Low-retraction optical cable and preparation method thereof

Abstract

The invention discloses a low-retraction optical cable and a preparation method thereof, and belongs to the technical field of optical cable preparation, the low-retraction optical cable comprises a reinforcing core, and a plurality of optical units are twisted on the periphery of the reinforcing core; and the bonding layer is arranged between the reinforcing core and the optical unit, the bonding layer at least partially bonds the contact surfaces of the optical unit and the reinforcing core, and a plurality of bonding points are formed on the optical unit and the reinforcing core along the axis of the optical cable. According to the low-retraction optical cable, the bonding layer is arranged between the reinforcing core and the optical unit, a plurality of bonding points arranged in the axial direction are formed between the reinforcing core and the optical unit through the bonding layer, and due to the fact that the reinforcing core has low shrinkage, and the bonding mode of the reinforcing core and the optical unit enables a sleeve of the optical unit to be bonded and fixed by the reinforcing core; therefore, the shrinkage of the sleeve of the optical unit is avoided, and the exposure of the optical fiber is avoided; meanwhile, the intermittent bonding mode of the optical unit and the reinforcing core prevents the optical unit and the reinforcing core from being bonded too tightly and facilitates the branching of the optical unit.

Description

Technical Field

[0001] The invention belongs to the technical field of optical cable preparation, and in particular relates to a low-shrinkage optical cable and a preparation method thereof. Background Art

[0002] Optical cables have the characteristics of high transmission bandwidth, long transmission distance and strong anti-interference ability, and are widely used in the fields of communication and data transmission. Optical fibers can transmit various types of signals such as digital signals, voice signals, and video signals, and are widely used in the fields of telephone, television, and computer networks.

[0003] Optical cables usually have optical fibers, loose tubes, and outer sheaths. Water-blocking structures and reinforcement structures are set inside the outer sheath to ensure the water-blocking and tensile properties of the optical cables. Since the optical fiber, tube, and outer sheath are made of different materials, the linear expansion coefficients of the materials are also different. During the storage of the optical cable, the external temperature and weather will cause the various layers of materials to shrink to varying degrees, causing the optical fiber to extend directly out of the tube. Since the optical fiber itself is relatively fragile, it is easy to be damaged after being exposed, resulting in the optical cable being unable to be used normally. Summary of the invention

[0004] In view of one or more of the above defects or improvement needs in the prior art, the present invention provides a low-retraction optical cable to solve the problem that the optical fiber is directly extended and exposed due to the large expansion margin of the casing in the existing optical cable structure.

[0005] To achieve the above object, the present invention provides a low-shrinkage optical cable, comprising:

[0006] Strengthen the core;

[0007] A plurality of optical units, wherein the plurality of optical units are twisted and arranged at the periphery of the reinforcing core;

[0008] The bonding layer is disposed between the reinforcing core and the optical unit, and the bonding layer at least partially bonds the connecting surfaces of the optical unit and the reinforcing core, and a plurality of bonding points are formed between the optical unit and the reinforcing core along the axial direction of the optical cable.

[0009] As a further improvement of the present invention, the bonding layer is at least one strip structure axially arranged along the outer periphery of the reinforcement core.

[0010] As a further improvement of the present invention, the adhesive layer is circumferentially coated on the outer periphery of the reinforcing core, and the adhesive layer is a plurality of layers arranged at intervals along the axial direction of the reinforcing core.

[0011] As a further improvement of the present invention, the outer periphery of the reinforcing core is coated with a friction layer, and the surface roughness of the friction layer is greater than 0.2.

[0012] As a further improvement of the present invention, the optical unit includes an optical fiber and a sleeve sleeved around the optical fiber, the sleeve is a double-layer sleeve structure, and the sleeve includes a PET and PBT blended layer arranged on the inner layer and a PBT layer arranged on the outer layer.

[0013] As a further improvement of the present invention, it also includes an armor layer and an outer sheath sequentially wrapped around the outer periphery of the plurality of optical units;

[0014] A concave structure arranged along the axial direction of the optical cable is formed on the outer periphery of the armor layer, and a part of the outer sheath facing the armor layer is embedded in the concave structure.

[0015] As a further improvement of the present invention, the armor layer is a steel belt, the steel belt forms a wavy tooth structure along the axial direction of the optical cable, and the outer sheath is embedded in the wavy tooth structure.

[0016] As a further improvement of the present invention, the armor layer is longitudinally wrapped around the outer periphery of the plurality of optical units, and an open cable is provided inside the armor layer, and the open cable is provided at the longitudinal overlap of the armor layer.

[0017] As a further improvement of the present invention, the outer periphery of the armor layer is covered with an adhesive film, and the outer periphery of the armor layer is coated with a water-blocking glue, and the outer sheath is made of the same material as the adhesive film.

[0018] The present application also includes a method for preparing a low-shrinkage optical cable, which comprises the following steps:

[0019] A friction layer is coated on the outer periphery of the reinforcing core;

[0020] Apply hot melt adhesive to the outer periphery of the reinforcing core before the twisting opening of the optical unit, and twist the optical unit to the outer periphery of the reinforcing core;

[0021] An armor layer is longitudinally wrapped around the periphery of the plurality of optical units;

[0022] Apply glue to the outer periphery of the armor layer and extrude the outer sheath around the armor layer.

[0023] As a further improvement of the present invention, the outer periphery of the reinforcing core is coated with hot melt adhesive, specifically comprising:

[0024] A hot melt adhesive extrusion device is provided, and the extrusion port of the hot melt adhesive extrusion device is aligned with one side of the friction layer, and the hot melt adhesive is extruded at a uniform speed. The hot melt adhesive is coated on the surface of the friction layer with the traction of the reinforcing core.

[0025] The above-mentioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0026] In general, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

[0027] (1) The low-shrinkage optical cable of the present invention provides an adhesive layer between the reinforcing core and the optical unit, and utilizes the adhesive layer to form a plurality of adhesive points arranged along the axial direction between the reinforcing core and the optical unit. Since the reinforcing core itself has low shrinkage, the reinforcing core and the optical unit are bonded and fixed to the sleeve of the optical unit by the reinforcing core, thereby avoiding shrinkage of the sleeve of the optical unit and exposure of the optical fiber. At the same time, the intermittent bonding between the optical unit and the reinforcing core enables the optical unit and the reinforcing core to be quickly peeled off when the optical fibers in the optical cable need to be branched, which greatly reduces the shrinkage rate of the optical unit without affecting the branching performance of the optical cable.

[0028] (2) The low-shrinkage optical cable of the present invention is formed by coating a friction layer on the outer periphery of the reinforcing core and selecting a friction layer with a surface roughness greater than 0.2, so that when the optical unit is attached to the outer periphery of the friction layer, the two have a large friction force along the axial direction of the optical cable, and the friction layer overcomes the shrinkage of the optical unit along the axial direction of the optical cable, thereby preventing the optical fiber from being exposed.

[0029] (3) The low-retraction optical cable of the present invention sets the surface of the armor layer as a recessed structure, embeds the inner side of the outer sheath into the recessed structure, and uses the armor layer to limit the shrinkage of the outer sheath, thereby avoiding the entire exposure of the optical unit and ensuring the protective performance of the outer sheath on the inner optical unit.

[0030] (4) The low shrinkage optical cable of the present invention reduces its shrinkage rate by setting the sleeve to a double-layer structure, by setting an inner layer of PET and PBT blend and an outer layer of PBT, thereby avoiding the problem of optical fiber exposure due to sleeve shrinkage. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 2 is a schematic diagram of the overall structure of a low-retraction optical cable according to an embodiment of the present invention;

[0032] Figure 2 Schematic diagram of bonding the reinforcing core and the sleeve of the low-shrinkage optical cable in Example 5 of the present invention;

[0033] Figure 3 It is a schematic diagram of bonding the reinforcing core and the sleeve of the low-shrinkage optical cable in Example 6 of the present invention.

[0034] In all the drawings, the same reference numerals represent the same technical features, specifically:

[0035] 1. Strengthening core; 2. Optical fiber; 3. Sleeve; 4. Adhesive layer; 5. Friction layer; 6. Armor layer; 7. Outer sheath; 8. Open cable; 9. Water-blocking yarn. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and 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.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0038] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0039] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0041] See also Figures 1 to 3 The low-retraction optical cable in the preferred embodiment of the present invention includes a reinforcing core 1, and a plurality of optical units are twisted and arranged on the periphery of the reinforcing core 1; an adhesive layer 4, which is arranged between the reinforcing core 1 and the optical unit, and the adhesive layer 4 at least partially bonds the contact surface of the optical unit and the reinforcing core 1, and the optical unit and the reinforcing core 1 form a plurality of bonding points along the axis of the optical cable.

[0042] The low-shrinkage optical cable of the present invention provides an adhesive layer 4 between the reinforcing core 1 and the optical unit, and utilizes the adhesive layer 4 to form a plurality of adhesive points arranged along the axial direction between the reinforcing core 1 and the optical unit. Since the reinforcing core 1 itself has low shrinkage, the reinforcing core 1 and the optical unit are bonded and fixed by the reinforcing core 1, thereby avoiding the shrinkage of the optical unit sleeve 3 and the exposure of the optical fiber 2. At the same time, the intermittent bonding between the optical unit and the reinforcing core 1 enables the optical fiber 2 in the optical cable to be quickly peeled off from the reinforcing core 1 when it needs to be branched, which greatly reduces the shrinkage of the optical unit without affecting the branching and lead-out performance of the optical cable.

[0043] Specifically, compared with conventional optical cables, the bonding form of the optical unit and the reinforcing core 1 of the low-retraction optical cable in the present application has the following advantages: the optical unit and the reinforcing core 1 in the present application are intermittently bonded, the bonding layer 4 is coated axially on the surface of the reinforcing core 1, and the sleeve 3 performs SZ stranding motion under the control of the cable stranding equipment. For each sleeve 3, the stranding pitch is relative to the bonding point. Compared with the conventional bonding form, by reducing the bonding point, the separation efficiency of the sleeve 3 and the reinforcing core 1 during bifurcation is increased. At the same time, when forming the bonding layer 4, the initial thickness of the glue on the surface of the reinforcing core 1 is 0.5-1.5 mm, the width along the circumferential direction of the reinforcing core 1 is 2-3 mm, and the glue is continuously coated along the axial direction of the reinforcing core 1. When the sleeve 3 is wound around the surface of the reinforcing core 1 at the stranding point, the shape of the glue changes under the extrusion of the optical unit, and the thickness direction of the glue becomes thinner, becoming 0.1-1 mm, and the width direction becomes wider, becoming 2.3-3.8 mm. The formed adhesive layer 4 is positively correlated with the initial coating amount of the glue, and is positively correlated with the projection length of a single optical unit in the circumferential direction of the reinforcing core 1. At the same time, the bonding thickness of the adhesive layer 4 is positively correlated with the peeling force between the reinforcing core 1 and the optical unit, and the coating area of ​​the adhesive layer 4 is negatively correlated with the shrinkage rate of the reinforcing core 1 and the optical unit. The structure of the adhesive layer 4 in the present application does not significantly affect the peeling force between the reinforcing core 1 and the optical unit, which facilitates the separation of the optical unit; at the same time, the axial bonding force between the reinforcing core 1 and the optical unit is greatly increased, so that the reinforcing core 1 can limit the shrinkage of the optical unit and avoid damage to the exposed optical fiber 2.

[0044] As an optional embodiment of the present invention, the adhesive layer 4 in the present application is at least one strip structure arranged axially along the outer periphery of the reinforcing core 1. Specifically, the adhesive layer 4 forms a linear structure along the axial direction of the reinforcing core 1. Since the optical units are twisted on the outer periphery of the reinforcing core 1, each optical unit will contact the adhesive layer 4, so that each optical unit forms a continuous point contact bonding form on the outer periphery of the reinforcing core 1. The continuous point contact form allows each optical unit to be bonded to the reinforcing core 1 in the axial direction of the optical cable, which can avoid the shrinkage of the optical unit; at the same time, the point bonding form can avoid the optical unit from being too firmly bonded to the reinforcing core 1, making it convenient for the optical unit to be quickly separated from the reinforcing core 1, and facilitating the divergence of the optical fiber 2. Optionally, the present application can also form a plurality of strip bonding structures in the circumferential direction of the reinforcing core 1, which can increase the bonding points between the optical unit and the reinforcing core 1, thereby reducing the shrinkage rate of the optical unit.

[0045] As an optional embodiment of the present invention, the adhesive layer 4 in the present application is circumferentially coated on the outer periphery of the reinforcing core 1, and the adhesive layer 4 is a plurality of adhesive layers arranged at intervals along the axial direction of the reinforcing core 1. Specifically, the adhesive layer 4 forms an annular structure and is arranged at intervals along the axial direction of the reinforcing core 1. Due to the twisting characteristics of the optical unit, the annular structure formed by the adhesive layer 4 is bonded to multiple optical units on the same annular surface, and by forming a plurality of spaced arrangements, each optical unit is intermittently bonded to the reinforcing core 1 along the axial direction of the optical cable to avoid shrinkage of the optical unit. Similarly, the intermittent arrangement of the adhesive layer 4 can avoid the optical unit from being too firmly bonded to the reinforcing core 1, facilitate the separation of the optical unit from the reinforcing core 1, and facilitate the divergence of the optical fiber 2. Preferably, the above-mentioned adhesive layers 4 are evenly spaced along the axial direction of the reinforcing core 1, and the distance between each adhesive layer 4 along the axial direction of the reinforcing core 1 is less than the twisting pitch of the optical unit, which can ensure the bonding density between the optical unit and the reinforcing core 1 to reduce the shrinkage rate of the optical unit.

[0046] Further preferably, the arrangement of the above-mentioned two types of adhesive layers 4 is such that the optical unit and the reinforcing core 1 form a sheet-like adhesive surface, and the adhesive surface along the axial direction of the optical cable is larger than the adhesive thickness along the radial direction of the optical cable, so that it is difficult to separate the optical unit from the reinforcing core 1 along the axial direction of the optical cable (the axial shrinkage rate of the optical unit is low), and the optical unit and the reinforcing core 1 are easy to separate along the radial direction of the optical cable (the optical unit is easy to peel off the reinforcing core 1).

[0047] Further preferably, in the present application, the outer periphery of the reinforcing core 1 is coated with a friction layer 5, and the surface roughness of the friction layer 5 is greater than 0.2. Specifically, the reinforcing core 1 usually adopts a steel wire structure, and the sheath outside the optical unit is plastic, and the two will produce interface separation, resulting in a weak bonding between the optical unit and the reinforcing core 1. Therefore, the present application sets a friction layer 5 on the outer periphery of the reinforcing core 1, and the friction layer 5 specifically adopts MDPE (medium density polyethylene). By adjusting the extrusion preparation process, the surface roughness of the friction layer 5 is greater than 0.2, and it can generate friction with the surface of the optical unit without bonding through the adhesive layer 4, so as to reduce the shrinkage of the optical unit; and the rough surface of the friction layer 5 is convenient for bonding with the optical unit through the adhesive layer 4. At the same time, when the outer periphery of the reinforcing core 1 is coated with the friction layer 5, it is equivalent to replacing part of the steel wire structure with MDPE, which can appropriately reduce the cable weight.

[0048] Furthermore, the optical unit in the present application includes an optical fiber 2 and a sleeve 3 sleeved on its periphery, and the sleeve 3 preferably adopts a double-layer structure, which includes a PET (polyethylene terephthalate) and PBT (polybutylene terephthalate) blended layer arranged on the side close to the optical fiber 2, and a PBT (polybutylene terephthalate) layer arranged on the outside. The blended structure of PET and PBT makes the inner layer have high crystallinity, and the outer PBT layer improves the lateral pressure resistance of the sleeve. While increasing the shrinkage rate, it prevents the sleeve from being damaged by the yarn during processing, and can alleviate the overall shrinkage rate of the sleeve 3 to a certain extent, preventing the optical fiber 2 from extending out of the sleeve 3.

[0049] Optionally, the sleeve 3 in the present application may also directly adopt a single-layer structure, which is a PBT layer. It is worth noting that when the PBT layer is produced, a compacting and traction process is adopted, and multiple sets of traction wheels are used to control the stretching rate of the PBT layer during the production and preparation process, so that the axial expansion rate of the sleeve 3 is low after the preparation is completed, so that even if the optical cable shrinks during use, its shrinkage rate is also small.

[0050] Preferably, the optical fiber 2 in the present application is preferably a ribbon cable structure, and the ribbon cable structure is preferably an optical fiber 2 ribbon structure prepared from 180μm optical fiber 2. Compared with 245μm optical and traditional ribbon cables, the 180μm optical fiber 2 has a higher optical fiber 2 density, can accommodate more optical fiber 2 cores under the same optical cable outer diameter, and the optical fiber 2 is more convenient to connect.

[0051] Furthermore, as a preferred embodiment of the present invention, the low-retraction optical cable in the present application also includes an armor layer 6 and an outer sheath 7 sequentially wrapped around the periphery of multiple optical units; and a recessed structure arranged along the axial direction of the optical cable is formed on the periphery of the armor layer 6, and the outer sheath 7 is partially embedded in the recessed structure on one side facing the armor layer 6. During the overall expansion and contraction process of the optical cable, the outer sheath 7 will also shrink to a certain extent, resulting in the overall exposure of the optical unit, so it is necessary to limit the shrinkage rate of the outer sheath 7 accordingly. Based on this, the present application correspondingly sets the armor layer 6 and the outer sheath 7, and through the recessed structure on the periphery of the armor layer 6, a protrusion that matches the recessed structure is formed when the outer sheath 7 is extruded, forming a mutually meshing structure to reduce the axial shrinkage rate of the outer sheath 7.

[0052] Furthermore, the armor layer 6 in the present application is a steel belt, which forms a wavy tooth structure along the axial direction of the optical cable, and the outer sheath 7 is embedded in the wavy tooth structure. Preferably, the base belt thickness of the steel belt in the present application is 0.2-0.25 mm, and the difference between the inner diameter of the cylindrical structure formed by the longitudinal wrapping of the steel belt and the diameter of the optical unit is 1.4-1.6 mm, which can increase the friction between the steel belt and the optical unit and improve the torsion resistance of the optical cable. When the difference between the diameter of the cylindrical structure formed by the longitudinal wrapping of the steel belt and the optical unit is less than 1.4 mm, the steel belt is difficult to form, which increases the failure rate of the sheath bulging. Preferably, the surface corrugation depth of the steel belt in the present application is 0.4-0.6 mm. The embossing depth of the traditional steel strip is about 0.7mm. The deeper the embossing depth is, the more sheath material is embedded in it, which will cause the internal receiving shrinkage of the outer sheath 7 to increase. When the embossing depth is too small, the tensile and bending resistance of the optical cable will be reduced. Therefore, in this application, the embossing depth of the steel strip surface is controlled to be about 0.4-0.6mm, ensuring the molding of the outer sheath 7 while ensuring the tensile and bending resistance of the optical cable.

[0053] Furthermore, the armor layer 6 in the present application is longitudinally wrapped around the outer periphery of the plurality of optical units, and a cable opening rope 8 is provided inside the armor layer 6, and the cable opening rope 8 is provided at the longitudinal overlap of the armor layer 6. The present application is a low-retraction optical cable, which can be used in a special environment at -60°C. When in an extremely cold environment, the hardness of the outer sheath 7 is high, and the cable opening rope 8 inside the optical cable is difficult to open. The present application adopts 1500T aramid as the cable opening rope 8, and its breaking force is ≥720N to meet the cable opening requirements of the optical cable under extremely cold conditions.

[0054] Further preferably, the outer periphery of the armor layer 6 in the present application is also coated with an adhesive film, and the outer sheath 7 is made of the same material as the adhesive film, which facilitates the bonding of the armor layer 6 and the outer sheath 7 and reduces the shrinkage rate of the outer sheath 7. Preferably, the adhesive film is a PE (polyethylene) film, the outer periphery of the armor layer 6 is coated with a water-blocking adhesive, and the outer sheath 7 is also made of PE. When the armor layer 6 is made of a steel belt, it is longitudinally wrapped around the outer periphery of the optical unit, which causes the steel belt to form an overlap surface when it is longitudinally wrapped. There will be a water-blocking problem at the overlap, so the outer periphery of the armor layer 6 in the present application is coated with a water-blocking adhesive to ensure the water-blocking performance of the armor layer 6. At the same time, the water-blocking adhesive itself has adhesion, and the armor layer 6 can be bonded to the outer sheath 7, and the axial expansion and contraction rate of the outer sheath 7 can be reduced through the armor layer 6 to prevent the optical unit from being exposed.

[0055] Furthermore, a water-blocking layer is provided on the inner side of the armor layer 6 of the present application. The water-blocking layer is formed by coating with a water-blocking tape, and the thickness of the water-blocking tape is 0.1 to 0.15 mm. A water-blocking yarn 9 is coated on the outer periphery of the water-blocking tape, which can improve the tensile properties of the optical cable while having a rat-proof capability.

[0056] Furthermore, the water blocking tape in the present application is overlapped and coated on the outer periphery of the light unit.

[0057] Furthermore, a water-blocking yarn 9 is twisted around the outer periphery of the reinforcing core 1 . The water-blocking yarn 9 is spirally wound around the outer periphery of the reinforcing core 1 , and the water-blocking yarn 9 will not block the reinforcing core 1 from being bonded to the optical unit.

[0058] Specifically, with respect to the above-mentioned low-shrinkage optical cable, the present application also includes a method for preparing the low-shrinkage optical cable, which comprises the following steps:

[0059] A friction layer 5 is plastically sleeved on the outer periphery of the reinforcing core 1 ; the structure of plastically sleeved on the outer periphery of the reinforcing core 1 friction layer 5 can be obtained by prior preparation or can be directly purchased.

[0060] Pull the reinforcing core 1, and twist the optical unit on the outer periphery of the reinforcing core 1, and set a glue coating device in front of the twisting mouth of the optical unit to coat the glue on the surface of the reinforcing core 1;

[0061] An armor layer 6 is longitudinally wrapped around the optical unit;

[0062] A water-blocking adhesive is coated on the outer periphery of the armor layer 6 , and an outer sheath 7 is extruded on the outer periphery of the armor layer 6 .

[0063] Furthermore, the adhesive coated on the outer periphery of the reinforcing core 1 is hot melt adhesive, and the hot melt adhesive coating method is:

[0064] Aim the glue outlet of the glue coating device at the surface of the friction layer 5 , heat the glue and extrude it at a uniform speed, and the hot melt glue is coated on the surface of the friction layer 5 along with the reinforcement core 1 .

[0065] The present application uses hot melt adhesive to bond the reinforcing core 1 to the optical unit. The hot melt adhesive is in a molten state at 150-160°C and exhibits good adhesion after cooling. After being sprayed out by a glue coating device, the fluid hot melt adhesive can be well adhered to the surface of the reinforcing core 1. When the optical unit is twisted around the outer periphery of the reinforcing core 1, the hot melt adhesive adheres to the surface where the reinforcing core 1 and the optical unit meet. As the twisting proceeds, the hot melt adhesive gradually cools and exhibits adhesion, thereby achieving adhesion between the optical unit and the reinforcing core 1.

[0066] Preferably, the extrusion preparation temperature of the outer sheath 7 in the present application is 180±5°C, and the conventional extrusion preparation temperature of the outer sheath 7 is about 220°C. The present application uses a lower extrusion preparation temperature, which can appropriately reduce the shrinkage rate of the sheath material from the extruder after heating and extrusion, to the cooling water tank, and finally to the final winding process.

[0067] Embodiment 1:

[0068] A 3.2mm non-metallic glass fiber is used as a reinforcing core 1, and a friction layer 5 is plastically sheathed on the outer periphery of the reinforcing core 1. The surface roughness of the friction layer 5 is 0.3, and the thickness of the friction layer 5 is 3.3mm. With the reinforcing core 1 as the center, 6.4mm×6 optical units are twisted on the outer periphery of the reinforcing core 1. The optical unit uses a PBT layer with a thickness of 0.5mm as a sleeve 3, and the optical unit twisting pitch is 420mm. A water-blocking tape and an armor layer 6 are sequentially coated on the outer periphery of the optical unit, and finally an outer sheath 7 is extruded, wherein the water-blocking tape has a thickness of 0.1mm, the steel belt has a thickness of 0.2mm, the steel belt has a corrugation depth of 0.6mm, and the outer sheath 7 is made of PE.

[0069] Embodiment 2:

[0070] A 3.2mm non-metallic glass fiber is used as a reinforcing core 1, and a friction layer 5 is plastically sheathed on the outer periphery of the reinforcing core 1. The surface roughness of the friction layer 5 is 0.3, and the thickness of the friction layer 5 is 3.3mm. With the reinforcing core 1 as the center, 6.4mm×6 optical units are twisted on the outer periphery of the reinforcing core 1. The optical unit uses a PBT layer with a thickness of 0.5mm as a sleeve 3, and the optical unit twisting pitch is 420mm. A water-blocking tape and an armor layer 6 are sequentially coated on the outer periphery of the optical unit, and finally an outer sheath 7 is extruded, wherein the water-blocking tape has a thickness of 0.1mm, the steel belt has a thickness of 0.2mm, the steel belt has a corrugation depth of 0.4mm, and the outer sheath 7 is made of PE.

[0071] Embodiment 3:

[0072] A 3.2mm non-metallic glass fiber is used as a reinforcing core 1, and a friction layer 5 is plastically sheathed on the outer periphery of the reinforcing core 1. The surface roughness of the friction layer 5 is 0.3, and the thickness of the friction layer 5 is 3.3mm. With the reinforcing core 1 as the center, 6.4mm×6 optical units are twisted on the outer periphery of the reinforcing core 1. The optical unit uses a PBT layer with a thickness of 0.5mm as a sleeve 3, and the optical unit twisting pitch is 420mm. A water-blocking tape and an armor layer 6 are sequentially coated on the outer periphery of the optical unit, and finally an outer sheath 7 is extruded, wherein the water-blocking tape has a thickness of 0.1mm, the steel belt has a thickness of 0.25mm, the steel belt has a corrugation depth of 0.4mm, and the outer sheath 7 is made of PE.

[0073] Embodiment 4:

[0074] A 3.2 mm non-metallic glass fiber is used as a reinforcing core 1, and a friction layer 5 is plastically coated on the outer periphery of the reinforcing core 1. The surface roughness of the friction layer 5 is 0.3, and the thickness of the friction layer 5 is 3.3 mm. With the reinforcing core 1 as the center, a 6.4 mm × 6 optical unit is twisted on the outer periphery of the reinforcing core 1. The optical unit adopts a double-layer co-extrusion process of an inner layer of PBT&PET mixed material (blended at a ratio of 3:1) + an outer layer of PBT to make a sleeve 3. The twisting pitch of the optical unit is 420 mm. A water-blocking tape and an armor layer 6 are sequentially coated on the outer periphery of the optical unit, and finally an outer sheath 7 is extruded, wherein the water-blocking tape has a thickness of 0.1 mm, the steel belt has a thickness of 0.25 mm, the steel belt has a corrugation depth of 0.4 mm, and the outer sheath 7 is made of PE.

[0075] Embodiment 5:

[0076] A 3.2 mm non-metallic glass fiber is used as a reinforcing core 1, and a friction layer 5 is plastically coated on the outer periphery of the reinforcing core 1. The surface roughness of the friction layer 5 is 0.3, and the thickness of the friction layer 5 is 3.3 mm. With the reinforcing core 1 as the center, a 6.4 mm × 6 optical unit is twisted on the outer periphery of the reinforcing core 1. The optical unit adopts a double-layer co-extrusion process of an inner layer of PBT&PET mixed material (blended at a ratio of 3:1) + an outer layer of PBT to make a sleeve 3. A hot melt adhesive is coated between the reinforcing core 1 and the optical unit for bonding. The hot melt adhesive forms a linear bonding surface on the outer periphery of the reinforcing core 1. The twisting pitch of the optical unit is 420 mm, and the distance between adjacent bonding points of the same optical unit and the reinforcing core 1 is 420 mm (close to the twisting pitch). A water-blocking tape and an armor layer 6 are sequentially coated on the outer periphery of the optical unit, and finally an outer sheath 7 is extruded, wherein the thickness of the water-blocking tape is 0.1 mm, the thickness of the steel belt is 0.25 mm, the corrugation depth of the steel belt is 0.4 mm, and the outer sheath 7 is made of PE.

[0077] Embodiment 6:

[0078] A 3.2 mm non-metallic glass fiber is used as a reinforcing core 1, and a friction layer 5 is plastically coated on the outer periphery of the reinforcing core 1. The surface roughness of the friction layer 5 is 0.3, and the thickness of the friction layer 5 is 3.3 mm. With the reinforcing core 1 as the center, a 6.4 mm × 6 optical unit is twisted on the outer periphery of the reinforcing core 1. The optical unit adopts a double-layer co-extrusion process of an inner layer of PBT&PET mixed material (blended at 3:1) + an outer layer of PBT to make a sleeve 3. A hot melt adhesive is coated between the reinforcing core 1 and the optical unit for bonding. The hot melt adhesive is applied in an annular interval on the outer periphery of the reinforcing core 1. The optical unit twisting pitch is 420 mm, and the distance between adjacent bonding points of the same optical unit and the reinforcing core 1 is 420 mm (close to the twisting pitch). A water-blocking tape and an armor layer 6 are sequentially coated on the outer periphery of the optical unit, and finally an outer sheath 7 is extruded, wherein the water-blocking tape has a thickness of 0.1 mm, the steel belt has a thickness of 0.25 mm, the steel belt corrugation depth is 0.4 mm, and the outer sheath 7 is made of PE.

[0079] Embodiment 7:

[0080] A 3.2 mm non-metallic glass fiber is used as a reinforcing core 1, and a friction layer 5 is sheathed on the outer periphery of the reinforcing core 1. The surface roughness of the friction layer 5 is 0.3, and the thickness of the friction layer 5 is 3.3 mm. With the reinforcing core 1 as the center, a 6.4 mm × 6 optical unit is twisted on the outer periphery of the reinforcing core 1. The optical unit adopts a double-layer co-extrusion process of an inner layer of PBT & PET mixed material (blended at a ratio of 3:1) + an outer layer of PBT to make a sleeve 3. Hot melt adhesive is applied between the reinforcing core 1 and the optical unit for Bonding: The hot melt adhesive forms two symmetrically arranged linear bonding surfaces on the periphery of the reinforcing core 1. The twisting pitch of the optical unit is 420 mm. The distance between adjacent bonding points of the same optical unit and the reinforcing core 1 is 420 mm (close to the twisting pitch). The water-blocking tape and the armor layer 6 are sequentially coated on the periphery of the optical unit, and finally the outer sheath 7 is extruded. The thickness of the water-blocking tape is 0.1 mm, the thickness of the steel belt is 0.25 mm, the embossing depth of the steel belt is 0.4 mm, and the outer sheath 7 is made of PE.

[0081] Blank example:

[0082] A 6.8 mm non-metallic glass fiber is used as a reinforcing core 1. With the reinforcing core 1 as the center, 6.4×6 optical units are twisted on the periphery of the reinforcing core 1. The optical unit uses a PBT layer with a thickness of 0.5 mm as a sleeve 3. The optical unit twisting pitch is 420 mm. A water-blocking tape is coated on the periphery of the optical unit. Finally, an outer sheath 7 is extruded. The water-blocking tape has a thickness of 0.1 mm and is coated on the periphery of the optical unit. The outer sheath 7 is made of PE.

[0083] The shrinkage rates of the sleeve 3 and the outer sheath 7 in the above embodiment are tested below: specifically, a 20m optical cable is selected for testing, the test low temperature is -40°C, the test high temperature is 70°C, and the test is kept warm for 2h in low and high temperature environments respectively, and then the temperature is raised from low temperature to high temperature, and then dropped from high temperature to low temperature, each lasting for 10h, a total of 24h, and a cycle of 24h is continued for 25 times. When the relative elongation of the outer sheath 7 to all components does not exceed 50mm (the shrinkage rate of the outer sheath 7 does not exceed 0.2%), it means that the product is qualified.

[0084]

[0085] By comparing the above-mentioned Example 1 with the blank example, it can be seen that when the armor layer 6 is buried inside the optical cable, the shrinkage rate of the outer sheath 7 can be greatly reduced by using a corrugated steel belt, and at the same time, the friction layer 5 is sheathed on the outer periphery of the reinforcing core 1, which can increase the friction between the reinforcing core 1 and the optical unit, and reduce the shrinkage rate of the optical unit; by comparing Example 2 with Example 1, it can be seen that when the corrugation depth of the steel belt is appropriately reduced, the constraint of the armor layer 6 on the outer sheath 7 can be increased, so that the shrinkage of the outer sheath 7 relative to the casing 3, the reinforcing core 1 and the optical fiber 2 is greatly reduced; by comparing Example 3 with Example 2, it can be seen that when the corrugation depth of the steel belt is appropriately increased, the outer sheath 7 can be greatly reduced. The thickness of the steel belt can further reduce the shrinkage rate of the outer sheath 7; by comparing Example 4 with Example 3, it can be seen that when the sleeve 3 of the optical unit is prepared by PET&PBT blending, the shrinkage rate of the optical unit can be appropriately reduced to avoid exposure of the optical fiber 2; by comparing Examples 5, 6, and 7 with Example 4, it can be seen that when hot melt adhesive is applied between the reinforcing core 1 and the optical unit, the hot melt adhesive can greatly improve the bonding force between the reinforcing core 1 and the optical unit, greatly improve the axial separation force between the optical unit and the reinforcing core 1, slightly improve the radial separation force between the optical unit and the reinforcing core 1, and greatly reduce the shrinkage rate of the optical unit relative to the outer sheath 7. It can be seen that by sheathing the friction layer 5 on the outer periphery of the reinforcing core 1, using hot melt adhesive to bond the reinforcing core 1 to the optical unit, and using a steel belt with embossing, the relative shrinkage rate between the outer sheath 7, the sleeve 3, and the optical fiber 2 can be greatly reduced to avoid exposure of the optical fiber 2 and the optical unit.

[0086] 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 low shrinkage optical cable, characterized in that: include: Strengthen the core; A plurality of optical units, wherein the plurality of optical units are twisted and arranged at the periphery of the reinforcing core; The bonding layer is disposed between the reinforcing core and the optical unit, and the bonding layer at least partially bonds the connecting surfaces of the optical unit and the reinforcing core, and a plurality of bonding points are formed between the optical unit and the reinforcing core along the axial direction of the optical cable.

2. The low-shrinkage optical cable according to claim 1, characterized in that: The bonding layer is at least one strip structure axially arranged along the outer periphery of the reinforcement core.

3. The low-shrinkage optical cable according to claim 1, characterized in that: The adhesive layer is circumferentially coated on the outer periphery of the reinforcing core, and the adhesive layer is a plurality of layers arranged at intervals along the axial direction of the reinforcing core.

4. The low-shrinkage optical cable according to claim 1, characterized in that: The outer periphery of the reinforcing core is coated with a friction layer, and the surface roughness of the friction layer is greater than 0.

2.

5. The low-shrinkage optical cable according to claim 1, characterized in that: The optical unit comprises an optical fiber and a sleeve sleeved around the optical fiber, wherein the sleeve is a double-layer sleeve structure, and comprises an inner layer of a PET and PBT blended layer and an outer layer of a PBT layer.

6. The low-shrinkage optical cable according to claim 1, characterized in that: It also includes an armor layer and an outer sheath sequentially wrapped around the outer periphery of the plurality of optical units; A concave structure arranged along the axial direction of the optical cable is formed on the outer periphery of the armor layer, and a part of the outer sheath facing the armor layer is embedded in the concave structure.

7. The low-shrinkage optical cable according to claim 6, characterized in that: The armor layer is a steel belt, which forms a wavy tooth structure along the axial direction of the optical cable, and the outer sheath is embedded in the wavy tooth structure.

8. The low-shrinkage optical cable according to claim 7, characterized in that: The outer periphery of the armor layer is covered with an adhesive film, and the outer periphery of the armor layer is coated with a water-blocking adhesive, and the outer sheath is made of the same material as the adhesive film.

9. A method for preparing a low-shrinkage optical cable, characterized in that: The steps include: A friction layer is coated on the outer periphery of the reinforcing core; The reinforcing core is pulled, and the optical unit is twisted on the outer periphery of the reinforcing core, and a glue coating device is arranged in front of the twisting opening of the optical unit to coat the glue on the surface of the reinforcing core; An armor layer is longitudinally wrapped around the optical unit; A water-blocking adhesive is coated on the outer periphery of the armor layer, and an outer sheath is extruded on the outer periphery of the armor layer.

10. The method for preparing a low-shrinkage optical cable according to claim 9, characterized in that: The adhesive coating on the outer periphery of the reinforcing core is hot melt adhesive, and the hot melt adhesive coating method is: Aim the glue outlet of the glue coating device at the surface of the friction layer, heat the glue and extrude it at a uniform speed, and the hot melt glue is coated on the surface of the friction layer along with the reinforcement core.

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