A soft-cased air-blown optical cable

Abstract

The present invention relates to a soft-tube air-blown optical cable, comprising a cable core and an outer sheath covering the cable core. The cable core is a layer-stranded cable core, comprising a central reinforcement member and a loose tube twisted around the outer periphery of the central reinforcement member. An optical communication unit is mounted in the loose tube. The loose tube is characterized in that the loose tube is made of a flexible sheathing material having an elastic modulus of 100 to 700 MPa, and the outermost layer is the outer sheath. The optical cable of the present invention has a simple structure, a small diameter, a light weight, a high optical fiber density, and good air-blown laying performance. The loose tube is made of a flexible sheathing material, which is soft and easy to bend without breaking. It can be coiled with a small bending radius in a splice box, so that the branched optical fibers are better protected without having to interrupt the optical fibers, thereby greatly facilitating the branching and splicing of the optical cable and improving construction efficiency.

Description

Technical Field

[0001] The invention relates to a soft sleeve air-blown optical cable, belonging to the technical field of photoelectric transmission. Background Art

[0002] Air-blown microcables are optical cables that can be laid using an air-blown method. They offer high fiber density, small diameter, light weight, and efficient air-blown installation. They are widely used in backbone networks, local area networks, and access networks. Air-blown microcables with a large fiber count typically adopt a stranded structure. The cable core is twisted in a SZ direction with a central reinforcement and loose tube, then bound with yarns. A sheath is then extruded over the core. The loose tube is made of a secondary sheathing material, PBT, which has a high elastic modulus of approximately 2200 MPa.

[0003] During air-blown microcable construction, after the optical fiber enters the optical cross-connect box or splice closure for splicing or branching, it needs to be coiled. With existing air-blown microcables, PBT loose tubes cannot be directly coiled because the material used has a large modulus and the splice closure has a small space. Directly coiling the tubes can cause bending and damage to the fibers, affecting transmission performance. Therefore, the fibers must be broken and protected with soft tubes before being spliced and coiled. If the fibers are not broken and protected with soft tubes, the tubes are still prone to bending during use, causing breakage of the fibers and thus affecting transmission performance.

[0004] Fiber density affects pipeline occupancy costs and construction efficiency. Therefore, increasing fiber density is the industry's development trend. While maintaining the same fiber count, methods for reducing cable diameter primarily include reducing the fiber diameter, casing diameter, and jacket wall thickness. However, reducing both fiber and casing diameters increases fiber attenuation and makes the casing more susceptible to bending. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a soft-sleeved air-blown optical cable to address the deficiencies in the above-mentioned prior art. The soft-sleeved air-blown optical cable not only has the characteristics of high optical fiber density, small diameter, and light weight, but also the loose-sleeved cable branched out is easy to bend without breaking, and can achieve small-radius bending and coiling to improve construction efficiency.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows: the cable core comprises a cable core and an outer sheath covering the cable core, the cable core is a layer-stranded cable core, comprises a central reinforcement member and a loose tube twisted around the outer periphery of the central reinforcement member, an optical communication unit is mounted in the loose tube, and the loose tube is characterized in that the loose tube is made of a flexible sheathing material with an elastic modulus of 100 to 700 MPa, and the outermost layer is the outer sheath.

[0007] According to the above solution, the elastic modulus of the flexible sheathing material is 410-590 MPa, which not only ensures the flexibility of the loose tube, but also has good processing, mechanical and other comprehensive properties to minimize the wall thickness of the tube and increase the fiber density.

[0008] According to the above solution, the flexible sheathing material can be thermoplastic polyester elastomer (TPEE), thermoplastic polyurethane elastomer (TPU) or thermoplastic vulcanized rubber (TPV).

[0009] According to the above solution, the shrinkage rate of the loose tube is between 0% and 0.5%, which can reduce the microbending of the optical fiber in the loose tube and ensure the transmission performance of the optical fiber in the loose tube when the temperature changes.

[0010] According to the above scheme, the wall thickness of the loose tube on one side is 0.1-0.25 mm, the diameter of the 12F / T (12 cores / each) loose tube can be reduced to 1.15 mm, and the diameter of the 24F / T (24 cores / each) loose tube can be reduced to 1.55 mm. The proportion of optical fibers in each loose tube is greater than or equal to 50%, and the optical fiber density in the optical cable is greater than or equal to 3F / mm 2 .

[0011] According to the above solution, the minimum bending diameter of the loose tube is 5 times the diameter D of the loose tube, that is, the minimum bending diameter reaches 5D.

[0012] According to the above solution, the optical communication unit is an optical fiber, an optical fiber ribbon or an optical fiber bundle.

[0013] According to the above scheme, the optical fiber is a bend-resistant single-mode optical fiber, and the outer surface of the optical fiber is coated with inner and outer coatings. The elastic modulus of the inner coating is less than or equal to 1MPa, and the elastic modulus of the outer coating is less than or equal to 1000MPa (test temperature 25°C).

[0014] According to the above solution, the microbending sensitivity of the bend-resistant single-mode optical fiber is ≤2dB / km@1550nm.

[0015] According to the above solution, the additional attenuation of the bend-resistant single-mode optical fiber at -30 to +70° C. is ≤0.05 dB / km@1550 nm.

[0016] According to the above solution, the outer diameter D of the loose tube is 1.1-2.0 mm, and the inner diameter is 0.8-1.6 mm; the loose tube is filled with water-blocking material.

[0017] According to the above solution, the outer sheath material is HDPE, MDPE, LDPE, PA11 or PA12, and the single-side wall thickness is 0.3-0.6 mm.

[0018] The beneficial effects of the present invention are as follows: 1. The optical cable has a simple structure, small diameter, light weight, high optical fiber density, and good air-blowing laying performance; 2. The loose tube is made of a flexible sheathing material with good flexibility and is easy to bend without breaking. It can almost reach the minimum bending radius of the optical fiber without bending. It can be coiled with a small bending radius in a joint box, so that the optical fiber coiled in the branch is better protected without breaking the optical fiber, thereby greatly facilitating the branch connection of the optical cable and improving construction efficiency. 3. The elastic modulus of the flexible sheathing material is 100-700 MPa. The tube material is flexible and easy to bend, so it can achieve a smaller wall thickness without bending, thereby reducing the tube diameter and increasing the optical fiber density. At the same time, it can ensure that the loose tube has a certain strength, thereby protecting the optical fiber in the loose tube and avoiding the puncture marks caused by the yarn on the tube surface. 4. The optical fiber is a bending-resistant single-mode optical fiber, which can further improve the bending performance of the present invention. By optimizing the modulus of the optical fiber's inner and outer coatings, as well as the secondary sheathing material, the present invention minimizes the diameter of the optical fiber and sheathing, while also ensuring excellent transmission performance of the optical fiber in the cable at temperatures between -30°C and +70°C. The outer sheath has high strength and hardness, resulting in a rigid outer-soft inner cable structure that facilitates air-blown installation and provides excellent cable protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a radial cross-sectional view of an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Examples of embodiments of the present invention include Figure 1As shown, it includes an outer sheath 1 and a cable core coated in the outer sheath, the cable core includes a non-metallic central strength member 5 and a loose tube 2 twisted around the outer periphery of the central strength member, the loose tube is bound by a yarn after SZ stranding, an optical communication unit 3 is set in the loose tube, and filled with a water-blocking material 4, the water-blocking material is a water-blocking powder or a water-blocking grease, and the loose tube is extruded by TPEE, TPU or TPV material at 200-240°C, and its elastic modulus is about 450MPa; the optical communication unit 3 is a bend-resistant single-mode optical fiber, and the outer surface of the optical fiber is coated with an inner and outer coating, the inner coating elastic modulus is 0.6-0.8MPa, and the outer coating elastic modulus is 700-900MPa (test temperature 25°C). The number of optical fiber cores in each soft tube is 12 or 24, and the optical fiber accounts for more than 50% in the loose tube. The loose tube bending diameter reaches 5D and will not bend. Water-blocking yarn 6 can also be laid in the cable core. The outermost layer of the optical cable is the outer sheath. The outer sheath is made of HDPE, MDPE, LDPE, PA11 or PA12. The outer sheath has high strength and hardness, thus forming an optical cable structure with a hard outer layer and a soft inner layer. To facilitate cable opening, a cable opening rope 7 is provided between the cable core and the outer sheath. Table 1 is a list of parameters of the five embodiments of the present invention. The fiber density is 3F / mm 2 above.

[0022] Table 1

[0023]

Claims

1. A soft-tube air-blown optical cable comprising a cable core and an outer sheath covering the cable core, wherein the cable core is a stranded cable core comprising a central reinforcement member and a loose tube stranded around the outer periphery of the central reinforcement member, wherein an optical communication unit is mounted in the loose tube, characterized in that The loose tube is made of a flexible sheathing material with an elastic modulus of 100-700 MPa, and the outermost layer is an outer sheath; the single-side wall thickness of the loose tube is 0.1-0.25 mm, the optical fiber ratio in the loose tube is greater than or equal to 50%, and the optical fiber density in the optical cable is greater than or equal to 3F / mm 2 ; The shrinkage rate of the loose tube is between 0 and 0.5%.

2. The soft sleeve air-blown optical cable according to claim 1, characterized in that The elastic modulus of the flexible sheathing material is 410-590 MPa.

3. The soft sleeve air-blown optical cable according to claim 1 or 2, characterized in that The flexible sheathing material is TPEE, TPU, or TPV.

4. The soft sleeve air-blown optical cable according to claim 1 or 2, characterized in that The outer diameter D of the loose tube is 1.1-2.0 mm, and the inner diameter is 0.8-1.6 mm; the minimum bending diameter of the loose tube is 5 times the diameter D, that is, the minimum bending diameter reaches 5D.

5. The soft sleeve air-blown optical cable according to claim 1 or 2, characterized in that The optical communication unit is an optical fiber, an optical fiber ribbon or an optical fiber bundle.

6. The soft sleeve air-blown optical cable according to claim 5, characterized in that The optical fiber is a bend-resistant single-mode optical fiber. The outer surface of the optical fiber is coated with inner and outer coatings. The elastic modulus of the inner coating is less than or equal to 1MPa, and the elastic modulus of the outer coating is less than or equal to 1000MPa.

7. The soft sleeve air-blown optical cable according to claim 6, characterized in that The microbending sensitivity of the bend-resistant single-mode optical fiber is ≤2dB / km@1550nm; the additional attenuation of the bend-resistant single-mode optical fiber at -30 to +70°C is ≤0.05dB / km@1550nm.

8. The soft sleeve air-blown optical cable according to claim 1 or 2, characterized in that The outer diameter D of the loose tube is 1.0-2.0 mm, and the inner diameter is 0.8-1.6 mm; the loose tube is filled with water-blocking material.

9. The soft sleeve air-blown optical cable according to claim 1 or 2, characterized in that The outer sheath material is HDPE, MDPE, LDPE, PA11 or PA12.

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