Optical unit with easy-to-open and strip loose sleeve, preparation method thereof and optical cable

Abstract

The present invention discloses an optical unit with an easy-to-strip loose sleeve, a preparation method thereof and an optical cable. The optical unit comprises an optical fiber assembly and a composite loose sleeve for accommodating the optical fiber assembly; the composite loose sleeve comprises an inner layer and an outer layer; a circumferential contact surface is provided between the inner layer and the outer layer; the inner layer has an easy-to-tear portion and a skeleton portion that penetrate radially; the outer layer has an easy-to-tear portion and a skeleton portion that penetrate radially; the easy-to-tear portion of the inner layer and the easy-to-tear portion of the outer layer are discontinuously distributed in the circumferential direction of the circumferential contact surface, so that the skeleton portions of the inner layer and the outer layer form a shingle shape. The optical unit is prepared by extrusion using a four-layer co-extrusion head. The present invention realizes a two-dimensional composite structure by stratifying the loose sleeve inside and outside, and a radially easy-to-tear portion is distributed on each layer, so that the optical unit has an easy-to-strip performance; the skeleton portion is formed into a shingle shape through an inner and outer two-layer structure, which is continuously distributed in the circumferential direction and penetrates in the axial direction, thereby ensuring the lateral pressure resistance and tensile resistance of the optical unit.

Description

Technical Field

[0001] The present invention belongs to the field of optical communication, and more specifically, relates to an optical unit with an easy-to-open and strippable sleeve, a preparation method thereof, and an optical cable. Background Art

[0002] The optical fiber loose tube optical unit is formed by wrapping several optical fibers or water-blocking materials and then extruding a layer of plastic protective tube. It mainly provides direct protection for the optical fiber. The tensile and compression resistance performance indicators are important performance indicators of the loose tube.

[0003] During the construction of optical cables (such as branching or splicing), it is necessary to strip the loose tube and take out the optical fiber for branching or splicing. The plastic protective tube commonly used for loose tubes is PBT, which is hard and generally more than 0.1mm thick. When stripping, it is necessary to use a knife to cut the plastic protective tube and then pull it out along the direction of the optical fiber. On the one hand, there is a risk of damaging the optical fiber, and on the other hand, the friction between the optical fiber and the inner wall of the tube is large and it is not easy to take it out. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides an optical unit with an easy-to-strip loose tube, a preparation method thereof and an optical cable, the purpose of which is to obtain an optical unit loose tube with good tensile and compression resistance and easy radial tearing and can be stripped by hand through a two-dimensional composite loose tube structure, taking into account a radially penetrating easy-to-tear portion and a circumferentially continuous skeleton portion, thereby solving the technical problem of the prior art that the optical unit is not easy to strip while improving the tensile and compression resistance.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided an optical unit with an easy-to-strip loose tube, which comprises an optical fiber assembly, and a composite loose tube for receiving the optical fiber assembly;

[0006] The composite loose tube comprises an inner layer and an outer layer; a circumferential contact surface is provided between the inner layer and the outer layer;

[0007] The inner layer has a radially extending easy-tear portion and a skeleton portion; the outer layer has a radially extending easy-tear portion and a skeleton portion; the easy-tear portion of the inner and outer layers has an elongation at break of 5-50%, a tensile strength of 5-15 MPa, and the skeleton portion of the inner and outer layers has an elongation at break of 100-500%, a tensile strength of 20-60 MPa, and a modulus of 700-2500 MPa;

[0008] The easy-tear portion of the inner layer and the easy-tear portion of the outer layer are discontinuously distributed in the circumferential direction of the circumferential contact surface, so that the skeleton portions of the inner layer and the outer layer form a shingle shape.

[0009] Preferably, in the optical unit with the easy-to-open and peel loose sleeve, the minimum distance between the inner easy-to-tear portion and the outer easy-to-tear portion on the circumferential contact surface is 0.05-1 mm.

[0010] Preferably, the optical unit with an easy-to-open and peel loose sleeve has an inner layer thickness of 0.05-0.5 mm, and an area ratio of the skeleton portion to the easy-to-tear portion in its cross section of 10-2:1; the outer layer thickness of 0.1-1.0 mm, and an area ratio of the skeleton portion to the easy-to-tear portion in its cross section of 10-2:1.

[0011] Preferably, in the optical unit with the easy-to-open and peel loose sleeve, the easy-to-tear portions of the inner layer and / or the outer layer are evenly distributed in the circumferential direction.

[0012] Preferably, in the optical unit with the easy-to-open and peel loose sleeve, the easy-to-tear portions of the outer layer and the inner layer have reduced areas along the radial direction of force applied during tearing.

[0013] Preferably, in the optical unit with the easy-to-open and peelable sleeve, the cross-section of the easy-to-tear portion of the outer layer is V-shaped, U-shaped, and / or fan-shaped.

[0014] Preferably, in the optical unit with the easy-to-open and peel sleeve, the easy-to-tear portions of the outer layer and the inner layer are spiral along the axial direction, and the spiral is an S-shaped spiral or an SZ-shaped spiral with a pitch of 5 to 50 times the outer diameter of the sleeve.

[0015] Preferably, the optical unit with an easy-to-open loose sleeve has the easy-to-tear portion made of LLDPE added with an easy-to-tear raw material, and the easy-to-tear raw material contains:

[0016] 20-60wt% LLDPE linear low-density polyethylene, 10-40wt% LDPE low-density polyethylene, 10-40wt% MPE metallocene polyethylene, 10-30% inorganic filler, 0%-1% compatibilizer, and 1-2wt% processing aid.

[0017] Preferably, the material of the outer skeleton of the optical unit with the easy-to-open loose sleeve is selected from PBT, PC, TPEE, PTFE, PVDF or nylon; and the material of the inner skeleton is selected from TPEE or PP.

[0018] According to another aspect of the present invention, a method for preparing the optical unit with an easy-to-open and peel loose sleeve is provided, which comprises the following steps:

[0019] A four-layer co-extrusion die is used to extrude a composite loose tube on the outside of the optical fiber assembly; wherein:

[0020] The first and second layers of extruded materials on the inner side of the four-layer co-extrusion die form the inner layer of the composite loose tube through the inner layer outlet die;

[0021] The first and second layers of extruded materials on the outer side of the four-layer co-extrusion die are formed into the outer layer of the composite loose tube through the outer layer outlet die.

[0022] The inner layer outlet mold and the outer layer outlet mold are concentrically nested annular molds.

[0023] Preferably, in the method for preparing the optical unit with an easy-to-open and peel loose sleeve, the inner layer outlet mold and the outer layer outlet mold rotate synchronously around their common center with a fixed phase difference.

[0024] According to another aspect of the present invention, there is provided an optical cable, which comprises the optical unit with an easy-to-strip loose sleeve provided by the present invention;

[0025] When the optical cable is a central tube type optical cable, it has an optical unit with an easy-to-open loose sleeve, and the outer side of the optical unit has an outer sheath with a built-in reinforcement member;

[0026] When the optical cable is a layer-stranded optical cable, it has a plurality of optical units with easy-to-open loose sleeves; it also includes a central reinforcement member, the optical units and the central reinforcement member are twisted to form a cable core, and the outer side of the cable core is provided with an outer sheath.

[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 optical unit with an easy-to-strip loose sleeve provided by the present invention realizes a two-dimensional composite structure by stratifying the loose sleeve inside and outside, and a radially tearable portion is distributed on each layer, so that the optical unit has easy-to-strip performance; the skeleton portion is formed into a shingle shape through the inner and outer two-layer structure, which is continuously distributed in the circumferential direction and penetrates axially, thereby ensuring the lateral pressure resistance and tensile strength of the optical unit.

[0029] The optical unit with an easy-to-open loose sleeve provided by the present invention is prepared by a multi-layer co-extrusion method and can form a tightly combined two-dimensional composite structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the cross-sectional structure of a layer-twisted, easy-to-strip loose-tube optical cable provided in Example 1 of the present invention;

[0031] Figure 2 It is a schematic diagram of the cross-sectional structure of an optical unit with an easy-to-open loose sleeve provided in Example 1 of the present invention;

[0032] Figure 3 This is a schematic diagram of the cross-sectional structure of a central tube type easy-to-strip loose tube optical cable provided in Example 2 of the present invention;

[0033] Figure 4It is a schematic diagram of the cross-sectional structure of an optical unit with an easy-to-open loose sleeve provided in Embodiment 2 of the present invention;

[0034] Figure 5 It is the easy-to-open and peel loose casing forming mold provided in Examples 3 and 4 of the present invention.

[0035] In all the drawings, the same figure numbers are used to represent the same elements or structures, among which: 1 is an optical unit with an easy-to-strip loose sleeve, 1.1 is an optical fiber assembly, 1.2 is a water-blocking element in the optical unit, 1.3 is a composite loose sleeve, 1.3.1 is an easy-to-tear portion of the inner layer, 1.3.2 is a skeleton portion of the inner layer, 1.3.3 is an easy-to-tear portion of the outer layer, 1.3.4 is a skeleton portion of the outer layer, 2 is a reinforcement member, 3 is a water-blocking element, 4 is an outer sheath, 5 is a mold core, 6 is an inner mold cover, and 7 is an outer mold cover. DETAILED DESCRIPTION

[0036] 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.

[0037] The optical unit with an easy-to-strip loose tube provided by the present invention comprises: an optical fiber assembly and a composite loose tube for accommodating the optical fiber assembly;

[0038] The composite loose tube comprises an inner layer and an outer layer; a circumferential contact surface is provided between the inner layer and the outer layer;

[0039] The inner layer has an easy-tear portion and a skeleton portion extending radially;

[0040] The outer layer has an easy-to-tear portion and a skeleton portion extending radially;

[0041] The tearable parts of the inner layer and the outer layer have an elongation at break of 5 to 50% and a tensile strength of 5 to 15 MPa;

[0042] The skeleton parts of the inner layer and the outer layer have a breaking elongation of 100-500%, a tensile strength of 20-60 MPa, and a modulus of 700-2500 MPa;

[0043] The easy-tear portion of the inner layer and the easy-tear portion of the outer layer are discontinuously distributed in the circumferential direction of the circumferential contact surface, so that the skeleton portions of the inner layer and the outer layer form a shingle shape.

[0044] The function of loose tube is to protect the optical fiber it contains. Generally, it is required to have good tensile and compressive properties, high elongation at break and tensile strength. However, the loose tube material that can provide good protection obviously leads to poor tearing performance. Generally, it cannot be peeled open by hand and needs a blade or wire stripper to cut it open, which can easily cause injuries to installers or damage to the optical fiber. Materials with easy-tear properties generally have low elongation at break and tensile strength. As a loose tube material alone, it cannot well protect the optical fiber contained inside.

[0045] In order to solve the contradiction between the tearing performance of loose tube and tensile and compression resistance, the present invention adopts the scheme of forming loose tube by compounding easy-tear material and skeleton material with good compression and tensile resistance. However, the thickness ratio of easy-tear material and skeleton material in radial direction still causes the contradiction between the two: if the skeleton material accounts for a high proportion, it is difficult to tear; if the easy-tear material accounts for a high proportion, the lateral pressure resistance and tensile resistance are weakened. Especially the easy-tear material generally needs to run through the loose tube to more conveniently peel off the optical cable loose tube, and once the easy-tear material runs through in radial direction, then because the skeleton material can not form a complete circumference in the circumferential direction, it is easy to deform under the lateral pressure effect, and the bonding part of the easy-tear material and the skeleton material is easy to form stress accumulation, causing fracture, and the compression resistance drops sharply. Therefore, simply compounding a section of easy-tear material on the circumference formed by the skeleton material is not enough to solve the contradiction between the tearing performance of loose tube and the compression resistance. Therefore, the present application divides the loose tube into two layers, the inner and outer layers, and the skeleton parts of the inner and outer layers form a shingle shape, which are connected in the circumferential direction to form a complete circumference. When subjected to lateral pressure, the skeleton parts of the inner and outer layers are combined to withstand the lateral pressure, and are not easy to deform and cause stress accumulation; at the same time, in the radial direction of the loose tube, the inner and outer layers are connected with radially penetrating easy-tear parts, and the easy-tear parts are close to each other, so as to be close to the penetrating easy-tear parts, and can be peeled off more easily. The present invention realizes the compounding of the easy-tear part and the skeleton part in the radial direction and the circumferential direction respectively, forming a loose tube structure with a two-dimensional compound, so that when the loose tube structure is complete, the skeleton part is axially continuous and the easy-tear part is circumferentially discontinuous, which can well resist the lateral pressure, and the axial tensile performance is good; and after applying shear force to destroy the integrity of the skeleton part between the easy-tear parts close to each other, the loose tube can be easily peeled off by hand.

[0046] The minimum distance between the inner layer easy-tear portion and the outer layer easy-tear portion on the circumferential contact surface is 0.05-1mm. The minimum distance of the easy-tear portion is the portion that needs to be destroyed along a small distance in the circumferential direction when the loose tube of the optical cable is stripped. If it is too wide, it will make it difficult to strip the loose tube, and if it is too narrow, it will cause the shingle structure of the skeleton part to be unstable. The thickness of the inner layer is 0.05-0.5mm, and the ratio of the area of ​​the skeleton part to the easy-tear portion on its cross section is 10-2:1; the thickness of the outer layer is 0.1-1.0mm, and the ratio of the area of ​​the skeleton part to the easy-tear portion on its cross section is 10-2:1. Too thin loose tubes are difficult to manufacture and also bring about the problem of unstable shingle structure. At the same time, the area proportion of the easy-tear portion should not be too much. Too much will lead to a decrease in the tensile and compressive properties of the loose tube in the complete state. If the proportion is too small, it will be difficult to manufacture and it will be difficult to disperse the easy-tear portion. Too concentrated distribution of the easy-tear portion, such as the only easy-tear portion, will lead to strong circumferential asymmetry and obvious anisotropy of the loose tube. Therefore, in a preferred embodiment, the easy-to-tear portions of the inner layer and / or the outer layer are evenly distributed in the circumferential direction.

[0047] The areas of the easy-tear parts of the outer layer and the inner layer decrease along the radial direction of force applied during tearing, so that a greater pressure is formed on the circumferential contact surface of the easy-tear parts close to each other when force is applied, thereby destroying the skeleton part. For example, when the diameter of the loose tube is small, the force applied during tearing of the loose tube is applied radially from the outside to the inside, and the cross-sectional shapes of the easy-tear parts of the inner layer and the outer layer are both larger in outer area than in inner area. Figure 2 When the loose tube has a large diameter, the force direction of the loose tube when it is torn is from the outside to the inside of the outer layer and from the inside to the outside of the inner layer. The force directions of the inner and outer sides are opposite, so a greater pressure is formed on the circumferential contact surface. At this time, the outer layer's easy-to-tear portion is designed to have a cross-sectional shape with an outer area larger than the inner area, while the inner layer's easy-to-tear portion is designed to have a cross-sectional shape with an inner area larger than the outer area. Figure 4 The cross section of the easy-to-tear portion of the outer layer is preferably V-shaped, U-shaped, and / or fan-shaped.

[0048] The outer and inner tear-prone parts are spirally shaped along the axial direction, and the spiral is an S-shaped spiral or an SZ-shaped spiral with a pitch of 5 to 50 times the outer diameter of the casing. Since a radial and circumferential two-dimensional composite loose casing structure is adopted, the spiral structure in the axial direction ensures that the mechanical properties are more uniform on the one hand, and the loose casing obtains better bending properties on the other hand.

[0049] The easy-tear portion is made of LLDPE and easy-tear raw materials, and the easy-tear raw materials contain:

[0050] 20-60wt% LLDPE linear low-density polyethylene, 10-40wt% LDPE low-density polyethylene, 10-40wt% MPE metallocene polyethylene, 10-30% inorganic filler, 0%-1% compatibilizer, and 1-2wt% processing aid.

[0051] The material of the outer skeleton part and the inner skeleton part can be the same, using commonly used loose tube materials. The outer and inner skeleton parts can also use different loose tube materials. Specifically, the material of the outer skeleton part is selected from PBT, PC, TPEE, PTFE, PVDF or nylon; the inner skeleton material is selected from TPEE or PP. The outer material is strong and the inner material is flexible. By using the principle of double-layer composite, not only the loose tube as a whole has both flexibility and strength, but more cleverly, by using the difference in elongation at break between the two, the skeleton parts between the mutually close easy-tear parts are more easily damaged under the relatively applied tension at the circumferential contact surface. The optical cable loose tube can be peeled off by hand without the help of tools, and the compressive performance does not decrease significantly under the action of lateral pressure, which is equivalent to the existing homogeneous loose tube.

[0052] The method for preparing an optical unit with an easy-to-open and strippable sleeve provided by the present invention comprises the following steps:

[0053] A four-layer co-extrusion die is used to extrude a composite loose tube on the outside of the optical fiber assembly; wherein:

[0054] The first and second layers of extruded materials on the inner side of the four-layer co-extrusion die form the inner layer of the composite loose tube through the inner layer outlet die;

[0055] The first and second layers of extruded materials on the outer side of the four-layer co-extrusion die form the outer layer of the composite loose tube through the outer layer outlet die;

[0056] The inner layer outlet die and the outer layer outlet die are concentrically nested annular dies. The inner layer outlet die and the outer layer outlet die rotate synchronously around their common center with a fixed phase difference.

[0057] The optical cable provided by the present invention comprises an optical unit with an easy-to-open and strippable sleeve provided by the present invention;

[0058] When the optical cable is a central tube type optical cable, it has an optical unit with an easy-to-open loose sleeve, and the outer side of the optical unit has an outer sheath with a built-in reinforcement member;

[0059] When the optical cable is a layer-stranded optical cable, it has a plurality of optical units with easy-to-open loose sleeves; it also includes a central reinforcement member, the optical units and the central reinforcement member are twisted to form a cable core, and the outer side of the cable core is provided with an outer sheath.

[0060] The following are examples:

[0061] Example 1

[0062] Embodiment 1 provides a layer-twisted, easy-to-strip loose-tube optical cable, such as Figure 1 As shown, it comprises a plurality of optical units 1 with easy-to-open and peel sleeves and a central reinforcement member 2 twisted together to form a cable core, the cable core is filled with a water-blocking element 3, and the outer side of the cable core is provided with an outer sheath 4. The optical unit 1 with easy-to-open and peel sleeves, as shown Figure 2 As shown, it comprises an optical fiber 1.1, a water-blocking element 1.2 and a composite loose tube 1.3 for accommodating the optical fiber assembly 1.1 and the water-blocking element 1.2;

[0063] The optical fiber unit is 12 single-mode optical fibers;

[0064] The water-blocking element is ointment, water-blocking yarn or water-blocking powder;

[0065] The composite loose sleeve 1.3 has an outer diameter of 2.5 mm and includes an inner layer and an outer layer; a circumferential contact surface is provided between the inner layer and the outer layer; the inner layer has an easy-to-tear portion 1.3.1 and a skeleton portion 1.3.2 that penetrate the radial direction; the outer layer has an easy-to-tear portion 1.3.3 and a skeleton portion 1.3.4 that penetrate the radial direction; the easy-to-tear portion of the inner layer and the easy-to-tear portion of the outer layer are discontinuously distributed in the circumferential direction of the circumferential contact surface, so that the skeleton portions of the inner layer and the outer layer form a shingle shape.

[0066] The easy-to-tear portions 1.3.1 and 1.3.3 of the inner layer and the outer layer have a V-shaped cross-section; the easy-to-tear portions of the outer layer and the inner layer are S-shaped along the axial direction, with a pitch of 30 times the outer diameter of the casing;

[0067] The minimum distance D between the inner layer easy-tear portion and the outer layer easy-tear portion on the circumferential contact surface is 0.16 mm. The inner layer is 0.15 mm thick, and the ratio of the area of ​​the skeleton portion to the easy-tear portion on its cross section is 3.41:1; the outer layer is 0.2 mm thick, and the ratio of the area of ​​the skeleton portion to the easy-tear portion on its cross section is 2.18:1.

[0068] The easy-tear portion is made of LLDPE and easy-tear raw materials, and the easy-tear raw materials contain:

[0069] 35wt% LLDPE linear low-density polyethylene, 25wt% LDPE low-density polyethylene, 10wt% MPE metallocene polyethylene, 28% inorganic filler, 0.5% compatibilizer, 1.5wt% processing aid. Elongation at break is about 30%, tensile strength is 10MPa;

[0070] The material of the outer skeleton part 1.3.4 is selected from PC, with an elongation of about 120% and a tensile strength of 45MPa; the material of the inner skeleton part 1.3.2 is selected from TPEE, with an elongation of about 300%, a tensile strength of 25MPa, and a modulus of about 700MPa.

[0071] Example 2

[0072] Embodiment 2 provides a central tube type easy-to-open loose tube optical cable, such as Figure 3 As shown, it comprises an optical unit 1 with an easy-to-open loose tube, an outer sheath 4 is provided on the outside, and four reinforcing members 2 are embedded in the outer sheath 4. The optical unit 1 with an easy-to-open loose tube, as shown Figure 4 As shown, it comprises an optical fiber unit 1.1, a water-blocking element 1.2 and a composite loose tube 1.3 for accommodating the optical fiber assembly 1.1 and the water-blocking element 1.2;

[0073] The optical fiber unit is 12 12-core optical fiber ribbons;

[0074] The water-blocking element is ointment, water-blocking yarn, water-blocking powder or water-blocking tape;

[0075] The composite loose tube 1.3 has an outer diameter of 10 mm, and comprises an inner layer and an outer layer; a circumferential contact surface is provided between the inner layer and the outer layer; the inner layer has an easy-to-tear portion 1.3.1 and a skeleton portion 1.3.2 extending through the radial direction; the outer layer has an easy-to-tear portion 1.3.1 and a skeleton portion 1.3.3 extending through the radial direction; the easy-to-tear portion of the inner layer and the easy-to-tear portion of the outer layer are discontinuously distributed in the circumferential direction of the circumferential contact surface, so that the skeleton portions of the inner layer and the outer layer form a shingle shape.

[0076] The easy-to-tear portions 1.3.1 of the inner layer and the outer layer have a V-shaped cross-section; the easy-to-tear portions of the outer layer and the inner layer are S-shaped along the axial direction, with a pitch of 10 times the outer diameter of the casing;

[0077] The minimum distance D between the inner layer easy-tear portion and the outer layer easy-tear portion on the circumferential contact surface is 0.68 mm. The inner layer is 0.4 mm thick, and the ratio of the area of ​​the skeleton portion to the easy-tear portion on its cross section is 4.21:1; the outer layer is 0.6 mm thick, and the ratio of the area of ​​the skeleton portion to the easy-tear portion on its cross section is 2.49:1.

[0078] The easy-tear portion is made of LLDPE and easy-tear raw materials, and the easy-tear raw materials contain:

[0079] 35wt% LLDPE linear low-density polyethylene, 25wt% LDPE low-density polyethylene, 10wt% MPE metallocene polyethylene, 28% inorganic filler, 0.5% compatibilizer, 1.5wt% processing aid. Elongation at break is about 30%, tensile strength is 10MPa;

[0080] The material of the outer skeleton is selected from nylon, with an elongation of about 250% and a tensile strength of 50 MPa; the material of the inner skeleton is selected from PP, with an elongation of about 300%, a tensile strength of 25 MPa and a modulus of about 1200 MPa.

[0081] Example 3 Preparation of optical cable of Example 1

[0082] Embodiment 3 is the preparation method of embodiment 1, comprising the following steps:

[0083] 1) After the 12 optical fibers are released by the pay-off unit, they are coated with water-blocking grease and passed through a four-layer extruder head.

[0084] Through Figure 5 The molding die is cooled to form the loose tube.

[0085] The mold is composed of a mold core 5, an inner mold cover 6 and an outer mold cover 7. The outer side of the mold core 5 is provided with a diverter groove corresponding to the number of tear strips in the inner layer of the loose tube, and the outer side of the inner mold cover 6 is provided with a diverter groove corresponding to the number of tear strips in the outer layer of the loose tube. The diverter groove has the same cross-sectional shape as the tear strip.

[0086] The first and second layers of extruded materials on the inner side of the four-layer co-extrusion head are divided into a main channel and a diverter groove passing through a mold core 5, and an inner mold cover 6, forming the inner layer of the composite loose tube; the TPEE processing temperature is 210-250°C, and the easy-tear material processing temperature is 160-180°C.

[0087] The first and second layers of extruded materials on the outer side of the four-layer co-extrusion head pass through the main flow channel and the diverter groove of the inner die cover 6 and the outer die cover 7 to form the outer layer of the composite loose tube; the PC processing temperature is 250-280°C, and the easy-to-tear material processing temperature is 160-180°C.

[0088] The inner layer outlet die and the outer layer outlet die are concentrically nested annular dies. The inner layer outlet die and the outer layer outlet die rotate synchronously around their common center with a fixed phase difference.

[0089] 2) The 6 loose tubes and the central reinforcement are released by the pay-off unit and passed through the twisting table. The loose tubes are SZ twisted around the central reinforcement and then bound with yarn and coated with water-blocking grease to form a cable core.

[0090] 3) The cable core passes through an extruder head, and a sheath layer is extruded on the surface to form the optical cable.

[0091] Example 4 Preparation of optical cable of Example 2

[0092] Embodiment 4 is the preparation method of embodiment 2, comprising the following steps:

[0093] 4) 12 12-core optical fiber ribbons are released by the pay-off unit and wrapped with water-blocking tape, and then pass through a four-layer extruder head.

[0094] Through Figure 5 The molding die is cooled to form the loose tube.

[0095] The mold is composed of a mold core 5, an inner mold cover 6 and an outer mold cover 7. The outer side of the mold core 5 is provided with a diverter groove corresponding to the number of tear strips in the inner layer of the loose tube, and the outer side of the inner mold cover 6 is provided with a diverter groove corresponding to the number of tear strips in the outer layer of the loose tube. The diverter groove has the same cross-sectional shape as the tear strip.

[0096] The first and second layers of extruded materials on the inner side of the four-layer co-extrusion head pass through the main flow channel and the diverter groove of the mold core 5, and the inner mold cover 6 to form the inner layer of the composite loose tube; the PP processing temperature is 180-220°C, and the easy-to-tear material processing temperature is 160-180°C.

[0097] The first and second layers of extruded materials on the outer side of the four-layer co-extrusion die head pass through the main flow channel and the diverter groove of the inner die cover 6 and the outer die cover 7 to form the outer layer of the composite loose tube;

[0098] The inner layer outlet die and the outer layer outlet die are concentrically nested annular dies. The inner layer outlet die and the outer layer outlet die rotate synchronously around their common center with a fixed phase difference.

[0099] 5) One dry loose tube and four reinforcements are released through the pay-off unit and passed through the extruder head.

[0100] A sheath layer with a reinforcing member embedded therein is extruded on the surface of the loose tube to form the optical cable.

[0101] 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. An optical unit with an easy-to-open loose sleeve, characterized in that: It includes an optical fiber assembly and a composite loose tube for receiving the optical fiber assembly; The composite loose tube comprises an inner layer and an outer layer; a circumferential contact surface is provided between the inner layer and the outer layer; The inner layer has an easy-tear portion and a skeleton portion that penetrate the radial direction; the outer layer has an easy-tear portion and a skeleton portion that penetrate the radial direction; the easy-tear portion of the inner and outer layers has an elongation at break of 5-50%, a tensile strength of 5-15 MPa, and the skeleton portion of the inner and outer layers has an elongation at break of 100-500%, a tensile strength of 20-60 MPa, and a modulus of 700-2500 MPa; the thickness of the inner layer is 0.05-0.5 mm, and the ratio of the area of ​​the skeleton portion to the easy-tear portion on its cross section is 10-2:1; the thickness of the outer layer is 0.1-1.0 mm, and the ratio of the area of ​​the skeleton portion to the easy-tear portion on its cross section is 10-2:1; The easy-to-tear portion of the inner layer and the easy-to-tear portion of the outer layer are discontinuously distributed in the circumferential direction of the circumferential contact surface, so that the skeleton portions of the inner layer and the outer layer form a shingle shape.

2. The optical unit with an easy-to-strip sleeve according to claim 1, characterized in that: The minimum distance between the inner layer easy-to-tear portion and the outer layer easy-to-tear portion on the circumferential contact surface is 0.05-1 mm.

3. The optical unit with an easy-to-strip sleeve according to claim 1, characterized in that: The easy-tear portions of the inner layer and / or the outer layer are evenly distributed in the circumferential direction.

4. The optical unit with an easy-to-strip sleeve according to claim 1, characterized in that: The areas of the easy-tear portions of the outer layer and the inner layer decrease along the radial force direction during tearing.

5. The optical unit with an easy-to-strip sleeve according to claim 1, characterized in that: The cross section of the easy-to-tear portion of the outer layer is V-shaped, U-shaped, and / or fan-shaped.

6. The optical unit with an easy-to-strip loose sleeve according to claim 1, characterized in that: The easy-to-tear parts of the outer layer and the inner layer are spirally shaped along the axial direction. The spiral shape is an S-shaped spiral or an SZ-shaped spiral, and the pitch is 5 to 50 times the outer diameter of the casing.

7. The optical unit with an easy-to-strip sleeve according to claim 1, characterized in that: The easy-tear portion is made of LLDPE and easy-tear raw materials, and the easy-tear raw materials contain: 20-60wt% LLDPE linear low-density polyethylene, 10-40wt% LDPE low-density polyethylene, 10-40wt% MPE metallocene polyethylene, 10-30% inorganic filler, 0%-1% compatibilizer, and 1-2wt% processing aid.

8. The optical unit with an easy-to-strip sleeve according to claim 1, characterized in that: The material of the outer skeleton is selected from PBT, PC, TPEE, PTFE, PVDF or nylon; the material of the inner skeleton is selected from TPEE or PP.

9. The method for preparing an optical unit with an easy-to-strip loose sleeve according to any one of claims 1 to 8, characterized in that: The following steps are involved: A four-layer co-extrusion die is used to extrude a composite loose tube on the outside of the optical fiber assembly; wherein: The first and second layers of extruded materials on the inner side of the four-layer co-extrusion die form the inner layer of the composite loose tube through the inner layer outlet die; The first and second layers of extruded materials on the outer side of the four-layer co-extrusion die are formed into the outer layer of the composite loose tube through the outer layer outlet die. The inner layer outlet mold and the outer layer outlet mold are concentrically nested annular molds.

10. The method for preparing an optical unit with an easy-to-strip loose sleeve according to claim 9, characterized in that: The inner layer outlet die and the outer layer outlet die rotate synchronously around their common center with a fixed phase difference.

11. An optical cable, characterized in that: An optical unit having an easy-to-strip loose sleeve as claimed in any one of claims 1 to 8; When the optical cable is a central tube type optical cable, it has an optical unit with an easy-to-open loose sleeve, and the outer side of the optical unit has an outer sheath with a built-in reinforcement member; When the optical cable is a layer-stranded optical cable, it has a plurality of optical units with easy-to-open loose sleeves; it also includes a central reinforcement member, the optical units and the central reinforcement member are twisted to form a cable core, and the outer side of the cable core is provided with an outer sheath.

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