Low-core-number layer-stranded thin-diameter optical cable and preparation method thereof

Abstract

The invention discloses a layer-stranded thin-diameter optical cable with a small number of cores. The layer-stranded thin-diameter optical cable comprises three to four sleeve units, thin wires and an outer sheath, the sleeve units are twisted around the thin wires SZ arranged in the center to form a cable core. On the cross section of the cable core, the cross sections of the sleeve units are stacked and adjacent to each other; hot melt adhesive is filled between the stranded sleeve units, and the hot melt adhesive is attached to the surfaces of the fine wires to form a hot melt adhesive core; and the cable core is accommodated in the outer sheath. According to the small-core layer-stranded thin-diameter optical cable, a three-unit or four-unit stranded structure is adopted, a filling unit is omitted, the loose tubes are bonded together through the hot melt adhesive core of a composite structure to form a whole, the diameter of the small-core layer-stranded thin-diameter optical cable is obviously reduced, cost is reduced, reliable tensile performance is provided, and a reinforcing core does not need to be additionally arranged in the cable core.

Description

Technical Field

[0001] The present invention belongs to the field of optical communication, and more specifically, relates to a small-core layer twisted thin-diameter optical cable and a preparation method thereof. Background Art

[0002] Generally, the number of optical fiber cores in outdoor optical cables varies greatly, ranging from more than 12 cores to even 1,000 cores. Optical cables with different core counts are suitable for different structures. Among them, the number of cores of low-core optical cables ranges from more than 24 cores to less than 50 cores. The demand for low-core optical cables is large and they are widely used in the layout of communication trunk networks and metropolitan area networks.

[0003] The low-core optical cable generally adopts two structures: layer-twisted and central bundle tube. The central bundle tube structure can accommodate a limited number of optical fiber cores, and it is not easy to identify and construct because there is no sleeve unit. Layer-twisted optical cable needs to adopt a central reinforcing core with a suitable diameter and tensile modulus, and the loose tube is twisted around the central reinforcing core for SZ forward and reverse twisting. Therefore, in order to achieve structural integrity, layer-twisted low-core optical cable generally needs to adopt a twisted structure of more than 5 units. When the number of sleeves is insufficient, it is necessary to supplement it with a filling rope. Specifically, if the sleeve unit is 3 or 4 units, it is necessary to use a filling rope to supplement it to at least 5 units. The cable core diameter of layer-twisted optical cable is large, above 5.0mm, which is difficult to meet the needs of further miniaturization of optical cables and is not conducive to reducing costs. However, unlike the conductor with good plasticity, the optical unit has strong elasticity and toughness. In the case of incomplete cross-sectional structure, directly twisting 3 or 4 units of loose tubes will make the cable core unstable and easy to open. Even if yarn binding is used, it will also lead to excessive transmission loss due to the need to use a relatively dense yarn binding trace. Especially when using an SZ stranded structure, it is currently not possible to strand only 3-unit or 4-unit loose tubes.

[0004] At the same time, the diameter of the small-core stranded optical cable is further reduced, and the space for the reinforcement is compressed, which poses a challenge to the tensile performance of the optical cable. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a small-core, layered, thin-diameter optical cable and a preparation method thereof, the purpose of which is to form a hot-melt adhesive core by means of a thin wire arranged in the center and a hot-melt adhesive filled between the twisted sleeve units, thereby providing good tensile performance and stabilizing the twisted structure of the sleeve units, thereby solving the technical problems of incomplete cross-sectional structure and unstable and easily opened cable core caused by the small-core, layered, twisted optical cable having only 3 or 4 units.

[0006] To achieve the above object, according to one aspect of the present invention, a small-core layer stranded thin-diameter optical cable is provided, comprising 3 to 4 casing units, thin wires, and an outer sheath;

[0007] The sleeve unit is twisted around the thin wire SZ arranged in the center to form a cable core; on the cross section of the cable core, the cross sections of the sleeve unit are stacked and adjacent to each other; the diameter d of the thin wire and the diameter D of the sleeve unit meet the following relationship:

[0008]

[0009] Wherein, d is the diameter of the thin wire, D is the diameter of the casing unit, n is the number of casing units, n = 3 or 4, α is the margin coefficient, and the value is 1.2;

[0010] Hot melt adhesive is filled between the twisted sleeve units, and the hot melt adhesive is attached to the surface of the thin wire to form a hot melt adhesive core;

[0011] The cable core is received in the outer sheath.

[0012] Preferably, the diameter of the thin wire of the small-core stranded thin-diameter optical cable, i.e., the maximum distance between two points on the cross-sectional profile of the thin wire, is preferably circular;

[0013] Preferably, the thin wires of the few-core layer twisted fine-diameter optical cable are selected from one or a combination of water-blocking yarn, aramid fiber, PBT wire, PC wire, PE wire, and yarn.

[0014] Preferably, the outer wall of the sleeve of the small-core layer stranded fine-diameter optical cable is attached with a hot-melt adhesive layer; the hot-melt adhesive layer attached to the outer wall of the sleeve is fused with the hot-melt adhesive core.

[0015] Preferably, the hot melt adhesive layer of the small-diameter optical cable with a small number of cores and layers is axially discontinuous and passes over the folding part of the SZ twisting.

[0016] Preferably, the plurality of sheath units of the small-core layer stranded fine-diameter optical cable have auxiliary stabilizing elements on the outside, and the auxiliary stabilizing elements are binding yarns for binding the cable core, wrapped water-blocking tapes, and / or longitudinally wrapped metal tapes.

[0017] Preferably, in the few-core layer-twisted fine-diameter optical cable, the unit diameter of the sleeve is between 1.7 mm and 2.5 mm, and the number of cores in the sleeve is between 6 and 12.

[0018] Preferably, the outer sheath of the small-core layer stranded thin-diameter optical cable has a circular cross-section and has parallel reinforcement members inside; or

[0019] The cross section of the outer sheath is in the shape of an 8, the cable core is located in the first inner cavity of the 8-shaped sheath, and a reinforcement piece is arranged in the second inner cavity of the 8-shaped sheath.

[0020] According to another aspect of the present invention, a method for preparing the small-core layer stranded thin-diameter optical cable is provided, comprising the following steps:

[0021] Spray hot melt adhesive of preset thickness on the surface of the thin line set in the center to form a hot melt adhesive core;

[0022] When the hot melt adhesive core is in a molten state, the three to four sleeve units are twisted around the hot melt adhesive core SZ;

[0023] The hot melt adhesive core is cooled to obtain a cable core;

[0024] A sheath material is extruded outside the cable core to form a cable.

[0025] Preferably, the method for preparing the small-core layer stranded thin-diameter optical cable comprises the following steps:

[0026] Hot melt adhesive is sprayed on the surface of the sleeve unit, and SZ twisting is performed when the hot melt adhesive on the outer wall of the sleeve unit is in a molten state, so that the hot melt adhesive on the outer wall of the sleeve unit is fused with the hot melt adhesive core.

[0027] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0028] The few-core layer stranded thin-diameter optical cable provided by the present invention adopts a 3-unit or 4-unit stranded structure, eliminates the filling unit, and uses a composite structure of hot-melt adhesive core to bond the loose tube together to form a whole, which not only significantly reduces its diameter and reduces the cost, but also provides reliable tensile performance, and no additional reinforcement core is required in the cable core. It is particularly suitable for the use of overhead optical cables. The tube fixed with hot-melt adhesive avoids slippage under actual use conditions such as large arc suspension and wind vibration, which is conducive to ensuring the stable performance and safe use of the optical cable.

[0029] The preferred solution does not require yarn binding, which not only reduces production costs, but also avoids the risk of defective products such as casing damage and cable core breakage caused by the use of yarn binding, while facilitating the stripping of casing units during construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 1 is a schematic diagram of the structure of a small-core layer stranded thin-diameter optical cable according to Embodiment 1 of the present invention;

[0031] Figure 2 Schematic diagram of the structure of a small-core stranded thin-diameter optical cable according to Embodiment 2 of the present invention;

[0032] Figure 3 3 is a schematic diagram of the structure of a small-core layer stranded thin-diameter optical cable according to Embodiment 3 of the present invention;

[0033] Figure 4 1 is a schematic diagram of the structure of a small-core layer stranded thin-diameter optical cable according to Embodiment 4 of the present invention;

[0034] Figure 5It is a schematic diagram of the structure of a small-core layer twisted thin-diameter optical cable according to Example 5 of the present invention.

[0035] Figure 6 This is a side view of the return point of the SZ-stranded optical fiber in the stranded optical cable.

[0036] In all drawings, the same reference numerals are used to represent the same elements or structures, wherein 1 is an optical fiber, 2 is a sleeve, 3 is a thin wire, 4 is a hot melt adhesive core, 5 is hot melt adhesive, 6 is an auxiliary stabilizing element, 7 is a reinforcement member, and 8 is a sheath. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] The invention provides a small-core layer-stranded thin-diameter optical cable, comprising 3 to 4 casing units, thin wires, and an outer sheath;

[0039] The sleeve unit is twisted around the thin wire SZ arranged in the center to form a cable core; on the cross section of the cable core, the cross sections of the sleeve unit are stacked and adjacent to each other; the diameter d of the thin wire and the diameter D of the sleeve unit meet the following relationship:

[0040]

[0041] Wherein, d is the diameter of the thin wire, D is the diameter of the sleeve unit, n is the number of sleeve units, n=3 or 4; α is the margin coefficient, which is 1.2. The unit diameter of the sleeve is between 1.7mm and 2.5mm, and the number of sleeve cores is between 6 and 12. Since the arrangement of the sleeve greatly reduces the outer diameter of the cable, there is no need to use a thinner diameter sleeve unit, which makes it difficult to set the center thin wire. Such a design is more conducive to a fully dry optical unit.

[0042] If the cross-sections of the casing units are closely packed, the maximum diameter of the central fine line can be theoretically calculated as:

[0043]

[0044] However, in actual production, it is very difficult to make the casing unit fit tightly together by twisting, and it is not easy to be stable and easy to open. Experiments show that when the margin coefficient α=1.2, the twisted structure is stable and the fine wire diameter is within αd max The following does not affect the cabling stability.

[0045] Hot melt adhesive is filled between the twisted sleeve units, and the hot melt adhesive is attached to the surface of the thin wire to form a hot melt adhesive core; the hot melt adhesive filled between the sleeve units and the thin wires can effectively fix the sleeve units, limit the mutual sliding between the sleeve units, and keep them in a stable twisted state; at the same time, due to the composite center piece formed by the solidification of the hot melt adhesive and the thin wires, the hot melt adhesive area between the adjacent sleeves is equivalent to a convex ridge, which can effectively improve the tensile strength of the center piece. Even if the standard specification of the center reinforcement member is not used, it can provide good tensile performance for the optical cable, solving the contradiction between the tensile performance of the optical cable and the cable diameter.

[0046] The cable core is received in the outer sheath.

[0047] The diameter of the thin wire, that is, the maximum distance between two points on the cross-sectional profile of the thin wire, is preferably a circular cross-sectional profile.

[0048] The thin wire is selected from one or a combination of water-blocking yarn, aramid fiber, PBT wire, PC wire, PE wire, and yarn. Using water-blocking yarn as the thin wire is beneficial to the water blocking of the cable core, and is used to prepare a fully dry or semi-dry cable core. Generally, the diameter of the fully dry casing unit is slightly larger. The structure provided by the present invention can effectively reduce the diameter of the optical cable and balance the increase in cable diameter caused by the larger diameter of the loose casing of the fully dry optical cable; using aramid fiber as the thin wire, using the good tensile properties of aramid fiber, and cleverly using the center gap generated by the casing stacking, while further reducing the diameter of the few-core layer twisted optical cable, it can provide good tensile properties without the need for additional reinforcement space. PBT wire, PC wire, and PE wire have excellent mechanical properties, and can be continuously formed by extrusion molding technology, and the equipment can be better integrated with the production line; the yarn cost is low, and can be mixed with other materials to make a thin wire set in the center.

[0049] In a preferred embodiment, a hot melt adhesive layer is attached to the outer wall of the sleeve; the hot melt adhesive layer attached to the outer wall of the sleeve is fused with the hot melt adhesive core; further preferably, the hot melt adhesive layer is axially discontinuous and passes over the folding part of the SZ twisting. The hot melt adhesive attached to the outer wall of the sleeve can further stabilize the twisting state of the cable core after cooling and shaping, which can save the yarn binding of the optical cable, reduce the cable diameter and reduce the loss while facilitating the peeling of the sleeve unit during construction. The hot melt adhesive layer attached to the outer wall is fused with the hot melt adhesive core, which can better limit the slippage between the sleeve units and stabilize the twisted structure. However, an axially continuous hot melt adhesive layer not only has a high cost, but also may cause a decrease in the overall bending performance of the optical cable. Fusion with the hot melt adhesive core may also excessively restrict the free state of the loose sleeve, thereby increasing the transmission loss. An axially discontinuous hot melt adhesive layer can solve this problem well, as long as the folding part of the SZ twisting where the cable core structure is the most unstable is reinforced, such as Figure 6As shown, good structural stability can be achieved and it is convenient to peel off the casing unit during construction.

[0050] The outer sides of the plurality of sleeve units are provided with auxiliary stabilizing elements, which are binding yarns for binding the cable core, water-blocking tapes for wrapping, and / or longitudinally wrapped metal tapes. These structures can help stabilize the twisted structure of the cable core while providing functions such as water blocking and armoring.

[0051] The outer sheath has a circular cross section and has parallel reinforcements inside; or the outer sheath has an 8-shaped cross section, the cable core is in the first inner cavity of the 8-shaped sheath, and the second inner cavity of the 8-shaped sheath is provided with reinforcements. The reinforcements in the sheath can further improve the tensile strength of the entire optical cable.

[0052] The method for preparing a small-core layer stranded thin-diameter optical cable provided by the present invention comprises the following steps:

[0053] A preset thickness of hot melt adhesive is sprayed on the surface of the thin line set in the center to form a hot melt adhesive core; the thickness of the sprayed hot melt adhesive can be calculated according to the unit volume that the hot melt adhesive needs to fill, which is generally between 0.2 and 0.6 mm

[0054] When the hot melt adhesive core is in a molten state, the three to four sleeve units are twisted around the hot melt adhesive core SZ;

[0055] The hot melt adhesive core is cooled to obtain a cable core;

[0056] A sheath material is extruded outside the cable core to form a cable.

[0057] Hot melt adhesive is sprayed on the surface of the sleeve unit, and SZ twisting is performed when the hot melt adhesive on the outer wall of the sleeve unit is in a molten state, so that the hot melt adhesive on the outer wall of the sleeve unit is fused with the hot melt adhesive core.

[0058] The following are examples:

[0059] Example 1

[0060] The embodiment provides a small number of cores and a thin diameter optical cable, such as Figure 1 As shown: it has 3 sleeve units, hot melt adhesive core, no yarn binding, and the outer wall of the sleeve is coated with glue at the return point, and the hot melt adhesive layer attached to the outer wall is fused with the hot melt adhesive core in the center of the cable core. The diameter of the sleeve unit is 2.4mm, and the number of sleeve cores is 6. The thin wire set in the center of the hot melt adhesive core is made of PC material with a diameter of 0.4mm; the cross-section of the outer sheath is circular, and there are parallel reinforcements inside, using FRP reinforcements; the outer side of the cable core has a longitudinal metal belt.

[0061] Preparation method: Spray 0.2mm thick sol on the surface of the central circular thin wire to form a hot melt adhesive core and keep it in a molten state, and perform SZ stranding around the hot melt adhesive core. Spray hot melt adhesive at the turning point of the loose tube after stranding to make it penetrate into the gap between the loose tubes, and tightly bond the loose tubes to form a whole, ensuring the stability of the structure. Extrude the sheath material on the outside of the cable core to form a cable. Two parallel reinforcements are placed in the outer sheath.

[0062] Example 2

[0063] The embodiment provides a small number of cores and a thin diameter optical cable, such as Figure 2 As shown: it has 3 sleeve units, hot melt adhesive core, and is bound with yarn outside the cable core. The sleeve unit diameter is 2.4mm, and the number of sleeve cores is 6. The thin wire set in the center of the hot melt adhesive core is made of PC material with a diameter of 0.4mm; the cross-section of the outer sheath is circular, and there are parallel reinforcements inside, using FRP reinforcements; the outer side of the cable core has a longitudinal metal belt.

[0064] Preparation method: spray 0.2mm thick sol on the surface of the central circular fine wire to form a hot melt adhesive core and keep it in a molten state, SZ twist three sleeve units around the hot melt adhesive core, and bind them by yarn binding to obtain a cable core; wrap a metal tape longitudinally on the outside of the cable core and extrude the sheath material to form a cable. Two parallel reinforcements are placed in the outer sheath.

[0065] Example 3

[0066] The embodiment provides a small number of cores and a thin diameter optical cable, such as Figure 3 As shown: it has 4 sleeve units, hot melt adhesive core, and no yarn binding. The outer wall of the sleeve is coated with glue at the turning point, and the hot melt adhesive layer attached to the outer wall is fused with the hot melt adhesive core in the center of the cable core. The diameter of the sleeve unit is 2.3mm, and the number of sleeve cores is 6. The fine wire set in the center of the hot melt adhesive core is made of PBT material and has a diameter of 1.0mm; the cross-section of the outer sheath is 8-shaped, and the cable core is in the first inner cavity of the 8-shaped sheath, and the second inner cavity of the 8-shaped sheath is provided with a steel strand reinforcement; the outer side of the cable core has a longitudinally wrapped metal belt.

[0067] Preparation method: spray 0.5mm thick sol on the surface of the central circular fine wire to form a hot melt adhesive core and keep it in a molten state, and perform SZ stranding around the hot melt adhesive core with four sleeve units; and spray hot melt adhesive at the turning point of the loose sleeve after stranding, so that it penetrates into the gap between the loose sleeves, and the loose sleeves are tightly bonded to form a whole, ensuring the stability of the structure. The metal belt is longitudinally wrapped on the outside of the cable core and a sheath material with an 8-shaped cross section is extruded. The cable core is in the first inner cavity of the 8-shaped sheath, and a reinforcement is placed in the second inner cavity of the 8-shaped sheath.

[0068] Example 4

[0069] The embodiment provides a small number of cores and a thin diameter optical cable, such as Figure 4 As shown: it has 4 sleeve units, hot melt adhesive core, and is bound with yarn outside the cable core. The sleeve unit diameter is 2.3mm, and the number of sleeve cores is 6. The fine wire set in the center of the hot melt adhesive core is made of PBT material with a diameter of 1.0mm; the cross-section of the outer sheath is circular, and there are parallel reinforcements inside, using FRP reinforcements; the outer side of the cable core has a longitudinal metal belt.

[0070] Preparation method: spray 0.4mm thick sol on the surface of the central circular thin wire to form a hot melt adhesive core and keep it in a molten state, wrap 4 sleeve units around the hot melt adhesive core for SZ stranding, and make the cable core by yarn binding; wrap the metal tape longitudinally on the outside of the cable core and extrude the sheath material to form a cable. Parallel reinforcements are placed in the outer sheath.

[0071] Example 5

[0072] The embodiment provides a small number of cores and a thin diameter optical cable, such as Figure 5 As shown: it has 4 casing units, hot melt adhesive core, no yarn binding, and the outer wall of the casing is coated with glue at the return point, and the hot melt adhesive layer attached to the outer wall is fused with the hot melt adhesive core in the center of the cable core. The diameter of the casing unit is 2.5mm, and the number of casing cores is 6. The fine wire set in the center of the hot melt adhesive core is made of PE material with a diameter of 1.1mm; the cross-section of the outer sheath is circular, and there are parallel reinforcements inside, and FRP reinforcements are used; the outer side of the multiple casing units has a wrapped water blocking tape.

[0073] Preparation method: Spray 0.4mm thick sol on the surface of the central circular fine wire to form a hot melt adhesive core and keep it in a molten state, and then SZ twist the four sleeve units around the hot melt adhesive core; spray hot melt adhesive at the turning point of the loose sleeve after twisting, so that it penetrates into the gap between the loose sleeves, and tightly bond the loose sleeves to form a whole, ensuring the stability of the structure. Then wrap the water-blocking tape to obtain the cable core; extrude the sheath material on the outside of the cable core to obtain the finished optical cable. Parallel reinforcements are placed in the outer sheath.

[0074] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A small-core stranded optical cable, characterized in that: It includes 3 to 4 casing units, thin wires, and an outer sheath; The sleeve unit is twisted around the thin wire SZ arranged in the center to form a cable core; on the cross section of the cable core, the cross sections of the sleeve unit are stacked and adjacent to each other; the diameter d of the thin wire and the diameter D of the sleeve unit meet the following relationship: Wherein, d is the diameter of the thin wire, D is the diameter of the casing unit, n is the number of casing units, n = 3 or 4, α is the margin coefficient, and the value is 1.2; Hot melt adhesive is filled between the twisted sleeve units, and the hot melt adhesive is attached to the surface of the thin wire to form a hot melt adhesive core; The cable core is received in the outer sheath.

2. The small-core stranded thin-diameter optical cable according to claim 1, characterized in that: The diameter of the thin wire is the maximum distance between two points on the cross-sectional profile of the thin wire. Preferably, the cross-sectional profile of the thin wire is circular.

3. The small-core stranded thin-diameter optical cable according to claim 1, characterized in that: The thin wire is selected from one or a combination of water-blocking yarn, aramid fiber, PBT wire, PC wire, PE wire, and yarn.

4. The small-core stranded thin-diameter optical cable according to claim 1, characterized in that: A hot melt adhesive layer is attached to the outer wall of the sleeve; the hot melt adhesive layer attached to the outer wall of the sleeve is fused with the hot melt adhesive core.

5. The small-core stranded thin-diameter optical cable according to claim 1, characterized in that: The hot melt adhesive layer is axially discontinuous and passes over the folding portion of the SZ twist.

6. The small-core stranded thin-diameter optical cable according to claim 1, characterized in that: Auxiliary stabilizing elements are provided on the outer sides of the plurality of casing units. The auxiliary stabilizing elements are binding yarns for binding the cable core, wrapped water-blocking tapes, and / or longitudinally wrapped metal tapes.

7. The small-core stranded thin-diameter optical cable according to claim 1, characterized in that: The unit diameter of the sleeve is between 1.7 mm and 2.5 mm, and the number of sleeve cores is between 6 and 12.

8. The small-core stranded thin-diameter optical cable according to claim 1, characterized in that: The outer sheath has a circular cross-section and has parallel reinforcement members therein; or The cross section of the outer sheath is in the shape of an 8, the cable core is located in the first inner cavity of the 8-shaped sheath, and a reinforcement piece is arranged in the second inner cavity of the 8-shaped sheath.

9. The method for preparing a small-core stranded thin-diameter optical cable according to any one of claims 1 to 8, characterized in that: The following steps are involved: Spray hot melt adhesive of preset thickness on the surface of the thin line set in the center to form a hot melt adhesive core; When the hot melt adhesive core is in a molten state, the three to four sleeve units are twisted around the hot melt adhesive core SZ; The hot melt adhesive core is cooled to obtain a cable core; A sheath material is extruded outside the cable core to form a cable.

10. The method for preparing a small-core stranded thin-diameter optical cable according to claim 9, characterized in that: The following steps are involved: Hot melt adhesive is sprayed on the surface of the sleeve unit, and SZ twisting is performed when the hot melt adhesive on the outer wall of the sleeve unit is in a molten state, so that the hot melt adhesive on the outer wall of the sleeve unit is fused with the hot melt adhesive core.

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