Composite sheath air-blowing optical cable suitable for high-temperature installation operation environment

Abstract

The invention discloses a composite sheath air-blowing optical cable suitable for a high-temperature installation operation environment, and the optical cable is characterized in that the optical cable comprises a composite sheath and a cable core with a sleeve; the cable core is accommodated in the outer sheath, and a sleeve of the cable core is in contact with the outer sheath; the composite sheath comprises a multi-layer structure, and the outermost layer of the composite sheath is made of a high-molecular thermoplastic material of which the vicat softening point is between 60 DEG C and 90 DEG C; the innermost layer of the sleeve is made of a macromolecular thermoplastic material, and the extrusion processing temperature of the macromolecular thermoplastic material of the innermost layer is lower than the melting point temperature of the sleeve. According to the composite sheath air-blowing optical cable suitable for the high-temperature installation operation environment provided by the invention, through the structural design of the composite sheath, the adverse effect on the shape stability of the sleeve caused by the increase of the extrusion processing temperature after the outer layer material of the sheath is optimized is solved, the consistency of excess length is kept while the air-blowing laying distance at a high temperature is increased, and the service life of the cable is prolonged. And transmission loss is improved.

Description

Technical Field

[0001] The present invention belongs to the field of optical communication, and more specifically, relates to a composite sheathed air-blown optical cable suitable for high-temperature installation working environment. Background Art

[0002] The technical principle of air-blown laying of air-blown micro-duct optical cable for communication is to use an air compressor to compress the air and inject it into the communication duct, forming a high-pressure, high-speed airflow in the communication duct. The airflow drives the optical cable to move rapidly in the micro-duct, thereby achieving the purpose of quick laying of the optical cable.

[0003] Long-term experimental exploration shows that the laying distance of air-blown optical cables is significantly shortened during summer construction. In order to overcome this problem, the Chinese patent application with application number 202211636746.2 uses a sheath material with a higher softening point to reduce the friction resistance of the air-blown optical cable during high-temperature installation operations.

[0004] However, when a sheath material with a higher softening point is used, it is observed that the excess length consistency of the air-blown optical cable decreases and the transmission loss increases. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a composite sheathed air-blown optical cable suitable for high-temperature installation working environments. Its purpose is to adopt a multi-layer outer sheath, whose outermost layer provides good surface properties to facilitate air-blowing laying and installation operations, and whose innermost layer has a lower extrusion processing temperature to protect the sleeve in contact with the outer sheath, and prevent secondary shrinkage crystallization due to the outer sheath molding process, thereby improving the consistency of excess length and avoiding increased transmission loss, thereby solving the technical problem of increased transmission loss of existing high-temperature resistant air-blown optical cables.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided a composite sheathed air-blown optical cable suitable for high-temperature installation working environment, comprising a composite sheath and a cable core with a casing;

[0007] The cable core is received in the outer sheath, and the sleeve is in contact with the outer sheath;

[0008] The composite sheath comprises a multi-layer structure, wherein the sheath material of the outermost layer is a polymer thermoplastic material with a Vicat softening point between 60°C and 90°C; the innermost layer is a polymer thermoplastic material, and the extrusion processing temperature of the polymer thermoplastic material of the innermost layer is lower than the melting point of the sheath.

[0009] Preferably, the composite sheathed air-blown optical cable suitable for high-temperature installation working environment has an outermost layer of polymer thermoplastic material having an extrusion processing temperature higher than 220°C and a melting point higher than 130°C.

[0010] Preferably, the composite sheathed air-blown optical cable suitable for high-temperature installation working environment has a polymer thermoplastic material of the outermost layer with a temperature in the range of 10° C. to 70° C. and a needle penetration of less than 1.25 mm.

[0011] Preferably, for the composite sheathed air-blown optical cable suitable for high-temperature installation working environments, the needle penetration of the polymer thermoplastic material in the outermost layer increases by no more than 0.1 mm for every 10°C increase in temperature.

[0012] Preferably, for the composite sheathed air-blown optical cable suitable for high-temperature installation working environment, the elastic modulus of the polymer thermoplastic material of the innermost layer is less than 180 MPa when tested at 23°C.

[0013] Preferably, the composite sheathed air-blown optical cable suitable for high-temperature installation working environment has a melting point of the polymer thermoplastic material of the innermost layer lower than 118°C and an extrusion processing temperature lower than 190°C.

[0014] Preferably, the composite sheathed air-blown optical cable suitable for high-temperature installation working environment has an innermost layer of polymer thermoplastic material having a melting point of less than 120°C and a crystallization temperature of less than 100°C, and a normal extrusion processing temperature of higher than 150°C and lower than 190°C.

[0015] Preferably, the composite sheathed air-blown optical cable suitable for high-temperature installation working environment, the sheath is made of crystalline material, the melting point of the material is greater than 215°C, and the crystallization temperature of the material is greater than 160°C.

[0016] Preferably, the composite sheathed air-blown optical cable suitable for high-temperature installation working environment, wherein the composite sheath comprises a two-layer structure, namely an outer layer and an inner layer, the outermost layer having a linear groove; the groove depth is above 0.05 mm, and the length occupied by the sheath on the circumference of the circle where the maximum outer diameter of the sheath cross-section is located is less than 50% of the circumference of the circle; the thickness of the innermost layer is greater than 0.08 mm.

[0017] Preferably, the composite sheathed air-blown optical cable suitable for high-temperature installation working environment has the composite sheath prepared by co-extrusion or multiple extrusion molding.

[0018] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0019] The composite sheathed air-blown optical cable suitable for high-temperature installation working environment provided by the present invention solves the adverse effect of the increase in extrusion processing temperature on the stability of the sheath shape after the optimization of the outer layer material of the sheath by designing the composite sheath structure, while increasing the air-blowing laying distance under high temperature, maintaining the consistency of the excess length and improving the transmission loss. Furthermore, compared with the sheath material that completely adopts a high Vicat softening point, the softer innermost layer makes the optical cable more conducive to turning and undulating terrain during air blowing, and is more conducive to increasing the air blowing distance during actual construction.

[0020] The composite sheathed air-blown optical cable suitable for high-temperature installation working environment provided by the present invention not only has high production efficiency but also has low overall cost due to the combination of high-Vicat softening point polymer thermoplastic material and low-cost conventional sheath material.

[0021] The present invention does not need to specially consider the influence of the construction working environment temperature, broadens the construction window period, and makes the promotion and application of air-blown laying technology more easily accepted; it solves the limitation of the application area of ​​air-blown optical cables, and can be constructed in summer or winter, whether used in cold areas of the northern hemisphere or tropical areas of the southern hemisphere. As long as the air blowing is carried out in pipelines of the same specifications, the same air-blown optical cable product can be used, without the need for multiple product development. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a diagram of the standard needle structure used for needle penetration in the embodiments;

[0023] Figure 2 Schematic diagram of the end face structure of the air-blown optical cable used in the embodiment of the present invention;

[0024] Figure 3 is a schematic diagram of the cross-sectional structure of the air blowing pipeline used in an embodiment of the present invention;

[0025] Figure 4 This is the principle diagram of optical cable air blowing laying;

[0026] Figure 5 This is a graph showing the results of a needle penetration test of a sheath material according to an embodiment of the present invention;

[0027] Figure 6 is a graph showing the test results of the friction coefficient of the air-blown cable provided in an embodiment of the present invention;

[0028] Figure 7 This is a graph showing the compression deformation test results of an air-blown cable provided in an embodiment of the present invention;

[0029] Figure 8 This is a graph showing the results of an air blowing distance test of an air blowing cable provided in an embodiment of the present invention;

[0030] Fig. 9It is the DSC analysis diagram of the sheath material and the casing material in the embodiment of the present invention.

[0031] In all the drawings, the same figure numbers are used to represent the same elements or structures, among which: 1 is a pressure seat, 2 is a standard needle, 3 is an optical fiber, 4 is a loose tube, 5 is an open cable, 6 is an inner layer of a composite sheath, 7 is an outer layer of a composite sheath, 8 is an air-blown cable, 9 is an air flow, and 10 is a pipeline. DETAILED DESCRIPTION

[0032] 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.

[0033] Generally, the extrusion processing temperature of the sheath material with a higher softening point during extrusion molding is higher than that of the existing sheath material. Existing sheath materials are mostly crystalline materials. The melting point of the typical sheath material PBT is around 225°C. If the extrusion processing temperature of the outer sheath material is higher than the melting point and crystallization temperature of the sheath material, the sheath material will undergo secondary crystallization and shrinkage, which will significantly affect the excess length of the optical cable, resulting in reduced consistency of the excess length and increased transmission loss. The higher the extrusion processing temperature of the sheath material is than the melting point of the sheath material, the more obvious the impact is, and the attenuation of the optical cable in high and low temperature environments becomes uncontrollable, affecting the performance of the optical cable.

[0034] The composite sheathed air-blown optical cable provided by the present invention is suitable for high-temperature installation working environment, comprising a composite sheath and a cable core with a sheath; the cable core is accommodated in the outer sheath, and the sheath is in contact with the outer sheath; the cable core can adopt a central tube structure, a layered twisted structure, etc.

[0035] The composite sheath comprises a multi-layer structure:

[0036] Its outermost layer, in contact with the air-blowing pipe, directly determines the surface performance of the optical cable, that is, the friction resistance between the air-blowing pipe and the air-blowing pipe at different temperatures, and the friction power between the gas and the cable body; the use of polymer thermoplastic materials with a Vicat softening point between 60°C and 90°C can effectively increase the air-blowing laying distance. In a preferred embodiment, the outermost layer of polymer thermoplastic material has a needle penetration of less than 1.25mm in the range of 10°C to 70°C. Within this temperature range, for every 10°C increase in temperature, the needle penetration of the outermost layer of polymer thermoplastic material increases by no more than 0.1mm as the temperature increases, so as to ensure that at a higher construction temperature, the cable body surface performance of the air-blown optical cable meets the requirements of air-blowing operations. See Chinese patent application number 202211636746.2. The polyethylene-based material commonly used in the outer sheath of the optical cable can control the Vicat softening point by adding a modifier or adjusting the degree of polymerization of the polyethylene. However, the polyethylene-based material that reaches the softening point range has a higher melting point, generally above 130°C. In order to ensure the fluidity of the extrudate during extrusion molding, the extrusion working temperature is increased compared to the extrusion processing temperature of the existing outer sheath, generally above 220°C.

[0037] The outermost thermoplastic polymer material is typically a high-density polyethylene material, and its Vicat softening point can be adjusted according to the distribution of polymerization degree. The higher the polymer polymerization degree, the greater the proportion, the higher the Vicat softening point and melting point, and the higher the extrusion processing temperature, which is about 10°C higher than the extrusion processing temperature of existing products. The extrusion processing temperature of the normal production die head is as high as about 230°C. Its needle penetration is below 1.25mm, preferably between 0.95 and 1.25mm; at the same time, for every 10° increase in temperature, the needle penetration of the outer layer material of the sheath increases by no more than 0.1mm with the increase in temperature; the needle penetration at 25°C does not exceed 1.0mm; in particular, the needle penetration at 40°C to 60°C does not exceed 1.15mm, preferably: the needle penetration at 40°C does not exceed 1.1mm; the needle penetration at 50°C does not exceed 1.13mm; the needle penetration at 60°C does not exceed 1.14mm.

[0038] The thickness of the outermost layer is preferably between 0.2 and 0.5 mm, so as to ensure the air-blowing laying distance without significantly increasing the outer diameter of the cable. In a preferred embodiment, the outermost layer has a linear groove; the groove depth is above 0.05 mm, and the length of the sheath on the circumference of the maximum outer diameter of the sheath cross section is less than 50% of the circumference of the circumference, so as to provide good air-blowing power.

[0039] The innermost layer is in contact with the sleeve to provide protection for the sleeve. The core of the air-blown optical cable can be a layer-twisted cable core with a sleeve or a central tube cable core with a sleeve. The air-blown optical cable has the characteristics of high optical fiber density and compact structural design. Generally speaking, there is contact between the sleeve and the outer sheath. During the preparation process, this compact structural design causes the temperature of the extruded material of the outer sheath to directly affect the cable core with the sleeve. When a hard polyethylene material is used and a high extrusion processing temperature is required, the sleeve material is heated and causes secondary crystallization and shrinkage. After repeated experiments and explorations, the secondary crystallization and shrinkage of the crystallized sleeve material is an important reason for the instability of the excess length and increased transmission loss of the air-blown optical cable with a hard outer sheath suitable for high-temperature installation working environment. In this patent, the innermost layer is formed by a sleeve material with a lower extrusion processing temperature on the inner side of the hard sheath material and the part in direct contact with the sleeve. The sleeve is mostly made of crystalline material, and the polymer thermoplastic material whose extrusion processing temperature is lower than the melting point temperature of the sleeve can improve the sleeve. The reduced consistency of the excess length and increased transmission loss caused by secondary crystallization can be improved. In a preferred embodiment, the melting point of the innermost polymer thermoplastic material is lower than 118°C, and its extrusion processing temperature is lower than 190°C, so as to match the currently mainly used casing material, such as HP-LDPE high pressure low density polyethylene material. When the adjacent sheath multilayer structure adopts polyethylene-based material, it has the advantages of tight interlayer interface bonding and no stratification. It should be noted that when the co-extrusion process is used to make the multilayer sheath, in order to ensure the quality stability of the sheath after the innermost layer and the outermost layer are extruded, the difference in the extrusion processing temperature should not be too large. In a preferred embodiment, the extrusion processing temperature of the innermost polymer thermoplastic material is higher than 150°C; the elastic modulus of the innermost polymer thermoplastic material is less than 180MPa@23°C (tested at 23°C), which provides good protection for the inner cable core. Generally speaking, the melting point of the innermost polymer thermoplastic material is less than 120°C, and the crystallization temperature is less than 100°C. The thickness of the innermost layer is greater than 0.08mm to provide sufficient lateral compression strength, and the cable body is kept under 5% compression deformation when the air blowing working environment temperature is between 0℃ and 45℃, preferably between 10℃ and 70℃, and the normal clamping force is generally between 1 and 5N, so as to facilitate the air blowing installation of the optical cable. Preferably, the thickness of the innermost layer is less than 0.2mm to maintain a small cable outer diameter.

[0040] Furthermore, when the composite sheath only includes two layers, namely, an outer layer and an inner layer, the inner layer and the outer layer are made of the same polar material, such as polyethylene-based materials. In the thin-wall extrusion method, when the inner layer and the outer layer are formed by co-extrusion preparation, not only can the interface be kept tightly bonded, but also the material stripping or other defects caused by the large difference in extrusion processing temperature and the mismatch with the different polarity casing materials can be avoided. Of course, the composite sheath can also be prepared by multiple extrusion molding.

[0041] The sleeve is made of a crystalline material, the melting point of which is greater than 215° C. and the crystallization temperature of which is greater than 160° C., typically PBT.

[0042] The outer diameter of the cable is 2.1mm to 4.2mm, and the thickness of the composite sheath is 0.25mm to 0.7mm, so that the compressive deformation of the air-blown optical cable is less than 5% at 10°C to 70°C.

[0043] The test method of needle penetration in the embodiment is as follows: a 3 mm thick pressed sheet is placed in a temperature cycle box and kept at the test temperature for 4 hours. A standard needle tip is pressed on the surface of the sheet with a tension of 50 N for 5 seconds, and the depth (mm) of penetration into the sheet is measured. Figure 1 As shown, the specifications refer to the needle tip in the material hardness test method, see "National Standard of the People's Republic of China GB-T2411-2008 Determination of Indentation Hardness (Shore Hardness) of Plastics and Ebonite Using a Durometer".

[0044] The penetration of the sheath material, the sheath thickness and the outer diameter of the cable all affect the ability of the cable to maintain its shape under lateral pressure during air blowing installation, i.e., the compressive deformation ΔDΔФ, which is characterized by the degree of deformation of the air-blown cable under a certain pressure. The specific calculation method of the compressive deformation ΔD is as follows:

[0045] ΔФ=(Фx-Фy) / Фx

[0046] Wherein, aФx is the length of the major axis of the cross section of the air-blown optical cable after compression deformation, and bФy is the length of the minor axis of the cross section of the air-blown optical cable after compression deformation.

[0047] The compressive deformation ΔDΔФ in the embodiment is measured according to the following method:

[0048] A pressure wheel with a bending radius of R=50mm and a width of 10mm is used as a pressure device; under the working environment temperature, the air-blown optical cable to be tested is placed in the middle of the pressure wheel, and a tension of 5N is applied for more than 5 seconds. The cable diameter in the force direction is detected as the short axis length Фy of the cross-section of the air-blown optical cable after compressive deformation, and the cable diameter in the vertical direction of the force is detected as the long axis length Фx of the cross-section of the air-blown optical cable after compressive deformation; the compressive deformation degree ΔФ of the air-blown optical cable is calculated.

[0049] The construction method of the air-blown optical cable in the embodiment comprises the following steps: laying the air-blown optical cable by air-blowing method; applying clamping force at the input and output ends of the cable so that the compressive deformation is less than 5%. For the central tube air-blown optical cable, the clamping force is generally between 1 and 5N; generally, when operating at high temperature, if the clamping force is too large, the surface properties of the sheath will be damaged, and the air-blown optical cable will be seriously deformed under pressure. At the same time, the surface wrinkles will appear in the process of pushing the air-blown optical cable, and the surface will be squeezed in severe cases; if the clamping force is too small, the air-blowing machine will slip and the sheath surface will be worn.

[0050] The input end applies a driving force to move the air-blown optical cable forward, and the upper limit of the driving force is less than or equal to 40N. The main function of the driving force is to overcome resistance. In theory, the greater the thrust, the better. Generally, in actual engineering applications, less than 20N will be selected for operation. The upper limit of the driving force is set based on the maximum thrust that does not cause the optical cable to break at the driving wheel and the entrance of the pipeline when the optical cable cannot be blown in the pipeline. The air-blown optical cable provided by the present invention can still maintain good penetration performance under the condition of temperature increase caused by the air-blowing operation due to the outer layer material of the sheath, which improves the laying distance to a certain extent, especially the laying distance at high temperature.

[0051] Compressed air is introduced into the input end, and the upper limit of compressed air pressure is 16BAR. The higher the compressed air pressure, the greater the forward momentum of the air-blown optical cable can be, and the air-blown laying distance can be increased within a certain range; however, when the compressed air pressure is too high, the compressed air will do work, which will cause the ambient temperature of the optical cable in the pipeline to further increase sharply compared with the external working environment temperature, and the friction resistance will increase accordingly. Increasing the compressed air pressure cannot further increase the laying distance. At this time, the compressed air pressure is the upper limit of the compressed air pressure.

[0052] The working environment temperature of air blowing is between 0℃ and 45℃, that is, the upper limit of the working environment temperature of air blowing is 45℃. In this working environment temperature range, no cooling or heat dissipation process or equipment is required, and no additional lubricant is required.

[0053] In the case of excellent degassing and blowing effect requirements, it is also required that the optical cable has a relatively stable excess length during the processing of the casing, reducing the difficulty of production and process control. At the same time, the optical cable also has a relatively stable excess length when used in high and low temperature environments to ensure that the optical fiber attenuation can adapt to the changes in the high and low temperature use environment; the reason is that the melting point of PBT, a common material for the casing in the optical cable, is approximately around 225°C. If the extrusion processing temperature of the outer sheath material is higher than the melting point and crystallization temperature of the casing material, the casing material will undergo secondary crystallization and shrinkage, which will have a very large impact on the excess length of the optical cable. The greater the temperature difference between the two, the more obvious the impact, and the attenuation of the optical cable in high and low temperature environments will become uncontrollable, affecting the use. Therefore, the composite sheath structure design provided by the present invention, through the low extrusion processing temperature of the inner layer material of the sheath (the normal extrusion processing temperature of the head is lower than 190°C), the extrusion processing temperature of the outer layer material of the isolation sheath is too high (increased from the original conventional extrusion processing temperature of 220°C to about 230°C), exceeding the melting point of the conventional casing material, avoiding the adverse effects of the casing secondary crystallization and shrinkage on the excess length and attenuation changes.

[0054] The following are examples:

[0055] This embodiment provides a central tube type air-blown optical cable with grooves: it relates to an air-blown optical cable suitable for operation and use in a wider temperature installation environment, such as Figure 2 As shown:

[0056] The outer diameter of the optical cable is 2.4mm, and it is composed of a composite polyethylene sheath inner layer 6.1 and an outer layer 6.2, a loose tube 4 in the sheath, and a reinforcing core 5 between the sheath and the loose tube. The tube contains an optical fiber 3. For 5 / 3.5mm specifications such as Figure 3 Air blowing is performed in the pipeline shown in the figure. The air blowing principle is as follows Figure 4 shown.

[0057] The sheath parameters used in the embodiments and comparative examples are shown in Table 1:

[0058] Table 1 Sheath parameters

[0059]

[0060] Embodiment A, double-layer structure, outer layer polyethylene material a is HP-LDPE high pressure low density polyethylene material with a polymerization degree distribution between 2000 and 6000, inner layer material c is HP-LDPE high pressure low density polyethylene material with a melting point below 120°C.

[0061] Embodiment B has a double-layer structure, wherein the outer layer polyethylene material b is HP-LDPE high-pressure low-density polyethylene material with a degree of polymerization between 4000 and 20000, and the inner layer material c is HP-LDPE high-pressure low-density polyethylene material with a melting point below 120°C.

[0062] Comparative example sheath C has a single-layer structure, and the polyethylene material a is HP-LDPE high-pressure low-density polyethylene material with a polymerization degree distribution between 2000 and 6000.

[0063] Comparative example sheath D, single-layer structure, polyethylene material b is HP-LDPE high-pressure low-density polyethylene material with a polymerization degree distribution between 4000 and 20000.

[0064] The outer layers of sheath material a and sheath material b both have a higher Vicat softening point and a smaller compressive deformation degree, and the specific tests are as follows.

[0065] Comparison of Vicat softening points of the outer layer materials of the optical cable sheaths of comparative example C / D and example A / B:

[0066] The test was carried out with reference to the B50 test method of Vicat softening temperature (VST) of thermoplastics GB / T 1633-2000. The Vicat softening point values ​​are shown in Table 1.

[0067] Penetration test of the outer material of the sheath of the comparative optical cable and the example optical cable:

[0068] Place a 3mm thick pressed sheet in a temperature cycle box and keep it at the test temperature for 4 hours. Press the standard needle tip on the surface of the sheet with a tension of 50N for 5 seconds and measure the depth (mm) of the sheet. Figure 5 As shown, the specifications refer to the needle tip in the material hardness test method, see "National Standard of the People's Republic of China GB-T 2411-2008 Determination of Indentation Hardness (Shore Hardness) of Plastics and Ebonite Using a Durometer". The test results are shown in Figure 5 shown.

[0069] Friction resistance test:

[0070] The friction coefficients of the comparative optical cable and the embodiment optical cable were compared under different working environment temperatures in the same pipeline. The comparative example and the embodiment of the central tube air-blown optical cable with this structure were placed in a temperature circulation box with the same standard air micro-tube 5 / 3.5mm. The relative friction coefficients of the optical cable and the micro-tube under different temperature conditions were measured by adjusting the working environment temperature of the temperature circulation box. The actual test results are shown in the comparison of friction coefficients at different temperature points.

[0071] from Figure 6 From the results, the Example optical cables A / B have approximately the same friction coefficient as the Comparative Example optical cables C / D when the outer layer materials are the same. When the working environment temperature is lower than 20°C, the Comparative Example optical cables and the Example optical cables have a less obvious difference in friction coefficient. When the working environment temperature reaches or exceeds the Vicat softening point temperature of the outer layer material of the sheath, the friction coefficient begins to rise significantly.

[0072] The test of the influence of temperature change on the compression deformation of the optical cable A / B in the embodiment relative to the optical cable C / D in the comparative example:

[0073] The compressive deformation of the optical cable directly reflects the ability of the air-blown optical cable to maintain its surface properties. There are two main aspects that affect the surface properties: one is the effect of the air-blowing clamping force on the surface properties. We know that during the air-blowing process, the air-blowing machine driving wheel will generally push the optical cable into the micro-tube with a clamping force not exceeding 5N, allowing the optical cable to move forward in the micro-tube; the other is the pressure on the air-blown optical cable when it turns in the pipe and the force on the pipe wall under the action of gravity. In order to compare the softness of the optical cable sheath, we selected a pair of pressure wheels with a bending radius of R=50mm and a width of 10mm. The optical cable was placed in the middle of the pressure wheels and a tension of 5N was applied. The deformation of the optical cable at different temperature points within 5 seconds was observed to simulate and compare the ability of the optical cable to maintain its surface properties during the clamping of the air-blowing machine or the air-blowing turning process. The actual results are shown in the figure. Figure 7 shown.

[0074] like Figure 7As shown, materials with high Vicat softening points have a certain ability to maintain surface properties; after exceeding the Vicat softening point of the material, under the action of the clamping force, the surface properties of the optical cable on the force-bearing surface will change to a certain extent.

[0075] Comparison of air blowing distance:

[0076] Comparative Example C / D and Example A / B air-blown optical cables were actually blown in an imported Emtelle 5 / 3.5 mm air-blowing pipeline. The length of the comparative air-blowing pipeline was 1200 m. The pipeline was laid in accordance with the standard IEC air-blowing site using a Plement Caesar mini-jet air-blowing machine. The actual distance was as follows: Figure 8 shown.

[0077] As can be seen from the figure, when air blowing is carried out at room temperature, the air blowing laying distance has no obvious difference, which can basically meet the actual engineering use needs. When the working environment temperature of the air blowing changes, especially when the working environment temperature rises to more than 30°C, the air blowing distance begins to change. When the outer layer materials of comparative example C / D and embodiment A / B are consistent, the air blowing distance is basically maintained at about the same level. However, the cable with a higher Vicat softening point temperature of the outer layer material has a more obvious advantage in air blowing distance, which can reflect that the optimization of the thermodynamic properties of the outer layer material of the sheath has obvious advantages in the air blowing performance in high temperature environment.

[0078] The comparison between Example A and Example B shows that the cable with a sheath material having a higher Vicat softening point temperature has a more obvious advantage in air blowing distance under a higher temperature environment.

[0079] Test on the effect of optimization of sheath material thermodynamic properties on excess length of optical cable.

[0080] In order to study the influence of thermodynamic performance material optimization and structural changes on the excess length of the optical cable, we selected comparative example C / D to compare with example A / B, and to better show the cause of the influence, we conducted thermodynamic (DSC) analysis on the casing material and the sheath material, such as Fig. 9 As shown:

[0081] The DSC graphs of the PBT material of the sleeve in the embodiment and the comparative example are shown in curve 1; the DSC graph of the inner layer material of embodiment A / B is HP-LDPE high pressure low density polyethylene material with a melting point lower than 120°C, and its DSC graph is shown in curve 3; the DSC graphs of the outer layer material with a higher Vicat softening point in embodiment B and comparative example D are shown in curve 2; the DSC graph of the sheath material of embodiment A and comparative example C is shown in curve 4. It can be seen from the DSC graph that the outer layer material b with a higher Vicat softening point in the embodiment has a higher melting point than the comparative example material a, and at the same time has a larger absorption heat, and therefore requires a higher extrusion processing temperature. If a single-layer structure is used, the extrusion temperature of the head during normal production needs to exceed 220°C, or even reach 230°C or above. This extrusion temperature is close to or even exceeds the melting point of the sheath material, which is easy to cause the sheath material to undergo secondary crystallization and shrinkage, causing a significant change in the excess length of the optical cable and affecting the attenuation of the optical fiber. However, in Example A / B, a composite sheath structure is used, and the inner layer material is thermodynamically optimized. The material melting point is less than 120°C, with a smaller absorption heat. The extrusion temperature during normal production is about 190°C, which is much lower than the melting point of the sheath material. Moreover, the crystallization temperature of the inner layer material is lower than the softening point of the sheath material, that is, during the crystallization of the inner layer sheath, the sheath material is in a non-softened state. It is precisely because the inner layer material of the sheath with a low extrusion temperature blocks the temperature of the outer layer material of the sheath with a high extrusion temperature during the processing that the secondary crystallization of the sheath material affects the excess length of the optical cable, thereby maintaining the attenuation performance of the optical fiber.

[0082] Tables 4-1 and 4-2 are comparison results of the effect of sheath materials on the excess length of optical cables in Examples A / B of the present invention and Comparative Examples C / D.

[0083] Table 4-1 Effect of sheath material on excess length of optical cable

[0084]

[0085]

[0086] Table 4-2 Effect of sheath material on excess length of optical cable

[0087]

[0088] Table 5 is a comparison of the effect of excess length of sheathed optical cable on attenuation results in Examples A / B of the present invention and Comparative Examples C / D

[0089] Table 5 Effect of excess length of optical cable on attenuation in embodiments and comparative examples 20°C

[0090]

[0091] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite sheathed air-blown optical cable suitable for high-temperature installation working environment, characterized in that: It includes a composite sheath and a cable core with a casing; The cable core is received in the outer sheath, and the sleeve is in contact with the outer sheath; The composite sheath comprises a multi-layer structure, wherein the sheath material of the outermost layer is a polymer thermoplastic material with a Vicat softening point between 60°C and 90°C; the innermost layer is a polymer thermoplastic material, and the extrusion processing temperature of the polymer thermoplastic material of the innermost layer is lower than the melting point of the sheath.

2. The composite sheathed air-blown optical cable suitable for high-temperature installation working environment according to claim 1, characterized in that: The outermost layer of high molecular thermoplastic material has an extrusion processing temperature higher than 220°C and a melting point higher than 130°C.

3. The composite sheathed air-blown optical cable suitable for high-temperature installation working environment according to claim 1, characterized in that: The outermost layer of high molecular thermoplastic material has a needle penetration of less than 1.25 mm at a temperature within a range of 10° C. to 70° C.

4. The composite sheathed air-blown optical cable suitable for high-temperature installation working environment according to claim 1, characterized in that: For every 10°C increase in temperature, the needle penetration of the outermost layer of high molecular thermoplastic material increases by no more than 0.1 mm.

5. The composite sheathed air-blown optical cable suitable for high-temperature installation working environment according to claim 1, characterized in that: The elastic modulus of the polymer thermoplastic material of the innermost layer is less than 180 MPa when tested at 23°C.

6. The composite sheathed air-blown optical cable suitable for high-temperature installation working environment according to claim 1, characterized in that: The melting point of the innermost layer of high molecular thermoplastic material is lower than 118°C, and its extrusion processing temperature is lower than 190°C.

7. The composite sheathed air-blown optical cable suitable for high-temperature installation working environment according to claim 1, characterized in that: The melting point of the innermost layer of high molecular thermoplastic material is less than 120°C, the crystallization temperature is less than 100°C, and the normal extrusion processing temperature is higher than 150°C and lower than 190°C.

8. The composite sheathed air-blown optical cable suitable for high-temperature installation working environment according to claim 1, characterized in that: The sleeve is made of crystalline material, the melting point of which is greater than 215°C and the crystallization temperature of which is greater than 160°C.

9. The composite sheathed air-blown optical cable suitable for high-temperature installation working environment according to any one of claims 1 to 8, characterized in that: The composite sheath comprises a two-layer structure, namely an outer layer and an inner layer; the outermost layer has a linear groove; the groove depth is above 0.05 mm, and the length of the sheath on the circumference of the circle where the maximum outer diameter of the sheath cross section is located is less than 50% of the circumference of the circle; the thickness of the innermost layer is greater than 0.08 mm.

10. The composite sheathed air-blown optical cable suitable for high-temperature installation working environment according to any one of claims 1 to 8, characterized in that: The composite sheath is prepared by co-extrusion or multiple extrusion molding.

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