical solution, the flame retardant comprises the following components in parts by weight: 25-45 parts of ammonium polyphosphate, 13-27 parts of N-hydroxymethyl-3-dimethylphosphonopropionamide, 15-45 parts of guanidine phosphate, 15-30 parts of aluminum hydroxide, and 30-56 parts of polyester adhesive.

[0017] As a preferred technical solution, the water-based flame retardant comprises the following components by weight: 3-8 parts by weight of hexabromocyclododecane, 20-50 parts by weight of aluminum dihydrogen phosphate polysilicate, 32-50 parts by weight of diammonium hydrogen phosphate, and 50-70 parts by weight of nitrogen-phosphorus flame retardant solution.

[0018] As a preferred technical solution, the inner sheath is made of a high flame-retardant, low-smoke, halogen-free flame-retardant sheath material with an oxygen index ≥40 and free of nitrogen and phosphorus flame retardants. The outer sheath is made of a high flame-retardant, low-smoke, halogen-free flame-retardant sheath material with an oxygen index ≥40 and free of nitrogen and phosphorus flame retardants. The outer sheath comprises the following components by weight: 50-70 parts by weight of ethylene-vinyl acetate copolymer resin, 5-15 parts by weight of polyethylene octene elastomer, 15-40 parts by weight of polyethylene resin, 8-20 parts by weight of special modified polyethylene resin, 90-150 parts by weight of aluminum hydroxide, 60-120 parts by weight of magnesium hydroxide, 1-3 parts by weight of antioxidant, 2-3 parts by weight of processing aid, and 2-3 parts by weight of carbon black.

[0019] The present invention provides a high-performance flame-retardant and low-smoke optical cable for rail transit, which has the following beneficial effects:

[0020] 1) The high-performance flame-retardant low-smoke optical cable for rail transit provided by the present invention can isolate the external open flame, improve the heat resistance of the optical cable, reduce the overall smoke emission of the optical cable when burning, and significantly improve the light transmittance after the optical cable is ignited. The optical cable can also be used normally when the external environment is burning or heated, and can be used to establish the transmission and connection of optical signals between rail transit lines, thereby improving the safety performance of the optical cable during use.

[0021] 2) The high-performance flame-retardant low-smoke optical cable for rail transit provided by this invention, after the mechanical properties of the optical cable meet the requirements of the YDT901-2019 standard, has a smoke density transmittance of ≥50%, which can significantly improve the transmittance of the optical cable after it catches fire.

[0022] 3) The high-performance flame-retardant low-smoke optical cable for rail transit provided by the present invention uses glass fiber yarn armor on the outside of the inner sheath to enhance the weather resistance and tensile strength of the optical cable, and has a certain anti-rodent biting effect, thus meeting the comprehensive performance requirements of rail optical cable. Attached Figure Description

[0023] Figure 1 The structural diagram of the high-performance flame-retardant low-smoke optical cable for rail transit provided by the present invention;

[0024] Figure 2 A flowchart illustrating the fabrication process of a high-performance flame-retardant, low-smoke optical cable for rail transit provided by this invention.

[0025] Among them, 1-central reinforcing member; 2-loose tube; 3-optical fiber; 4-optical unit layer; 5-fiber paste; 6-flame-retardant and water-blocking tape layer; 7-aluminum tape layer; 8-inner protective layer; 9-flame-retardant fiberglass yarn layer; 10-steel tape layer; 11-outer sheath; 12-first tear rope; 13-water-blocking yarn; 14-flame-retardant fiberglass yarn; 15-second tear rope. Detailed Implementation

[0026] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] It is understood that the present invention achieves its objectives through various embodiments, such as... Figure 1As shown, the high-performance flame-retardant low-smoke optical cable for rail transit provided by the present invention includes: a central reinforcing member 1, and an optical unit layer 4, a flame-retardant and water-blocking tape layer 6, an aluminum tape layer 7, an inner sheath 8, a flame-retardant fiberglass yarn layer 9, a steel tape layer 10, and an outer sheath 11 arranged sequentially around the central reinforcing member 1; the optical unit layer 4 includes: multiple loose tubes 2, which are arranged on the outer circumference of the central reinforcing member 1 to form a cable core, and multiple optical fibers 3 are arranged inside the loose tubes 2, with fiber grease 5 filling the space between the optical fibers 3 and the loose tubes 2; the flame-retardant and water-blocking tape layer 6 includes: a water-blocking tape base treated with a water-based flame retardant and a water-absorbing resin modified with flame-retardant filler, which work together longitudinally. The cable core is covered with a water-based flame retardant comprising the following components by weight: 3-8 parts hexabromocyclododecane, 20-50 parts aluminum dihydrogen phosphate polysilicate, 32-50 parts diammonium hydrogen phosphate, and 50-70 parts nitrogen-phosphorus flame retardant solution. A first tear cord 12 is provided on the flame-retardant fiberglass yarn layer 9, and a second tear cord 15 is provided on the steel strip layer 10. The first tear cord 12 and the second tear cord 15 are arranged opposite to each other, and both the first tear cord 12 and the second tear cord 15 are longitudinally wrapped around the steel strip layer 10. A water-blocking yarn 13 is provided opposite to the flame-retardant fiberglass yarn layer 9 and the steel strip layer 10. The steel strip layer 10 comprises a steel strip and a chrome-plated layer, with the chrome-plated layer covering the steel strip to form the steel strip layer 10. 0; The flame-retardant fiberglass yarn layer 9 comprises: multiple flame-retardant fiberglass yarns 14, which are uniformly arranged on the outer periphery of the inner protective layer 8, and are prepared by treating the fiberglass yarns with a flame retardant agent; the flame retardant agent comprises the following components by weight: 25-45 parts of ammonium polyphosphate, 13-27 parts of N-hydroxymethyl-3-dimethylphosphonopropionamide, 15-45 parts of guanidine phosphate, 15-30 parts of aluminum hydroxide, and 30-56 parts of polyester adhesive; the inner protective layer 8 is prepared using a high flame-retardant, low-smoke, halogen-free flame-retardant sheath material with an oxygen index ≥40 and free of nitrogen and phosphorus flame retardants; the outer sheath 11 is also prepared using a high flame-retardant, low-smoke, halogen-free flame-retardant sheath material with an oxygen index ≥40 and free of nitrogen and phosphorus flame retardants. The outer sheath 11, as prepared, comprises the following components by weight: 50-70 parts by weight of ethylene-vinyl acetate copolymer resin, 5-15 parts by weight of polyethylene octene elastomer, 15-40 parts by weight of polyethylene resin, 8-20 parts by weight of special modified polyethylene resin, 90-150 parts by weight of aluminum hydroxide, 60-120 parts by weight of magnesium hydroxide, 1-3 parts by weight of antioxidant, 2-3 parts by weight of processing aid, and 2-3 parts by weight of carbon black. This effectively isolates the optical cable from external open flames, improves its heat resistance, reduces the overall smoke emission during combustion, and significantly increases its light transmittance after ignition. Furthermore, the optical cable can function normally even when exposed to external combustion or heating, thus enhancing its safety performance during use.

[0028] like Figure 2 As shown, the method for preparing high-performance flame-retardant low-smoke optical cables for rail transit provided by the present invention includes the following steps:

[0029] S1 colores the optical fiber 3, and then extrudes the loose tube 2 through an extrusion mold on the outside of the colored optical fiber 3. Fiber grease 5 is filled between the loose tube 2 and the optical fiber 3. Multiple loose tubes 2 are set on the outer circumference of the central reinforcing member 1 to form the cable core.

[0030] S2 is formed by longitudinally wrapping the water-blocking tape base treated with water-based flame retardant and the water-absorbing resin modified with flame retardant filler on the outside of the cable core to form a flame-retardant water-blocking tape 6.

[0031] S3 is provided with an aluminum strip layer 7, an inner sheath 8, a flame-retardant fiberglass yarn layer 9, a steel strip layer 10 and an outer sheath 11 in sequence along the outer circumference of the flame-retardant and water-blocking strip 6. A first tear cord 12 is provided on the flame-retardant fiberglass yarn layer 9 and a second tear cord 15 is provided on the steel strip layer 10. The first tear cord 12 and the second tear cord 15 are arranged opposite to each other. Both the first tear cord 12 and the second tear cord 15 are longitudinally wrapped with the steel strip layer 10. Water-blocking yarn 13 is arranged opposite to each other between the flame-retardant fiberglass yarn layer 9 and the steel strip layer 10 to form a high-performance flame-retardant and low-smoke optical cable for rail transit.

[0032] High-performance flame-retardant low-smoke optical cable for S4 rail transit is now in service.

[0033] Each of the above steps S1 to S4 is tested to ensure the quality of high-performance flame-retardant low-smoke optical cables for rail transit. This can effectively isolate the optical cable from external open flames, improve its heat resistance, reduce the overall smoke emission during combustion, and significantly improve its light transmittance after ignition. The optical cable can also be used normally even when it is burning or heated externally, thus improving its safety performance during use.

[0034] In some embodiments, it includes: a central reinforcing member 1, and along the outside of the central reinforcing member 1 are arranged a light unit layer 4, a flame-retardant and water-blocking strip layer 6, an aluminum strip layer 7, an inner protective layer 8, a flame-retardant fiberglass yarn layer 9, a steel strip layer 10, and an outer protective sleeve 11.

[0035] In the above embodiment, the aluminum strip layer 7 uses an aluminum strip with a thickness in the range of 0.15 to 0.20 mm, and the aluminum strip overlaps by 9 to 17 mm. The aluminum strip layer 7 serves to prevent external flames from penetrating into the optical cable and to isolate heat from being transferred to the cable core. At the same time, it prevents the flame from igniting the inside of the optical cable core, reduces the rate of polymer decomposition inside the optical cable, and thus reduces the amount of smoke generated by the optical cable.

[0036] The steel strip layer 10 uses steel strips with a thickness of 0.15 to 0.25 mm and overlaps the steel strips by 7 to 12 mm. The steel strip layer 10 serves to prevent external flames from penetrating into the optical cable and to insulate heat from being transferred to the cable core. At the same time, it prevents the flames from igniting the cable core inside the optical cable, reduces the rate of polymer decomposition inside the optical cable, and thus reduces the amount of smoke generated by the optical cable.

[0037] Using flame-retardant fiberglass yarn to wrap the inner sheath can improve the heat resistance of the optical cable and its ability to isolate it from external open flames, prevent the inner sheath from cracking during combustion, and reduce the overall smoke emission of the optical cable during combustion; it also significantly improves the overall performance of the optical cable, including its mechanical properties, resistance to chemical corrosion, creep resistance, and rodent resistance.

[0038] Its structure is simple and easy to operate. It can isolate external open flames, improve the heat resistance of optical cables, reduce the overall smoke output of optical cables when burning, and significantly improve the light transmittance of optical cables after ignition. The light transmittance of optical cables with smoke density meets ≥50%. Optical cables can also be used normally when they are burned or heated in the outside, thus improving the safety performance of optical cables during use.

[0039] In some embodiments, the optical unit 4 includes: a plurality of loose tubes 2, the plurality of loose tubes 2 being disposed on the outer circumference of the central reinforcing member 1 to form a cable core, the loose tubes 2 being provided with a plurality of optical fibers 3, and the space between the optical fibers 3 and the loose tubes 2 being filled with fiber grease 5.

[0040] The above embodiment has a simple structure and is easy to operate. The loose tube 2 process improves the existing extrusion mold and optimizes the tension setting. The extrusion mold extrudes the loose tube 2 with a 12-core 1-tube structure, that is, the loose tube 2 can accommodate up to 12 optical fibers 3.

[0041] In some embodiments, the flame-retardant and water-blocking tape 6 comprises: a water-blocking tape base treated with a water-based flame retardant and a water-absorbing resin modified with flame-retardant filler, which are longitudinally wrapped around the cable core in combination with each other; the water-based flame retardant comprises the following components by weight: 3-8 parts by weight of hexabromocyclododecane, 20-50 parts by weight of aluminum dihydrogen phosphate polysilicate, 32-50 parts by weight of diammonium hydrogen phosphate, and 50-70 parts by weight of nitrogen-phosphorus flame retardant solution.

[0042] Using the above embodiments, the water-blocking tape base treated with water-based flame retardant and the water-absorbing resin modified with flame retardant filler are longitudinally wrapped around the cable core. When burning, the flame-retardant water-blocking tape 6 can exhibit a mesh-like shell-like structure, preventing and isolating external heat from penetrating into the optical cable, thereby reducing the amount of smoke generated when the flame-retardant water-blocking tape is burning.

[0043] In some embodiments, a first tear cord 12 is provided on the flame-retardant fiberglass yarn layer 9, and a second tear cord 15 is provided on the steel strip layer 10. The first tear cord 12 and the second tear cord 15 are arranged opposite to each other, and both the first tear cord 12 and the second tear cord 15 are longitudinally wrapped with the steel strip layer 10.

[0044] The above embodiments are simple in structure, easy to operate, and improve the mechanical performance of optical cables.

[0045] In some embodiments, water-blocking yarn 13 is provided between the flame-retardant fiberglass yarn layer 9 and the steel strip layer 10 in a relatively opposite manner.

[0046] The above embodiments are simple in structure, easy to operate, and improve the water-blocking performance of optical cables.

[0047] In some embodiments, the steel strip layer 10 includes a steel strip and a chromium plating layer, wherein the chromium plating layer covers the steel strip to form the steel strip layer 10.

[0048] The above embodiment has a simple structure and is easy to operate. A chromium-plated layer is wrapped around the steel strip to form a steel strip layer 10. The steel strip layer 10 improves the overall hardness, wear resistance, temperature resistance and corrosion resistance of the optical cable.

[0049] In some embodiments, the flame-retardant fiberglass yarn layer 9 comprises: multiple flame-retardant fiberglass yarns, which are uniformly disposed on the outer periphery of the inner protective layer, and are prepared by treating the fiberglass yarns with a flame retardant agent; the flame retardant agent comprises the following components by weight: 25-45 parts of ammonium polyphosphate, 13-27 parts of N-hydroxymethyl-3-dimethylphosphonopropionamide, 15-45 parts of guanidine phosphate, 15-30 parts of aluminum hydroxide, and 30-56 parts of polyester adhesive.

[0050] Using the above embodiments, the number of fiberglass yarns is 18 to 45, and the fiberglass yarn specifications are 785TEX or 1000TEX non-water-blocking fiberglass yarn. The fiberglass yarn treated with flame retardant is wrapped around the inner sheath, which can improve the heat resistance of the optical cable and the effect of isolating external open flames, prevent the inner sheath of the optical cable from cracking during the combustion process, and reduce the overall smoke emission of the optical cable during combustion; it can also significantly improve the comprehensive performance of the optical cable, such as mechanical properties, chemical corrosion resistance, creep resistance, and rodent bite prevention.

[0051] In some embodiments, the inner protective layer 8 is prepared using a high flame-retardant, low-smoke, halogen-free flame-retardant sheath material with an oxygen index ≥40 and no nitrogen or phosphorus flame retardants, and the thickness of the inner protective sheath is 1.5 to 2.0 mm.

[0052] In the above embodiments, the inner sheath 8 is replaced with a high flame-retardant, low-smoke, halogen-free flame-retardant sheath material that does not contain nitrogen and phosphorus flame retardants and has an oxygen index (OI) ≥ 40, which significantly reduces the amount of smoke generated by the optical cable, improves the weather resistance of the optical cable, and increases the service life of the optical cable.

[0053] In some embodiments, the outer sheath 11 is made of a high flame-retardant, low-smoke, halogen-free flame-retardant sheath material with an oxygen index ≥40 and free of nitrogen and phosphorus flame retardants. The outer sheath comprises the following components by weight: 50-70 parts by weight of ethylene-vinyl acetate copolymer resin, 5-15 parts by weight of polyethylene octene elastomer, 15-40 parts by weight of polyethylene resin, 8-20 parts by weight of special modified polyethylene resin, 90-150 parts by weight of aluminum hydroxide, 60-120 parts by weight of magnesium hydroxide, 1-3 parts by weight of antioxidant, 2-3 parts by weight of processing aid, and 2-3 parts by weight of carbon black. The thickness of the outer sheath 11 is ≥2.0 mm.

[0054] In the above embodiments, the outer sheath 11 is made of a high flame-retardant, low-smoke, halogen-free flame-retardant sheath material with no nitrogen and phosphorus flame retardants and an oxygen index (OI) ≥ 40, which reduces the amount of smoke generated by the outer sheath, improves the self-extinguishing properties of the flame during combustion and the shell-forming properties of the optical cable, reduces the decomposition of polymers inside the optical cable, and prevents the flame temperature from further penetrating into the interior of the optical cable.

[0055] The present invention provides a high-performance flame-retardant and low-smoke optical cable for rail transit, which has the following beneficial effects:

[0056] 1) The high-performance flame-retardant low-smoke optical cable for rail transit provided by the present invention can isolate the external open flame, improve the heat resistance of the optical cable, reduce the overall smoke emission of the optical cable when burning, and significantly improve the light transmittance after the optical cable is ignited. The optical cable can also be used normally when the external environment is burning or heated, and can be used to establish the transmission and connection of optical signals between rail transit lines, thereby improving the safety performance of the optical cable during use.

[0057] 2) The high-performance flame-retardant low-smoke optical cable for rail transit provided by this invention, after the mechanical properties of the optical cable meet the requirements of the YDT901-2019 standard, has a smoke density transmittance of ≥50%, which can significantly improve the transmittance of the optical cable after it catches fire.

[0058] 3) The high-performance flame-retardant low-smoke optical cable for rail transit provided by the present invention uses glass fiber yarn armor on the outside of the inner sheath to enhance the weather resistance and tensile strength of the optical cable, and has a certain anti-rodent bite effect, thus meeting the comprehensive performance requirements for use in rail optical cables.

[0059] It is understood that this invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are protected by this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of this invention.

Claims

1. A high-performance flame-retardant, low-smoke optical cable for rail transit, characterized in that, include: The central reinforcement is provided with, in sequence, a light unit layer, a flame-retardant and water-blocking strip layer, an aluminum strip layer, an inner protective layer, a flame-retardant fiberglass yarn layer, a steel strip layer and an outer protective sleeve along the outer circumference of the central reinforcement. The optical unit layer includes: multiple loose tubes, multiple optical fibers are provided inside the loose tubes, fiber grease is filled between the optical fibers and the loose tubes, and the multiple loose tubes are arranged on the outer circumference of the central reinforcing member to form a cable core. The flame-retardant and water-blocking tape layer comprises: a water-blocking tape base treated with a water-based flame retardant and a water-absorbing resin modified with flame-retardant filler, which are used to longitudinally wrap the cable core. The water-based flame retardant comprises the following parts by weight: 3-8 parts by weight of hexabromocyclododecane, 20-50 parts by weight of polyaluminum dihydrogen phosphate, 32-50 parts by weight of diammonium hydrogen phosphate, and 50-70 parts by weight of nitrogen-phosphorus flame retardant solution. The inner sheath is made of a high flame-retardant, low-smoke, halogen-free flame-retardant sheath material with an oxygen index ≥40 and free of nitrogen and phosphorus flame retardants. The outer sheath is also made of a high flame-retardant, low-smoke, halogen-free flame-retardant sheath material with an oxygen index ≥40 and free of nitrogen and phosphorus flame retardants. The outer sheath comprises the following components by weight: 50-70 parts by weight of ethylene-vinyl acetate copolymer resin, 5-15 parts by weight of polyethylene octene elastomer, 15-40 parts by weight of polyethylene resin, 8-20 parts by weight of special modified polyethylene resin, 90-150 parts by weight of aluminum hydroxide, 60-120 parts by weight of magnesium hydroxide, 1-3 parts by weight of antioxidant, 2-3 parts by weight of processing aid, and 2-3 parts by weight of carbon black.

2. The high-performance flame-retardant low-smoke optical cable for rail transit according to claim 1, characterized in that, A first tear cord is provided on the flame-retardant fiberglass yarn layer, and a second tear cord is provided on the steel strip layer. The first tear cord and the second tear cord are arranged opposite to each other, and both the first tear cord and the second tear cord are longitudinally wrapped with the steel strip layer.

3. The high-performance flame-retardant low-smoke optical cable for rail transit according to claim 1, characterized in that, Water-blocking yarn is provided between the flame-retardant fiberglass yarn layer and the steel strip layer in a relatively opposite manner.

4. The high-performance flame-retardant low-smoke optical cable for rail transit according to claim 1, characterized in that, The steel strip layer comprises: a steel strip and a chromium-plated layer, wherein the chromium-plated layer covers the steel strip to form the steel strip layer.

5. The high-performance flame-retardant low-smoke optical cable for rail transit according to claim 1, characterized in that, The flame-retardant fiberglass yarn layer includes: multiple flame-retardant fiberglass yarns, which are evenly arranged on the outer periphery of the inner protective layer. The flame-retardant fiberglass yarn is prepared by treating the fiberglass yarns with a flame retardant agent.

6. The high-performance flame-retardant low-smoke optical cable for rail transit according to claim 5, characterized in that, The flame retardant comprises the following parts by weight: 25-45 parts by weight of ammonium polyphosphate, 13-27 parts by weight of N-hydroxymethyl-3-dimethylphosphonopropionamide, 15-45 parts by weight of guanidine phosphate, 15-30 parts by weight of aluminum hydroxide, and 30-56 parts by weight of polyester adhesive.

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