Radiation-resistant optical cable

Abstract

The utility model discloses an irradiation-resistant optical cable, which comprises single-mode optical fibers, each single-mode optical fiber comprises a tightly-packaged optical fiber, a unit reinforcer and a unit sheath which are arranged from inside to outside, each tightly-packaged optical fiber comprises a pure silicon dioxide fiber core / fluorine-doped cladding optical fiber and an ETFE tightly-packaged layer, the outer sides of the plurality of single-mode optical fibers are wrapped by a wrapping tape and an outer sheath, and the wrapping tape is wrapped by the unit reinforcer and the unit sheath. A central reinforcing core is arranged between the single-mode optical fibers, and a pure SiO2 fiber core is manufactured through a VAD method, a fluorine-doped cladding and a pure SiO2 outer cladding are manufactured through a POVD process, wire drawing is conducted, a polyimide coating is manufactured, an ETFE tight cladding layer is extruded, and an irradiation crosslinking low-smoke halogen-free flame-retardant polyolefin sheath is extruded. Through the above mode, the irradiation-resistant optical cable provided by the utility model adopts the novel low-loss irradiation-resistant optical fiber which is made of the pure SiO2 fiber core and the fluorine-doped cladding, adopts the ETFE radiation-resistant optical cable sleeve plastic and adopts the sheath of the irradiation crosslinking low-smoke halogen-free flame-retardant polyolefin optical cable, thereby reducing the radiation-induced loss, and being suitable for being applied in an irradiation environment.

Description

Technical Field

[0001] The utility model relates to the field of communication optical cables, in particular to a radiation-resistant optical cable. Background Art

[0002] With the continuous development of modern communication technology, the applications where optical fiber and cable may encounter nuclear radiation include not only tactical or strategic military systems, but also monitoring of nuclear waste and underground nuclear tests, visual observation of thermal reactor equipment, spacecraft communications, dosimetry and medical radiation, etc. The key to breaking through the technical barriers of nuclear power cable products lies in improving the radiation resistance, flame retardancy and service life of optical fiber and cable.

[0003] Radiation-resistant optical cables can be used in technical fields such as spacecraft, aerospace vehicles, deep space exploration, and ground nuclear facility monitoring. At the same time, after improvement, the product can be promoted and applied in nuclear power plants, nuclear submarines, nuclear aircraft carriers, airborne optical fiber wiring, satellite antenna remote microwave optical fiber lines, satellite communication pulse forwarding, communication satellite phased array antennas, and launch vehicles, and has a very broad application prospect.

[0004] Radiation is divided into two categories: ionizing radiation and non-ionizing radiation. Alpha rays, beta rays, gamma rays, X-rays, protons and neutrons are ionizing radiation, while infrared rays, ultraviolet rays, microwaves and lasers are non-ionizing radiation. Ionizing radiation is usually referred to as radiation or radiation exposure. Radioactive isotopes release three types of radiation when they decay: alpha rays, beta rays and gamma rays. In addition, there is neutron radiation, which is not produced by decay, but mainly by nuclear reactions.

[0005] When quartz optical fiber is exposed to ionizing radiation (such as gamma rays or x-rays) or particle radiation (such as electrons, neutrons, protons or ions), electrons or holes are formed. These electrons or holes are captured at the location of defects or impurities to form "color centers". Generally, glass optical fiber cannot work in a high-dose radiation environment because the glass will become opaque due to staining under the irradiation of nuclear radiation. The glass is stained because under the action of radioactive radiation, the local free electrons generated in the glass can be captured by the positively charged ions present in the glass. At this time, the ions become atoms because of the electrons. For example, Si 4++4e=Si, if free electrons occupy the vacancies (negative ion vacancy) of the network structure lattice in the glass, new color centers can be formed, which can produce new absorption bands in the light-passing area of ​​the optical fiber. Therefore, the free electrons generated by radiation in the glass cause some ions to be reduced and form new color centers, thereby dyeing the glass black. In addition, high-energy particles can actually replace ions in the optical fiber to produce other defects, and can also cause fatigue bonds in the silica grid to break or oxygen in the grid to shift to form "color centers". The radiation-induced defect centers produced may have light absorption bands that increase the attenuation of the optical fiber. Among the irradiation conditions, the main irradiation radiation that threatens communication equipment and communication optical fibers is gamma rays.

[0006] Usually, in conventional optical fibers, the core is doped with germanium to increase the refractive index, and pure silica is used as the cladding to form the waveguide structure of the optical fiber. When GeO2 is doped in quartz optical fiber, Ge replaces Si in SiO4 tetrahedron, causing the tetrahedron to be distorted, generating stress in the optical fiber and eventually forming defects. Moreover, these impurity atoms have a strong electron affinity and are easy to capture the charge generated after irradiation to form "color centers". The color centers absorb light of a specific wavelength and cause increased loss, which makes it impossible for the optical fiber to transmit optical signals normally.

[0007] The common method currently adopted by the industry to improve the radiation resistance of optical fiber is: using high-purity silica as the core to avoid the radiation-resistant optical fiber to produce light absorption color centers under long-term low-dose rate and short-term high-dose rate radiation; adding a certain amount of fluorine element to silica to make a low-refractive index cladding to form the optical fiber's light-guiding interface. While ensuring the transmission performance of the optical fiber, the formation of radiation-induced defect color centers is avoided.

[0008] Considering that the radiation resistance of optical fiber is closely related to the precursor defects and stress therein, it is also necessary to understand the stress generation mechanism during the drawing process. During the drawing process, residual stress is caused by the difference in the properties of the materials that make up the core and cladding. The residual stress in optical fiber is usually divided into thermal stress and mechanical stress. The difference in thermal expansion coefficient between the core and cladding materials is the main cause of thermal stress, which has nothing to do with the drawing conditions; mechanical stress is caused by the difference in viscosity and Young's modulus between the core and cladding materials, and mechanical stress is correlated with the drawing tension. Therefore, defects will also occur in the optical fiber during the drawing process, especially pure silica core single-mode optical fiber requires extremely low tension drawing, and its radiation resistance is relatively dependent on the drawing process.

[0009] In view of the fact that the existing radiation-resistant optical fiber is mainly a "pure quartz core + fluorine-doped quartz cladding" structure, and the preparation process mainly involves the processing of the optical fiber, the radiation resistance of the optical fiber can be further improved by functionalizing the coating with radiation protection. The high-energy rays can be absorbed or blocked by the coating structure with radiation protection function, further alleviating the impact of radiation on the optical fiber performance, thereby improving the radiation resistance of the optical fiber.

[0010] The radiation-resistant coating of optical fiber mainly includes radiation-resistant UV-curable acrylic resin and polyimide resin. Polyimide has been used as a coating for optical fiber for a long time. Its operating temperature range is: -190℃~+385℃. It is one of the best heat-resistant varieties of engineering plastics at present, with advantages such as low thermal expansion coefficient and radiation resistance. There are no hydrophilic groups in the polyimide macromolecules, and the water absorption rate is low; there are a large number of imide group closed rings in the macromolecular chain, and the carbon-nitrogen bond is under the protection of the five-membered heterocyclic ring, which has good stability. These chemical structure characteristics determine that polyimide has good radiation resistance: polyimide film is 5×10 9 After irradiation with a dose of rad, the strength still remains at 86%. Some polyimide fibers are irradiated with 1×10 10 After rad fast electron radiation, its strength retention rate is 90%. Polyimide coated optical fiber is widely used in special environments, such as high temperature, chemical corrosion and radiation environments.

[0011] Structural materials of radiation-resistant optical cables, long-term radiation of various rays is an important reason for the degradation of polymer products, so it is very important to improve the radiation resistance of materials. The radiation resistance of polymers is related to their molecular structure, molecular weight and aggregation state. Polymers that do not absorb certain rays or produce photocrosslinks after absorbing rays have good radiation resistance, such as polystyrene, polyethylene, etc. On the contrary, polymers that decompose after radiation have poor radiation resistance. In addition, preventing the entry of rays or quenching excited free radicals caused by radiation are also important means to improve radiation resistance. Introducing a stable structure into the polymer molecule can constitute an intrinsic radiation-resistant polymer, and adding a stabilizer to the polymer can constitute a composite radiation-resistant material. Due to the characteristics of its molecular structure, radiation-resistant polymer materials usually have good high temperature resistance and flame retardancy at the same time.

[0012] In addition to optical fiber, the radiation-resistant optical cable structural materials mainly include plastic sheath materials (including tight sheath and loose sheath), tensile components, sheath materials and armor layers. The tensile components mainly include KFRP, aramid yarn and its braided layer.

[0013] ETFE is also one of the main options for radiation-resistant optical cable sheathing materials. ETFE (ethylene-tetrafluoroethylene) is a di-alternating copolymer of tetrafluoroethylene and ethylene. Because fluoroplastics contain fluorine atoms in their molecular structure, they have many excellent properties, such as excellent electrical insulation, high heat resistance, high flame retardancy, outstanding oil resistance, solvent resistance and wear resistance. ETFE is a tough fluoroplastic. While maintaining the good heat resistance, chemical resistance and electrical insulation properties of PTFE, it has greatly improved radiation resistance and mechanical properties. The tensile strength can reach 50MPa, which is nearly twice that of polytetrafluoroethylene. ETFE is a tough material with a good balance of various mechanical properties: tear resistance, high tensile strength, medium hardness, impact resistance, and long telescopic life. Unlike PTFE, ETFE is a thermoplastic material suitable for extrusion technology, so ETFE insulated wires are widely used on aircraft and satellites. However, ETFE has a disadvantage. Its temperature rating is low, at 150°C, which limits its application in aerospace. In order to make up for this disadvantage, people have developed X-ETFE insulated wires. X-ETFE insulated wires are made of special cross-linkable ETFE insulation materials. After being extruded into wires, they are cross-linked by electron beam irradiation. In addition to maintaining the original characteristics of ETFE, X-ETFE has a temperature rating of 200°C and its radiation resistance is greatly improved. Therefore, since the 1970s, this type of wire has been favored by the aerospace industry. At present, this type of cable is widely used in almost all aerospace aircraft, both military and civilian. X-ETFE has also become the main material for radiation-resistant optical cable sheathing. Although the performance of ETFE is not as good as that of PEEK, its price is much lower than that of PEEK. Because of its high performance ratio, it is widely used in radiation-resistant optical cables.

[0014] The sheath material of radiation-resistant optical cable is mostly made of radiation-crosslinked radiation-resistant low-smoke halogen-free flame-retardant polyolefin material. Radiation crosslinking is to increase the bond energy of the material through the action of high-energy particles of electron beams, improve the mechanical properties of the material, and transform the material from thermoplastic to thermosetting. After the polymer material is crosslinked by radiation, certain crosslinking points are formed between the polymer macromolecules, which increases the molecular weight of the polymer and forms a three-dimensional network structure of molecules, which affects the various physical properties of the polymer: improve thermal stability (including high temperature characteristics and thermal oxidation aging); improve tensile strength and reduce elasticity; especially improve tensile strength at high temperature. After radiation crosslinking, the tensile strength, wear resistance and other mechanical properties of the material can be improved. In addition, radiation can also improve the environmental stress tear resistance and low-temperature brittleness of polyolefins, but the most important thing is to improve the mechanical properties at high temperature.

[0015] The basic formula of the tape is aramid tape, which is similar to that of conventional low-smoke halogen-free polyolefin cable sheath materials. However, in order to increase the degree of crosslinking, a crosslinking agent needs to be added, such as triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), trimethylolpropane trimethacrylate (TMPTMA), etc. The crosslinking agent is a multifunctional compound that promotes the formation of a crosslinked network structure of the polymer. After crosslinking, the heat resistance, flame retardancy, solvent resistance and mechanical properties of the sheath material can be significantly improved.

[0016] Conventional sheath material base materials usually use ethylene-vinyl acetate copolymer (EVA) materials. Vinyl acetate -CH2CHCOOCH3- in EVA materials produces active free radicals (COO·) or active ions under long-term heat aging and a large amount of radiation exposure, and will further undergo chemical reactions. Active free radicals or active ions trigger degradation reactions, cross-linking reactions, oxidation reactions and molecular isomerization reactions of macromolecular chains. These reactions accelerate the molecular reaction rate of the material, and the material becomes brittle and the mechanical properties deteriorate, especially the elongation at break of the material drops significantly, affecting the use of the material. In order to improve the radiation resistance of EVA materials, anti-radiation agents are usually added to improve the radiation resistance of cable materials. The main anti-radiation agents are benzotriazole light stabilizers, boron nitride, boron carbide, high phenyl silicone rubber, phenylene silicone rubber, etc.

[0017] The tensile material of radiation-resistant optical cables is mainly aramid fiber. Aramid refers to synthetic fibers made from aromatic compounds through polycondensation spinning. Its full name is aromatic polyamide fiber. Aramid has excellent properties such as light weight, flame retardancy, temperature resistance, insulation, radiation resistance, high strength, and high elastic modulus. It is widely used in military defense, security protection, aerospace, environmental protection, electronic and electrical materials, etc.

[0018] Aramid fibers mainly include fully aromatic polyamide fibers and heterocyclic aromatic polyamide fibers, which can be divided into three types: ortho-aramid, para-aramid (PPTA) and meta-aramid (PMTA). Meta-aramid is polyisophthalamide, also known as aramid 1313. The fiber molecules are composed of meta-phenylene groups connected to each other by amide groups, and the molecular chain is linear and zigzag. Due to the strong hydrogen bonding between molecules, the fiber has excellent flame retardancy, high temperature resistance and radiation resistance. Meta-aramid has excellent radiation resistance. For example, at 1.2x10 -2 w / in 2 UV and 1.72x10 8 Even under long-term irradiation of γ-rays of rads, its intensity remains unchanged. Summary of the invention

[0019] The main technical problem solved by the utility model is to provide a radiation-resistant optical cable, which adopts a new type of low-loss radiation-resistant optical fiber made of a pure SiO2 core and a fluorine-doped cladding, adopts ETFE radiation-resistant optical cable sheathing and adopts a radiation-crosslinked low-smoke halogen-free flame-retardant polyolefin optical cable sheath, thereby reducing radiation-induced loss and being suitable for application in irradiated environments.

[0020] In order to solve the above technical problems, a technical solution adopted by the utility model is: to provide a radiation-resistant optical cable, including a single-mode optical fiber, the single-mode optical fiber includes a tight-wrapped optical fiber, a unit reinforcement and a unit sheath arranged from the inside to the outside, the tight-wrapped optical fiber includes a pure silica core / fluorine-doped cladding optical fiber and an ETFE tight cladding, the outer sides of multiple single-mode optical fibers are coated with a wrapping tape and an outer sheath, and a central reinforcement core is arranged between the single-mode optical fibers.

[0021] In a preferred embodiment of the present invention, the central reinforcing core is an aramid fiber reinforced optical cable reinforcing core, and the outer sheath is a radiation cross-linked, radiation-resistant, low-smoke, halogen-free, flame-retardant polyolefin sheath.

[0022] In a preferred embodiment of the present invention, the unit reinforcement is aramid yarn, and the unit sheath is a low-smoke halogen-free polyolefin sub-unit sheath.

[0023] In order to solve the above technical problems, another technical solution adopted by the utility model is: to provide a preparation process of a radiation-resistant optical cable, comprising the following steps: S1. to prepare a pure SiO2 fiber core by VAD method: the deposition surface is always kept at the position between the SiO2 core rod burner heads, purified air is introduced into the reaction container, the pure SiO2 burner head is used to deposit the pure SiO2 fiber core, the porous matrix of the prepared SiO2 core is sintered and dehydrated, and a glass core rod is formed in a sintering furnace; S2. POVD process for making fluorine-doped cladding and pure SiO2 outer cladding: plasma gas and source chemical gas are transported to the ion torch, the plasma torch moves along the length direction of the glass core rod, the high-frequency generator provides a high-frequency electric field to excite the plasma, the source chemical substance produces a chemical vapor reaction in the plasma to generate a pure SiO2 or fluorine-doped SiO2 deposited body, which directly forms a glass body under the high-temperature energy of the plasma. After the deposition is completed, the required fluorine-doped cladding and pure SiO2 outer cladding can be obtained; S3. Wire drawing: the above-mentioned glass preform rod is inserted into a wire drawing furnace for high-temperature wire drawing at 2200℃, and drawn into an optical fiber, and the drawing tension is set to 30-45g; S4. Preparation of polyimide coating: use pure water to clean the optical fiber, pass the cleaned and dried bare optical fiber through the coating device, and coat the polyimide solution on the optical fiber. The pre-coated optical fiber is solidified and then wound and taken up; S5. ETFE tight sheath extrusion: extrude the plastic layer in a plastic extruder, then use high-energy rays to radiate and cross-link the extruded uncross-linked cable on a radiation device, set a wrapping tape and extrude a low-smoke halogen-free polyolefin sub-unit sheath to obtain a single-mode optical fiber; S6. Radiation cross-linked low-smoke halogen-free flame-retardant polyolefin sheath extrusion process: extrude and radiate cross-linked low-smoke halogen-free flame-retardant polyolefin sheaths on the outside of multiple single-mode optical fibers and a central reinforcement core to obtain a radiation-resistant optical cable.

[0024] In a preferred embodiment of the utility model, the clamp in S1 holds the tail pipe and introduces purified air into the reaction vessel in the clean space, uses the method of oxidative hydrolysis to generate oxides, uses the pure SiO2 fiber core upper burner and the pure SiO2 fiber core lower burner to deposit the porous matrix of the pure SiO2 fiber core, and controls the rotation and lifting speed of the pure SiO2 fiber core porous matrix through PID control, so that the bottom deposition surface is always maintained at the position between the pure SiO2 fiber core upper burner and the pure SiO2 fiber core lower burner; the pressure inside the entire reaction vessel is controlled by a pressure sensor and transmitted to the control system, and then the pneumatic valve and the exhaust pump are adjusted through PID control to discharge the system. The waste gas generated during the manufacturing process is eliminated, and the pressure and airflow inside the reaction vessel are kept stable. The information collected by the camera and the pyrometer is transmitted to the monitor and the deposited body profile display, and then the control system is controlled by PID control. The ejection mass is 38g / min, the flame temperature is 1780℃, the exhaust pump discharges the waste gas, the pressure inside the reaction vessel is 5pa, and the surface temperature of the porous matrix of the deposited pure SiO2 fiber core is 1080℃. The rotation speed is maintained at 20r / min, and the position deviation should be 50μm. The porous matrix of the pure SiO2 fiber core is sintered and dehydrated to form a pure SiO2 glass core rod in a chlorine-doped sintering furnace.

[0025] In a preferred embodiment of the utility model, in said S2, the chlorine-doped fiber core rod is fixed on the lathe chuck, the chlorine-doped fiber core rod is driven to rotate by the lathe chuck, the plasma torch is fixed on the carriage, the carriage moves the plasma torch along the length direction of the chlorine-doped fiber core rod, so that the material is deposited on the chlorine-doped fiber core rod to form the required tubular outer cladding glass body, the plasma gas O2 and N2 and the source chemical gas SiCl4 and O2 are transported to the plasma torch, the high-frequency generator excites the plasma through the high-frequency electric field of the coil, and the source chemical substance produces a chemical vapor reaction in the plasma to generate pure SiO2 Or the fluorine-doped SiO2 deposit directly forms a glass body under the high temperature energy of plasma. The plasma gas is firstly removed from the water by a plasma gas dryer to ensure that its hydroxyl content is less than 2ppm. The carrier gas O2 of the reaction gas is firstly removed from the water by a dryer to ensure that its hydroxyl content is less than 0.5ppm, and then the source gas SiCl4 is taken out by a bubbler and transported to the plasma torch. The formation of the fluorine-doped sunken cladding is to control the F doping amount by controlling the SiF4 and SiF6 flow rates at the MFC. After the deposition is completed, the required fluorine-doped lower cladding and pure SiO2 outer cladding can be obtained.

[0026] In a preferred embodiment of the utility model, the polyimide coating process on the optical fiber surface in S4 includes four steps of cleaning, coating, pre-curing, and high-temperature curing. The process includes cleaning and drying, using pure water to clean the optical fiber and drying it by high-pressure gas. The cleaned and dried bare optical fiber is passed through the coating device under the traction of the traction device. The pre-coated optical fiber is passed through the curing assembly arranged under the coating device under the traction of the traction device for pre-curing. The pre-cured optical fiber is introduced into a horizontal oven by a V-shaped guide wheel group for curing. The cured optical fiber is passed through a diameter detection device under the guidance of a rotating guide wheel for detection and then wound onto a take-up device to complete coating. The viscosity of the polyimide solution is 4000-6000mPa.s.

[0027] In a preferred embodiment of the utility model, in step S5, ETFE needs to be pre-baked at 120°C for 3 hours before extrusion. To ensure uniform temperature inside and outside the ETFE sheath, the wire core needs to be preheated to 300°C, the extrusion temperature is from 280°C to 340°C, the stretch ratio is 50-200, 2-3 layers of 250-mesh filter screen should be added to the end of the extruder screw, the uncross-linked sheath is extruded in the plastic extruder, and then the extruded uncross-linked cable is cross-linked by radiation using electron beam or gamma ray in an electron accelerator or a cobalt-60 irradiation station.

[0028] In a preferred embodiment of the present invention, the aspect ratio of the extruder in S6 is 25:1, the compression ratio is 1: 1.2, the filter mesh is 40 / 80 / 40, the extrusion temperature of the feeding section is 100°C, the base temperature of the conveying section is 125°C, the extrusion temperature of the melting section is 135°C, and the extrusion temperature of the die is 140-145°C.

[0029] The beneficial effects of the utility model are as follows: the radiation-resistant optical cable of the utility model adopts a new type of low-loss radiation-resistant optical fiber made of a pure SiO2 core and a fluorine-doped cladding, adopts ETFE radiation-resistant optical cable sheathing and adopts a radiation-crosslinked low-smoke halogen-free flame-retardant polyolefin optical cable sheath, thereby reducing radiation-induced loss and being suitable for application in an irradiated environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0031] Figure 1 This is a structural schematic diagram of a preferred embodiment of the radiation-resistant optical cable of the utility model;

[0032] Figure 2 is the refractive index profile of a single-mode optical fiber;

[0033] Figure 3 This is a schematic diagram of the structure of pure silica fiber core made by VAD process;

[0034] Figure 4 This is a schematic diagram of the structure of the fluorine-doped cladding of optical fiber produced by the POVD process;

[0035] The components in the drawings are marked as follows: 101, tight-buffered optical fiber, 102, unit strength member, 103, unit sheath, 104, wrapping tape, 105, outer sheath, 106, central strength core. DETAILED DESCRIPTION

[0036] The technical scheme in the embodiment of the utility model will be described clearly and completely below. The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification, so that people familiar with this technology can understand and read them, and are not used to limit the limiting conditions that can be implemented in the utility model, so they have no substantial technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effect that can be produced by the utility model and the purpose that can be achieved, should still fall within the scope that the technical content disclosed in the utility model can cover. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and so on quoted in this specification are only for the convenience of narration, and are not used to limit the scope that can be implemented. The change or adjustment of the relative relationship, without substantial change of the technical content, should also be regarded as the scope that can be implemented in the utility model.

[0037] See also Figure 1 and Figure 2 . A radiation-resistant optical cable includes a single-mode optical fiber, the single-mode optical fiber includes a tight-wrapped optical fiber 101, a unit strength member 102 and a unit sheath 103 arranged from the inside to the outside, the tight-wrapped optical fiber includes a pure silica core / fluorine-doped cladding optical fiber and an ETFE tight cladding, the outer sides of multiple single-mode optical fibers are wrapped with a tape 104 and an outer sheath 105, and a central strength core 106 is arranged between the single-mode optical fibers. The central strength core 106 is an aramid fiber reinforced optical cable strength core, and the outer sheath 105 is an irradiation cross-linked radiation-resistant low-smoke halogen-free flame-retardant polyolefin sheath. The unit strength member 102 is an aramid yarn, and the unit sheath 103 is a low-smoke halogen-free polyolefin sub-unit sheath.

[0038] The preparation process of radiation-resistant optical cable is as follows:

[0039] (1) Using VAD method to make pure SiO2 core:

[0040] The VAD method is used to make the porous matrix of the pure SiO2 fiber core: the deposition surface is always kept in the position between the SiO2 core rod and the torch head; purified air is introduced into the reaction vessel, and the discharge pump in the exhaust pipe on one side of the reaction vessel ensures the stability of the internal pressure; the pure SiO2 torch head is used to deposit the pure SiO2 fiber core; the porous matrix of the SiO2 fiber core is sintered and dehydrated to form a glass core rod in the sintering furnace.

[0041] Using VAD method to make SiO2 fiber core: (such as Figure 3 shown)

[0042] The entire manufacturing process uses a fixture 1 to clamp the tail pipe in a clean space reaction container 9 to pass purified air 2 to achieve a Class 100 clean space effect, uses an oxidative hydrolysis method to generate oxides, uses a pure SiO2 core upper blowtorch 10 and a pure SiO2 core lower blowtorch 11 to deposit a pure SiO2 core porous matrix 8, and uses a PID control 16 to control the rotation and lifting speed of the pure SiO2 core porous matrix 8, so that the bottom deposition surface 12 is always maintained at a position between the pure SiO2 core upper blowtorch 10 and the pure SiO2 core lower blowtorch 11; the pressure inside the entire reaction container 9 is controlled by a pressure sensor 3 and transmitted to a control system 13, and then passed through The pneumatic valve 4 and the exhaust pump 5 are adjusted by the PID control 16 to discharge the waste gas generated in the manufacturing process, and at the same time, the pressure and airflow inside the reaction container 9 are kept stable. The camera 6 and the pyrometer 7 collect information and transmit it to the monitor 15 and the deposited body profile display 14, and then the control system 13 is controlled by the PID control 16. The ejection mass is 38g / min, the flame temperature is 1780℃, the exhaust pump 5 discharges the waste gas, the pressure inside the reaction container 9 is 5pa, and the surface temperature of the porous matrix 8 of the deposited pure SiO2 core is 180℃, the rotation speed is maintained at 20r / min, and the position deviation should be 50μm. The porous matrix 8 of the pure SiO2 core is sintered and dehydrated to form a pure SiO2 glass core rod 8a in a chlorine-doped sintering furnace.

[0043] The radiation-resistant optical fiber cladding is made of silicon dioxide doped with fluorine to reduce the refractive index to form a waveguide structure. Fluoride raw materials doped with fluorine include CCl2F2, C2F2, SiF4, SF6, CF4, etc. For example, if CCl2F2 (Freon) is used as the raw material, the chemical vapor reaction has the following reaction formula: 3CCl2F2+2SiCl4+3O2= 2SiO 1.5 F+7Cl2↑+3CO↑ +2F2↑. From the above reaction formula, it can be seen that fluorine exists in the molecular lattice array of silicon dioxide in the form of Si-F bonds in quartz glass. However, the following equilibrium reaction will also occur with this reaction formula: 4SiO 1.5F↔SiF4↑+SiO2, which means that during the fluorine doping process, fluorine is unstable inside quartz and is easily lost or diffused at high temperatures. At the same time, this also shows that SiF4 should be the best fluorine doping agent.

[0044] POVD process to produce fluorine-doped cladding and pure SiO2 outer cladding: (such as Figure 4 shown)

[0045] The chlorine-doped fiber core rod 8a is fixed on the lathe chuck 17, and the chlorine-doped fiber core rod 8a is driven to rotate by the lathe chuck 17. A plasma torch 18 is fixed on the carriage 20, and the carriage 19 moves the plasma torch 18 along the length direction of the chlorine-doped fiber core rod 8a, causing the material to be deposited on the chlorine-doped fiber core rod 8a to form the required tubular outer cladding glass body 20. The plasma gas (O2, N2) delivery pipe 21 and the source chemical gas (SiCl4, O2) delivery 22 are delivered to the plasma torch 18, and a high-frequency generator provides a high-frequency electric field with a frequency of 5.28+ / -0.13MHz and a power of 60KW through a coil (not shown) to excite the plasma, and the source chemical substance produces a chemical vapor reaction in the plasma to generate a deposit of pure SiO2 or fluorine-doped SiO2, which directly forms a glass body under the high temperature energy of the plasma. The plasma gas is firstly passed through the plasma gas dryer 23 to remove moisture, ensuring that its hydroxyl content is less than 2ppm; the carrier gas (O2) of the reaction gas is firstly passed through the dryer 24 to remove moisture, ensuring that its hydroxyl content is less than 0.5ppm, and then the source gas (SiCl4) is taken out through the bubbler 25 and transported to the plasma torch 18. The formation of the fluorine-doped sunken cladding is to control the F doping amount by controlling the SiF4 and SiF6 flow at the MFC26. After the deposition is completed, the desired fluorine-doped sunken cladding and pure SiO2 outer cladding can be obtained.

[0046] (3) Wire drawing

[0047] The glass preform is inserted into a drawing furnace for high-temperature drawing at 2200°C to form an optical fiber. The drawing tension is set to 30-45g. The optical fiber formed by these processing parameters is less susceptible to drawing-induced stress, which is detrimental to the optical transmission properties of the optical fiber (including waveguide propagation performance).

[0048] (II) Production process of polyimide coating:

[0049] The polyimide coating adopts a thermal curing process. The fiber diameter is 125+ / -1μm, and the coating diameter is 155+ / -5μm.

[0050] The optical fiber surface polyimide coating process includes four steps: cleaning, coating, pre-curing, and high-temperature curing:

[0051] A) Clean, clean and dry, use pure water to clean the optical fiber and dry it with high-pressure gas;

[0052] B) coating, the cleaned and dried bare optical fiber is passed through a coating device under the traction of a traction device;

[0053] C) pre-curing, the pre-coated optical fiber is pulled by the pulling device through a curing assembly arranged below the coating device for pre-curing (solvent volatilization);

[0054] D) High temperature curing: the pre-cured optical fiber is introduced into a horizontal oven for curing by a V-shaped guide wheel assembly. The cured optical fiber is guided by a rotating guide wheel and passed through a diameter detection device for detection. After that, it is wound onto a take-up device for coating.

[0055] The horizontal oven is divided into a volatilization zone and a synthesis zone. The temperature range of the volatilization zone is 120-300°C, the temperature range of the synthesis zone is 300-500°C, and the front and rear ends of the horizontal oven are respectively connected with an exhaust system and an air supply system.

[0056] The speed of the take-up device and the traction device is set to 4m / min.

[0057] Polyimide resin has good solubility and is easily soluble in solvents such as dimethylformamide and dimethylacetamide. The viscosity of the polyimide solution in the storage bottle is 4000-6000mPa.s, which is used to coat the polyimide solution on the optical fiber passing through the coating cup. The coating thickness is determined by the diameter of the optical cable entering the coating cup and the aperture of the coating cup.

[0058] (III) Extrusion process of X-ETFE optical fiber tight cladding

[0059] Extrusion process of X-ETFE: ETFE needs to be pre-baked at 120℃ for 3h before extrusion. To ensure uniform temperature inside and outside the ETFE plastic layer, the wire core needs to be preheated to 300℃ and the extrusion temperature is 280℃. o C (feed port) to 340℃ (die head). Stretch ratio 50-200. To improve the plasticization and mixing quality of the resin, 2-3 layers of 250 mesh filter should be added to the end of the extruder screw. Extrude the plastic layer (uncrosslinked) in the plastic extruder, and then place the extruded uncrosslinked cable on a radiation device (electron accelerator or cobalt-60 irradiation station) to perform radiation crosslinking using high-energy rays (electron beam or gamma ray).

[0060] (IV) Irradiation cross-linked low smoke halogen-free flame retardant polyolefin sheath extrusion process

[0061] Extrusion process: Irradiation cross-linked low-smoke halogen-free flame-retardant polyolefin cable materials can be processed on many existing wire and cable extrusion equipment. Equal-distance unequal-depth PVC screws with a compression ratio of 3 can also be extruded, but the screw speed should not be too fast and the discharge speed is slightly slow. Each zone of the extruder must have a cooling system. Generally, we recommend the following processing conditions:

[0062] Recommended equipment: φ45~150 single screw extruder, extruder length-diameter ratio (L / D) ~25: 1, compression ratio 1: 1.2 low compression ratio screw, filter mesh / mesh 40 / 80 / 40, extrusion temperature:

[0063] Feeding section Conveying section Melting section Machine head (mold) 100℃ 125℃ 135℃ 140-145℃

[0064] The sheath (uncrosslinked) is extruded in a plastic extruder, and then the extruded uncrosslinked cable is subjected to radiation crosslinking using high-energy rays (electron beam) on a radiation device (electron accelerator).

[0065] Different from the prior art, the radiation-resistant optical cable of the utility model adopts a new type of low-loss radiation-resistant optical fiber made of a pure SiO2 core and a fluorine-doped cladding, adopts ETFE radiation-resistant optical cable sheathing and a radiation-cross-linked low-smoke halogen-free flame-retardant polyolefin optical cable sheath, thereby reducing radiation-induced losses and being suitable for applications in irradiated environments.

[0066] The above schematically describes the present invention and its implementation methods, which are not restrictive. The drawings show only one implementation method of the present invention, and the actual structure is not limited thereto. Therefore, if ordinary technicians in this field are inspired by it and design structural methods and embodiments similar to the technical solution without creativity without departing from the purpose of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A radiation-resistant optical cable, characterized in that: It comprises a single-mode optical fiber, which comprises a tight-wrapped optical fiber, a unit reinforcement and a unit sheath arranged from the inside to the outside. The tight-wrapped optical fiber comprises a pure silica core / fluorine-doped cladding optical fiber and an ETFE tight cladding. The outer sides of multiple single-mode optical fibers are coated with a wrapping tape and an outer sheath, and a central reinforcement core is arranged between the single-mode optical fibers.

2. The radiation-resistant optical cable according to claim 1, characterized in that: The central reinforcing core is an aramid fiber reinforced optical cable reinforcing core, and the outer sheath is an irradiation cross-linked, radiation-resistant, low-smoke, halogen-free, flame-retardant polyolefin sheath.

3. The radiation-resistant optical cable according to claim 1, characterized in that: The unit reinforcement is aramid yarn, and the unit sheath is a low-smoke halogen-free polyolefin sub-unit sheath.

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