High-fiber-core-density air-blowing micro cable and preparation method thereof

Abstract

The invention discloses a high-fiber-core-density air-blowing micro-cable and a preparation method thereof, and belongs to the technical field of optical cable design, the high-fiber-core-density air-blowing micro-cable comprises a cable core and a sheath, optical fiber sleeves are arranged to be flexible sleeves, so that the multiple flexible sleeves can be extruded and deformed mutually, the utilization rate of the internal space of the cable core is improved, the optical fiber density is higher, and the optical fiber density is higher. The transmission capacity of the formed optical cable is larger, the outer protective layer is cooled and shaped through vacuum sizing to ensure the roundness of the appearance of the optical cable and facilitate the air-blowing construction of the air-blowing micro cable, and the machinable wall thickness of vacuum sizing becomes smaller and the size of the formed optical cable is smaller by setting the material of the outer protective layer as a high-melt-strength material. Or the armor layer is arranged between the cable core and the outer protective layer, and the armor layer is bonded with the outer protective layer, so that the strength of the outer protective layer is improved, the outer protective layer is not easy to crack after being subjected to vacuum sizing after extrusion molding, and the overall strength and rigidity of the optical cable are further improved.

Description

Technical Field

[0001] This invention belongs to the field of optical cable design technology, specifically relating to a high fiber core density air-blown microcable and its preparation method. Background Technology

[0002] In recent years, due to the increasing popularity of the Internet and the Internet of Things and the widespread application of emerging technologies, the amount of data transmission has continued to grow. However, single-core fiber transmission has approached the Shannon transmission limit, and the problem of expanding the capacity of optical communication has become an urgent issue for the optical communication industry.

[0003] Multi-core optical fiber, as a new type of optical fiber, has a special structure. Multiple fiber cores are designed within the same fiber cladding structure, and each fiber core is an independent transmission unit. This can multiply the transmission capacity of a single optical fiber. It is the most effective space division multiplexing technology to break through the Shannon limit of a single-mode optical fiber. It has broad application prospects in optical communication, optical sensors, data center connections and other fields, and has been successfully applied to various types of optical cables.

[0004] Although multi-core optical fiber cables can transmit multiple signals, their structure is relatively complex. The arrangement and protection mechanisms of multiple optical fibers result in a relatively large overall size of the cable, which cannot make full use of the space inside the cable and cannot meet customers' needs for miniaturization of optical cables. Summary of the Invention

[0005] In response to one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides a high fiber core density air-blown microcable and its preparation method, which can increase the fiber density of the air-blown microcable, ensure the roundness of the optical cable, and ensure that the sheath wall thickness is thin enough.

[0006] To achieve the above objectives, one aspect of the present invention provides a high fiber density air-blown microcable, comprising a cable core and a sheath;

[0007] The cable core includes multiple flexible sleeves, each flexible sleeve containing at least one optical fiber, and the flexible sleeves can be squeezed and deformed against each other.

[0008] The sheath includes a first outer sheath, which is made of a high melt strength material. The first outer sheath is formed by extruding the high melt strength material and then vacuum sizing it around the outer periphery of the cable core. The thickness of the first outer sheath is not less than 0.35 mm, and the out-of-roundness of the outer peripheral wall of the first outer sheath is less than 6%.

[0009] As a further improvement of the present invention, the MFR value of the high melt strength material at a test temperature of 190°C and a load of 2.16 kg is:

[0010] 0.1g / 10min≤MFR≤1.5g / 10min.

[0011] As a further improvement of the present invention, multiple optical fibers are disposed within the cladding of the flexible sleeve. The optical fibers are multi-core optical fibers, and a mark core is disposed in the cladding of the optical fibers. The optical fibers are numbered starting from the ones closest to the mark core, and the other optical fibers are numbered sequentially in a clockwise or counterclockwise direction.

[0012] The diameter of the mark core is different from the diameter of the fiber core, or the mark core is an irregularly shaped fiber core, in order to facilitate identification.

[0013] Another aspect of the present invention provides another high fiber core density air-blown microcable, comprising a cable core, an armor layer, and a sheath;

[0014] The cable core includes multiple flexible sleeves, each flexible sleeve containing at least one optical fiber, and the flexible sleeves can be squeezed and deformed against each other.

[0015] The armor layer covers the outer periphery of the cable core;

[0016] The sheath includes a second outer sheath, which is formed by extruding sheath material and then vacuum sizing and covering the outer periphery of the armor layer, and is bonded to the armor layer; and the thickness of the second outer sheath is not less than 0.2 mm, and the out-of-roundness of the outer peripheral wall of the second outer sheath is less than 6%.

[0017] As a further improvement of the present invention, the armor layer is an FRP layer, and the thickness of the FRP layer is not greater than 1.5 mm;

[0018] A coating is provided on the side of the FRP layer near the second outer sheath. The coating is a hot-melt material that bonds to the second outer sheath after being hot-melted.

[0019] As a further improvement of the present invention, multiple optical fibers are disposed within the cladding of the flexible sleeve. The optical fibers are multi-core optical fibers, and a mark core is disposed in the cladding of the optical fibers. The optical fibers are numbered starting from the ones closest to the mark core, and the other optical fibers are numbered sequentially in a clockwise or counterclockwise direction.

[0020] The diameter of the mark core is different from the diameter of the fiber core, or the mark core is an irregularly shaped fiber core, in order to facilitate identification.

[0021] As a further improvement of the present invention, the sheath further includes an inner sheath covering the outer periphery of the cable core, and the armor layer is disposed between the second outer sheath and the inner sheath.

[0022] Another aspect of the present invention provides a method for preparing a high fiber core density air-blown microcable, comprising the following steps:

[0023] (1) Multiple flexible optical fibers are threaded through a flexible sleeve and the multiple flexible sleeves are constrained into a single strand to form a cable core;

[0024] (2) The cable core is pulled into the extruder for extrusion and cooled and shaped in a vacuum sizing water tank to form an outer sheath, thus completing the optical cable preparation; wherein the pulling speed of the cable core is 10 to 40 m / min.

[0025] As a further improvement of the present invention, in step (1), multiple flexible sleeves are first weakly twisted, and then the multiple flexible sleeves are tied together by binding yarn; wherein, the twisting pitch of the weak twisting is 70mm to 300mm, and the binding yarn pitch is 20mm to 100mm.

[0026] Alternatively, intermittent adhesive can be applied along the longitudinal direction of the flexible sleeve to bond the flexible sleeves together to form a flexible sleeve strip.

[0027] Alternatively, multiple flexible sleeves can be drawn to an extruder and a thin film can be extruded around their periphery to bind the multiple flexible sleeves together.

[0028] As a further improvement of the present invention, in step (2), before entering the vacuum sizing water tank, pre-cooling is performed. The traction distance of the pre-cooling is 10 to 30 cm, so that the temperature of the outer protective layer material after pre-cooling is between the softening point and the melting point, forming a multi-stage cooling of the protective material.

[0029] And / or,

[0030] As a further improvement of the present invention, in step (2), before the cable core enters the extruder, an FRP layer is first longitudinally wrapped around the outer periphery of the cable core. A hot-melt coating is provided on the outer periphery of the FRP layer. After entering the extruder for extrusion, the hot-melt coating melts and bonds the FRP layer to the outer sheath.

[0031] The aforementioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0032] In summary, the beneficial effects of the above-described technical solutions conceived by this invention compared with the prior art include:

[0033] (1) The high fiber core density air-blown microcable of the present invention is made by setting the optical fiber sleeve as a flexible sleeve, so that multiple flexible sleeves can be squeezed and deformed to improve the utilization rate of the internal space of the cable core, so that the optical fiber density is higher under the same cable core size, and the transmission capacity of the optical cable is larger; at the same time, the outer sheath is cooled and shaped by vacuum sizing to ensure the roundness of the optical cable shape, which facilitates the air-blown construction of the air-blown microcable, and by setting the outer sheath material as a high melt strength material, the machinable wall thickness of vacuum sizing becomes smaller, and the size of the optical cable formed is smaller.

[0034] (2) The high fiber core density air-blown micro cable of the present invention provides an armor layer between the cable core and the outer sheath, and bonds the armor layer to the outer sheath as a whole, so as to reinforce the outer sheath through the armor layer without affecting the bending of the optical cable, making it less prone to breakage during the vacuum sizing process of the outer sheath, and further improving the overall strength and stiffness of the optical cable.

[0035] (3) The high fiber core density air-blown microcable of the present invention sets Mark cores in the multi-core optical fiber to number the multiple fiber cores in sequence, which facilitates the identification of each fiber core during the later construction process.

[0036] (4) The method for preparing high fiber core density air-blown microcable of the present invention pre-cools the outer sheath before vacuum sizing, so that the sheath material can be strengthened by a certain cooling, and further avoids the sheath breaking during vacuum sizing.

[0037] (5) The high fiber core density air-blown microcable and its preparation method of the present invention have a reasonable structural design. Under the condition that the size of the air-blown microcable is limited, the fiber density in the microcable can be increased, the diameter of the microcable can be reduced, and the roundness of the microcable shape can be guaranteed. It has good application prospects and promotion value. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the overall structure of the high fiber core density air-blown microcable according to the first embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the overall structure of the high fiber core density air-blown microcable according to the second embodiment of the present invention;

[0041] Figure 3 This is a schematic diagram of the overall structure of the high fiber density air-blown microcable with an inner sheath in an embodiment of the present invention;

[0042] Figure 4 This is a schematic diagram of the overall structure of the four-core optical fiber in an embodiment of the present invention;

[0043] Figure 5 This is a schematic diagram of the overall structure of the multi-core optical fiber in an embodiment of the present invention;

[0044] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1. Flexible sleeve; 2. Optical fiber; 201. Cladding; 202. Fiber core 1; 203. Fiber core 2; 204. Fiber core 3; 205. Fiber core 4; 206. Mark core; 3. First outer sheath; 4. Armor layer; 5. Inner sheath; 6. Second outer sheath. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0046] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0048] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0049] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0050] Example:

[0051] Please see Figures 1-5 The high fiber density air-blown microcable of the present invention includes a cable core and a sheath. The cable core is provided with a plurality of flexible sleeves 1. The plurality of flexible sleeves 1 can be squeezed and deformed to reduce the gap between the sleeves and increase the number of sleeves in the cable core under the same cable core size, thereby increasing the fiber density of the optical cable and thus enabling the optical cable to increase its transmission capacity while maintaining a small diameter.

[0052] Specifically, in a preferred embodiment, at least one optical fiber 2 is disposed within the flexible sleeve 1, such as... Figure 1 As shown, multiple optical fibers 2 are arranged inside the flexible sleeve 1, and the optical fibers 2 are further preferably multi-core optical fibers to further improve the optical fiber density of the cable core.

[0053] To facilitate differentiation and identification, each optical fiber 2 is colored with a different color-locked core. Since the cladding 201 contains a large number of fiber cores with limited color options, simply identifying the core color may not meet application requirements. Therefore, in a preferred embodiment, a mark core 206 is also provided within the cladding 201 to distinguish and mark each fiber core. In a preferred embodiment, the fiber core closest to the mark core 206 is numbered, and the other fiber cores are numbered sequentially in a clockwise or counterclockwise direction, depending on the actual needs.

[0054] like Figure 4 The diagram shows the end face of a four-core fiber. The four fiber cores are evenly arranged in a circumferential direction within the cladding 201. A mark core 206 is set on the periphery of the cladding 201. Since it is close to the fiber core on the upper right side, the fiber core on the upper right side is numbered as fiber core 1 202. The other fiber cores are numbered sequentially in a clockwise direction as fiber core 2 203, fiber core 3 204, and fiber core 4 205.

[0055] When the number of fiber cores is large, such as Figure 5As shown, the multiple fiber cores within the cladding 201 can adopt a multi-ring or spiral structure. When the mark core 206 is set on the outermost side, the outermost fiber cores can be numbered in the manner described above. For the numbering of the inner fiber cores, the fiber cores closest to fiber core 1 202 can be numbered first.

[0056] It is understandable that the diameter of the mark core is different from the diameter of the fiber core, and can be larger or smaller than the diameter of the fiber core, so as to facilitate differentiation from the fiber core; of course, one of the fiber cores can also be set to a shape that is easy to distinguish from other fiber cores, such as a small diameter or irregular shape, and this fiber core is designated as fiber core 202 and mark core 206, and then the other fiber cores are numbered sequentially.

[0057] Correspondingly, each flexible sleeve 1 can also be set to a different color for differentiation.

[0058] Furthermore, in the preferred embodiment, the sheath includes an outer sheath that covers the outer periphery of the cable core and protects the fiber core inside the cable core. However, since the multiple flexible sleeves 1 in the cable core of the present invention are irregular in shape and can be squeezed and deformed by each other, it is impossible to form an outer sheath with a regular circular cross-section if conventional extrusion coating molding is used.

[0059] To ensure the external shape of the outer sheath, the outer sheath of this invention is formed by extruding the material using an extruder and then cooling and shaping it using vacuum sizing. This results in good circumference of the outer sheath, with an out-of-roundness of less than 6%, meeting the construction requirements for air-blown microcable laying. However, the sheath produced using vacuum sizing generally has a thicker wall. When the wall thickness is less than about 1.2 mm, the sheath may easily break under pressure when facing a pressure difference due to insufficient melt strength of conventional sheath materials, affecting the quality of the finished product.

[0060] Therefore, in the first embodiment of the present invention, as Figure 1 As shown, a high melt strength material is preferably used as the sheath material to process the first outer sheath 3, which can maintain high strength even when the sheath wall thickness is thin, so as not to break during vacuuming.

[0061] Preferably, the thickness of the first outer sheath 3, which uses a high melt strength material as the sheath material and is cooled and shaped by vacuum sizing, is not less than 0.35 mm.

[0062] In actual production, this high melt strength material can be selected from closed-cell foamed PE (polyethylene), HDPE (high-density polyethylene), etc., and the MFR (melt flow rate) and melt strength can be balanced according to the actual application scenario and requirements.

[0063] MFR (Melt Fiber Retention) represents the relative viscosity of thermoplastic melt. A high MFR indicates a small molecular weight of the polymer and good flow properties during processing. However, an excessively high MFR may lead to increased shrinkage and poor dimensional stability in the finished product. Conversely, a low MFR indicates a large molecular weight of the polymer and poor flow properties during processing. Generally, MFR and melt strength show opposite trends numerically. Materials with high MFR are easier to process and mold, but may sacrifice some strength. Conversely, if the melt strength is too low, the finished product may break or crack during processing. Materials with low MFR have higher strength, but are more difficult to process. Therefore, in practical applications, it is necessary to select an appropriate MFR range based on specific requirements to balance processing performance and material strength.

[0064] Based on the above relationship, the present invention indirectly characterizes the melt strength of the sheath material by measuring the MFR value. The smaller the MFR value, the greater the melt strength of the corresponding material.

[0065] Under normal circumstances, the air pressure in a vacuum water bath is 0.02–0.06 MPa, while the external air pressure is typically 0.1 MPa. To ensure the sheath wall remains undamaged during sudden pressure changes, a high melt strength material is preferred, with the following MFR value at a test temperature of 190°C and a load of 2.16 kg:

[0066] 0.1g / 10min≤MFR≤1.5g / 10min.

[0067] In a preferred embodiment, closed-cell foamed PE is selected as the material of the first outer sheath 3, and the MFR value of the closed-cell foamed PE at a test temperature of 190°C and a load of 2.16KG is further preferred to be:

[0068] 0.1g / 10min≤MFR≤1.0g / 10min.

[0069] In the second embodiment of the present invention, as Figure 2 As shown, an armor layer 4 is provided between the second outer sheath 6 and the cable core. The armor layer 4 serves as a support layer to support and cover the flexible sleeve 1, increasing the outer periphery strength of the cable core. At the same time, the armor layer 4 increases the inner strength of the second outer sheath 6, making it less prone to breakage during vacuum sizing, even when using ordinary sheath materials during the production of the second outer sheath 6. In this case, it is preferable that the thickness of the second outer sheath 6 is not less than 0.8 mm to prevent the armor layer 4 from puncturing the second outer sheath 6 when the micro-cable is blown through a bend.

[0070] To further reduce the thickness of the second outer sheath 6, it is preferable to bond the second outer sheath 6 to the armor layer 4, making the second outer sheath 6 and the armor layer 4 form a whole, which is more conducive to the bending of the optical cable. At the same time, the armor layer 4 can further reinforce the second outer sheath 6, making the second outer sheath 6 less prone to breakage during vacuum sizing. Due to the integrity between the second outer sheath 6 and the armor layer 4, the machinable wall thickness of the second outer sheath 6 is not less than 0.2 mm, which is a thinner machinable wall thickness.

[0071] Preferably, the thickness of the armor layer 4 is no more than 1.5 mm, and more preferably no more than 1 mm, so as not to affect the flexibility of the air-blown microcable and facilitate the air blowing of the optical cable in the curved pipe.

[0072] Preferably, the armor layer 4 is formed by wrapping the cable core with an FRP (fiber-reinforced composite plastic) layer, and a coating is provided on the side of the FRP layer near the second outer sheath 6. This coating is a thermoplastic material, so that it can be melted by heating, thereby bonding the FRP layer to the second outer sheath 6. In actual installation, the FRP layer can be a longitudinally wrapped FRP strip, a flat FRP strip, etc.

[0073] Of course, the armor layer 4 and its specific configuration and specifications in the second embodiment can also be applied to the first embodiment to further increase the overall strength and stiffness of the air-blown microcable through the armor layer 4; that is, in the first embodiment, the armor layer 4 can also be provided between the first outer sheath 3 formed of high melt strength material and the cable core, and the armor layer 4 is bonded to the first outer sheath 3. The specific material and parameter selection of the armor layer 4 are referred to the second embodiment.

[0074] Furthermore, such as Figure 3 As shown, in the preferred embodiment, the sheath further includes an inner sheath 5, which is disposed between the cable core and the armor layer 4 to further protect the cable core. In the preferred embodiment, the material and formation method of the inner sheath 5 are preferably the same as those of the outer sheath. In actual production, if the optical cable size is small, the inner sheath 5 may not be provided.

[0075] Furthermore, the present invention prepares high fiber core density air-blown microcables using the following preparation method, specifically including the following steps:

[0076] (1) Cable core preparation: multiple flexible optical fibers 2 are threaded through a flexible sleeve 1 and the multiple flexible sleeves 1 are bound together to form a cable core;

[0077] The flexible multi-core optical fiber can be existing or fabricated on-site. When fabricating the optical fiber, each core is first colored with a different color-locked core, and then multiple cores are arranged in a ring in the same cladding 201. Preferably, a mark core 206 is set on the periphery of the cladding 201. Then, the fiber is drawn to form the optical fiber 2.

[0078] In addition to being compressible, the flexible sleeve 1 also possesses a certain degree of resilience, ensuring sufficient gaps between the flexible sleeves 1 and between the flexible sleeve 1 and the outer sheath, thus preventing the optical fiber from being subjected to excessive flattening force. Preferably, the Shore hardness of the flexible sleeve 1 is 15-54, avoiding the situation where the Shore hardness of the flexible sleeve 1 is too low, making it prone to wrinkling and breakage under external force, while also avoiding the situation where the Shore hardness of the flexible sleeve 1 is too high, which would affect the extrusion deformation performance.

[0079] When binding multiple flexible sleeves 1 together, the multiple flexible sleeves 1 can be weakly twisted first, with a twisting pitch preferably between 70mm and 300mm. Then, the multiple flexible sleeves 1 can be bound together by binding yarn. This way, while binding, the extrusion deformation of the flexible sleeves 1 is not affected, saving space. It is preferable to control the binding yarn tension between 15g and 90g and the binding yarn pitch between 20mm and 100mm to ensure that there are no obvious binding marks on the surface of the flexible sleeves 1. This avoids the fiber macro bending caused by excessively dense binding yarn, which leads to attenuation and affects the deformation of the flexible sleeves 1. Alternatively, if the binding yarn is too sparse, the flexible sleeves 1 will be too loose and will bulge after entering the extruder head, which may lead to cable breakage.

[0080] Of course, intermittent glue can also be applied along the longitudinal direction of the flexible sleeve 1 to bond each flexible sleeve 1 together to form a spider web-like flexible sleeve strip, thereby constraining multiple flexible sleeves 1 into a single strand.

[0081] Of course, multiple flexible sleeves 1 can also be directly pulled to an extruder and a thin film can be extruded on their outer periphery to bind the multiple flexible sleeves 1 into a single strand.

[0082] (2) Optical cable preparation: The cable core is pulled into the extruder for extrusion and then cooled and shaped in a vacuum sizing water tank to form an outer sheath, thus completing the optical cable preparation.

[0083] In actual production, the extrusion rate of the extruder is adjusted and selected according to the processing speed and the wall thickness of the optical cable. The preferred traction speed of the cable core is 10-40 m / min. This avoids the flexible sleeve 1 from staying in the extruder for too long due to the traction speed being too low, which would cause the surface of the flexible sleeve 1 to soften, resulting in the yarn getting stuck in the flexible sleeve 1 and causing marks, or even causing the flexible sleeve wall to crack and the optical fiber to be exposed.

[0084] Preferably, when an armor layer is provided between the outer sheath and the cable core, the FRP layer is first wrapped around the outer periphery of the cable core before the outer sheath is formed, and then extrusion molding is performed.

[0085] It is understandable that the hot-melt coating on the side of the FRP layer near the outer sheath is melted by the extrusion and heating of the molten sheath material, so that it can be well bonded to the sheath.

[0086] Preferably, pre-cooling is performed before vacuum sizing, and the preferred pre-cooling traction distance is 10-30cm, so that the temperature of the outer sheath material after pre-cooling is between the softening point and the melting point, forming a multi-stage cooling of the sheath material. For example, air cooling or high-temperature water cooling equipment can be added between the die head and the vacuum sizing water tank to cool the sheath material from the molten state to a certain extent, improve its strength, and reduce the risk of skin breakage during vacuum sizing.

[0087] Example 1:

[0088] The fiber optic cable uses 4-core optical fibers; each flexible sleeve contains 108 optical fibers, the flexible sleeve has a Shore hardness of 21, and each cable core contains 4 flexible sleeves, for a total of 1728 cores, with a core density of 14.78 cores / mm². 2 The stranding pitch is 70mm, and the binding pitch is 100mm. The outer sheath material is closed-cell foamed PE material, with an MFR value of 0.1g / 10min at a test temperature of 190℃ and a negative pressure of 2.16KG. The outer sheath is made with a thickness of 0.35mm and an outer wall non-circularity of ≤6% by vacuum sizing. The overall diameter of the optical cable is 12.2mm. After cabling, the wavelength attenuation at 1550nm is less than 0.22dB / km. The air-blown length can reach 600m. The mechanical, environmental, and optical properties meet the IEC-60794 international standard.

[0089] Example 2:

[0090] The optical fiber used is G.657.A2 single-mode fiber; each flexible sleeve contains 108 optical fibers, the flexible sleeve has a Shore hardness of 45, and each cable core contains 4 flexible sleeves, for a total of 432 cores, with a core density of 3.52 cores / mm². 2 The stranding pitch is 180mm, and the binding pitch is 60mm. The outer sheath material is closed-cell foamed PE material, with an MFR value of 0.3g / 10min at a test temperature of 190℃ and a negative pressure of 2.16KG. The outer sheath is made with a thickness of 0.5mm and an outer wall non-circularity of ≤6% by vacuum sizing. The overall diameter of the optical cable is 12.5mm. After cabling, the wavelength attenuation at 1550nm is less than 0.22dB / km. The air-blown length can reach 500m. The mechanical, environmental, and optical properties meet the IEC-60794 international standard.

[0091] Example 3:

[0092] The fiber optic cable uses 7-core fibers; each flexible sleeve contains 48 fibers, the flexible sleeve has a Shore hardness of 54, and each cable core contains 6 flexible sleeves, for a total of 2016 cores, with a core density of 10.68 cores / mm². 2 The stranding pitch is 300mm, the binding pitch is 20mm, and the armor layer thickness is 1.5mm. The outer sheath material is ordinary PE material, with an MFR value of 1.5g / 10min at a test temperature of 190℃ and a negative pressure of 2.16KG. The outer sheath is made with a thickness of 1mm and an outer wall non-circularity of ≤6% by vacuum sizing. The overall diameter of the optical cable is 15.5mm. After cabling, the wavelength attenuation at 1550nm is less than 0.22dB / km. The air-blown length can reach 600m. The mechanical, environmental, and optical properties meet the IEC-60794 international standard.

[0093] Example 4:

[0094] The fiber optic cable uses 4-core optical fibers; each flexible sleeve contains 48 optical fibers, the flexible sleeve has a Shore hardness of 21, and each cable core contains 6 flexible sleeves, for a total of 1152 cores, with a core density of 10.18 cores / mm². 2 Multiple flexible sleeves are bonded together to form a spider web sleeve by applying adhesive along the longitudinal direction of the cable core. The armor layer thickness is 0.5mm. The outer sheath material is ordinary PE material, with an MFR value of 0.8g / 10min at a test temperature of 190℃ and a negative pressure of 2.16KG. The outer sheath is made with a thickness of 0.5mm and an outer wall non-circularity of ≤6% by vacuum sizing. The overall diameter of the optical cable is 12mm. After cabling, the wavelength attenuation at 1550nm is less than 0.22dB / km. The air-blown length can reach 1000m. The mechanical, environmental, and optical performance meet the IEC-60794 international standard.

[0095] The high fiber core density air-blown microcable and its preparation method in this invention have a reasonable structural design. Under the condition of limiting the size of the air-blown microcable, the fiber density in the microcable can be increased, the diameter of the microcable can be reduced, and the roundness of the microcable shape can be guaranteed. It can provide high fiber density while maintaining sufficient structural, thermal, optical and mechanical properties, and has good application prospects and promotion value.

[0096] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. A high fiber core density air-blown microcable, characterized in that, Including the cable core and sheath; The cable core includes multiple flexible sleeves, each flexible sleeve containing at least one optical fiber, and the flexible sleeves can be squeezed and deformed against each other. The sheath includes a first outer sheath, which is made of a high melt strength material. The first outer sheath is formed by extruding the high melt strength material and then vacuum sizing it around the outer periphery of the cable core. The thickness of the first outer sheath is not less than 0.35 mm, and the out-of-roundness of the outer peripheral wall of the first outer sheath is less than 6%.

2. The high fiber core density air-blown microcable according to claim 1, characterized in that, The MFR value of the high melt strength material at a test temperature of 190℃ and a load of 2.16KG is: 0.1g / 10min≤MFR≤1.5g / 10min.

3. The high fiber core density air-blown microcable according to claim 1 or 2, characterized in that, The flexible sleeve has multiple optical fibers inside its cladding. The optical fibers are multi-core optical fibers, and a mark core is set in the cladding of the optical fibers. The optical fibers are numbered starting from the ones closest to the mark core, and the other optical fibers are numbered sequentially in a clockwise or counterclockwise direction. The diameter of the mark core is different from the diameter of the fiber core, or the mark core is an irregularly shaped fiber core, in order to facilitate identification.

4. A high fiber core density air-blown microcable, characterized in that, Including the cable core, armor layer, and sheath; The cable core includes multiple flexible sleeves, each flexible sleeve containing at least one optical fiber, and the flexible sleeves can be squeezed and deformed against each other. The armor layer covers the outer periphery of the cable core; The sheath includes a second outer sheath, which is formed by extruding sheath material and then vacuum sizing and covering the outer periphery of the armor layer, and is bonded to the armor layer; and the thickness of the second outer sheath is not less than 0.2 mm, and the out-of-roundness of the outer peripheral wall of the second outer sheath is less than 6%.

5. The high fiber core density air-blown microcable according to claim 4, characterized in that, The armor layer is an FRP layer, and the thickness of the FRP layer is no more than 1.5 mm; A coating is provided on the side of the FRP layer near the second outer sheath. The coating is a hot-melt material that bonds to the second outer sheath after being hot-melted.

6. The high fiber core density air-blown microcable according to claim 4 or 5, characterized in that, The flexible sleeve has multiple optical fibers inside its cladding. The optical fibers are multi-core optical fibers, and a mark core is set in the cladding of the optical fibers. The optical fibers are numbered starting from the ones closest to the mark core, and the other optical fibers are numbered sequentially in a clockwise or counterclockwise direction. The diameter of the mark core is different from the diameter of the fiber core, or the mark core is an irregularly shaped fiber core, in order to facilitate identification.

7. The high fiber core density air-blown microcable according to claim 4 or 5, characterized in that, The sheath also includes an inner sheath covering the outer periphery of the cable core, and the armor layer is disposed between the second outer sheath and the inner sheath.

8. A method for preparing a high fiber core density air-blown microcable, characterized in that, Includes the following steps: (1) Multiple flexible optical fibers are threaded through a flexible sleeve and the multiple flexible sleeves are constrained into a single strand to form a cable core; (2) The cable core is pulled into the extruder for extrusion and cooled and shaped in a vacuum sizing water tank to form an outer sheath, thus completing the optical cable preparation; wherein the pulling speed of the cable core is 10 to 40 m / min.

9. The method for preparing a high fiber core density air-blown microcable according to claim 8, characterized in that, In step (1), multiple flexible sleeves are first weakly twisted, and then the multiple flexible sleeves are tied together by binding yarn; wherein, the twisting pitch of the weak twisting is 70mm to 300mm, and the binding pitch is 20mm to 100mm. Alternatively, intermittent adhesive can be applied along the longitudinal direction of the flexible sleeve to bond the flexible sleeves together to form a flexible sleeve strip. Alternatively, multiple flexible sleeves can be drawn to an extruder and a thin film can be extruded around their outer periphery to bind the multiple flexible sleeves together.

10. The method for preparing a high fiber core density air-blown microcable according to claim 8 or 9, characterized in that, In step (2), before entering the vacuum sizing water tank, pre-cooling is performed. The traction distance of this pre-cooling is 10-30cm, so that the temperature of the outer protective layer material after pre-cooling is between the softening point and the melting point, forming a multi-stage cooling of the protective material. And / or, In step (2), before the cable core enters the extruder, an FRP layer is longitudinally wrapped around the outer periphery of the cable core. A hot-melt coating is provided on the outer periphery of the FRP layer. After extrusion in the extruder, the hot-melt coating melts and bonds the FRP layer to the outer sheath.

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