A fine round steel wire armored flexible optical cable and a method for manufacturing the same

Abstract

This invention discloses a flexible optical cable armored with fine round steel wire and its manufacturing method. From the inside out, it comprises a core layer, an inner support layer, a spiral armor tube layer, a first armor layer, a gradient buffer layer, a second armor layer, and an outer sheath layer. The outer layer of the spiral armor tube layer is also spirally wound with piezoelectric fiber bundles. The first armor layer is formed by multiple inner-layer fine round steel wires twisted in a first direction around the outer periphery of the spiral armor tube layer. The gradient buffer layer is composed of multiple sets of thermoplastic polyurethanes with different Shore hardnesses. The innermost and outermost thermoplastic polyurethane layers of the gradient buffer layer are filled with a first repair agent and a second repair agent, respectively. The second armor layer is formed by multiple outer-layer fine round steel wires twisted in a second direction around the outer periphery of the gradient buffer layer. The advantages of this invention are that it achieves self-repair function through a self-healing structure, while also having higher overall structural strength. Furthermore, the piezoelectric sensing structure enables monitoring of the mechanical condition, allowing for timely detection of problems.

Description

Technical Field

[0001] This invention relates to the field of optical cable technology, and in particular to a flexible optical cable armored with fine round steel wire and its preparation method. Background Technology

[0002] Armored optical cables, as a type of special optical cable with mechanical protection, are widely used in complex environments such as outdoor areas, industrial plants, and rail transportation. Their core function is to protect the internal optical fibers from damage by resisting external mechanical impacts, tension, and flattening through the armor layer, ensuring stable optical signal transmission. Currently, most armored optical cables on the market use a single-layer or double-layer thin round steel wire stranded armor structure, combined with a conventional polyethylene sheath. While this meets basic mechanical protection requirements, it has the following prominent drawbacks:

[0003] 1. The contradiction between flexibility and protective performance is prominent: In order to improve mechanical strength, existing thin round steel wire armored optical cables often use thicker steel wires or dense stranding methods, which leads to a significant decrease in the flexibility of the optical cable. The minimum bending radius is usually more than 10-15 times the diameter of the optical cable, making it difficult to adapt to laying scenarios with confined spaces and frequent bending. During the laying process, problems such as deformation of the armor layer and increased additional attenuation of the optical fiber are likely to occur, and even optical fiber breakage may occur. If thinner steel wires are used to reduce the stranding density, although flexibility can be improved, the mechanical protective performance will be significantly reduced, and it will be unable to withstand the impact of external forces in complex environments.

[0004] 2. No self-healing capability: After mechanical damage or chemical corrosion of the outer sheath, water can easily enter the gap between the armor layer and the loose tube. Furthermore, the thin round steel wire is prone to corrosion when exposed to humid and salt spray environments for a long time, which leads to a decrease in the strength of the armor layer and thus affects the overall reliability of the optical cable. Traditional optical cables have no self-repair capability, and the mean time to repair (MTTR) is as long as 4-8 hours.

[0005] 4. Damage is imperceptible: Existing optical cables have a "black box" structure, and damage cannot be located in real time. It is necessary to rely on OTDR offline detection, which makes the location difficult. Summary of the Invention

[0006] The purpose of this invention is to provide a flexible optical cable armored with fine round steel wire and its preparation method. It can achieve self-repair function through a damage self-repair structure, while the overall structural strength is higher. In addition, the piezoelectric induction structure can realize mechanical condition monitoring and timely detection of problems.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A flexible optical cable armored with fine round steel wire comprises, from the inside out, a core layer, an inner support layer, a spiral armor tube layer, a first armor layer, a gradient buffer layer, a second armor layer, and an outer sheath layer. The spiral armor tube layer is formed by spirally overlapping aluminum tape around the outer periphery of the inner support layer. A piezoelectric fiber bundle is also spirally wound around the outer layer of the spiral armor tube layer. The first armor layer is formed by twisting multiple inner-layer fine round steel wires around the outer periphery of the spiral armor tube layer in a first twist direction. The gradient buffer layer consists of three layers of thermoplastic polyurethane with different Shore A hardnesses, comprising, from the inside out, an inner layer of thermoplastic polyurethane with a Shore A hardness of 60A and a middle layer of thermoplastic polyurethane with a Shore A hardness of 85A and a thickness of 0.30mm, respectively. The gradient buffer layer consists of an outer layer of thermoplastic polyurethane with a thickness of 0.35 mm and a Shore hardness of 95A. The innermost and outermost thermoplastic polyurethane layers are filled with a first repair agent and a second repair agent, respectively. Multiple sets of mandrels with a diameter of 0.25 mm are axially parallel to each other inside the innermost and outermost thermoplastic polyurethane layers of the gradient buffer layer. The outer wall of each mandrel has a spiral groove with a depth of 0.10 mm. The first and second repair agents are injected into their respective spiral grooves and then mixed and cured. The second armor layer is formed by multiple outer thin round steel wires twisted together in a second direction around the periphery of the gradient buffer layer.

[0008] Preferably, the cable core layer includes a central reinforcing member and multiple tight-buffered optical fibers stranded around the central reinforcing member. The central reinforcing member is made of phosphated steel wire or glass fiber reinforced plastic with a diameter of 1.5 to 3.0 mm. The inner part of the tight-buffered optical fiber is a bend-insensitive optical fiber with a core diameter of 9 μm. The outer part of the tight-buffered optical fiber is a tight-buffered layer made of low-modulus polyolefin material with a thickness of 0.2 to 0.3 mm. A PBT loose tube is also sleeved around the tight-buffered optical fiber. The PBT loose tube is filled with water-blocking fiber grease with a viscosity of 15000 to 25000 mPa·s (25°C).

[0009] Preferably, the inner support layer is low-density polyethylene foam, wherein the foaming ratio of the low-density polyethylene foam in the inner support layer is 3 to 5 times and the thickness is 0.3 to 0.5 mm.

[0010] Preferably, the aluminum strip of the spiral armor layer has a thickness of 0.08 to 0.12 mm and a width of 3 to 6 mm. The outer surface of the aluminum strip has a rough embossing at the unoverlapping part. The piezoelectric fiber bundle is spirally wound with the aluminum strip surface at the rough embossing part. The piezoelectric fiber bundle and the aluminum strip surface are also coated with conductive silver paste.

[0011] Preferably, the inner layer of fine round steel wire has a diameter of 0.25±0.02mm, a stranding pitch of 8~12mm, a coverage rate of ≥85%, and a single wire gap of 0.05~0.10mm; the outer layer of fine round steel wire has a diameter of 0.20±0.02mm, a stranding pitch of 6~10mm, a coverage rate of ≥90%, and a single wire gap of 0.03~0.08mm; the first stranding direction is opposite to the second stranding direction; and the tensile strength of both the inner and outer layer of fine round steel wire is ≥1800MPa.

[0012] Preferably, the first repair agent is a hydrogen-terminated silicone oil, and the second repair agent is a vinyl silicone oil containing 0.1% to 3.5% by mass of a platinum catalyst, wherein the platinum catalyst is a Karstedt catalyst.

[0013] Preferably, the outer sheath layer is a modified thermoplastic polyurethane elastomer material, the outer sheath thickness is 0.8~1.2mm, and the modified thermoplastic polyurethane elastomer material of the outer sheath further includes the following components by mass fraction: 2%~5% nano silica, 0.5%~1.5% silane coupling agent KH-550, 0.3%~0.5% ultraviolet absorber UV-327, and 0.4%~0.6% antioxidant, wherein the antioxidant is a mixture of hindered phenol 1010 and phosphite 168 in a mass ratio of 1:1.

[0014] A method for preparing a flexible optical cable armored with fine round steel wire includes the following steps: S1, take a bend-insensitive optical fiber, and use an extrusion process to coat the outside of the bare optical fiber with a low-modulus polyolefin tight-buffered layer. The extrusion temperature is 160~180℃ and the extrusion speed is 10~15m / min to obtain a tight-buffered optical fiber. S2, multiple tight-buffered optical fibers are twisted together around the central reinforcing member in an SZ twisting process to form an optical fiber unit. The twisting pitch is 60-120mm. During the twisting process, the tension of the tight-buffered optical fibers is controlled at 0.5-1.5N and the twisting angle is 15°-20°. The twisted bundle enters the extruder and is extruded into a PBT loose tube with an outer diameter of 1.8±0.1mm and a wall thickness of 0.35±0.05mm. Water-blocking fiber paste is injected into the PBT loose tube under pressure, with a filling degree of ≥90%, to obtain the cable core layer. S3, low-density polyethylene foam is extruded outside the cable core layer as an inner support layer, and the extrusion temperature is 140~180℃. S4, aluminum strip is wound around the outer periphery of the inner support layer in a spiral overlapping manner to form a spiral armor tube layer. During the winding process, the wire tension of the aluminum strip is controlled to be 5-10N and the overlap rate is 15%-25%. After the overlap is completed, piezoelectric fiber bundles are spirally wound on the outer surface of the aluminum strip, and then conductive silver paste is coated on the contact end between the aluminum strip and the piezoelectric fiber bundle. S5, multiple inner layer fine round steel wires are twisted together in the first twisting direction using a planetary stranding machine on the outer periphery of the spiral armored tube layer. After twisting, online prestress release treatment is performed. The prestress release temperature is 120-150℃ and the treatment time is 30-60s to form the first armored layer. S6 employs a three-layer co-extrusion crosshead to composite three layers of melt—inner, middle, and outer thermoplastic polyurethane—within the outermost layer of the first armor layer. At the diehead, mandrels with spiral grooves on the outer walls of the two layers are fixedly arranged at different radial intervals. The mixture is formed through a die sleeve, extruded, and then subjected to gradient cooling to form a gradient buffer layer. A first repair agent and a second repair agent are then injected into the spiral grooves of the mandrels inside the inner and outer thermoplastic polyurethane layers, respectively. The injection pressure is 0.18 MPa, and the injection flow rate is 2.8 mL / min. After injection, the joint is sealed by ultrasonic welding. S7, Multiple outer thin round steel wires are twisted together in the second twisting direction at the outer periphery of the gradient buffer layer using a planetary stranding machine to form the second armor layer; S8. All components of the outer sheath are added to the extrusion equipment and heated to 170~190℃ to melt them. Then, the outer layer of the second armor layer is wrapped at a speed of 6~8m / min to ensure that the bonding transition layer completely fills the gap of the second armor layer. The thickness of the outer sheath layer is 0.8~1.2mm. After the wrapping is completed, it is cooled to room temperature by water cooling to obtain a fine round steel wire armored flexible optical cable.

[0015] Preferably, in step S6, the extrusion temperature of the inner layer thermoplastic polyurethane is 170-185℃ and the screw speed is 20 rpm; the extrusion temperature of the middle layer thermoplastic polyurethane is 185-200℃ and the screw speed is 25 rpm; the extrusion temperature of the outer layer thermoplastic polyurethane is 200-215℃ and the screw speed is 30 rpm; and the gradient cooling is achieved by sequentially passing through a three-stage cooling water tank: the first stage water temperature is 60℃, the second stage water temperature is 40℃, and the third stage water temperature is 20℃.

[0016] In summary, the present invention has the following beneficial effects: 1. This invention uses piezoelectric fiber bundles and aluminum foil to form an electromechanical coupling structure, and forms an interface conductive connection layer through conductive silver paste. The piezoelectric fiber bundles constitute independent sensing units to sense local stress waves, which are then led out to the end of the optical cable through a waterproof connector for detection. The impact positioning is achieved by combining the stress wave propagation time difference algorithm.

[0017] 2. This invention injects two sets of repair agents into the inner and outer layers of the gradient buffer layer, respectively. When the gradient buffer layer is damaged and the repair agent leaks, the two can achieve a two-component hydrosilylation reaction under the action of a platinum catalyst, and finally solidify to form a repair layer, thereby preventing external moisture or impurities from continuing to enter, thus achieving a self-repairing effect.

[0018] 3. This invention introduces a three-layer gradient modulus buffer layer into the optical cable armor structure. Through the hardness gradient of the inner soft, middle hard and outer hard layers, it achieves the dual functions of stress dispersion and interlayer lubrication. The inner soft layer allows for large deformation and absorbs stress, the middle layer disperses stress, and the outer hard layer protects the integrity of the armor layer structure.

[0019] 4. This invention employs an asymmetrical design with different diameters, densities, and opposite stranding directions. The inner layer uses thicker steel wires with a larger pitch, primarily bearing tensile and impact resistance; the outer layer uses thinner steel wires with a smaller pitch, primarily providing anti-biting and uniform stress distribution. The reverse stranding creates a "self-locking" effect where the two layers of wires intersect, increasing the interlayer static friction coefficient to 0.35-0.45, effectively preventing interlayer slippage caused by laying tension. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the cross-sectional structure of the fine round steel wire armored flexible optical cable of the present invention; Figure 2 This is a schematic diagram of the piezoelectric fiber bundle mounting structure of the present invention; Figure 3 This is a schematic diagram of the cross-sectional structure of the mandrel of the present invention; Among them, 1-Cable core layer, 11-Central reinforcement, 12-Tight-buffered optical fiber, 13-Tight-buffered layer, 14-PBT loose tube, 15-Water-blocking fiber paste, 2-Inner support layer, 3-Spiral armor tube layer, 31-Piezoelectric fiber bundle, 4-First armor layer, 5-Gradient buffer layer, 51-Inner thermoplastic polyurethane layer, 52-Middle thermoplastic polyurethane layer, 53-Outer thermoplastic polyurethane layer, 54-Core rod, 55-Spiral groove, 6-Second armor layer, 7-Outer sheath layer. Detailed Implementation

[0021] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. These embodiments do not constitute a limitation on the present invention.

[0022] like Figures 1 to 3The illustrated flexible optical cable with fine round steel wire armor comprises, from the inside out, a core layer 1, an inner support layer 2, a spiral armor tube layer 3, a first armor layer 4, a gradient buffer layer 5, a second armor layer 6, and an outer sheath layer 7. The spiral armor tube layer 3 is formed by spirally overlapping aluminum tape around the outer periphery of the inner support layer 2. A piezoelectric fiber bundle 31 is also spirally wound around the outer layer of the spiral armor tube layer 3. The first armor layer 4 is formed by multiple inner-layer fine round steel wires twisted in a first twist direction around the outer periphery of the spiral armor tube layer 3. The gradient buffer layer 5 consists of three layers of thermoplastic polyurethane with different Shore A hardnesses, from the inside out including an inner thermoplastic polyurethane layer 51 with a Shore A hardness of 60A and a middle thermoplastic polyurethane layer 51 with a Shore A hardness of 85A and a thickness of 0.30mm, respectively. The gradient buffer layer 5 consists of a polyurethane 52 and an outer thermoplastic polyurethane 53 with a Shore hardness of 95A and a thickness of 0.35mm. The innermost and outermost thermoplastic polyurethane layers are filled with a first repair agent and a second repair agent, respectively. Multiple sets of core rods 54 are axially parallel to each other inside the outermost and innermost thermoplastic polyurethane layers 51 of the gradient buffer layer 5. The core rods 54 have a diameter of 0.25mm and a spiral groove 55 with a depth of 0.10mm on the outer wall of the core rods 54. The first repair agent and the second repair agent are injected into the corresponding spiral grooves 55, and the first repair agent and the second repair agent are mixed and cured. The second armor layer 6 is formed by multiple outer thin round steel wires twisted together in a second direction around the outer periphery of the gradient buffer layer 5.

[0023] The core layer 1 includes a central reinforcing member 11 and multiple tight-buffered optical fibers 12 twisted around the central reinforcing member 11. The central reinforcing member 11 is made of phosphated steel wire or glass fiber reinforced plastic with a diameter of 1.5 to 3.0 mm. The internal fiber of the tight-buffered optical fiber 12 is a bend-insensitive fiber with a core diameter of 9 μm. The outer part of the tight-buffered optical fiber 12 is a tight-buffered layer 13, which is made of low-modulus polyolefin material with a thickness of 0.2 to 0.3 mm. The tight-buffered optical fiber 12 is also surrounded by a PBT loose tube 14, which is filled with water-blocking fiber paste 15 with a viscosity of 15000 to 25000 mPa·s (25℃).

[0024] The inner support layer 2 is a low-density polyethylene foam with a foaming ratio of 3 to 5 times and a thickness of 0.3 to 0.5 mm.

[0025] The aluminum strip of the spiral armor layer 3 has a thickness of 0.08 to 0.12 mm and a width of 3 to 6 mm. The outer surface of the aluminum strip has a rough embossing at the middle of the non-overlapping area. The piezoelectric fiber bundle 31 is spirally wound with the aluminum strip surface at the rough embossing area. The piezoelectric fiber bundle 31 and the aluminum strip surface are also coated with conductive silver paste 32.

[0026] The inner layer of fine round steel wire has a diameter of 0.25±0.02mm, a stranding pitch of 8~12mm, a coverage rate of ≥85%, and a single wire gap of 0.05~0.10mm. The outer layer of fine round steel wire has a diameter of 0.20±0.02mm, a stranding pitch of 6~10mm, a coverage rate of ≥90%, and a single wire gap of 0.03~0.08mm. The first stranding direction is opposite to the second stranding direction. The tensile strength of both the inner and outer layers of fine round steel wire is ≥1800MPa.

[0027] The first repair agent is a hydrogen-terminated silicone oil, and the second repair agent is a vinyl silicone oil containing 0.1% to 3.5% by mass of a platinum catalyst, wherein the platinum catalyst is a Karstedt catalyst.

[0028] The outer sheath layer 7 is made of modified thermoplastic polyurethane elastomer material. The thickness of the outer sheath is 0.8~1.2mm. The modified thermoplastic polyurethane elastomer material of the outer sheath also includes the following components by mass fraction: 2%~5% nano silica, 0.5%~1.5% silane coupling agent KH-550, 0.3%~0.5% ultraviolet absorber UV-327, and 0.4%~0.6% antioxidant. The antioxidant is a mixture of hindered phenol 1010 and phosphite 168 in a mass ratio of 1:1.

[0029] A method for preparing a flexible optical cable armored with fine round steel wire includes the following steps: S1. Take a bend-insensitive optical fiber and use an extrusion process to coat the outside of the bare optical fiber with a low-modulus polyolefin tight-buffered layer 13. The extrusion temperature is 160~180℃ and the extrusion speed is 10~15m / min to obtain a tight-buffered optical fiber 12. S2, multiple tight-buffered optical fibers 12 are twisted around the central reinforcing member 11 in an SZ twisting process to form an optical fiber unit. The twisting pitch is 60-120mm. During the twisting process, the tension of the tight-buffered optical fibers 12 is controlled to be 0.5-1.5N and the twisting angle is 15°-20°. The twisted bundle enters the extruder and is extruded into a PBT loose tube 14 with an outer diameter of 1.8±0.1mm and a wall thickness of 0.35±0.05mm. Water-blocking fiber paste 15 is injected into the PBT loose tube 14 under pressure, with a filling degree of ≥90%, to obtain the cable core layer 1. S3, low-density polyethylene foam is extruded outside the cable core layer 1 as an inner support layer 2, and the extrusion temperature is 140~180℃. S4, aluminum strip is wound around the outer periphery of the inner support layer 2 in a spiral overlapping manner to form a spiral armor tube layer 3. During the winding process, the wire tension of the aluminum strip is controlled to be 5-10N and the overlap rate is 15%-25%. After the overlap is completed, piezoelectric fiber bundles 31 are spirally wound on the outer surface of the aluminum strip, and then conductive silver paste 32 is coated on the contact end between the aluminum strip and the piezoelectric fiber bundles 31. S5, a planetary stranding machine is used to strand multiple inner layer fine round steel wires in the first stranding direction on the outer periphery of the spiral armored tube layer 3. After stranding, online prestress release treatment is performed. The prestress release temperature is 120-150℃ and the treatment time is 30-60s to form the first armored layer 4. S6, using a three-layer co-extrusion crosshead, the three-layer melt formed by the inner layer thermoplastic polyurethane 51, the middle layer thermoplastic polyurethane 52 and the outer layer thermoplastic polyurethane 53 are compounded in the die head around the first armor layer 4. At the die head, the mandrels 54 with spiral grooves 55 on the outer walls of the two layers are fixedly arranged at different radial intervals, formed by the die sleeve, and after extrusion, gradient cooling is performed to form a gradient buffer layer 5. Then, the first repair agent and the second repair agent are injected into the spiral grooves 55 of the mandrels 54 inside the inner layer thermoplastic polyurethane 51 and the outer layer thermoplastic polyurethane 53, respectively. The injection pressure is 0.18MPa and the injection flow rate is 2.8mL / min. After injection, the joint is sealed by ultrasonic welding. S7, Multiple outer thin round steel wires are twisted together in the second twisting direction on the outer periphery of the gradient buffer layer 5 using a planetary stranding machine to form the second armor layer 6. S8. Add all components of the outer sheath layer 7 into the extrusion equipment and heat it to 170~190℃ to melt it. Then wrap it around the outer layer of the second armor layer 6 at a speed of 6~8m / min to ensure that the bonding transition layer completely fills the gap of the second armor layer 6. The thickness of the outer sheath layer 7 is 0.8~1.2mm. After the wrapping is completed, cool it to room temperature by water cooling to obtain the fine round steel wire armored flexible optical cable.

[0030] In step S6, the extrusion temperature of the inner layer thermoplastic polyurethane 51 is 170-185℃ and the screw speed is 20 rpm; the extrusion temperature of the middle layer thermoplastic polyurethane 52 is 185-200℃ and the screw speed is 25 rpm; the extrusion temperature of the outer layer thermoplastic polyurethane 53 is 200-215℃ and the screw speed is 30 rpm; and the gradient cooling is achieved by sequentially passing through a three-stage cooling water tank: the first stage water temperature is 60℃, the second stage water temperature is 40℃, and the third stage water temperature is 20℃.

[0031] Example 1: 4-core fine round steel wire armored flexible optical cable Cable core layer 1: The central reinforcing member 11 is 1.8mm thick, and the tight-buffered optical fiber 12 consists of four groups; Inner support layer 2: foaming ratio of 4 times, thickness of 0.3mm; Spiral armor layer 3: The aluminum strip has a thickness of 0.08 mm and a width of 4 mm; First armor layer 4: The inner layer of fine round steel wire has a diameter of 0.25±0.02mm, a tensile strength ≥1800MPa, a stranding pitch of 8mm, a coverage rate of ≥85%, and a single wire gap of 0.05~0.10mm; Gradient buffer layer 5: The second repair agent is vinyl silicone oil containing 0.1% by mass of platinum catalyst; Second armor layer 6: The outer layer of fine round steel wire has a diameter of 0.20±0.02mm, a tensile strength of ≥1800MPa, a stranding pitch of 6mm, a coverage rate of ≥90%, and a single wire gap of 0.03~0.08mm; Outer sheath layer 7: The outer sheath thickness is 0.8mm. The modified thermoplastic polyurethane elastomer material of the outer sheath also includes the following components by mass fraction: 2% nano silica, 1.5% silane coupling agent KH-550, 0.3% ultraviolet absorber UV-327, and 0.4% antioxidant. The antioxidant is a mixture of hindered phenol 1010 and phosphite 168 in a mass ratio of 1:1.

[0032] Example 2: 6-core fine round steel wire armored flexible optical cable Cable core layer 1: The central reinforcing member 11 is 2.0mm thick, and the tight-buffered optical fiber 12 consists of six groups; Inner support layer 2: foaming ratio of 3 times, thickness of 0.4 mm; Spiral armor layer 3: Aluminum strip thickness is 0.10mm and width is 6mm; First armor layer 4: The inner layer of fine round steel wire has a diameter of 0.25±0.02mm, a tensile strength ≥1800MPa, a stranding pitch of 10mm, a coverage rate ≥85%, and a single wire gap of 0.05~0.10mm; Gradient buffer layer 5: The second repair agent is vinyl silicone oil containing 0.3% by mass of platinum catalyst; Second armor layer 6: The outer layer of fine round steel wire has a diameter of 0.20±0.02mm, a tensile strength of ≥1800MPa, a stranding pitch of 8mm, a coverage rate of ≥90%, and a single wire gap of 0.03~0.08mm; Outer sheath layer 7: The outer sheath thickness is 1.0 mm. The modified thermoplastic polyurethane elastomer material of the outer sheath also includes the following components by mass fraction: 3% nano silica, 0.5% silane coupling agent KH-550, 0.4% ultraviolet absorber UV-327, and 0.5% antioxidant. The antioxidant is a mixture of hindered phenol 1010 and phosphite 168 in a mass ratio of 1:1.

[0033] Example 3: 8-core fine round steel wire armored flexible optical cable Cable core layer 1: The central reinforcing member 11 is 3.0mm thick, and the tight-buffered optical fiber 12 consists of eight groups; Inner support layer 2: foaming ratio of 5 times, thickness of 0.5 mm; Spiral armor layer 3: The aluminum strip is 0.12mm thick and 6mm wide; First armor layer 4: The inner layer of fine round steel wire has a diameter of 0.25±0.02mm, a tensile strength ≥1800MPa, a stranding pitch of 12mm, a coverage rate ≥85%, and a single wire gap of 0.05~0.10mm; Gradient buffer layer 5: The second repair agent is vinyl silicone oil containing 0.1% by mass of platinum catalyst; Second armor layer 6: The outer layer of fine round steel wire has a diameter of 0.20±0.02mm, a tensile strength of ≥1800MPa, a stranding pitch of 10mm, a coverage rate of ≥90%, and a single wire gap of 0.03~0.08mm; Outer sheath layer 7: The outer sheath thickness is 1.2mm. The modified thermoplastic polyurethane elastomer material of the outer sheath also includes the following components by mass fraction: 5% nano silica, 1.0% silane coupling agent KH-550, 0.5% UV absorber UV-327, and 0.6% antioxidant. The antioxidant is a mixture of hindered phenol 1010 and phosphite 168 in a mass ratio of 1:1.

[0034] The performance of the fine round steel wire armored flexible optical cables prepared in Examples 1 to 3 was compared with that of mainstream armored optical cables on the market. Comparative Examples 1 and 2 are both commercially available traditional armored optical cables, which adopt the structure of ordinary galvanized steel wire + conventional PE buffer + ordinary TPU sheath.

[0035] Minimum bending radius, tensile strength, compressive strength, impact resistance, high and low temperature aging, and salt spray corrosion resistance were tested according to YD / T 769 and IEC60794 standards. A 2mm deep, 10mm long straight scratch was made on the sheath surface using a blade. After standing at room temperature (25℃), the self-healing test of the sheath scratch was conducted by recording the crack closure rate and surface integrity at 2h, 6h, and 24h. The water resistance and abrasion resistance after repair were also tested. The water-sealing effect of puncture damage was tested by artificially puncturing the inner support layer 2 of the example or the outer layer of the optical fiber in the comparative example, immersing it in clean water for 24 hours, and detecting longitudinal water seepage and internal moisture absorption to verify the expansion self-healing sealing effect. The microcrack cold flow self-healing test was conducted using a bending fatigue testing machine, repeatedly bending the fiber 5000 times to generate surface microcracks, standing for 12 hours, and observing the microcrack closure and mechanical recovery rate. Specific test results are shown in the table below.

[0036]

[0037] As can be seen from the data in the table above, the self-healing capability and mechanical performance of the present invention are superior to those of existing armored optical cables.

[0038] This invention injects two sets of repair agents into the inner and outer layers of a gradient buffer layer, respectively. When the gradient buffer layer is damaged and the repair agents leak, the two can achieve a two-component hydrosilylation reaction under the action of a platinum catalyst, and finally solidify to form a repair layer, thereby preventing external moisture or impurities from continuing to enter, thus achieving a self-repairing effect.

[0039] This invention introduces a three-layer gradient modulus buffer layer into the optical cable armor structure. Through the hardness gradient of the inner soft, medium hard and outer hard layers, it achieves the dual functions of stress dispersion and interlayer lubrication. The inner soft layer allows for large deformation and absorbs stress, the middle layer disperses stress, and the outer hard layer protects the integrity of the armor structure.

[0040] This invention employs an asymmetrical design with different diameters, densities, and opposite stranding directions. The inner layer uses thicker steel wires with a larger pitch, primarily bearing tensile and impact resistance; the outer layer uses thinner steel wires with a smaller pitch, primarily providing anti-biting and uniform stress distribution. The reverse stranding creates a "self-locking" effect where the two layers of wires intersect, increasing the interlayer static friction coefficient to 0.35-0.45, effectively preventing interlayer slippage caused by laying tension.

[0041] In addition, this invention presses piezoelectric fiber bundles with aluminum foil to form an electromechanical coupling structure, and forms an interface conductive connection layer through conductive silver paste. The piezoelectric fiber bundles constitute independent sensing units to sense local stress waves, and then lead them out to the end of the optical cable through a waterproof connector for detection. Combined with the stress wave propagation time difference algorithm, impact positioning is achieved.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within the scope of its essence and protection. Such modifications or equivalent substitutions should also be considered to fall within the protection scope of the present invention.

Claims

1. A flexible optical cable armored with fine round steel wire, characterized in that, From the inside out, the cable consists of a core layer, an inner support layer, a spiral armor tube layer, a first armor layer, a gradient buffer layer, a second armor layer, and an outer sheath layer. The spiral armor tube layer is formed by spirally overlapping aluminum tape around the outer periphery of the inner support layer. The outer layer of the spiral armor tube layer also has piezoelectric fiber bundles spirally wound around it. The first armor layer is formed by multiple inner layer thin round steel wires twisted together in a first twist direction around the outer periphery of the spiral armor tube layer. The gradient buffer layer consists of three layers of thermoplastic polyurethane with different Shore A hardnesses: from the inside out, an inner layer of thermoplastic polyurethane with a Shore A hardness of 60A and a thickness of 0.30mm; a middle layer of thermoplastic polyurethane with a Shore A hardness of 85A and a thickness of 0.15mm; and a third layer of thermoplastic polyurethane with a Shore A hardness of 85A and a thickness of 0.15mm. The outer layer of thermoplastic polyurethane with a Shore hardness of 95A and a thickness of 0.35mm is used. The innermost and outermost thermoplastic polyurethane layers of the gradient buffer layer are filled with a first repair agent and a second repair agent, respectively. Multiple sets of mandrels with a diameter of 0.25mm are axially parallel to each other inside the innermost and outermost thermoplastic polyurethane layers of the gradient buffer layer. The mandrels have spiral grooves with a depth of 0.10mm on their outer walls. The first and second repair agents are injected into their respective spiral grooves and then mixed and cured. The second armor layer is formed by multiple outer thin round steel wires twisted together in a second direction around the periphery of the gradient buffer layer.

2. The flexible optical cable armored with fine round steel wire according to claim 1, characterized in that: The cable core layer includes a central reinforcing member and multiple tight-buffered optical fibers stranded around the central reinforcing member. The central reinforcing member is made of phosphated steel wire or glass fiber reinforced plastic with a diameter of 1.5 to 3.0 mm. The inner part of the tight-buffered optical fiber is a bend-insensitive optical fiber with a core diameter of 9 μm. The outer part of the tight-buffered optical fiber is a tight-buffered layer made of low-modulus polyolefin material with a thickness of 0.2 to 0.3 mm. The tight-buffered optical fiber is also surrounded by a PBT loose tube, which is filled with water-blocking fiber grease. The viscosity of the water-blocking fiber grease is 15,000 to 25,000 mPa·s at 25°C.

3. The flexible optical cable armored with fine round steel wire according to claim 1, characterized in that: The inner support layer is a low-density polyethylene foam, with a foaming ratio of 3 to 5 times and a thickness of 0.3 to 0.5 mm.

4. The flexible optical cable armored with fine round steel wire according to claim 1, characterized in that: The thickness of the aluminum strip in the spiral armor layer is 0.08-0.12 mm and the width is 3-6 mm. The outer surface of the aluminum strip has a rough embossing at the middle of the non-overlapping part. The piezoelectric fiber bundle is spirally wound with the aluminum strip surface at the rough embossing part. The piezoelectric fiber bundle and the aluminum strip surface are also coated with conductive silver paste.

5. The flexible optical cable armored with fine round steel wire according to claim 1, characterized in that: The inner layer of fine round steel wire has a diameter of 0.25±0.02mm, a stranding pitch of 8~12mm, a coverage rate of ≥85%, and a single wire gap of 0.05~0.10mm. The outer layer of fine round steel wire has a diameter of 0.20±0.02mm, a stranding pitch of 6~10mm, a coverage rate of ≥90%, and a single wire gap of 0.03~0.08mm. The first stranding direction is opposite to the second stranding direction. The tensile strength of both the inner and outer layer of fine round steel wire is ≥1800MPa.

6. The flexible optical cable armored with fine round steel wire according to claim 1, characterized in that: The first repair agent is a hydrogen-terminated silicone oil, and the second repair agent is a vinyl silicone oil containing 0.1% to 3.5% by mass of a platinum catalyst, wherein the platinum catalyst is a Karstedt catalyst.

7. The flexible optical cable armored with fine round steel wire according to claim 1, characterized in that: The outer sheath is made of modified thermoplastic polyurethane elastomer material, and the thickness of the outer sheath is 0.8~1.2mm. The modified thermoplastic polyurethane elastomer material of the outer sheath also includes the following components by mass fraction: 2%~5% nano silica, 0.5%~1.5% silane coupling agent KH-550, 0.3%~0.5% ultraviolet absorber UV-327, and 0.4%~0.6% antioxidant. The antioxidant is a mixture of hindered phenol 1010 and phosphite 168 in a mass ratio of 1:

1.

8. A method for preparing a flexible optical cable armored with fine round steel wire according to any one of claims 1 to 7, characterized in that: Includes the following steps: S1, take a bend-insensitive optical fiber, and use an extrusion process to coat the outside of the bare optical fiber with a low-modulus polyolefin tight-buffered layer. The extrusion temperature is 160~180℃ and the extrusion speed is 10~15m / min to obtain a tight-buffered optical fiber. S2, multiple tight-buffered optical fibers are twisted together around the central reinforcing member in an SZ twisting process to form an optical fiber unit. The twisting pitch is 60-120mm. During the twisting process, the tension of the tight-buffered optical fibers is controlled at 0.5-1.5N and the twisting angle is 15°-20°. The twisted bundle enters the extruder and is extruded into a PBT loose tube with an outer diameter of 1.8±0.1mm and a wall thickness of 0.35±0.05mm. Water-blocking fiber paste is injected into the PBT loose tube under pressure, with a filling degree of ≥90%, to obtain the cable core layer. S3, low-density polyethylene foam is extruded outside the cable core layer as an inner support layer, and the extrusion temperature is 140~180℃. S4, aluminum strip is wound around the outer periphery of the inner support layer in a spiral overlapping manner to form a spiral armor tube layer. During the winding process, the wire tension of the aluminum strip is controlled to be 5-10N and the overlap rate is 15%-25%. After the overlap is completed, piezoelectric fiber bundles are spirally wound on the outer surface of the aluminum strip, and then conductive silver paste is coated on the contact end between the aluminum strip and the piezoelectric fiber bundle. S5, multiple inner layer fine round steel wires are twisted together in the first twisting direction using a planetary stranding machine on the outer periphery of the spiral armored tube layer. After twisting, online prestress release treatment is performed. The prestress release temperature is 120-150℃ and the treatment time is 30-60s to form the first armored layer. S6 employs a three-layer co-extrusion crosshead to composite three layers of melt—inner, middle, and outer thermoplastic polyurethane—within the outermost layer of the first armor layer. At the diehead, mandrels with spiral grooves on the outer walls of the two layers are fixedly arranged at different radial intervals. The mixture is formed through a die sleeve, extruded, and then subjected to gradient cooling to form a gradient buffer layer. A first repair agent and a second repair agent are then injected into the spiral grooves of the mandrels inside the inner and outer thermoplastic polyurethane layers, respectively. The injection pressure is 0.18 MPa, and the injection flow rate is 2.8 mL / min. After injection, the joint is sealed by ultrasonic welding. S7, Multiple outer thin round steel wires are twisted together in the second twisting direction at the outer periphery of the gradient buffer layer using a planetary stranding machine to form the second armor layer; S8. All components of the outer sheath are added to the extrusion equipment and heated to 170~190℃ to melt them. Then, the outer layer of the second armor layer is wrapped at a speed of 6~8m / min to ensure that the bonding transition layer completely fills the gap of the second armor layer. The thickness of the outer sheath layer is 0.8~1.2mm. After the wrapping is completed, it is cooled to room temperature by water cooling to obtain a fine round steel wire armored flexible optical cable.

9. The method for preparing a flexible optical cable armored with fine round steel wire according to claim 8, characterized in that: In step S6, the extrusion temperature of the inner layer thermoplastic polyurethane is 170-185℃ and the screw speed is 20 rpm; the extrusion temperature of the middle layer thermoplastic polyurethane is 185-200℃ and the screw speed is 25 rpm; the extrusion temperature of the outer layer thermoplastic polyurethane is 200-215℃ and the screw speed is 30 rpm; and the gradient cooling is achieved by sequentially passing through a three-stage cooling water tank: the first stage water temperature is 60℃, the second stage water temperature is 40℃, and the third stage water temperature is 20℃.

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