Multi-layer stranded optical cable and performance evaluation method

Abstract

The invention relates to a multi-layer stranded optical cable and a performance evaluation method. The multi-layer stranded optical cable comprises a central reinforcing piece, a multi-layer stranded element layer and a sheath which are sequentially arranged from inside to outside, each stranded element layer comprises a connection reinforcing belt and a plurality of stranded elements, at least one stranded element is a sleeve, and an optical fiber is arranged in the sleeve; for the innermost twisted element layer, the connection reinforcing belt is arranged on the central reinforcing piece, and the twisted elements are twisted on the central reinforcing piece and are fixed with the central reinforcing piece through the connection reinforcing belt; for any two adjacent twisted element layers, the connection reinforcing band of the twisted element layer on the outer side is arranged on the twisted element layer on the inner side, and the twisted elements of the twisted element layer on the outer side are twisted on the twisted element layer on the inner side and are fixed with the twisted element layer on the inner side through the connection reinforcing band. The optical fiber extra length generated by sleeve sliding can be offset as much as possible, and the situation that optical fiber additional attenuation is unqualified in a low-temperature environment due to the fact that the optical fiber extra length is increased is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of optical fiber cables, and in particular to a multi-layer stranded optical cable and a performance evaluation method. Background Art

[0002] With the implementation of the digital economy development strategy and the all-round rise of artificial intelligence and AI technology, the communications industry has developed rapidly. The demand for large-volume data transmission is growing, and the demand for large-core-count optical cables has exploded. Traditional single-layer twisted optical cables are greatly restricted in the expansion of large core counts. Double-layer twisted, triple-layer twisted and other multi-layer twisted optical cables have become the expansion direction of large-core-count optical cables.

[0003] At present, the multi-layer twisted optical cables prepared by existing technology have problems with tensile and low-temperature performance in the outer layer due to process, design and material reasons. The two most basic properties of optical cables are mechanical performance and environmental performance. Most traditional layer-twisted optical cables have only one layer of casing, and the structure is relatively simple. Optical cables that meet the requirements can be prepared through simple control. The preparation of optical cables mainly focuses on the mechanical properties of optical cables for structural design, material selection and process adjustment, while the derivation method for estimating the low-temperature performance of optical cables is rarely involved. Conclusions are only drawn through experience and environmental performance tests after the optical cables are offline. This evaluation method has limitations, lags and waste of resources.

[0004] As the number of optical cable layers increases, performance problems frequently occur in the outer sheath of optical cables prepared by existing technologies. This is mainly because the existing technology has defects and there is no method to derive the low-temperature performance of optical cables. The process can only increase the pay-off tension of the outer sheath to offset the excess length of optical fiber caused by sheath slippage. However, there is no theoretical support for the effect of the tension applied to the sheath on the low-temperature performance of the optical cable. If the tension is too large, the strain of the tensile fiber will exceed the standard. If the force is too small, the problem of low-temperature optical fiber attenuation cannot be completely solved. Summary of the invention

[0005] The embodiments of the present application provide a multi-layer twisted optical cable and a performance evaluation method, which can offset the excess optical fiber length caused by sleeve slippage as much as possible, and avoid unqualified additional optical fiber attenuation in a low-temperature environment due to increased excess optical fiber length.

[0006] In a first aspect, a multi-layer stranded optical cable is provided, which includes a central strength member, a plurality of stranded element layers, and a sheath arranged in sequence from the inside to the outside;

[0007] Each layer of the twisted element layer comprises a connection reinforcement tape and a plurality of twisted elements, at least one of the twisted elements is a sleeve, and an optical fiber is arranged in the sleeve;

[0008] For the innermost layer of twisted elements, its connection reinforcement tape is arranged on the central reinforcement member, and its twisted elements are twisted on the central reinforcement member and fixed to the central reinforcement member through the connection reinforcement tape;

[0009] For any two adjacent layers of the twisted element layers, the connection reinforcement tape of the outer twisted element layer is arranged on the inner twisted element layer, the twisted elements of the outer twisted element layer are twisted on the inner twisted element layer, and are fixed to the inner twisted element layer by the connection reinforcement tape.

[0010] In some embodiments, the connection reinforcement tape is formed by curing an adhesive resin;

[0011] and / or, the width of the connecting reinforcement strip is 20 to 50% of the circumference of the outer periphery of the central reinforcement member;

[0012] And / or, the connection reinforcement belt is arranged on the central reinforcement member or the twisted element layer in a spiral twisting manner, and the spiral twisting pitch is 100-200mm; or, the connection reinforcement belt is arranged on the central reinforcement member or the twisted element layer in a straight line.

[0013] In some embodiments, the sleeve comprises polybutylene terephthalate PBT and polycarbonate PC, and the mass fraction of polycarbonate PC is 30-50%;

[0014] And / or, the linear expansion coefficient of the sleeve is 7.9×10 -5 / ℃, elastic modulus is 2300Mpa.

[0015] In some embodiments, in at least one layer of the twisted elements, at least one of the twisted elements is a filling rope, and the size of the filling rope is the same as the size of the casing.

[0016] In some embodiments, the number of twisted elements contained in the twisted element layer is b+6×(c-1), wherein the innermost twisted element layer is the first layer, b is the number of twisted elements in the twisted element layer of the first layer, and c is the layer number of the twisted element layer.

[0017] In some embodiments, the sheath includes, by weight: 70-80 parts of HDPE polyethylene recycled material, 10-15 parts of LLDPE linear low-density polyethylene resin, 1-5 parts of nucleating agent and 3-7 parts of filler masterbatch.

[0018] In some embodiments, the nucleating agent includes: one or more of calcium oxide and carbon black;

[0019] The filler masterbatch comprises: one or more of kaolin and calcium carbonate.

[0020] In a second aspect, a performance evaluation method for a multi-layer twisted optical cable is provided, wherein the multi-layer twisted optical cable comprises a central strength member, a multi-layer twisted element layer and a sheath arranged in sequence from the inside to the outside, each layer of the twisted element layer comprises a plurality of twisted elements, at least one of the twisted elements is a sleeve, and an optical fiber is arranged in the sleeve; for the innermost twisted element layer, its twisted elements are twisted on the central strength member; for any two adjacent twisted element layers, the twisted elements of the outer twisted element layer are twisted on the inner twisted element layer;

[0021] The method includes performing a low temperature environment performance qualification determination, and the low temperature environment performance qualification determination includes:

[0022] Perform A and B judgments. If the results of both A and B are greater than, the low temperature environment performance is qualified; otherwise, it is unqualified;

[0023] A is judged as: the maximum excess length of optical fiber ε that each layer of casing can withstand in a low temperature environment z Is it greater than the excess length of the optical fiber ε caused by the contraction of the optical cable in a low temperature environment? D ;

[0024] B is judged as: the actual excess length of optical fiber in each layer of casing under low temperature environment ε s Whether the bending radius ρ of the lower optical fiber is greater than the radius threshold.

[0025] In some embodiments, the radius threshold is 50 mm.

[0026] In some embodiments, based on the comprehensive linear expansion coefficient α of the optical cable, the low temperature environment temperature T D , the excess length of the optical fiber caused by the contraction of the optical cable in low temperature environment is obtained D .

[0027] In some embodiments, based on the elastic modulus, linear expansion coefficient and cross-sectional area of ​​each element included in the multi-layer stranded optical cable, the comprehensive linear expansion coefficient α of the optical cable is obtained;

[0028] The components of a multilayer stranded optical cable include a central strength member, stranded elements and a sheath.

[0029] In some embodiments, based on the excess fiber length ε1 outside the optical cable stranding, the excess fiber length ε2 in the sleeve before stranding, the excess fiber length ε3 consumed by the sleeve under the pay-off tension during stranding, and the excess fiber length ε4 increased by the shrinkage of the central reinforcement behind the sheath, the maximum excess fiber length ε that each layer of the sleeve can withstand in a low temperature environment is obtained. z .

[0030] In some embodiments, the excess length ε1 of the stranded outer optical fiber of the optical cable is obtained based on the outer diameter of the sleeve, the wall thickness of the sleeve, the outer diameter of the central reinforcement member, the equivalent diameter of the optical fiber bundle and the twisting pitch of the sleeve.

[0031] In some embodiments, the actual excess fiber length ε of each layer of the sleeve in a low temperature environment is obtained based on the outer diameter of the sleeve, the outer diameter of the central reinforcement, the distance X from the optical fiber bundle to the center of the sleeve, and the twisting pitch of the sleeve. s About the mapping relationship of distance X;

[0032] Based on the excess fiber length ε2 in the sleeve before stranding, the excess fiber length ε3 consumed by the sleeve under the tension of the wire during stranding, and the excess fiber length ε caused by the contraction of the optical cable in the low temperature environment D The excess fiber length ε4 increased by the shrinkage of the central reinforcement after the sheath is obtained to obtain the actual excess fiber length ε of each layer of the sheath under low temperature environment s ;

[0033] The actual excess length of optical fiber ε in each layer of casing under low temperature environment s Substitute the mapping relationship and inversely calculate the distance X;

[0034] The fiber bending radius ρ is obtained based on the outer diameter of the sleeve, the wall thickness of the sleeve, the outer diameter of the central reinforcement, the equivalent diameter of the optical fiber bundle, the twist pitch of the sleeve and the distance X.

[0035] In some embodiments, the stretched fiber strain qualification determination is performed, and the stretched fiber strain qualification determination includes:

[0036] Determine whether the optical fiber tensile strain of each layer of casing is less than the required value;

[0037] If so, the tensile fiber strain is qualified; otherwise, it is unqualified.

[0038] In some embodiments, the optical fiber tensile strain of each layer of casing is obtained based on the comprehensive elastic modulus of the optical cable, the comprehensive tensile window of the optical cable of each layer of casing, the tensile force value of the optical cable and the cross-sectional area of ​​the optical cable.

[0039] In some embodiments, the comprehensive elastic modulus of the optical cable is obtained based on the elastic modulus and cross-sectional area of ​​each element included in the multi-layer stranded optical cable and the cross-sectional area of ​​the optical cable;

[0040] The components of a multilayer stranded optical cable include a central strength member, stranded elements and a sheath.

[0041] In some embodiments, based on the outer diameter of the sleeve, the wall thickness of the sleeve, the outer diameter of the central reinforcement, the equivalent diameter of the optical fiber bundle and the twisting pitch of the sleeve, the optical cable stretching window ε5 when the optical fiber bundle is located in the center of the sleeve is obtained;

[0042] Based on the excess fiber length ε2 in the sleeve before stranding, the excess fiber length ε3 consumed by the sleeve under the pay-off tension during stranding, the cable stretching window ε5 when the fiber bundle is located in the center of the sleeve, and the excess fiber length ε4 increased by the shrinkage of the central reinforcement behind the sheath, the comprehensive cable stretching window ε of each layer of the sleeve is obtained. L .

[0043] In some embodiments, based on the pay-off tension applied only on the surface of the sleeve, the elastic modulus of the sleeve and the cross-sectional area of ​​the sleeve, as well as the pay-off tension applied simultaneously on the sleeve and the optical fiber bundle therein, the equivalent elastic modulus of the sleeve and the optical fiber bundle therein, and the total cross-sectional area of ​​the sleeve and the optical fiber bundle therein, the excess length ε3 of the optical fiber consumed by the sleeve under the pay-off tension during twisting is obtained.

[0044] In some embodiments, based on the pay-off tension, elastic modulus and cross-sectional area of ​​the central strength member, the excess length ε4 of the optical fiber increased by the post-shrinkage of the central strength member behind the sheath is obtained.

[0045] In a third aspect, a performance evaluation method for a multi-layer twisted optical cable is provided, wherein the multi-layer twisted optical cable comprises a central strength member, a multi-layer twisted element layer and a sheath arranged in sequence from the inside to the outside, each layer of the twisted element layer comprises a plurality of twisted elements, at least one of the twisted elements is a sleeve, and an optical fiber is arranged in the sleeve; for the innermost twisted element layer, its twisted elements are twisted on the central strength member; for any two adjacent twisted element layers, the twisted elements of the outer twisted element layer are twisted on the inner twisted element layer;

[0046] The method includes performing a qualified determination of the stretched fiber strain, and the qualified determination of the stretched fiber strain includes:

[0047] Determine whether the optical fiber tensile strain of each layer of casing is less than the required value;

[0048] If so, the tensile fiber strain is qualified; otherwise, it is unqualified.

[0049] In some embodiments, the optical fiber tensile strain of each layer of casing is obtained based on the comprehensive elastic modulus of the optical cable, the comprehensive tensile window of the optical cable of each layer of casing, the tensile force value of the optical cable and the cross-sectional area of ​​the optical cable.

[0050] In some embodiments, the comprehensive elastic modulus of the optical cable is obtained based on the elastic modulus and cross-sectional area of ​​each element included in the multi-layer stranded optical cable and the cross-sectional area of ​​the optical cable;

[0051] The components of a multilayer stranded optical cable include a central strength member, stranded elements and a sheath.

[0052] In some embodiments, based on the outer diameter of the sleeve, the wall thickness of the sleeve, the outer diameter of the central reinforcement, the equivalent diameter of the optical fiber bundle and the twisting pitch of the sleeve, the optical cable stretching window ε5 when the optical fiber bundle is located in the center of the sleeve is obtained;

[0053] Based on the excess fiber length ε2 in the sleeve before stranding, the excess fiber length ε3 consumed by the sleeve under the pay-off tension during stranding, the cable stretching window ε5 when the fiber bundle is located in the center of the sleeve, and the excess fiber length ε4 increased by the shrinkage of the central reinforcement behind the sheath, the comprehensive cable stretching window ε of each layer of the sleeve is obtained. L .

[0054] In some embodiments, based on the pay-off tension applied only on the surface of the sleeve, the elastic modulus of the sleeve and the cross-sectional area of ​​the sleeve, as well as the pay-off tension applied simultaneously on the sleeve and the optical fiber bundle therein, the equivalent elastic modulus of the sleeve and the optical fiber bundle therein, and the total cross-sectional area of ​​the sleeve and the optical fiber bundle therein, the excess length ε3 of the optical fiber consumed by the sleeve under the pay-off tension during twisting is obtained.

[0055] In some embodiments, based on the pay-off tension, elastic modulus and cross-sectional area of ​​the central strength member, the excess length ε4 of the optical fiber increased by the post-shrinkage of the central strength member behind the sheath is obtained.

[0056] The beneficial effects of the technical solution provided by this application include:

[0057] The embodiment of the present application provides a multi-layer twisted optical cable and a performance evaluation method, which connects the various layers of the casing to form a whole by applying a connection reinforcement tape in each layer of the casing, thereby preventing the outer casing from slipping alone under the action of the sheath contraction, thereby offsetting the excess length of the optical fiber caused by the casing slippage as much as possible, and avoiding the additional attenuation of the optical fiber being unqualified in a low-temperature environment due to the increase in the excess length of the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0059] Figure 1 A schematic diagram of a multi-layer stranded optical cable provided in an embodiment of the present application;

[0060] Figure 2 Schematic diagram of the spiral twisting of the connection reinforcement tape provided in an embodiment of the present application.

[0061] In the figure: 1. Central reinforcement member; 2. Twisted element layer; 21. Connecting reinforcement belt; 22. Twisted element; 3. Sheath. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0063] See also Figure 1 and Figure 2 As shown, an embodiment of the present application provides a multi-layer twisted optical cable, which includes a central reinforcement member 1, a multi-layer twisted element layer 2 and a sheath 3 arranged in sequence from the inside to the outside; each layer of the twisted element layer 2 includes a connecting reinforcement tape 21 and a plurality of twisted elements 22, and in each layer of the twisted element layer 2, at least one of the twisted elements 22 is a sleeve, and an optical fiber is arranged in the sleeve, and the number of optical fibers in the sleeve can be set according to actual needs. For example, as an example, the number of optical fibers in the sleeve is 12-36 cores, so that the cable core contains at least 144 cores of optical fibers, and multiple optical fibers can form an optical fiber bundle.

[0064] For the innermost twisted element layer 2 , its connection reinforcement tape 21 is arranged on the central reinforcement member 1 , and its twisted elements 22 are twisted on the central reinforcement member 1 and fixed to the central reinforcement member 1 through the connection reinforcement tape 21 .

[0065] For any two adjacent layers of the twisted element layers 2, the connecting reinforcement tape 21 of the outer twisted element layer 2 is arranged on the inner twisted element layer 2, and the twisted elements 22 of the outer twisted element layer 2 are twisted on the inner twisted element layer 2 and fixed to the inner twisted element layer 2 by the connecting reinforcement tape 21.

[0066] The present application provides a multi-layer twisted optical cable, which connects the various layers of casing to form a whole by applying a connection reinforcement tape in each layer of casing, thereby preventing the outer casing from slipping alone under the action of sheath contraction, thereby offsetting the excess length of optical fiber caused by casing slippage as much as possible, and avoiding unqualified additional attenuation of optical fiber in a low-temperature environment due to increased excess length of optical fiber.

[0067] In the present application, the connection reinforcement belt 21 is formed by curing an adhesive resin; the adhesive resin is a resin material, such as a silicone gel.

[0068] The width of the connection reinforcement strip 21 is 20-50% of the circumference of the central reinforcement member 1 to achieve the best bonding effect between the two layers of components.

[0069] There are many ways to arrange the connection reinforcement belt 21. For example, as an example, the connection reinforcement belt 21 is arranged on the central reinforcement member 1 or the twisted element layer 2 in a spiral twisting manner, and the spiral twisting pitch is 100 to 200 mm; for another example, the connection reinforcement belt 21 is arranged in a straight line on the central reinforcement member 1 or the twisted element layer 2.

[0070] In the present application, the sleeve is a low shrinkage material, which includes polybutylene terephthalate PBT and polycarbonate PC. PBT and PC are blended and granulated. Specifically, after certain conditions such as 26h and 110°C vacuum drying, melt mixing and granulation are carried out in a certain proportion using a twin-screw extruder. In order to avoid stratification problems between different materials, the mass fraction of polycarbonate PC is 30-50%. When the PC component is less than 30%, the two materials are in an incompletely fused state. When the PC component is higher than 50%, the risk of stress cracking of the prepared sleeve increases sharply. The higher the proportion of PC component in the blended material, the smaller the linear expansion coefficient of the material.

[0071] When PBT is used alone, the linear expansion coefficient is 9×10 -5 / ℃, elastic modulus is 2300MPa.

[0072] When the mass ratio of PBT:PC is 1:1, the linear expansion coefficient is 7.9×10 -5 / ℃, elastic modulus is 2300MPa.

[0073] It is understandable that a filling rope may be added to the optical cable, so in at least one layer of the twisted element layer 2, at least one of the twisted elements 22 is a filling rope, and the size of the filling rope is the same as that of the sleeve.

[0074] In the present application, the number of the twisted elements 22 contained in the twisted element layer 2 is b+6×(c-1), wherein the innermost twisted element layer 2 is the first layer, b is the number of the twisted elements 22 of the twisted element layer 2 of the first layer, and c is the number of layers where the twisted element layer 2 is located. In two adjacent layers, the number of the twisted elements 22 follows the principle that the outer layer has 6 more than the inner layer to ensure the roundness of the cable core twisting.

[0075] In the present application, the sheath 3 is a low shrinkage HDPE material, which is stirred for 3 hours at 100°C and then melt-mixed and granulated using a twin-screw extruder to form a low shrinkage HDPE material. In terms of weight, the sheath 3 includes: 70 to 80 parts of HDPE polyethylene recycled material, 10 to 15 parts of LLDPE linear low-density polyethylene resin, 1 to 5 parts of nucleating agent and 3 to 7 parts of filling masterbatch.

[0076] The linear expansion coefficient of the low shrinkage HDPE material in this application is 12×10 -5 / ℃, elastic modulus is 500MPa, and elongation at break is 676%.

[0077] The linear expansion coefficient of conventional HDPE material is 20×10 -5 / ℃, elastic modulus is 500MPa, and elongation at break is 650%.

[0078] Wherein, the nucleating agent includes one or more of calcium oxide and carbon black;

[0079] The filler masterbatch comprises one or more of kaolin and calcium carbonate.

[0080] The present application ensures that the rigidity of the central reinforcement member can resist the shrinkage of the optical cable by selecting low-shrinkage sleeves and sheath materials, so that the increase in the excess length of the optical fiber in the optical cable caused by the post-shrinkage of the material is reduced to zero.

[0081] Furthermore, the present application designs a performance evaluation method suitable for optical cables in low-temperature environments. With the help of the linear expansion coefficient and the excess fiber length, a comprehensive evaluation is performed on the maximum excess fiber length that the sheath can withstand in a low-temperature environment and the bending radius of the optical fiber, to determine whether it can work normally in a specified low-temperature environment. Based on this, the direction of improving the low-temperature performance of the optical cable is explored, and the factors affecting the low-temperature performance are introduced to further judge the mechanical properties. By combining theoretical deduction with experiments, a suitable solution is selected to improve the overall performance of the optical cable.

[0082] Specifically, the performance evaluation method of the multi-layer stranded optical cable provided in the present application includes performing a low-temperature environment performance qualification determination, and the low-temperature environment performance qualification determination includes:

[0083] Perform A and B judgments. If the results of both A and B are greater than, the low temperature environment performance is qualified; otherwise, it is unqualified;

[0084] A is judged as: the maximum excess length of optical fiber ε that each layer of casing can withstand in a low temperature environment z Is it greater than the excess length of the optical fiber ε caused by the contraction of the optical cable in a low temperature environment? D ;

[0085] B is judged as: the actual excess length of optical fiber in each layer of casing under low temperature environment ε s Whether the bending radius ρ of the lower optical fiber is greater than the radius threshold.

[0086] It can be understood that the above-mentioned radius threshold can be set according to actual needs. For example, as an example, the radius threshold is 50 mm.

[0087] Among them, the excess length of optical fiber ε caused by the contraction of the optical cable in the low temperature environment in the above judgment A is D Calculate according to the following steps: Based on the comprehensive linear expansion coefficient α of the optical cable, the low temperature environment temperature T D, the excess length of the optical fiber caused by the contraction of the optical cable in low temperature environment is obtained D .

[0088] Specifically, it is calculated according to the following first formula:

[0089] ε D =α×(T 00 -T D ) (1)

[0090] Among them, the above T 00 is the default room temperature, which can be set according to actual conditions, for example, the value can be 20° to 24°. The above-mentioned optical cable comprehensive linear expansion coefficient α is calculated according to the following steps: Based on the elastic modulus, linear expansion coefficient and cross-sectional area of ​​each component included in the multi-layer stranded optical cable, the optical cable comprehensive linear expansion coefficient α is obtained; the various components included in the multi-layer stranded optical cable include a central reinforcement member 1, a stranded element 22 and a sheath 3.

[0091] Specifically, it is calculated according to the following second formula:

[0092]

[0093] Where n is the total number of components contained in the multi-layer stranded optical cable. The components contained in the multi-layer stranded optical cable are numbered. 0i is the linear expansion coefficient of the element numbered i, E 0i is the elastic modulus of the element numbered i, S 0i is the cross-sectional area of ​​the component numbered i.

[0094] For example, as an example, the central reinforcement member 1 is numbered 1, the twisted element 22 is numbered 2, and the sheath 3 is numbered 3, and it can be obtained that α 01 is the linear expansion coefficient of the central reinforcement 1, E 01 is the elastic modulus of the central reinforcement 1, S 01 is the cross-sectional area of ​​the central reinforcement 1; α 02 is the linear expansion coefficient of the stranded element 22 such as the sleeve, E 02 is the elastic modulus of the stranded element 22 such as a sleeve, S 02 is the cross-sectional area of ​​the stranded element 22 such as a sleeve; α 03 is the linear expansion coefficient of the sheath 3, E 03 is the elastic modulus of the sheath 3, S 03 is the cross-sectional area of ​​the sheath 3.

[0095] It can be understood that according to the above example numbering, the elastic modulus E of the sleeve is 02 The elastic modulus E of the sleeve after the text 3-1 are consistent, the cross-sectional area S of the casing 02The cross-sectional area S of the sleeve after the text 3-1 are consistent.

[0096] Elastic modulus E of central reinforcement 1 01 This is consistent with the elastic modulus E4 of the central reinforcement member 1 in the following text. The cross-sectional area S of the central reinforcement member 1 is 01 This is consistent with the cross-sectional area S4 of the central reinforcement member 1 described later.

[0097] Among them, the maximum excess fiber length ε that each layer of casing can withstand in a low temperature environment in the above A judgment is z According to the following steps, the calculation is performed: the excess fiber length ε1 outside the cable stranding, the excess fiber length ε2 in the sleeve before stranding, the excess fiber length ε3 consumed by the sleeve under the tension of the wire during stranding, and the excess fiber length ε4 increased by the shrinkage of the central reinforcement 1 behind the sheath, and the maximum excess fiber length ε that each layer of the sleeve can withstand in a low temperature environment is obtained. z .

[0098] Specifically, it is calculated according to the following third formula:

[0099] ε Z =ε1-ε2+ε3-ε4 (3)

[0100] Among them, the excess length ε2 of the optical fiber in the sleeve before twisting is a known quantity.

[0101] Among them, when the excess length of the optical fiber in the casing is 0, the optical fiber is in the middle of the casing. When the excess length of the optical fiber in the optical cable decreases or increases, the optical fiber will move to the inside or outside of the casing. The above-mentioned optical cable stranded outer optical fiber excess length ε1, that is, when the excess length of the optical fiber in the optical cable increases, the optical fiber moves toward the outside of the casing until it is close to the outer inner wall and reaches the limit position. At this time, the corresponding optical fiber excess length is the stranded outer optical fiber excess length. The above-mentioned optical cable stranded outer optical fiber excess length ε1 is calculated according to the following steps: based on the outer diameter d1 of the casing, the wall thickness β of the casing, the outer diameter d2 of the central reinforcement 1, and the equivalent diameter d f And the twisting pitch h of the sleeve, we can get the excess length ε1 of the twisted outer optical fiber of the optical cable.

[0102] Specifically, it is calculated according to the following fourth formula:

[0103]

[0104] Among them, the excess optical fiber length ε3 consumed by the sleeve in the above-mentioned twisting under the pay-off tension is calculated according to the following steps: based on the pay-off tension applied only on the sleeve surface, the elastic modulus of the sleeve and the cross-sectional area of ​​the sleeve, as well as the pay-off tension applied simultaneously on the sleeve and the optical fiber bundle therein, the equivalent elastic modulus of the sleeve and the optical fiber bundle therein, and the total cross-sectional area of ​​the sleeve and the optical fiber bundle therein, the excess optical fiber length ε3 consumed by the sleeve in the twisting under the pay-off tension is obtained.

[0105] Fiber bundle equivalent diameter N is the number of optical fibers, d 光纤 is the fiber diameter.

[0106] Specifically, it is calculated according to the following fifth formula:

[0107]

[0108] Among them, F 3-1 E is the pay-off tension applied only on the casing surface, that is, the pay-off tension applied on the casing surface and only the casing bears the force; 3-1 is the elastic modulus of the casing; S 3-1 is the cross-sectional area of ​​the casing; F 3-2 The pay-off tension is applied to both the sleeve and the optical fiber bundle inside it, that is, the pay-off tension is applied to the surface of the sleeve, and both the sleeve and the optical fiber bundle bear the force; E 3-2 is the equivalent elastic modulus of the sleeve and the optical fiber bundle inside it; S 3-2 is the total cross-sectional area of ​​the tube and the optical fiber bundle inside it.

[0109]

[0110] E 3-3 is the elastic modulus of the optical fiber, S 3-3 is the cross-sectional area of ​​the fiber bundle;

[0111] F 3-1 With F 3-2 The two states of the pay-off tension applied to the sleeve. Knowing the pay-off tension of the sleeve and the excess length of the optical fiber in the sleeve before twisting, the required tension F when the sleeve has zero excess length can be calculated. 3-1 , F 3-2 The remaining casing pay-off tension will be applied to the casing and the optical fiber bundle at the same time, and the excess optical fiber length consumed under the casing pay-off tension can be further calculated.

[0112] Among them, the excess length ε4 of the optical fiber increased by the post-shrinkage of the central reinforcement member 1 behind the sheath is calculated according to the following steps: based on the pay-off tension, elastic modulus and cross-sectional area of ​​the central reinforcement member 1, the excess length ε4 of the optical fiber increased by the post-shrinkage of the central reinforcement member 1 behind the sheath is obtained.

[0113] Specifically, it is calculated according to the following sixth formula:

[0114]

[0115] Wherein, F4 is the pay-off tension of the central reinforcement member 1 , E4 is the elastic modulus of the central reinforcement member 1 , and S4 is the cross-sectional area of ​​the central reinforcement member 1 .

[0116] The optical fiber bending radius ρ in the above judgment B is calculated using the following steps:

[0117] 101: Based on the outer diameter d1 of the sleeve, the outer diameter d2 of the central reinforcement member 1, the distance X from the optical fiber bundle to the center of the sleeve, and the twisting pitch h of the sleeve, the actual optical fiber excess length ε of each layer of the sleeve under low temperature environment is obtained. s About the mapping relationship of distance X.

[0118] Specifically, it is calculated according to the following seventh formula:

[0119]

[0120] 102: Based on the excess fiber length ε2 in the sleeve before stranding, the excess fiber length ε3 consumed by the sleeve under the tension of the wire during stranding, and the excess fiber length ε caused by the contraction of the optical cable in low temperature environment D The excess fiber length ε4 increased by the shrinkage of the central reinforcement 1 behind the sheath is used to obtain the actual excess fiber length ε of each layer of the sheath under low temperature environment. s .

[0121] Specifically, it is calculated according to the following eighth formula:

[0122] ε s =ε2-ε3+ε D +ε4 (8)

[0123] 103: Combine the seventh formula and the eighth formula to calculate the actual fiber excess length ε of each layer of casing in the low temperature environment s Substitute the mapping relationship and inversely calculate to obtain the distance X.

[0124] 104: Based on the outer diameter d1 of the sleeve, the wall thickness β of the sleeve, the outer diameter d2 of the central reinforcement 1, and the equivalent diameter d f , the twisting pitch h of the sleeve and the distance X, and the optical fiber bending radius ρ is obtained.

[0125] Specifically, it is calculated according to the following ninth formula:

[0126]

[0127] Furthermore, the present application also includes performing a qualified determination of the stretched fiber strain, and the qualified determination of the stretched fiber strain includes:

[0128] Determine whether the optical fiber tensile strain of each layer of casing is less than the required value;

[0129] If so, the tensile fiber strain is qualified; otherwise, it is unqualified.

[0130] It can be understood that the above required values ​​can be determined or assigned according to actual needs.

[0131] The optical fiber tensile strain W of each layer of casing is calculated according to the following steps: Based on the comprehensive elastic modulus E of the optical cable and the comprehensive tensile window ε of each layer of casing,L , the optical cable tensile force F (known quantity) and the optical cable cross-sectional area S, and the optical fiber tensile strain W of each layer of casing is obtained.

[0132] Specifically, it is calculated according to the following tenth formula:

[0133]

[0134] Among them, the comprehensive elastic modulus E of the optical cable is calculated according to the following steps: based on the elastic modulus and cross-sectional area of ​​each component contained in the multi-layer twisted optical cable, and the cross-sectional area S of the optical cable, the comprehensive elastic modulus of the optical cable is obtained; the various components contained in the multi-layer twisted optical cable include a central reinforcement member 1, a twisted element 22 and a sheath 3.

[0135] Specifically, it is calculated according to the following eleventh formula:

[0136]

[0137] Where n is the total number of components contained in the multi-layer stranded optical cable. The components contained in the multi-layer stranded optical cable are numbered. 0i is the elastic modulus of the element numbered i, S 0i is the cross-sectional area of ​​the element numbered i, for example, the central reinforcement member 1 is numbered 1, the twisted element 22 is numbered 2, and the sheath 3 is numbered 3.

[0138] Among them, the comprehensive tensile window of the optical cable of each layer of casing ε L Follow these steps to calculate:

[0139] 201: Based on the outer diameter d1 of the sleeve, the wall thickness β of the sleeve, the outer diameter d2 of the central reinforcement 1, and the equivalent diameter d f and the twisting pitch h of the sleeve, the cable stretching window ε5 is obtained when the optical fiber bundle is located in the center of the sleeve.

[0140] Specifically, it is calculated according to the following twelfth formula:

[0141]

[0142] The tensile window is the amount of elongation of the optical cable when it is subjected to external tensile force. The elongation of the optical cable before the optical fiber is strained is the tensile window of the optical cable.

[0143] 201: Based on the excess fiber length ε2 in the sleeve before stranding, the excess fiber length ε3 consumed by the sleeve under the pay-off tension during stranding, the cable stretching window ε5 when the fiber bundle is located in the center of the sleeve, and the excess fiber length ε4 increased by the shrinkage of the central reinforcement 1 behind the sheath, the comprehensive cable stretching window ε of each layer of the sleeve is obtained. L .

[0144] Specifically, it is calculated according to the following thirteenth formula:

[0145] ε L =ε2-ε3+ε4+ε5 (13)

[0146] The following is a derivation of the performance evaluation in a low temperature environment through several embodiments.

[0147] Example 1

[0148] A performance evaluation method for a double-layer twisted optical cable in a low temperature environment is as follows:

[0149] Prepared with the existing technology, the optical cable structure is GYFY-288 (1+9+15), and there is no connecting reinforcement tape in each layer of components, so that the optical cable cannot form a whole.

[0150] The specific structure is as follows: the central reinforcement is made of FRP and a PE layer is arranged on the surface, with a size of 3.3mmFRP+PE=4.8mm; the size of the sleeve is 2.4 / 1.8 / 12 core PBT sleeve (where 2.4mm is the outer diameter of the sleeve, 1.8mm is the inner hollow diameter of the sleeve, and 12 is the number of optical fibers, the same understanding applies hereinafter), the first layer has 9 sleeves with a twisting pitch of 90mm, the second layer has 15 sleeves with a twisting pitch of 140mm, and the sleeve wall thickness is 1.7mm.

[0151] The specific production process of the optical cable is as follows: the excess length of the optical fiber in the casing before twisting is ε2=0.4‰, the pay-off tension of each layer of casing is 6N, and the pay-off tension of the central reinforcement 3.3mmFRP+PE=4.8mm is 180N.

[0152] The specific materials of optical cable are:

[0153] The sheath is conventional HDPE, with a linear expansion coefficient of 20×10 -5 / ℃, elastic modulus of HDPE sheath material is 0.5Gpa.

[0154] The sleeve is made of PBT material with a linear expansion coefficient of 9×10 -5 / ℃, PBT elastic modulus 2.3Gpa.

[0155] The central reinforcement is FRP+PE, with a linear expansion coefficient of 0.65×10 -5 / ℃, FRP elastic modulus 50Gpa.

[0156] The elastic modulus of optical fiber is 7.2Gpa.

[0157] The performance requirements of optical cables are specifically for low temperature ambient temperature T D =-30℃.

[0158] Second layer:

[0159] Since there is no connecting reinforcement band between the sleeves, the components of each layer do not form a whole, and the comprehensive linear expansion coefficient of each material only includes the second layer of sleeves and sheaths, so the comprehensive linear expansion coefficient of the optical cable at this time is α = (9×10 -5 ×2.3×1.98×15+20×10 -5 × 0.5 × 85.98) / (2.3 × 1.98 × 15 + 0.5 × 85.98) = 13.25 × 10 -5 / ℃.

[0160] The excess length of optical fiber ε caused by low temperature shrinkage of optical cable D =13.25×10 -5 ×(20+30)=6.63‰.

[0161] The excess length of the outer optical fiber of the twisted optical cable ε1 = {[(2×2.4+9.6-2×0.3-1.0046)×3.14]^2+140^2}^0.5 / {[(2.4+9.6)×3.14]^2+140^2}^0.5-1 = 4.62‰.

[0162] The excess length of optical fiber in the sleeve before twisting is ε2=0.4‰. The test method is to manually throw out 15 turns of the whole sleeve and then take out 5m of sleeve. The percentage of the difference between the length of the optical fiber in the sleeve and the length of the sleeve without tension is the excess length of optical fiber in the sleeve before the optical cable is twisted.

[0163] The excess length of optical fiber consumed by the sleeve under the pay-off tension during stranding is ε3=1.8 / (1.979×2300)+4.2 / (2.772×3350)=0.848‰.

[0164] The excess length of the optical fiber increased by the shrinkage of the central reinforcement behind the sheath is ε4=180 / (8.55×50000)=0.421‰.

[0165] The maximum excess fiber length ε that the casing can withstand in low temperature environment z is: z =ε1-ε2+ε3-

[0166] ε4=4.62-0.4+0.848-0.421=4.647‰.

[0167] Actual excess fiber length ε of the sleeve in low temperature environment s Calculation process: ε s =ε2-ε3+ε D +

[0168] ε4=0.4-0.848+6.63+0.421=6.603‰.

[0169] The distance X between the fiber bundle and the center of the sleeve is based on the actual excess fiber length ε of the sleeve under low temperature environment.s It is found that: 6.603‰ = {[(2.4+9.6+2X)×3.14]^2+140^2}^0.5 / {[(2.4+9.6)×3.14]^2+140^2}^0.5-1, X=1.

[0170] The optical fiber bending radius ρ in a low temperature environment is 78 mm.

[0171] Judgment: The maximum excess length of optical fiber ε that the casing can withstand in a low temperature environment z =4.647‰<Excess fiber length ε caused by low temperature contraction of optical cable D =6.63‰, the optical fiber bending radius ρ in low temperature environment is 78mm>50mm, and the second layer infers that the performance in low temperature environment is unqualified.

[0172] Example 2

[0173] A performance evaluation method for a three-layer twisted optical cable in a low temperature environment is as follows:

[0174] The model is GYFY-540 (1+9+15+21) prepared by the existing technology. There is no connecting reinforcement tape in each layer of components, so that the optical cable cannot form a whole.

[0175] The specific structure is as follows: the central reinforcement is the same as in Example 1, with a size of 3.3mm FRP+PE=4.8mm; the sleeve size is 2.4 / 1.8 / 12 core PBT sleeve, the first layer has 9 sleeves, a twisted pitch of 90mm, the second layer has 15 sleeves, a twisted pitch of 140mm, the third layer has 21 sleeves, a twisted pitch of 200mm, and the sleeve wall thickness is 1.7mm.

[0176] The specific production process of the optical cable is as follows: the excess length of the optical fiber in the casing before twisting is ε2=0.4‰, the pay-off tension of each layer of casing is 6N, and the pay-off tension of the central reinforcement 3.3mmFRP+PE=4.8mm is 180N.

[0177] The specific materials of optical cable are:

[0178] The sheath is conventional HDPE, with a linear expansion coefficient of 20×10 -5 / ℃, elastic modulus of HDPE sheath material is 0.5Gpa.

[0179] The sleeve is made of PBT material with a linear expansion coefficient of 9×10 -5 / ℃, PBT elastic modulus 2.3Gpa.

[0180] The central reinforcement is FRP+PE, with a linear expansion coefficient of 0.65×10 -5 / ℃, FRP elastic modulus 50Gpa.

[0181] The elastic modulus of optical fiber is 7.2Gpa.

[0182] The performance requirements of optical cables are specifically for low temperature ambient temperature T D =-30℃.

[0183] Third layer:

[0184] Since there is no connecting reinforcement band between the sleeves, the components of each layer do not form a whole, and the comprehensive linear expansion coefficient of each material only includes the third layer of sleeves and the outer sheath. Therefore, the comprehensive linear expansion coefficient of the optical cable at this time is α = (9×10 -5 ×2.3×1.98×21+20×10 -5 × 0.5 × 111.6) / (2.3 × 1.98 × 21 + 0.5 × 111.6) = 13.05 × 10 -5 / ℃.

[0185] The excess length of optical fiber ε caused by low temperature shrinkage of optical cable D =13.05×10 -5 ×(20+30)=6.53‰.

[0186] The excess length of the outer optical fiber of the twisted optical cable ε1 = {[(2×2.4+14.4-2×0.3-1.0046)×3.14]^2+200^2}^0.5 / {[(2.4+14.4)×3.14]^2+200^2}^0.5-1 = 3.15‰.

[0187] The excess length of optical fiber in the sleeve before twisting is ε2=0.4‰. The test method is to manually throw out 15 turns of the whole sleeve and then take out 5m of sleeve. The percentage of the difference between the length of the optical fiber in the sleeve and the length of the sleeve without tension is the excess length of optical fiber in the sleeve before the optical cable is twisted.

[0188] The excess length of optical fiber consumed by the sleeve under the pay-off tension during stranding is ε3=1.8 / (1.979×2300)+4.2 / (2.772×3350)=0.848‰.

[0189] The excess length of the optical fiber increased by the shrinkage of the central reinforcement behind the sheath is ε4=180 / (8.55×50000)=0.421‰.

[0190] The maximum excess fiber length ε that the casing can withstand in low temperature environment z is: z =ε1-ε2+ε3-

[0191] ε4=3.15-0.4+0.848-0.421=3.177‰.

[0192] Actual excess fiber length ε of the sleeve in low temperature environment s Calculation process: ε s =ε2-ε3+ε D +

[0193] ε4=0.4-0.848+6.53+0.421=6.503‰.

[0194] The distance X between the fiber bundle and the center of the sleeve is based on the actual fiber excess length ε of the sleeve under low temperature environment. s It is found that: 6.503‰ = {[(2.4+14.4+2X)×3.14]^2+200^2}^0.5 / {[(2.4+14.4)×3.14]^2+200^2}^0.5-1, X = 1.8.

[0195] The optical fiber bending radius ρ in a low temperature environment is (2.4+14.4+2×1.8) / 2×{1+[200 / (3.14×(2.4+14.4+2×1.8))]^2}=109 mm.

[0196] Judgment: The maximum excess length of optical fiber ε that the casing can withstand in a low temperature environment z =3.177‰<Excess fiber length ε caused by low temperature contraction of optical cable D =6.53‰, the optical fiber bending radius ρ in low temperature environment is 109mm>50mm, and the third layer infers that the performance in low temperature environment is unqualified.

[0197] Example 3

[0198] A performance evaluation method for a three-layer twisted optical cable in a low temperature environment is as follows:

[0199] Prepared according to the present application, its model is GYFY-540 (1+9+15+21).

[0200] The specific structure is as follows: the central reinforcement is the same as in Example 1, with a size of 3.3mm FRP+PE=4.8mm; the sleeve size is 2.4 / 1.8 / 12 core PBT sleeve, the first layer has 9 sleeves, a twisted pitch of 90mm, the second layer has 15 sleeves, a twisted pitch of 140mm, the third layer has 21 sleeves, a twisted pitch of 180mm, and the sleeve wall thickness is 1.7mm.

[0201] The specific production process of the optical cable is as follows: the excess length of the optical fiber in the casing before twisting is ε2=0.4‰, the pay-off tension of each layer of casing is 6N, and the pay-off tension of the central reinforcement 3.3mmFRP+PE=4.8mm is 180N.

[0202] The specific materials of optical cable are:

[0203] The sheath is made of low shrinkage HDPE material with a linear expansion coefficient of 12×10-5 / ℃, low shrinkage HDPE sheath material elastic modulus is 0.5Gpa.

[0204] The sleeve is made of low shrinkage material with a linear expansion coefficient of 7.9×10 -5 / ℃, elastic modulus 2.3Gpa.

[0205] The central reinforcement is FRP+PE, with a linear expansion coefficient of 0.65×10 -5 / ℃, FRP elastic modulus 50Gpa.

[0206] The elastic modulus of optical fiber is 7.2Gpa.

[0207] The performance requirements of optical cables are specifically for low temperature ambient temperature T D =-30℃, mechanical properties: the allowable optical fiber strain under 5000N tension is no more than 0.05%.

[0208] (1) Low temperature performance

[0209] Each layer of the optical cable is connected to form a whole through the reinforcement tape. The comprehensive linear expansion coefficient, elastic modulus and cross-sectional area of ​​each material are configured. The comprehensive linear expansion coefficient of the optical cable is α = (0.65×10 -5 ×50×8.55+12×10 -5 ×0.5×9.54+7.9×10 -5 ×2.3×1.98×45+12×10 -5 × 0.5 × 111.62) / (50 × 8.55 + 0.5 × 9.54 + 2.3 × 1.98 × 45 + 0.5 × 111.62) = 3.785 × 10 -5 / ℃.

[0210] The excess length of optical fiber ε caused by low temperature shrinkage of optical cable D =3.785×10 -5 ×(20+30)=1.89‰.

[0211] First layer:

[0212] The excess length of the outer optical fiber of the twisted optical cable ε1 = {[(2×2.4+4.8-2×0.3-1.0046)×3.14]^2+90^2}^0.5 / {[(2.4+4.8)×3.14]^2+90^2}^0.5-1 = 6.9‰.

[0213] The excess length of optical fiber in the sleeve before twisting is ε2=0.4‰. The test method is to manually throw out 15 turns of the whole sleeve and then take out 5m of sleeve. The percentage of the difference between the length of the optical fiber in the sleeve and the length of the sleeve without tension is the excess length of optical fiber in the sleeve before the optical cable is twisted.

[0214] The excess length of optical fiber consumed by the sleeve under the pay-off tension during stranding is ε3=1.8 / (1.979×2300)+4.2 / (2.772×3350)=0.848‰.

[0215] The excess length of the optical fiber increased by the shrinkage of the central reinforcement behind the sheath is ε4=180 / (8.55×50000)=0.421‰.

[0216] The maximum excess fiber length ε that the casing can withstand in low temperature environment z is: z =ε1-ε2+ε3-

[0217] ε4=6.9-0.4+0.848-0.421=6.927‰.

[0218] Actual excess fiber length ε of the sleeve in low temperature environment s Calculation process: ε s =ε2-ε3+ε D +

[0219] ε4=0.4-0.848+1.89+0.421=1.863‰.

[0220] The distance X between the fiber bundle and the center of the sleeve is based on the actual excess fiber length ε of the sleeve under low temperature environment. s It is found that: 1.863‰ = {[(2.4+4.8+2X)×3.14]^2+90^2}^0.5 / {[(2.4+4.8)×3.14]^2+90^2}^0.5-1, X = 0.135.

[0221] The optical fiber bending radius ρ in a low temperature environment is (2.4+4.8+2×0.135) / 2×{1+[90 / (3.14×(2.4+4.8+2×0.135))]^2}=58 mm.

[0222] Judgment: The maximum excess length of optical fiber ε that the casing can withstand in a low temperature environment z =6.927‰>Excess optical fiber length ε caused by low temperature contraction of optical cable D =1.89‰, the optical fiber bending radius ρ in low temperature environment is 58mm>50mm, and the first layer infers that the performance in low temperature environment is qualified.

[0223] Second layer:

[0224] The excess length of the outer optical fiber of the twisted optical cable ε1 = {[(2×2.4+9.6-2×0.3-1.0046)×3.14]^2+140^2}^0.5 / {[(2.4+9.6)×3.14]^2+140^2}^0.5-1 = 4.62‰.

[0225] The excess length of optical fiber in the sleeve before twisting is ε2=0.4‰. The test method is to manually throw out 15 turns of the whole sleeve and then take out 5m of sleeve. The percentage of the difference between the length of the optical fiber in the sleeve and the length of the sleeve without tension is the excess length of optical fiber in the sleeve before the optical cable is twisted.

[0226] The excess length of optical fiber consumed by the sleeve under the pay-off tension during stranding is ε3=1.8 / (1.979×2300)+4.2 / (2.772×3350)=0.848‰.

[0227] The excess length of the optical fiber increased by the shrinkage of the central reinforcement behind the sheath is ε4=180 / (8.55×50000)=0.421‰.

[0228] The maximum excess fiber length ε that the casing can withstand in low temperature environment z is: z =ε1-ε2+ε3-

[0229] ε4=4.62-0.4+0.848-0.421=4.647‰.

[0230] Actual excess fiber length ε of the sleeve in low temperature environment s Calculation process: ε s =ε2-ε3+ε D +

[0231] ε4=0.4-0.848+1.89+0.421=1.863‰.

[0232] The distance X between the fiber bundle and the center of the sleeve is based on the actual fiber excess length ε of the sleeve under low temperature environment. s It is found that: 1.863‰ = {[(2.4+9.6+2X)×3.14]^2+140^2}^0.5 / {[(2.4+9.6)×3.14]^2+140^2}^0.5-1, X = 0.31.

[0233] The optical fiber bending radius ρ in a low temperature environment is 85 mm.

[0234] Judgment: The maximum excess length of optical fiber ε that the casing can withstand in a low temperature environment z =4.647‰>Excess optical fiber length ε caused by low temperature contraction of optical cable D =1.89‰, the optical fiber bending radius ρ in low temperature environment is 85mm>50mm, and the second layer infers that the performance in low temperature environment is qualified.

[0235] Third layer:

[0236] The excess length of the outer optical fiber of the twisted optical cable ε1 = {[(2×2.4+14.4-2×0.3-1.0046)×3.14]^2+180^2}^0.5 / {[(2.4+14.4)×3.14]^2+180^2}^0.5-1 = 3.83‰.

[0237] The excess length of optical fiber in the sleeve before twisting is ε2=0.4‰. The test method is to manually throw out 15 turns of the whole sleeve and then take out 5m of sleeve. The percentage of the difference between the length of the optical fiber in the sleeve and the length of the sleeve without tension is the excess length of optical fiber in the sleeve before the optical cable is twisted.

[0238] The excess length of optical fiber consumed by the sleeve under the pay-off tension during stranding is ε3=1.8 / (1.979×2300)+4.2 / (2.772×3350)=0.848‰.

[0239] The excess length of the optical fiber increased by the shrinkage of the central reinforcement behind the sheath is ε4=180 / (8.55×50000)=0.421‰.

[0240] The maximum excess fiber length ε that the casing can withstand in low temperature environment z is: z =ε1-ε2+ε3-

[0241] ε4=3.83-0.4+0.848-0.421=3.857‰.

[0242] Actual excess fiber length ε of the sleeve in low temperature environment s Calculation process: ε s =ε2-ε3+ε D +

[0243] ε4=0.4-0.848+1.89+0.421=1.863‰.

[0244] The distance X between the fiber bundle and the center of the sleeve is based on the actual fiber excess length ε of the sleeve under low temperature environment. s It is found that: 1.863‰ = {[(2.4+14.4+2X)×3.14]^2+180^2}^0.5 / {[(2.4+14.4)×3.14]^2+180^2}^0.5-1, X = 0.49.

[0245] The optical fiber bending radius ρ in a low temperature environment is (2.4+14.4+2×0.49) / 2×{1+[180 / (3.14×(2.4+14.4+2×0.49))]^2}=101 mm.

[0246] Judgment: The maximum excess length of optical fiber ε that the casing can withstand in a low temperature environment z =3.857‰>Excess optical fiber length ε caused by low temperature contraction of optical cableD =1.89‰, the optical fiber bending radius ρ in low temperature environment is 101mm>50mm, and the second layer infers that the performance in low temperature environment is qualified.

[0247] (2) Mechanical tensile properties

[0248] The elastic modulus E of each component of the optical cable 0i , cross-sectional area S 0i And the overall cross-sectional area S of the optical cable is configured, and the comprehensive elastic modulus of the optical cable is obtained as E=(50000×8.55+500×9.54+2300×1.98×45+500×111.62) / 401.1=2917Mpa.

[0249] First layer:

[0250] d1 is the outer diameter of the casing, d2 is the outer diameter of the central reinforcement, β is the wall thickness of the casing, and d f is the equivalent diameter of the optical fiber bundle, h is the twisting pitch of the sleeve, and it can be concluded that when the optical fiber bundle is located in the center of the sleeve, the cable stretching window ε5 = (90^2 + ((2.4 + 4.8) × 3.14)^2 - ((4.8 + 2 × 0.3 + 1.004) × 3.14)^2)^0.5 / 90-1 = 0.657%.

[0251] ε2 is the excess length of the optical fiber in the sleeve before stranding, ε3 is the excess length of the optical fiber consumed by the sleeve under the tension of the pay-off during stranding, ε4 is the excess length of the optical fiber increased by the shrinkage of the central reinforcement after the sheath, and ε5 is the optical cable stretching window when the optical fiber bundle is located in the center of the sleeve. The comprehensive stretching window of the optical cable of the first layer of the sleeve ε L for:

[0252] ε L =ε2-ε3+ε4+ε5=0.04-0.0848+0.0421+0.657=0.6543%.

[0253] F is the tensile force of the optical cable, S is the cross-sectional area of ​​the optical cable, E is the comprehensive elastic modulus of the optical cable, and the comprehensive tensile window ε of the optical cable is L , it is obtained that the tensile strain of the optical fiber in the first layer of the casing is W=5000 / (2917×401.1)-0.006543=-0.23%.

[0254] Judgment of qualified tensile fiber strain: The tensile strain of the optical fiber in the first layer of casing W = -0.23% < required value 0.05%, the tensile strength is qualified.

[0255] Second layer:

[0256] d1 is the outer diameter of the casing, d2 is the outer diameter of the central reinforcement, β is the wall thickness of the casing, and d fis the equivalent diameter of the optical fiber bundle, h is the twisting pitch of the sleeve, and it can be concluded that when the optical fiber bundle is located in the center of the sleeve, the cable stretching window ε5 = (140^2 + ((2.4 + 9.6) × 3.14)^2 - ((9.6 + 2 × 0.3 + 1.004) × 3.14)^2)^0.5 / 140-1 = 0.463%.

[0257] ε2 is the excess length of the optical fiber in the sleeve before stranding, ε3 is the excess length of the optical fiber consumed by the sleeve under the tension of the pay-off during stranding, ε4 is the excess length of the optical fiber increased by the shrinkage of the central reinforcement after the sheath, and ε5 is the optical cable stretching window when the optical fiber bundle is located in the center of the sleeve. The comprehensive stretching window of the optical cable of the first layer of the sleeve ε L for:

[0258] ε L =ε2-ε3+ε4+ε5=0.04-0.0848+0.0421+0.463=0.4603%.

[0259] F is the tensile force of the optical cable, S is the cross-sectional area of ​​the optical cable, E is the comprehensive elastic modulus of the optical cable, and the comprehensive tensile window ε of the optical cable is L , it is obtained that the tensile strain of the optical fiber in the first layer of the casing is W=5000 / (2917×401.1)-0.004603=-0.033%.

[0260] Judgment of qualified tensile fiber strain: The tensile strain of the optical fiber in the second layer of casing W = -0.033% < required value 0.05%, the tensile strength is qualified.

[0261] Third layer:

[0262] d1 is the outer diameter of the casing, d2 is the outer diameter of the central reinforcement, β is the wall thickness of the casing, and d f is the equivalent diameter of the optical fiber bundle, h is the twisting pitch of the sleeve, and it can be concluded that when the optical fiber bundle is located in the center of the sleeve, the cable stretching window ε5 = (180^2 + ((2.4 + 14.4) × 3.14)^2 - ((14.4 + 2 × 0.3 + 1.004) × 3.14)^2)^0.5 / 180-1 = 0.396%.

[0263] ε2 is the excess length of the optical fiber in the sleeve before stranding, ε3 is the excess length of the optical fiber consumed by the sleeve under the tension of the pay-off during stranding, ε4 is the excess length of the optical fiber increased by the shrinkage of the central reinforcement after the sheath, and ε5 is the optical cable stretching window when the optical fiber bundle is located in the center of the sleeve. The comprehensive stretching window of the optical cable of the first layer of the sleeve ε L for:

[0264] ε L =ε2-ε3+ε4+ε5=0.04-0.0848+0.0421+0.396=0.3933%

[0265] F is the tensile force of the optical cable, S is the cross-sectional area of ​​the optical cable, E is the comprehensive elastic modulus of the optical cable, and the comprehensive tensile window ε of the optical cable is L , it is obtained that the tensile strain of the optical fiber in the first layer of the casing is W=5000 / (2917×401.1)-0.003933=0.034%.

[0266] Judgment of qualified tensile fiber strain: The tensile strain of the optical fiber in the third layer of casing W = 0.034% < required value 0.05%, the tensile strength is qualified.

[0267] Embodiment 1 and Embodiment 2 are prior art, and Embodiment 3 is an application technology. A multi-layer twisted optical cable is provided. The low temperature environment performance derivation method is used to verify the effects of the two technologies on the same structure optical cable. The reliability of the performance theory derivation method is further verified in combination with actual performance tests, as shown in Table 1 below:

[0268] Table 1

[0269]

[0270] From the data in Table 1 above, it can be concluded that the use of the technology of the present application can solve the problem of the outer layer of the multi-layer optical cable failing to meet the low temperature requirements, and the results derived from the low temperature performance are consistent with the actual situation, which has great guiding significance.

[0271] In the description of the present application, it should be noted that the terms "upper", "lower", etc. 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 application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0272] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0273] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A multi-layer stranded optical cable, characterized in that: It comprises a central reinforcement member (1), a plurality of twisted element layers (2) and a sheath (3) which are arranged in sequence from the inside to the outside; Each of the twisted element layers (2) comprises a connection reinforcement tape (21) and a plurality of twisted elements (22), at least one of the twisted elements (22) is a sleeve, and an optical fiber is arranged in the sleeve; For the innermost twisted element layer (2), its connection reinforcement tape (21) is arranged on the central reinforcement member (1), and its twisted elements (22) are twisted on the central reinforcement member (1) and fixed to the central reinforcement member (1) through the connection reinforcement tape (21); For any two adjacent layers of the twisted element layers (2), the connection reinforcement tape (21) of the outer twisted element layer (2) is arranged on the inner twisted element layer (2), and the twisted elements (22) of the outer twisted element layer (2) are twisted on the inner twisted element layer (2) and fixed to the inner twisted element layer (2) by the connection reinforcement tape (21).

2. The multi-layer stranded optical cable according to claim 1, characterized in that: The connection reinforcement belt (21) is formed by curing the adhesive resin; and / or, the width of the connecting reinforcement strip (21) is 20 to 50% of the circumference of the outer circumference of the central reinforcement member (1); And / or, the connection reinforcement belt (21) is arranged on the central reinforcement member (1) or the twisted element layer (2) in a spiral twisting manner, and the spiral twisting pitch is 100 to 200 mm; or, the connection reinforcement belt (21) is arranged in a straight line on the central reinforcement member (1) or the twisted element layer (2).

3. The multi-layer stranded optical cable according to claim 1, characterized in that: The sleeve comprises polybutylene terephthalate (PBT) and polycarbonate (PC), and the mass fraction of the polycarbonate (PC) is 30-50%; And / or, the linear expansion coefficient of the sleeve is 7.9×10 -5 / ℃, elastic modulus is 2300Mpa.

4. The multi-layer stranded optical cable according to claim 1, characterized in that: In at least one layer (2) of the twisted element layer, at least one of the twisted elements (22) is a filling rope, and the size of the filling rope is the same as the size of the sleeve.

5. The multi-layer stranded optical cable according to claim 1, characterized in that: The number of twisted elements (22) contained in the twisted element layer (2) is b+6×(c-1), wherein the innermost twisted element layer (2) is the first layer, b is the number of twisted elements (22) in the twisted element layer (2) of the first layer, and c is the layer number of the twisted element layer (2).

6. The multi-layer stranded optical cable according to claim 1, characterized in that: Calculated by weight, the sheath (3) comprises: 70-80 parts of HDPE polyethylene recycled material, 10-15 parts of LLDPE linear low-density polyethylene resin, 1-5 parts of nucleating agent and 3-7 parts of filler masterbatch.

7. The multi-layer stranded optical cable according to claim 6, characterized in that: The nucleating agent includes: one or more of calcium oxide and carbon black; The filler masterbatch comprises: one or more of kaolin and calcium carbonate.

8. A method for evaluating the performance of a multilayer stranded optical cable, characterized in that: The multi-layer twisted optical cable comprises a central strength member (1), a plurality of twisted element layers (2) and a sheath (3) arranged in sequence from the inside to the outside, each of the twisted element layers (2) comprises a plurality of twisted elements (22), at least one of the twisted elements (22) is a sleeve, and an optical fiber is arranged in the sleeve; for the innermost twisted element layer (2), its twisted elements (22) are twisted on the central strength member (1); for any two adjacent twisted element layers (2), the twisted elements (22) of the outer twisted element layer (2) are twisted on the inner twisted element layer (2); The method includes performing a low temperature environment performance qualification determination, and the low temperature environment performance qualification determination includes: Perform A and B judgments. If the results of both A and B are greater than, the low temperature environment performance is qualified; otherwise, it is unqualified; A is judged as: the maximum excess length of optical fiber ε that each layer of casing can withstand in a low temperature environment z Is it greater than the excess length of the optical fiber ε caused by the contraction of the optical cable in a low temperature environment? D ; B is judged as: the actual excess length of optical fiber in each layer of casing under low temperature environment ε s Whether the bending radius ρ of the lower optical fiber is greater than the radius threshold.

9. The performance evaluation method of a multi-layer stranded optical cable according to claim 8, characterized in that: The radius threshold is 50 mm.

10. The performance evaluation method of a multi-layer stranded optical cable according to claim 8, characterized in that: Based on the comprehensive linear expansion coefficient α of the optical cable and the low temperature environment temperature T D , the excess length of the optical fiber caused by the contraction of the optical cable in low temperature environment is obtained D .

11. The performance evaluation method of a multi-layer stranded optical cable according to claim 10, characterized in that: Based on the elastic modulus, linear expansion coefficient and cross-sectional area of ​​each component included in the multi-layer stranded optical cable, the comprehensive linear expansion coefficient α of the optical cable is obtained; The components of the multi-layer stranded optical cable include a central strength member (1), a stranded element (22) and a sheath (3).

12. The performance evaluation method of a multi-layer stranded optical cable according to claim 8, characterized in that: Based on the excess fiber length ε1 outside the cable stranding, the excess fiber length ε2 in the sleeve before stranding, the excess fiber length ε3 consumed by the sleeve under the tension of the wire during stranding, and the excess fiber length ε4 increased by the shrinkage of the central reinforcement (1) behind the sheath, the maximum excess fiber length ε that each layer of the sleeve can withstand in a low temperature environment is obtained. z .

13. The performance evaluation method of a multi-layer stranded optical cable according to claim 12, characterized in that: Based on the outer diameter of the sleeve, the wall thickness of the sleeve, the outer diameter of the central reinforcement member (1), the equivalent diameter of the optical fiber bundle and the twisting pitch of the sleeve, the excess length ε1 of the twisted outer optical fiber of the optical cable is obtained.

14. The performance evaluation method of a multi-layer stranded optical cable according to claim 8, characterized in that: Based on the outer diameter of the sleeve, the outer diameter of the central reinforcement member (1), the distance X from the optical fiber bundle to the center of the sleeve, and the twisting pitch of the sleeve, the actual optical fiber excess length ε of each layer of the sleeve under low temperature environment is obtained. s About the mapping relationship of distance X; Based on the excess fiber length ε2 in the sleeve before stranding, the excess fiber length ε3 consumed by the sleeve under the tension of the wire during stranding, and the excess fiber length ε caused by the contraction of the optical cable in the low temperature environment D The extra length of optical fiber ε4 increased by the shrinkage of the central reinforcement member (1) behind the sheath is used to obtain the actual extra length of optical fiber ε of each layer of sheath under low temperature environment. s ; The actual excess length of optical fiber ε in each layer of casing under low temperature environment s Substitute the mapping relationship and inversely calculate the distance X; Based on the outer diameter of the sleeve, the wall thickness of the sleeve, the outer diameter of the central reinforcement member (1), the equivalent diameter of the optical fiber bundle, the twisting pitch of the sleeve and the distance X, the optical fiber bending radius ρ is obtained.

15. The performance evaluation method of a multi-layer stranded optical cable according to claim 8, characterized in that: Also includes: Performing a qualified determination of the stretched fiber strain, the qualified determination of the stretched fiber strain comprising: Determine whether the optical fiber tensile strain of each layer of casing is less than the required value; If so, the tensile fiber strain is qualified; otherwise, it is unqualified.

16. The performance evaluation method of a multi-layer stranded optical cable according to claim 15, characterized in that: Based on the comprehensive elastic modulus of the optical cable, the comprehensive tensile window of the optical cable of each layer of the casing, the tensile force value of the optical cable and the cross-sectional area of ​​the optical cable, the tensile strain of the optical fiber of each layer of the casing is obtained.

17. The performance evaluation method of a multi-layer stranded optical cable according to claim 16, characterized in that: Based on the elastic modulus and cross-sectional area of ​​each component included in the multi-layer stranded optical cable and the cross-sectional area of ​​the optical cable, the comprehensive elastic modulus of the optical cable is obtained; The components of the multi-layer stranded optical cable include a central strength member (1), a stranded element (22) and a sheath (3).

18. The performance evaluation method of a multi-layer stranded optical cable according to claim 16, characterized in that: Based on the outer diameter of the sleeve, the wall thickness of the sleeve, the outer diameter of the central reinforcement member (1), the equivalent diameter of the optical fiber bundle and the twisting pitch of the sleeve, the optical cable stretching window ε5 when the optical fiber bundle is located in the center of the sleeve is obtained; Based on the excess fiber length ε2 in the sleeve before stranding, the excess fiber length ε3 consumed by the sleeve under the pay-off tension during stranding, the cable stretching window ε5 when the fiber bundle is located in the center of the sleeve, and the excess fiber length ε4 increased by the shrinkage of the central reinforcement (1) behind the sheath, the comprehensive cable stretching window ε of each layer of the sleeve is obtained. L .

19. The performance evaluation method of a multi-layer stranded optical cable according to claim 12, 14 or 18, characterized in that: Based on the pay-off tension applied only on the surface of the sleeve, the elastic modulus of the sleeve and the cross-sectional area of ​​the sleeve, as well as the pay-off tension applied simultaneously on the sleeve and the optical fiber bundle therein, the equivalent elastic modulus of the sleeve and the optical fiber bundle therein, and the total cross-sectional area of ​​the sleeve and the optical fiber bundle therein, the excess length ε3 of the optical fiber consumed by the sleeve under the pay-off tension during twisting is obtained.

20. The performance evaluation method of a multi-layer stranded optical cable according to claim 12, 14 or 18, characterized in that: Based on the pay-off tension, elastic modulus and cross-sectional area of ​​the central reinforcement member (1), the excess length ε4 of the optical fiber increased by the rear shrinkage of the central reinforcement member (1) behind the sheath is obtained.

21. A method for evaluating the performance of a multilayer stranded optical cable, characterized in that: The multi-layer twisted optical cable comprises a central strength member (1), a plurality of twisted element layers (2) and a sheath (3) arranged in sequence from the inside to the outside, each of the twisted element layers (2) comprises a plurality of twisted elements (22), at least one of the twisted elements (22) is a sleeve, and an optical fiber is arranged in the sleeve; for the innermost twisted element layer (2), its twisted elements (22) are twisted on the central strength member (1); for any two adjacent twisted element layers (2), the twisted elements (22) of the outer twisted element layer (2) are twisted on the inner twisted element layer (2); The method includes performing a qualified determination of the stretched fiber strain, and the qualified determination of the stretched fiber strain includes: Determine whether the optical fiber tensile strain of each layer of casing is less than the required value; If so, the tensile fiber strain is qualified; otherwise, it is unqualified.

22. The performance evaluation method of a multi-layer stranded optical cable according to claim 21, characterized in that: Based on the comprehensive elastic modulus of the optical cable, the comprehensive tensile window of the optical cable of each layer of the casing, the tensile force value of the optical cable and the cross-sectional area of ​​the optical cable, the tensile strain of the optical fiber of each layer of the casing is obtained.

23. The performance evaluation method of a multi-layer stranded optical cable according to claim 22, characterized in that: Based on the elastic modulus and cross-sectional area of ​​each component included in the multi-layer stranded optical cable and the cross-sectional area of ​​the optical cable, the comprehensive elastic modulus of the optical cable is obtained; The components of the multi-layer stranded optical cable include a central strength member (1), a stranded element (22) and a sheath (3).

24. The performance evaluation method of a multi-layer stranded optical cable according to claim 22, characterized in that: Based on the outer diameter of the sleeve, the wall thickness of the sleeve, the outer diameter of the central reinforcement member (1), the equivalent diameter of the optical fiber bundle and the twisting pitch of the sleeve, the optical cable stretching window ε5 when the optical fiber bundle is located in the center of the sleeve is obtained; Based on the excess fiber length ε2 in the sleeve before stranding, the excess fiber length ε3 consumed by the sleeve under the pay-off tension during stranding, the cable stretching window ε5 when the fiber bundle is located in the center of the sleeve, and the excess fiber length ε4 increased by the shrinkage of the central reinforcement (1) behind the sheath, the comprehensive cable stretching window ε of each layer of the sleeve is obtained. L .

25. The performance evaluation method of a multi-layer stranded optical cable according to claim 24, characterized in that: Based on the pay-off tension applied only on the surface of the sleeve, the elastic modulus of the sleeve and the cross-sectional area of ​​the sleeve, as well as the pay-off tension applied simultaneously on the sleeve and the optical fiber bundle therein, the equivalent elastic modulus of the sleeve and the optical fiber bundle therein, and the total cross-sectional area of ​​the sleeve and the optical fiber bundle therein, the excess length ε3 of the optical fiber consumed by the sleeve under the pay-off tension during twisting is obtained.

26. The performance evaluation method of a multi-layer stranded optical cable according to claim 24, characterized in that: Based on the pay-off tension, elastic modulus and cross-sectional area of ​​the central reinforcement member (1), the excess length ε4 of the optical fiber increased by the rear shrinkage of the central reinforcement member (1) behind the sheath is obtained.

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