High-fiber density compact air blown microcable

Abstract

The application belongs to the technical field of communication cables, and particularly relates to a high-fiber-density compact air-blow microcable. The high-fiber-density compact air-blow microcable comprises, from inside to outside, a light-cured non-metallic reinforcing member, at least one layer of light unit stranding layer and an outer sheath layer; the light unit stranding layer is obtained by stranding the light unit on the outside of the non-metallic reinforcing member; the light unit comprises, from inside to outside, a fine-diameter optical fiber layer, a fiber paste layer and a loose tube; secondary pre-coating technology is adopted for overmolding, so that the fiber paste fullness is achieved; the cable has excellent mechanical properties, meets the laying requirements in complex environments, has a short-term 1 min tension of 1000 N, an optical fiber strain of <0.5%, and a residual additional attenuation of the optical fiber under tension, flattening and impact conditions of ≤0.1 dB@1550 nm. The attenuation change of the microcable under high and low temperature cycles is at most 0.033 dB / km, the air-blowing distance can reach more than 1.5 km, and the microcable shows good laying performance.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication technology, specifically relating to a high fiber density compact air-blown microcable. Background Technology

[0002] With the rapid development of 5G networks, data centers, smart cities and the Internet of Things, air-blown microcables have gained increasing market recognition due to their advantages such as convenient construction and low overall cost.

[0003] Air-blown microduct cable technology is an installation method that uses compressed air to blow microduct cables into pre-laid microducts. It separates cable laying from duct construction, providing extremely high flexibility and future expansion capabilities. The microducts are typically made of high-density polyethylene, possessing good flexibility, pressure resistance, chemical corrosion resistance, and a low coefficient of friction inner wall. The core characteristics of microduct cables are small diameter, light weight, high density, compact structure, and smooth surface. They primarily use bend-insensitive fibers to accommodate bending within confined spaces. The fiber core count ranges widely, from a few cores to hundreds. The increasing use of 200μm fibers allows for more fibers to be accommodated in microducts of the same outer diameter. The sheath material typically employs special low-friction, high-abrasion-resistant, and highly flexible materials to ensure smooth blowing within the microduct and protect the fiber.

[0004] In air-blown microcable technology, after the micro-duct network is built, optical cables of different core counts and types can be blown in as needed to achieve on-demand capacity expansion and avoid excessive initial investment. Micro-duct bundles can fully utilize the space in the main duct, and the micro-cables themselves have small diameters and high core density, greatly saving duct resources. The blowing speed is much faster than traditional traction methods, making it particularly suitable for long-distance routes with many bends. It reduces manhole operation time. The air-blowing process provides more precise and uniform tension control for the optical cable, avoiding excessive tension or surges that may be caused by traction, reducing the risk of fiber damage and additional attenuation during construction. Compared to traditional large-cable traction, air-blown microcables can have more relaxed requirements on the curvature, continuity, and smoothness of the duct route, offering significant advantages, especially in complex routes.

[0005] Driven by the continued growth in demand for fiber optic networks, the market is increasingly looking for air-blown microcables with higher fiber density and smaller cable diameters. Air-blown microcables typically have a fiber density of 5–6 cores / mm². 2 Increasing fiber density and reducing sheath wall thickness can easily lead to sheath flattening under stress, resulting in substandard fiber attenuation. Furthermore, the air-blowing distance for high-core-count air-blown microcables is difficult to meet requirements of 1.5km or more. Therefore, a high-fiber-density, compact air-blown microcable needs to be designed. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides the following technical solution:

[0007] This invention provides a high fiber density compact air-blown microcable, comprising a non-metallic reinforcing member, at least one optical unit stranded layer, and an outer sheath layer arranged sequentially from the inside out; the optical unit stranded layer is obtained by stranding optical units to the outside of the non-metallic reinforcing member; the optical unit is composed of an optical fiber layer, a fiber grease layer, and a loose tube arranged sequentially from the inside out;

[0008] The outer sheath layer is composed of the following materials by weight percentage: 70-80% high-density polyethylene, 4-9% lubricant, 6-17% low-shrinkage modifier, 3-8% wear-resistant filler, 0.5-1.5% titanate coupling agent and 0.2-0.5% antioxidant.

[0009] The antioxidant is selected from primary antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) and secondary antioxidant 168 (tris[2,4-di-tert-butylphenyl]phosphite) in a mass ratio of 1:1.

[0010] The relative molecular mass of the high-density polyethylene is 100,000 to 350,000.

[0011] Preferably, the lubricant is selected from stearic acid, and the low-shrinkage modifier is selected from hydrated magnesium silicate (Mg3Si4O3). 10 (OH)2), the titanate coupling agent is selected from isopropyl tris(dioctyl pyrophosphate) titanate (CAS No. 67691-13-8), and the wear-resistant filler is selected from zirconium oxide and silicone masterbatch.

[0012] Preferably, the optical fiber layer consists of 22-26 optical fibers; the diameter of the optical fibers is 170-190 μm.

[0013] Preferably, the optical unit is prepared using a two-stage pre-coating process during the molding process. The inner optical fibers are pre-coated using a high-flowability, ultra-low viscosity fiber paste (viscosity (25℃) 6S). -1 The outermost optical fiber is coated with a second viscosity fiber paste with a viscosity of 8000–13000 mPa·s. The viscosity of the second viscosity fiber paste is 15000–20000 mPa·s (viscosity (25℃) 6S). -1 This is used to achieve fullness of the fiber paste and improve the fullness of the fiber paste between the inner fiber layers.

[0014] Preferably, the raw material of the loose sleeve is composed of the following substances by weight percentage: 45-65% polybutylene terephthalate, 23-45% glass fiber, 3-8% mica, 4-10% calcium carbonate, 1-5% toughening agent, 0.2-1% silane coupling agent, 1-3% elastomer, 0.5-2% epoxy chain extender and 0.5-1% lubricant.

[0015] The CAS number of the polybutylene terephthalate is 26062-94-2, and the relative molecular mass is 30,000-40,000.

[0016] Furthermore, the epoxy chain extender is selected from styrene-glycerol acrylate copolymer ADR-4370, purchased from BASF AG, Germany.

[0017] Preferably, the silane coupling agent is selected from 3-(2,3-epoxypropoxy)propyltrimethoxysilane (C9H 20 The elastomer is selected from ethylene-octene copolymer grafted glycidyl methacrylate (POE-g-GMA), and the lubricant is selected from glyceryl monostearate, both purchased from BASF AG, Germany.

[0018] Preferably, the toughening agent is methyl methacrylate-butadiene-styrene terpolymer (MBS), which is purchased from BASF AG, Germany.

[0019] Preferably, a padding layer is provided between the non-metallic reinforcing member and the optical unit stranded layer, and the thickness of the padding layer is 0.3-0.5mm.

[0020] Preferably, the outer side of the non-metallic reinforcing member is provided with water-resistant yarn.

[0021] Furthermore, the water-blocking yarn is arranged in a passive winding manner.

[0022] Preferably, two water-resistant aramid yarns are provided between the optical unit stranded layer and the outer sheath layer.

[0023] Preferably, a tear cord is provided between the optical unit stranded layer and the outer sheath layer.

[0024] Preferably, the wall thickness of the loose sleeve is 0.08-0.12 mm.

[0025] Preferably, the high-fiber-density compact air-blown microcable has a fiber density greater than 8.4 cores / mm². 2 The fiber optic duty cycle is 68-70%.

[0026] Preferably, the non-metallic reinforcing member is a lightweight, high-strength photocurable fiber-reinforced composite material (FRP), and the flexural modulus of the lightweight, high-strength photocurable fiber-reinforced composite material is not less than 56 GPa.

[0027] The technical solution of the present invention has the following advantages compared with the prior art:

[0028] (1) High fiber density compact air-blown microcable has excellent tensile, flattening and impact performance, which can meet the laying requirements in complex environments. It has excellent temperature cycling performance and the air-blowing distance can reach more than 1.5km, showing good laying performance.

[0029] (2) Each loose tube contains 22-26 small-sized optical fibers of 170-190μm and is filled with grease. The tube wall thickness is only 0.1mm. Requirements are made for the tube material formula to ensure the tube is round and to avoid the optical fibers being subjected to lateral force, which would lead to unqualified attenuation.

[0030] (3) In order to ensure that the air blowing distance of the finished air-blown microcable can meet more than 1.5km, a low-friction, low-shrinkage HDPE outer sheath material was developed. Attached Figure Description

[0031] Figure 1 This is a cross-sectional structural diagram of the high fiber density compact air-blown microcable in Example 1.

[0032] Figure 2 This is a cross-sectional structural diagram of the high fiber density compact air-blown microcable in Example 2.

[0033] Figure 3 This is a diagram illustrating the secondary pre-coating process of fiber optic paste.

[0034] Explanation of reference numerals in the attached diagram: 1-Water-blocking aramid yarn, 2-Optical fiber, 3-Loose tube, 4-Fiber paste, 5-Lightweight high-strength light-cured fiber-reinforced composite non-metallic reinforcing component, 6-Water-blocking yarn, 7-Outer sheath layer, 8-Tear rope, 9-Material layer. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0036] Example 1:

[0037] A high fiber density compact air-blown microcable, with a lightweight, high-strength light-cured fiber-reinforced composite non-metallic reinforcing member 5 and a padding layer 9 at its center, the padding layer 9 having a thickness of 0.4 mm.

[0038] A lightweight, high-strength, light-cured fiber-reinforced composite non-metallic reinforcing member 5 and a padding layer 9 are passively wound with a water-blocking yarn 6. A layer of optical unit stranded layer is arranged around the outside of the water-blocking yarn 6. This optical unit stranded layer consists of a ring of identical high-hardness loose tubes 3. Each loose tube 3 contains 24 small-sized optical fibers 2 (180μm) and is filled with fiber grease 4. The wall thickness of the loose tubes 3 is 0.1mm. Two low-shrinkage water-blocking aramid yarns 1 and a tear cord 8 are used outside the optical unit stranded layer. The outer periphery of the stranded layer is covered with a low-friction, low-shrinkage outer sheath layer 7. Figure 1 As shown.

[0039] This high-fiber-density compact air-blown microcable has a fiber density greater than 8.4 cores / mm². 2 The fiber optic duty cycle is 69%.

[0040] The lightweight, high-strength, light-cured, fiber-reinforced composite material non-metallic reinforcing member 5 is a fiber-reinforced composite plastic, and the flexural modulus of the fiber-reinforced composite plastic is not less than 56 GPa.

[0041] Each 100g of outer sheath layer 7 contains: 76g of high-density polyethylene (HDPE, relative molecular mass 250,000), 6.5g of stearic acid, and 11g of hydrated magnesium silicate (Mg3Si4O3). 10 The outer sheath consists of (OH)2, 2g of zirconium oxide, 3g of silicone masterbatch, 1g of isopropyl tris(dioctyl pyrophosphate)titanate, and 0.5g of antioxidant (0.25g of primary antioxidant 1010 and 0.25g of secondary antioxidant 168). During preparation, the outer sheath is thinner, has a smaller outer diameter, and a higher fiber density. A low-friction, low-shrinkage HDPE outer sheath ensures the air-blowing performance of the microcable and reduces the impact of sheath shrinkage on optical cable attenuation.

[0042] The specific preparation method of the outer sheath layer 7 is as follows:

[0043] The core of this formulation is to achieve full dispersion of the filler and uniform action of the titanate coupling agent, while preventing polymer degradation.

[0044] Process flow: Raw material pretreatment → Premixing → Melt extrusion granulation → Cooling → Drying → Packaging.

[0045] 1. Raw material pretreatment:

[0046] Hydrated magnesium silicate and zirconium oxide inorganic fillers were thoroughly dried. They were dried at 105°C for 3 hours to remove surface-adsorbed water. This is because moisture affects the efficiency of the titanate coupling agent and may cause HDPE to hydrolyze at high temperatures (although HDPE is highly resistant to hydrolysis, trace amounts of moisture can still cause problems at high temperatures).

[0047] 2. Premixing:

[0048] HDPE granules, hydrated magnesium silicate, zirconium oxide, silicone masterbatch, stearic acid, antioxidant, and isopropyl tris(dioctyl pyrophosphoryloxy) titanate (titanium ester coupling agent, liquid, to be carefully sprayed in) are poured into a high-speed mixer.

[0049] The titanate coupling agent is added to the high-speed rotating mixture via spraying to ensure uniform coating of the filler surface. The mixing time is 6 minutes. Silicone masterbatches are typically large particles; to avoid excessive shearing, they are sometimes added via a side feeder, but can also be added at this step.

[0050] 3. Twin-screw extruder melt extrusion:

[0051] Temperature settings (from feed inlet to machine head):

[0052] HDPE has a relatively wide processing temperature range. As it is a crystalline polymer, its melting point is approximately 130-137℃.

[0053] Zone 1 (Feeding Area): 160℃ (to ensure smooth material transport);

[0054] Zone 2: 180℃;

[0055] Zone 3: 190℃ (main melting, reaction, and mixing zone);

[0056] Zone 4: 195℃;

[0057] Zone 5: 200℃;

[0058] Head temperature: 200℃;

[0059] Excessive temperature will accelerate degradation, while excessively low temperature will result in high melt viscosity and excessive shear force, which may also lead to degradation.

[0060] Screw speed: 310 rpm; sufficient speed to provide the shear force required to disperse the filler, but not too high to avoid HDPE molecular chain breakage or frictional overheating.

[0061] Vacuum degassing: Turning on the vacuum degassing function can remove trace amounts of small alcohol molecules (such as isopropanol) that may be generated during the coupling reaction of the coupling agent, as well as water vapor in the raw materials, thereby improving coupling efficiency and preventing the formation of bubbles in the product.

[0062] The total residence time of the material inside the screw is relatively short, so 1 minute is chosen.

[0063] 4. Granulation, cooling and packaging:

[0064] The extruded strip-shaped melt is cooled in a water bath and then pelletized by a pelletizer.

[0065] Each 100g of loose tubing 3 contains: 57g of polybutylene terephthalate (relative molecular mass 30,000-40,000), 25g of glass fiber, 4g of mica, 6g of calcium carbonate, 4g of toughening agent methyl methacrylate-butadiene-styrene terpolymer (MBS), and 0.5g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane (silane coupling agent C9H). 20 The mixture consists of 1.5g of ethylene-octene copolymer grafted with glycidyl methacrylate (POE-g-GMA), 1.5g of styrene-glyceryl acrylate copolymer ADR-4370, and 0.5g of glyceryl monostearate. During the cabling process, the sheath of the thin-walled microtubes is easily compressed, necessitating control of the binding tension.

[0066] In this embodiment, the mixing and granulation of the loose tube 3 formulation is completed by a co-rotating twin-screw extruder, whose strong shear force and mixing ability are very suitable for completing the above-mentioned chemical reaction and dispersion tasks.

[0067] Process flow: Raw material pretreatment → Premixing → Melt extrusion granulation → Cooling → Drying → Packaging.

[0068] The preparation method of loose sleeve 3 is as follows:

[0069] 1. Raw material pretreatment:

[0070] The above-mentioned polybutylene terephthalate (PBT resin), glass fiber, mica, and calcium carbonate were dried in an oven at 120°C for 5 hours to remove moisture and prevent PBT from undergoing hydrolytic degradation during processing.

[0071] 2. Premixing:

[0072] Pour the dried PBT resin, mica, calcium carbonate, toughening agent, silane coupling agent, POE-g-GMA, ADR-4370, and glyceryl monostearate powder / granular raw materials into a high-speed mixer and mix for 10 minutes to ensure that each component is evenly dispersed.

[0073] Glass fibers are typically fed through a side feeder in the middle of the extruder to avoid excessive shear breakage and maintain the length-to-diameter ratio.

[0074] 3. Twin-screw extruder melt extrusion:

[0075] Temperature settings (from feed inlet to machine head):

[0076] Zone 1 (Feeding Zone): 200℃ (lower temperature to prevent bridging and ensure stable feeding);

[0077] Zone 2: 230℃;

[0078] Zone 3: 240℃;

[0079] Zone 4: 240℃ (main melting, reaction, and mixing zone);

[0080] Zone 5 (glass fiber side feeding zone): 240℃ (slightly lower the temperature to protect the glass fiber);

[0081] Zone 6: 245℃;

[0082] Zone 7: 245℃;

[0083] Head temperature: 245℃;

[0084] Screw speed: 300 rpm;

[0085] Vacuum degassing: After the reaction zone (the next segment after the glass fiber is added), vacuum degassing is activated to remove small molecules (such as methanol, water vapor, etc.) generated during the reaction, promote the forward reaction, and prevent the product from generating bubbles.

[0086] Residence time: The residence time of the entire material inside the screw is typically 2 minutes. This time is sufficient to complete the interfacial coupling and chain extension reactions described above.

[0087] 4. Granulation, cooling and packaging:

[0088] The extruded strip melt is cooled in a water bath and then cut into cylindrical pellets by a pelletizer.

[0089] Example 2:

[0090] A high-fiber-density compact air-blown microcable, with a lightweight, high-strength photocurable fiber-reinforced composite non-metallic reinforcing member 5 at its center.

[0091] A lightweight, high-strength, light-cured fiber-reinforced composite non-metallic reinforcing member 5 passively wraps a water-blocking yarn 6. Two layers of optical unit stranded layers are arranged around the outside of the water-blocking yarn 6. Each optical unit stranded layer consists of two identical high-hardness loose tubes 3. Each loose tube 3 contains 24 small-sized optical fibers 2 (180μm) and is filled with fiber grease 4. The wall thickness of the loose tubes 3 is 0.1mm. Two low-shrinkage water-blocking aramid yarns 1 and a tear cord 8 are used outside the optical unit stranded layer. The stranded layer is covered with a low-friction, low-shrinkage outer sheath layer 7. Figure 2 As shown.

[0092] This high-fiber-density compact air-blown microcable has a fiber density greater than 8.4 cores / mm². 2 The fiber optic duty cycle is 69%.

[0093] The flexural modulus of the lightweight, high-strength, light-cured fiber-reinforced composite non-metallic reinforcing member 5 is not less than 56 GPa.

[0094] Each 100g of outer sheath layer 7 contains: 76g of high-density polyethylene (HDPE, relative molecular mass 250,000), 6.5g of stearic acid, and 11g of hydrated magnesium silicate (Mg3Si4O3). 10 (OH)2), 2g of zirconium oxide and 3g of silicone masterbatch, 1g of isopropyl tris(dioctyl pyrophosphoryloxy)titanate and 0.5g of antioxidant (0.25g of primary antioxidant 1010 and 0.25g of secondary antioxidant 168).

[0095] Each 100g of loose tubing 3 contains: 57g of polybutylene terephthalate (relative molecular mass 30,000-40,000), 25g of glass fiber, 4g of mica, 6g of calcium carbonate, 4g of toughening agent methyl methacrylate-butadiene-styrene terpolymer (MBS), and 0.5g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane (C9H 20 O5Si), 1.5g of ethylene-octene copolymer grafted with glycidyl methacrylate, 1.5g of styrene-glyceryl acrylate copolymer ADR-4370 (epoxy chain extender) and 0.5g of glyceryl monostearate.

[0096] The preparation process of the outer sheath layer 7 and the loose tube 3 in this embodiment is the same as that in embodiment 1.

[0097] Effect Evaluation 1:

[0098] The high fiber density compact air-blown microcable using 180μm optical fiber has excellent tensile, flattening and impact properties, which can meet the laying requirements in complex environments. In Example 2, under a short-term tensile force of 1000N for 1min, the fiber strain is <0.5%, and the residual additional attenuation of the fiber is ≤0.1dB@1550nm under tensile, flattening and impact conditions.

[0099] The microcable in Example 2 exhibits a maximum attenuation change of 0.033 dB / km under high and low temperature cycling, demonstrating excellent temperature cycling performance. Its air-blowing distance can reach over 1.5 km, showcasing good laying performance.

[0100] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A high-fiber-density compact air-blown microcable, characterized in that, It includes a non-metallic reinforcing member arranged from the inside out, at least one optical unit stranded layer and an outer sheath layer (7); the optical unit stranded layer is obtained by stranding optical units on the outside of the non-metallic reinforcing member; the optical unit is composed of an optical fiber layer, a fiber grease layer (4) and a loose tube (3) arranged from the inside out. By weight percentage, the outer sheath layer (7) is composed of the following materials: 70-80% high-density polyethylene, 4-9% lubricant, 6-17% low-shrinkage modifier, 3-8% wear-resistant filler, 0.5-1.5% titanate coupling agent, and 0.2-0.5% antioxidant; the optical fiber layer consists of 22-26 optical fibers (2); the diameter of the optical fiber (2) is 170-190 μm; the optical unit is subjected to a two-stage pre-coating process during the molding process, with the inner layer of optical fibers coated with a first viscosity fiber paste and the outermost layer of optical fibers coated with a second viscosity fiber paste; the viscosity of the first viscosity fiber paste is 8000-13000 mPa·s; the viscosity of the second viscosity fiber paste is 15000-20000 mPa·s. mPa.s; by weight percentage, the raw materials of the loose sleeve (3) consist of the following substances: 45-65% polybutylene terephthalate, 23-45% glass fiber, 3-8% mica, 4-10% calcium carbonate, 1-5% toughening agent, 0.2-1% silane coupling agent, 1-3% elastomer, 0.5-2% epoxy chain extender and 0.5-1% lubricant.

2. The high fiber density compact air-blown microcable as described in claim 1, characterized in that, A pad (9) is provided between the non-metallic reinforcing member and the optical unit stranded layer, and the thickness of the pad (9) is 0.3-0.5 mm.

3. The high fiber density compact air-blown microcable as described in claim 1, characterized in that, The non-metallic reinforcing member is provided with water-blocking yarn (6) on its outer side.

4. The high fiber density compact air-blown microcable as described in claim 1, characterized in that, Water-resistant aramid yarn (1) is provided between the optical unit stranded layer and the outer sheath layer (7).

5. The high fiber density compact air-blown microcable as described in claim 1, characterized in that, A tear cord (8) is also provided between the optical unit stranded layer and the outer sheath layer (7).

6. The high fiber density compact air-blown microcable as described in claim 1, characterized in that, The high-fiber-density compact air-blown microcable has a fiber density greater than 8.4 cores / mm². 2 The fiber optic duty cycle is 68-70%.

7. The high fiber density compact air-blown microcable as described in claim 1, characterized in that, The non-metallic reinforcing member is a lightweight, high-strength photocurable fiber reinforced composite material, and the flexural modulus of the lightweight, high-strength photocurable fiber reinforced composite material is not less than 56 GPa.

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