A high-temperature resistant carbon-coated optical fiber and its preparation method and system

Abstract

This invention discloses a high-temperature resistant carbon-coated optical fiber, characterized by comprising a core layer, a cladding layer, a carbon coating layer, and a resin coating layer arranged sequentially from the inside out. The carbon coating layer includes a first carbon film layer and a second carbon film layer. The first carbon film layer is a graphite-like amorphous carbon film; the second carbon film layer is a diamond-like amorphous carbon film, or a graphite-like amorphous carbon film, or a combined carbon film layer formed by stacking at least one graphite-like amorphous carbon film and at least one diamond-like amorphous carbon film in the thickness direction. This invention also discloses a corresponding preparation method and system, solving the problem that traditional cold-wall chemical vapor deposition cannot preheat optical fibers with a carbon film deposited on them. The graphite-like amorphous carbon film deposited in the inner layer of the optical fiber of this invention can bond tightly with the optical fiber, providing good sealing, while the diamond-like amorphous carbon film deposited in the outer layer has high mechanical strength and good wear resistance, providing excellent protection for the optical fiber.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber manufacturing technology, specifically relating to a high-temperature resistant carbon-coated optical fiber and its preparation method and system. Background Technology

[0002] Carbon-coated optical fiber, also known as carbon-sealed optical fiber or carbon-coated fiber, has a thin carbon film on the surface of the glass fiber. This film has excellent sealing properties, improving the reliability of the glass fiber. On the one hand, it prevents moisture from attacking the glass fiber surface and causing strength degradation; on the other hand, it prevents hydrogen molecules from diffusing into the fiber core. Conventional polymer protective layers can block liquid water to a certain extent, but they cannot prevent the diffusion of water molecules or even smaller hydrogen molecules. Water molecules accelerate the propagation of cracks on the glass fiber surface, and hydrogen molecules intruding into the core layer cause a significant increase in optical fiber loss. Carbon-coated optical fiber effectively solves these problems.

[0003] The fabrication of carbon-coated optical fibers requires the preparation of a carbon film of tens of nanometers on the cladding surface before applying conventional optical fiber coatings. Carbon film preparation utilizes vapor deposition (PVD) to deposit carbon and other elements onto the bare fiber surface, forming an amorphous carbon film. Based on the principle, PVD can be classified into physical vapor deposition (PVD) and chemical vapor deposition (CVD). Common methods include magnetron sputtering, plasma-enhanced chemical vapor deposition (PECVD), and thermochemical vapor deposition (TCVD). Currently, the mainstream carbon film deposition method is TCVD. TCVD utilizes a heat source to induce a chemical reaction between gaseous raw material molecules at the gas phase or gas-solid interface, achieving the deposition of a carbon film on the bare optical fiber.

[0004] In the carbon film deposition process, the heat to activate the reaction is generally provided in two ways: one is to introduce hydrocarbons or other raw material gases into the reaction chamber to heat the reaction chamber, causing the raw material gas to undergo thermal decomposition in the gas phase. The microparticles produced by the reaction are deposited on the surface of the optical fiber to complete the carbon film deposition. This method is called hot-wall chemical vapor deposition. In hot-wall chemical vapor deposition, the overall temperature of the reaction chamber is relatively high. While the carbon film is deposited on the surface of the optical fiber cladding, it is also deposited on the reaction chamber wall. After the reaction has been going on for a period of time, it is easy to accumulate, which will affect the continued reaction.

[0005] Another method involves introducing a raw material gas into the reaction chamber without heating the chamber itself. Instead, the optical fiber is heated using preheating or directional heating, causing the gas to first adsorb onto the fiber surface before undergoing a pyrolysis reaction. This method is called cold-wall chemical vapor deposition (CCVD). CCVD reacts only on the fiber cladding surface, producing fewer byproducts and theoretically making it easier to produce long sections of carbon-coated fiber with high-quality carbon films. However, during CCVD, the preheated fiber temperature drops rapidly, making it difficult to control the reaction temperature. Furthermore, heating the carbon film leads to oxidation, meaning this deposition method can only produce a single carbon film, resulting in a simple carbon film structure. Consequently, the carbon-coated fiber formed has poor resistance to mechanical damage and cannot meet the harsh environmental requirements of special applications. Summary of the Invention

[0006] To address one or more of the above-mentioned defects or improvement needs in the existing technology, this invention provides a method, system, and product for preparing high-temperature resistant carbon-coated optical fibers. This solves the problem that traditional cold-wall chemical vapor deposition cannot preheat optical fibers with a carbon film deposited on them. Furthermore, the graphite-like amorphous carbon film deposited on the inner layer of the optical fiber can be tightly bonded to the optical fiber, providing good sealing performance, while the diamond-like amorphous carbon film deposited on the outer layer has high mechanical strength and good wear resistance, providing excellent protection throughout the entire lifespan of the optical fiber.

[0007] To achieve the above objectives, according to a first aspect of the present invention, a high-temperature resistant carbon-coated optical fiber is provided, comprising a core layer, a cladding layer, a carbon coating layer and a resin coating layer arranged sequentially from the inside to the outside.

[0008] The carbon coating layer includes a first carbon film layer and a second carbon film layer;

[0009] The first carbon film layer is a graphite-like amorphous carbon film;

[0010] The second carbon film layer is a diamond-like amorphous carbon film, or a graphite-like amorphous carbon film, or the second carbon film layer is a combined carbon film layer formed by stacking at least one graphite-like amorphous carbon film and at least one diamond-like amorphous carbon film in the thickness direction.

[0011] As a further improvement of the present invention, the carbon-coated optical fiber includes carbon-coated single-mode optical fiber and carbon-coated multimode optical fiber. After being placed in a hydrogen environment at 85°C and 11 atm for 7 days, the carbon-coated single-mode optical fiber has an additional attenuation of <0.2dB / km at a wavelength of 1240nm, and the carbon-coated multimode optical fiber has an additional attenuation of <0.2dB / km at a wavelength of 850nm.

[0012] According to a second aspect of the present invention, a method for preparing a high-temperature resistant carbon-coated optical fiber is provided, comprising the following steps:

[0013] S1, After heating the optical fiber, it is placed in the first carbon coating reaction chamber for carbon film deposition, so that a first carbon film layer is formed on the surface of the optical fiber. The first carbon film layer is a graphite-like amorphous carbon film.

[0014] S2, the optical fiber with the first carbon film layer deposited on its surface is placed in the second carbon coating reaction chamber for carbon film deposition, so that a second carbon film layer is formed on the surface of the optical fiber. The second carbon film layer is a graphite-like amorphous carbon film or a diamond-like amorphous carbon film, or the second carbon film layer is a combined carbon film layer formed by stacking at least one graphite-like amorphous carbon film and at least one diamond-like amorphous carbon film in the thickness direction.

[0015] The second carbon-coated reaction chamber has a first induction coil on its outer periphery, which controls the temperature of the optical fiber surface reaction zone inside the second carbon-coated reaction chamber.

[0016] S3, after coating the surface of the optical fiber with the second carbon film layer with a thermosetting coating, it is placed in a curing device for thermosetting to obtain a high-temperature resistant carbon-coated optical fiber.

[0017] As a further improvement of the present invention, a second induction coil is provided on the outer periphery of the curing device, and the curing temperature of the thermosetting coating in the curing device is controlled by the second induction coil.

[0018] As a further improvement of the present invention, in step S1, the temperature of the optical fiber entering the first carbon coating reaction chamber is controlled to be 800~1100℃, so that the first carbon film layer is a graphite-like amorphous carbon film.

[0019] As a further improvement of the present invention, in step S2, the temperature of the optical fiber entering the second carbon coating reaction chamber is controlled to be 800~1100℃, thereby making the second carbon film a graphite-like amorphous carbon film; or,

[0020] In step S2, the temperature of the optical fiber entering the second carbon coating reaction chamber is controlled to be greater than 1100°C, so that the second carbon film layer is a diamond-like amorphous carbon film.

[0021] As a further improvement of the present invention, the raw material gas in the first carbon coating reaction chamber and the second carbon coating reaction chamber includes hydrocarbon gas and protective gas, with the proportion of hydrocarbon gas in the raw material gas being 15% to 75%; the feed rate of the raw material gas is 250 ml / min to 2 L / min, the exhaust rate is 0.5-1 L / min greater than the feed rate, and the wire drawing speed is 40 to 250 m / min.

[0022] As a further improvement of the present invention, in step S3, the spacing between each turn of the second induction coil gradually decreases from the fiber inlet end to the fiber outlet end of the curing device.

[0023] According to a third aspect of the present invention, a system for preparing high-temperature resistant carbon-coated optical fibers is provided, applicable to the method for preparing the aforementioned high-temperature resistant carbon-coated optical fibers, comprising, in sequence, a drawing furnace, a first carbon coating reaction chamber, at least one second carbon coating reaction chamber, and at least one set of resin coating and curing devices; wherein;

[0024] The drawing furnace is used to heat and draw optical fiber preforms to obtain optical fibers; at the same time, it can use the residual heat to heat the optical fibers.

[0025] The first carbon coating reaction chamber is the reaction chamber for forming the first carbon film layer;

[0026] The second carbon coating reaction chamber is a reaction chamber for forming the second carbon film layer, and a first induction coil is provided on its outer periphery;

[0027] The resin coating and curing apparatus includes a resin coating device and a curing device; the resin coating device is used to coat a thermosetting coating; the curing device is used to cure the thermosetting coating.

[0028] As a further improvement of the present invention, a second induction coil is provided on the outer periphery of the curing device.

[0029] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0030] (1) The high-temperature resistant carbon-coated optical fiber of the present invention has a multi-layer composite structure in which the carbon coating layer is tightly bonded to each other and to the cladding. The innermost graphite-like amorphous carbon film is mainly composed of a high content of SP2 bonds, which has good sealing and ductility, can reduce the erosion of the optical fiber by hydrogen and water vapor, and can prevent the propagation of microcracks on the cladding surface, thus greatly improving the life of the optical fiber. The diamond-like amorphous carbon film is composed of a certain content of SP3 and SP2 bonds. The SP3 bond gives the carbon film a high hardness and good mechanical strength, which can improve the mechanical damage resistance of the optical fiber cladding and the graphite-like amorphous carbon film, and can significantly improve the service life of the high-temperature resistant carbon-coated optical fiber under harsh high-temperature environments.

[0031] (2) The method for preparing the high-temperature carbon-coated optical fiber of the present invention firstly draws a preform into an optical fiber, then deposits a carbon film on the cladding surface of the optical fiber by conventional cold-wall chemical vapor deposition, and then deposits one or more layers of carbon film by induction heating to activate the deposition reaction. Finally, a thermosetting coating is applied and thermosetting is achieved by induction heating. The carbon film directly serves as the heat source for subsequent deposition or curing, solving the problem that traditional cold-wall chemical vapor deposition cannot preheat the optical fiber with a carbon film deposited on it. Furthermore, the inner layer of the carbon coating is mainly a graphite-like amorphous carbon film, which forms SI-C bonds with the optical fiber, resulting in a tight bond and good sealing performance. At the same time, the SI-C bonds make the structure of the optical fiber to the carbon layer a gradual transition. The outer layer is mainly a diamond-like amorphous carbon film, which has high mechanical strength and good wear resistance, and can play a good protective role throughout the entire life cycle of the optical fiber.

[0032] (3) The method for preparing high-temperature carbon-coated optical fiber of the present invention uses the deposition area as the heat source, which has the advantages of less by-products and easier production of long optical fibers compared to traditional cold-wall chemical vapor deposition. Furthermore, the present invention uses carbon film as a heat source, which results in fast heating rate, high heating efficiency and easy control with low energy consumption.

[0033] (4) The method for preparing high-temperature carbon-coated optical fiber of the present invention uses induction heating to cure the thermosetting coating. The thermosetting process is carried out from the inside out, resulting in high curing quality and less bubbling and other problems, which can improve the curing quality of the coating.

[0034] (5) In the high-temperature carbon-coated optical fiber preparation system of the present invention, the induction coil is located outside the corresponding reaction chamber, which can prevent contamination and avoid the problem of excessive carbon film and by-products deposited on the coil due to its internal placement, which affects the induction heating effect. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the preparation method of high-temperature resistant carbon-coated optical fiber according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the fabrication system for high-temperature resistant carbon-coated optical fiber in one embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram illustrating the structure of a high-temperature carbon-coated optical fiber fabrication system according to another embodiment of the present invention.

[0038] Figure 4 This is a schematic diagram of the first carbon coating reaction chamber structure involved in the high-temperature carbon-coated optical fiber preparation system of this invention.

[0039] Figure 5This is a schematic diagram of the second carbon coating reaction chamber structure involved in the high-temperature carbon-coated optical fiber preparation system of this invention.

[0040] Figure 6 This is a schematic diagram of the curing device structure involved in the high-temperature carbon-coated optical fiber preparation system according to an embodiment of the present invention;

[0041] Figure 7 This is a schematic diagram of the high-temperature resistant carbon-coated optical fiber structure prepared in Embodiment 1 of the present invention;

[0042] Figure 8 This is a schematic diagram of the high-temperature resistant carbon-coated optical fiber structure prepared in Example 2 of the present invention.

[0043] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1-first carbon coating reaction chamber, 2-second carbon coating reaction chamber, 3-resin coating cup, 4-curing device, 5-optical fiber heating furnace, 6-drawing furnace, 7-preform;

[0044] 11-First deposition chamber, 12-First sealing chamber; 21-Second deposition chamber, 22-Second sealing chamber, 23-First induction coil; 41-Cure chamber, 42-Second induction coil;

[0045] 10 - Core layer, 20 - Cladding layer, 30 - Carbon coating layer, 40 - Resin coating layer, 50 - Inner resin coating layer, 60 - Outer resin coating layer; Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0047] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0048] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0049] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0050] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0051] like Figure 1 As shown, the method for preparing high-temperature resistant carbon-coated optical fiber according to an embodiment of the present invention includes carbon film deposition and high-temperature resistant coating coating and curing, specifically including the following steps:

[0052] (1) Set up a first carbon coating reaction chamber; after heating the optical fiber, carbon film deposition is performed in the first carbon coating reaction chamber, so that the raw material gas in the first carbon coating reaction chamber forms a first carbon film layer on the surface of the optical fiber.

[0053] The optical fiber of this invention comprises a core layer and a cladding layer disposed on the outside of it. The optical fiber is obtained by heating and drawing a preform in a drawing furnace. In this step, the optical fiber is heated to 800~1100°C using the residual heat of the drawing furnace (approximately 2000°C) or by using a heating device, so that the temperature of the optical fiber entering the first carbon coating reaction chamber is 800~1100°C. After entering the first carbon coating reaction chamber, the raw material gas reacts on the surface of the optical fiber cladding to form a carbon film, which is the first carbon film layer.

[0054] The thickness of the first carbon film layer generated in this step is 20~40nm. In addition, the surface roughness of the first carbon film layer is ≤3nm. The carbon film deposition is uniform, which makes the first carbon film layer have good sealing performance, low stress on the fiber cladding, and thus little impact on the strength of the fiber.

[0055] In a preferred embodiment, the feed gas includes hydrocarbon gases and a protective gas. The hydrocarbon gases include, but are not limited to, benzene, methane, and acetylene, while the protective gas is an inert gas or nitrogen. The hydrocarbon gases and protective gas are mixed in a certain proportion to form the feed gas, which is then introduced into the first carbon coating reaction chamber. The specific proportion and flow rate of the hydrocarbon gases and protective gas depend on the specific process conditions and the designed deposition thickness, etc. The hydrocarbon gas content in the feed gas is preferably between 15% and 75%, the total flow rate of the feed gas (i.e., the feed rate) is preferably between 250 ml / min and 2 L / min, the exhaust velocity needs to be 0.5-1 L / min greater than the feed rate, and the fiber drawing speed is 40-250 m / min.

[0056] In step (1), since the temperature of the optical fiber entering the first carbon coating reaction chamber is 800~1100℃, the reaction temperature of the raw material gas in the first carbon coating reaction chamber is ensured to be 800~1100℃, thus forming a graphite-like amorphous carbon film. The carbon atoms of this carbon film are mainly of sp2 hybrid structure. Three of the four electrons outside the carbon atom form chemical bonds with adjacent atoms in the plane, and the fourth electron forms a weaker bond through van der Waals forces, ultimately forming a dense graphite-like layered structure. The percentage of sp2 bonds in the carbon atoms of the graphite-like layered structure is more than 95%. The layers are connected by van der Waals forces, which can achieve a certain degree of slippage. At the same time, the inner carbon film bonds with the silicon on the cladding surface at high temperature to achieve a tight connection with the cladding. Therefore, the first deposited carbon film can play a sealing role in blocking hydrogen and water. The bonding between the first carbon film layer and the cladding layer comes from the reaction of C and Si at high temperature, which occurs simultaneously with the deposition of the graphite-like carbon layer.

[0057] (2) At least one second carbon coating reaction chamber is provided, and a first induction coil is provided on its outer periphery; the first induction coil is used to heat the optical fiber covered with the first carbon film layer in the corresponding second carbon coating reaction chamber to perform at least one carbon film deposition, so that the raw material gas in the second carbon coating reaction chamber forms a second carbon film layer outside the first carbon film layer.

[0058] The second carbon film deposition of the present invention utilizes the induction electrothermal effect to provide heat for the deposition reaction. Specifically, an induction coil is provided around the corresponding carbon coating reaction chamber. During the preparation process, an alternating current is passed through the coil, and an alternating magnetic field is generated around the induction coil. The first carbon film layer generates an induced potential under the action of the alternating magnetic field, and eddy currents are formed in the carbon film, generating high temperature, which triggers the reaction and deposition of the raw materials around the carbon film to form the second carbon film layer.

[0059] In a preferred embodiment, the feed gas includes hydrocarbon gases and a protective gas. The hydrocarbon gases include, but are not limited to, benzene, methane, acetylene, and other hydrocarbon gases; the protective gas includes inert gases or nitrogen. The hydrocarbon gases and protective gases are mixed in a certain proportion to form the feed gas, which is then introduced into the second carbon coating reaction chamber. The specific proportion and flow rate of the hydrocarbon gases and protective gases depend on the specific process conditions and the designed deposition thickness, etc. The hydrocarbon gas content in the feed gas is preferably between 15% and 75%, the total flow rate of the feed gas (i.e., the feed rate) is preferably between 250 ml / min and 2 L / min, the exhaust velocity needs to be 0.5-1 L / min greater than the feed rate, and the fiber drawing speed is 40-250 m / min.

[0060] In step (2), the second carbon film layer can be a diamond-like amorphous carbon film or a graphite-like amorphous carbon film. A uniform temperature field is obtained by designing the density and diameter of the induction coil. If the temperature of the reaction zone on the surface of the optical fiber in the second carbon coating reaction chamber is controlled to be greater than 1100℃ (preferably 1100~1300℃) by controlling the parameters of the induced current, a diamond-like amorphous carbon film is obtained. The carbon atoms in the film mainly form an SP3 hybrid structure, and the percentage of SP3 bonds in the carbon atoms is more than 95%. The four electrons outside the nucleus of the carbon atom form chemical bonds with the valence electrons of the adjacent atoms, ultimately forming a diamond-like structure. Therefore, it has high hardness and good wear resistance. It can not only protect the sealing effect of the inner carbon film, but also provide a certain protective effect on the optical fiber after the resin coating is damaged, which greatly improves the reliability of the optical fiber in harsh environments.

[0061] In addition, if the temperature of the optical fiber surface reaction zone in the second carbon-coated reaction chamber is controlled to 800~1100℃ by the parameters of the induced current, a new layer of graphite-like amorphous carbon film can be formed on the first layer of graphite-like amorphous carbon film.

[0062] Understandably, because the graphite-like amorphous carbon film is conductive, the alternating current in the induction coil generates an alternating magnetic field, inducing eddy currents and heating within the graphite-like amorphous carbon film. Therefore, it is necessary to first deposit a carbon film (the first carbon film layer). Only with a carbon film on the outside of the optical fiber can the principle of electromagnetic induction be used to generate heat for subsequent deposition.

[0063] It should be noted that a second carbon film layer can be formed by one or multiple depositions on the outer layer of the first carbon film layer as needed, meaning the second carbon film layer includes at least one layer. Furthermore, the second carbon film layer can be a diamond-like amorphous carbon film, or a graphite-like amorphous carbon film, or it can be a combined carbon film layer formed by stacking at least one graphite-like amorphous carbon film and at least one diamond-like amorphous carbon film in the thickness direction. That is, only a diamond-like amorphous carbon film can be coated on the outer layer of the first carbon film layer, or two carbon films with different arrangements can be coated on the outer layer of the first carbon film layer. Comparatively, coating two carbon films with different arrangements on the outer layer of the first carbon film layer, compared to coating only a diamond-like amorphous carbon film, can to some extent avoid the problem of excessively thick diamond-like amorphous carbon film, which would cause high stress and increase the impact on optical fiber strength.

[0064] If the second carbon film formed by the above method is a diamond-like amorphous carbon film, then the thickness of the second carbon film is 20~60nm, and the surface roughness of the second carbon film is ≤3nm. The carbon film deposition is uniform, the carbon film has high hardness, and can withstand high lateral stress.

[0065] If the second carbon film formed by the above method is a graphite-like amorphous carbon film, then the thickness of the second carbon film is 10~30nm, and the surface roughness of the second carbon film is ≤3nm. The carbon film deposition is uniform and has good sealing performance.

[0066] If the second carbon film layer formed by the above method is a composite carbon film layer formed by stacking at least one layer of graphite-like amorphous carbon film and at least one layer of diamond-like amorphous carbon film in the thickness direction, then the thickness of each layer of graphite-like amorphous carbon film is 10~20nm, and the surface roughness is ≤3nm; the thickness of each layer of diamond-like amorphous carbon film is 10~30nm, and the surface roughness is ≤3nm. The total thickness of the composite carbon film layer is ≤150nm. If the composite carbon film layer is too thick, the overall stress of the carbon film layer will be large.

[0067] Preferably, each deposition has a corresponding second carbon coating reaction chamber, and each reaction chamber deposits one layer of carbon film. By setting multiple depositions, on the one hand, the thickness can be easily and quickly controlled as needed by adjusting the current magnitude, etc. The alternating current magnitude affects the magnitude of the eddy current generated inside the carbon film, thereby affecting the temperature. The higher the temperature, the higher the reaction rate, and the thicker the deposition thickness. On the other hand, under the condition of the same total deposition thickness, multiple depositions can also achieve a faster fiber drawing speed (the faster the speed, the thinner the single deposition thickness under the same conditions). Furthermore, better optical fiber performance can be achieved through the design of carbon film structures with different layers. Different amorphous states can be formed in each layer by different temperature control. The heating temperature for forming graphite-like amorphous carbon film is 800~1100℃, and the heating temperature for forming diamond-like amorphous carbon film is >1100℃. Because of the different temperatures, the way atoms arrange themselves during chemical reactions differs (each carbon atom in graphite-like carbon films has three electrons that form covalent bonds with electrons from other carbon atoms, while each carbon atom in diamond-like carbon films has four outer electrons that form covalent bonds with outer electrons from other carbon atoms), thus forming different amorphous states. Graphite-like amorphous carbon films are mainly composed of graphite structures, so their properties are similar to graphite. Diamond-like amorphous carbon films are mainly composed of diamond structures, so their properties are relatively close to those of diamond, thus enabling different functional orientations.

[0068] For example, a two-layer structure with an inner graphite-like layer and an outer diamond-like carbon film can achieve both good sealing performance and ensure the mechanical properties of the carbon film; while a continuous multi-layer structure of graphite-like + diamond-like + graphite-like + diamond-like can maintain the ductility of the carbon film while increasing the sealing performance and mechanical properties of the carbon film layer.

[0069] In addition, graphite-like amorphous carbon films have better heating effects, while diamond-like amorphous carbon films have poorer conductivity and poorer inductive heating effects compared to graphite-like amorphous carbon films. Therefore, when a diamond-like carbon film is redeposited on top of a diamond-like carbon film, the heating is mainly achieved through the first-deposited graphite-like amorphous carbon film.

[0070] (3) A curing device is set up, and a second induction coil is provided on its outer periphery; a thermosetting coating is coated on the surface of the second carbon film layer, and the thermosetting coating is thermosetting from the inside to the outside in the curing device through the second induction coil, and at least one coating and curing process of the thermosetting coating is performed to obtain the high temperature resistant carbon coated optical fiber;

[0071] In a preferred embodiment, a uniform temperature field is obtained by designing the density and diameter of the second induction coil, and the curing temperature of the coating in the curing device is controlled to be 80~350℃ by controlling the parameters of the induced current, thereby obtaining a resin coating layer.

[0072] The thermosetting coating is a high-temperature resistant thermosetting resin, including but not limited to polyimide resin and acrylic resin. In a preferred embodiment, the thermosetting coating is applied by dipping a coating cup, and the curing device is preferably a glass cavity. An optical fiber coated with a carbon coating passes through a coating cup containing polyimide and enters the glass cavity. The thermosetting coating is cured in a protective gas atmosphere (inert gas or nitrogen). A second induction coil, coaxial with the outer periphery of the glass cavity, is provided. During the curing process, an alternating current is passed through the coil, generating an alternating magnetic field around the coil. Under the action of the alternating magnetic field, the carbon film (mainly a graphite-like amorphous carbon film) generates an induced potential, forming eddy currents in the carbon film and generating high temperatures, thus initiating the curing of the polyimide surrounding the carbon film.

[0073] This invention utilizes induction heating to cure thermosetting coatings. The thermosetting process proceeds from the inside out, resulting in high-quality curing and minimizing issues such as bubbling, thus improving coating curing quality. Induction heating curing offers precise temperature control, rapid heating, and uniform heating, and allows for the convenient and rational setting of different curing processes, thereby increasing the stringing speed of the thermosetting coating.

[0074] It should be noted that the coating and curing process of the thermosetting coating can be repeated multiple times in this step to achieve a suitable coating thickness.

[0075] It should be noted that the resin coating can also be cured by heating in a conventional heating furnace in this embodiment.

[0076] The carbon-coated optical fibers prepared by the above method, after being kept in a hydrogen environment at 85°C and 11 atm for 7 days, exhibit an additional attenuation of <0.2 dB / km at a wavelength of 1240 nm for single-mode carbon-coated optical fibers and <0.2 dB / km at a wavelength of 850 nm for multimode carbon-coated optical fibers.

[0077] The method for preparing high-temperature carbon-coated optical fiber of the present invention first involves drawing a preform into an optical fiber, then depositing a carbon film on the cladding surface of the optical fiber using conventional cold-wall chemical vapor deposition (CVD). On this basis, one or more layers of carbon film are deposited using induction heating, which activates the deposition reaction. Finally, a thermosetting coating is applied and thermoset using induction heating, with the carbon film directly serving as the heat source for subsequent deposition or curing. This invention solves the problem that traditional cold-wall CVD cannot preheat optical fibers with a carbon film deposited on them. The heat source in this invention is the deposition area, which has the advantages of fewer byproducts and easier production of long optical fibers compared to traditional cold-wall CVD. Furthermore, this invention utilizes the carbon film as a heat source, resulting in rapid heating, high heating efficiency, and easy control with low energy consumption.

[0078] The high-temperature resistant carbon-coated optical fiber prepared by the method of the present invention has amorphous carbon films deposited first and later, but with slight differences in structural composition. The inner layer is mainly a graphite-like amorphous carbon film, which forms SI-C bonds with the optical fiber, resulting in a tight bond and good sealing effect. At the same time, the SI-C bonds make the structure of the optical fiber to the carbon layer a gradual transition. The outer layer is mainly a diamond-like amorphous carbon film, which has a dense structure and high mechanical strength. It can protect the sealing effect of the graphite-like amorphous carbon film and has a certain degree of wear resistance, providing good protection throughout the entire life cycle of the optical fiber.

[0079] Furthermore, such as Figures 2 to 5 As shown in the figure, this embodiment of the invention also provides a high-temperature resistant carbon-coated optical fiber fabrication system, comprising a drawing furnace, a first carbon coating reaction chamber, at least one second carbon coating reaction chamber, and at least one set of resin coating and curing devices arranged sequentially. The resin coating and curing devices include a resin coating device and a curing device.

[0080] In the first embodiment of the invention, as Figure 2 As shown, the high-temperature carbon-coated optical fiber preparation system of this embodiment includes a drawing furnace 6, an optical fiber heating furnace 5, a first carbon coating reaction chamber 1, a second carbon coating reaction chamber 2, a resin coating cup 3, and a curing device 4 arranged in sequence.

[0081] The first carbon coating reaction chamber 1 is the reaction chamber for forming the first carbon film layer. The first carbon coating reaction chamber 1 is preferably a glass cylindrical structure, including a first deposition chamber 11 and a first sealing chamber 12, wherein the first sealing chamber 12 is located at both axial ends of the first deposition chamber 11. The first sealing chamber 12 is provided with a protective gas inlet. During the reaction process, a protective gas (inert gas or nitrogen) is continuously introduced through the corresponding protective gas inlet to prevent air from entering the first deposition chamber 11, achieving the purpose of gas sealing. Preferably, the inner diameter of the first carbon coating reaction chamber 1 is 20-40 mm, and its length is 300-400 mm. The inner diameter of the first sealing chamber 12 is the same as that of the first deposition chamber 11, and the length of the first sealing chamber 12 is preferably 20-40 mm. The first deposition chamber 11 has corresponding optical fiber through holes at both axial ends for optical fiber entry and exit, and the diameter of the optical fiber through holes is preferably 5-15 mm.

[0082] The first deposition chamber 11 is provided with a raw material gas inlet and a raw material gas outlet. Preferably, the raw material gas inlet is located at the end of the first deposition chamber 11 near the optical fiber inlet, and the raw material gas outlet is located at the end of the first deposition chamber 11 near the optical fiber outlet. In the first deposition chamber 11, the raw material gas enters the chamber through the raw material gas inlet, and then decomposes at high temperature to generate a carbon film that is deposited on the optical fiber. Finally, other products are discharged through the raw material gas outlet.

[0083] The first carbon coating reaction chamber 1 is located near the drawing furnace 6 and can use the residual heat to heat the optical fiber. Therefore, the present invention can use the residual heat of the optical fiber to carry out the reaction in the first carbon coating reaction chamber 1 to form the first carbon film layer. Preferably, an optical fiber heating device (optical fiber heating furnace 5) is provided in the optical fiber moving path between the drawing furnace 6 and the first carbon coating reaction chamber 1. Therefore, the residual heat of the drawing furnace 6 can be used for heating, and the optical fiber heating furnace 5 can be used for heating to provide heat for the deposition reaction and control the temperature of the bare optical fiber.

[0084] The second carbon coating reaction chamber 2 is the reaction chamber for forming the second carbon film layer. The second carbon coating reaction chamber 2 is preferably a glass cylindrical structure, including a second deposition chamber 21 and a second sealing chamber 22, wherein the second sealing chamber 22 is located at both axial ends of the second deposition chamber 21. The second deposition chamber 21 is provided with a protective gas inlet. During the reaction process, a protective gas (inert gas or nitrogen) is continuously introduced through the corresponding protective gas inlet to prevent air from entering the second deposition chamber 21, achieving the purpose of gas sealing. A first induction coil 23, coaxial with the second deposition chamber 21, is provided on its outer periphery. Compared to the first carbon coating reaction chamber 1, the second carbon coating reaction chamber 2 has an additional induction coil around its reaction area. The induction coil is coaxial with the reaction chamber, and an alternating current is connected to its end, providing heat for the deposition reaction through the induced electrothermal effect.

[0085] Preferably, the inner diameter of the second carbon coating reaction chamber 2 is 20-40 mm, and the length is 300-400 mm. The inner diameter of the second sealing chamber 22 is the same as that of the second deposition chamber 21, and the length of the second sealing chamber 22 is preferably 20-40 mm. The second deposition chamber 21 has corresponding optical fiber through holes at both ends of its axial direction for optical fiber entry and exit, and the diameter of the optical fiber through holes is preferably 5-15 mm.

[0086] Preferably, the inner diameter of the first induction coil 23 (referring to the radial distance of the induction coil outside the carbon-coated reaction chamber) is 50mm to 70mm, the diameter of the first induction coil 23 (referring to the diameter of the wire used) is preferably 1mm to 4mm, and the interval between each turn of the induction coil is approximately twice the diameter, preferably between 2mm and 8mm. The temperature of the reaction zone depends on the thickness of the first deposited carbon film, as well as multiple factors such as coil specifications and alternating current.

[0087] The resin coating cup 3 is preferably a coating cup containing polyimide, and the coating is completed when the optical fiber passes through the middle. The resin coating device of the present invention adopts existing technology, as long as it can achieve resin coating.

[0088] The curing device 4 is a resin curing device. The main structure of the curing device is a curing chamber 41, preferably a glass tube. The curing chamber 41 is open at both axial ends, and an exhaust port is located near the axial end of the curing chamber 41. The exhaust port is connected to an exhaust device. A second induction coil 42, coaxial with the curing chamber 41, is located around the periphery of the curing chamber 41. After the resin-coated optical fiber enters the curing device, an alternating current is passed through the induction coil. The heat induced in the carbon film (mainly a graphite-like amorphous carbon film) heats and cures the coating. The waste gas generated during curing (such as solvents volatilized during the polyimide curing process) is discharged from the exhaust port. The inner diameter of the curing device 4 chamber is preferably 100-200 mm, and the length is preferably 500-1500 mm.

[0089] Preferably, the inner diameter of the second induction coil 42 (referring to the radial distance of the induction coil outside the curing device) is 130~230mm, which needs to be slightly larger than the outer diameter of the curing device to ensure the heating effect. The diameter of the second induction coil 42 (referring to the diameter of the wire used) is preferably 1mm~4mm. The spacing of the second induction coils 42 gradually decreases from top to bottom (from the fiber optic inlet end to the fiber optic outlet end of the curing device), from 50mm to 10mm. The gradual reduction in spacing is to make the temperature inside the curing device cavity relatively uniform. Because the heat inside the curing cavity will rise, if the coil spacing is uniformly set, the temperature at the top of the curing tube will be significantly higher than that at the bottom. Excessive temperature will cause the polyimide solvent to boil, resulting in bubbles in the high-temperature resistant coating. Excessive temperature will not achieve a good curing effect.

[0090] In addition, the first induction coil surrounding the second carbon coating reaction chamber 2 and the second induction coil surrounding the curing device 4 are located outside the corresponding reaction chambers, which can prevent contamination and avoid the problem of excessive carbon film and by-products depositing on the coils due to their internal placement, thus affecting the induction heating effect.

[0091] In a second embodiment of the invention, as Figure 3 As shown, the high-temperature carbon-coated optical fiber fabrication system of this embodiment includes a drawing furnace 6, an optical fiber heating furnace 5, a first carbon coating reaction chamber 1, two second carbon coating reaction chambers 2, a resin coating cup 3, and a curing device 4 arranged sequentially. The difference between this embodiment and the first embodiment is the inclusion of two second carbon coating reaction chambers 2.

[0092] It is understood that the appendix to this invention... Figure 2 and 3 The high-temperature carbon-coated optical fiber fabrication system shown includes one second carbon coating reaction chamber 2 and two second carbon coating reaction chambers 2, respectively, which are used for one and two induction coil heating carbon film depositions. When multiple carbon film depositions are required, the number of second carbon coating reaction chambers 2 can be increased accordingly based on the number of carbon film depositions.

[0093] Furthermore, this embodiment of the invention also provides a high-temperature resistant carbon-coated optical fiber prepared by the above-described method, comprising a core layer, a cladding layer, a carbon coating layer, and a resin coating layer arranged sequentially from the inside out. The deposition process of the carbon coating layer is a cold-wall chemical vapor deposition method, formed by multiple depositions of nanoscale carbon films; the inner layer of the carbon coating layer is a first carbon coating layer, and the outer layer is a second carbon coating layer. The first carbon film layer is a graphite-like amorphous carbon film; the second carbon film layer is a diamond-like amorphous carbon film, or, alternatively, a graphite-like amorphous carbon film, or a combined carbon film layer formed by stacking at least one layer of graphite-like amorphous carbon film and at least one layer of diamond-like amorphous carbon film in the thickness direction. The resin coating layer is a thermosetting coating layer, preferably polyimide, formed by one or more coating and curing processes using a thermosetting coating.

[0094] The thickness of the first carbon film layer is preferably 20-40 nm. If the first carbon film layer is too thin, no current can be induced subsequently, resulting in low efficiency of subsequent carbon film deposition or thermosetting coating curing. If the first carbon film layer is too thick, the stress in the first carbon film layer will be too high. A further preferred thickness is 30-40 nm. The surface roughness of the first carbon film layer is ≤3 nm, ensuring uniform carbon film deposition, resulting in good sealing of the first carbon film layer, low stress on the optical fiber cladding, and thus minimal impact on the strength of the optical fiber.

[0095] If the second carbon film is only a diamond-like carbon film, its thickness is 20-60 nm, and its surface roughness is ≤3 nm. The carbon film deposition is uniform, and its hardness is high, allowing it to withstand high lateral stress. If the second carbon film is too thin, its mechanical protection is poor; if it is too thick, the stress within the second carbon film is high. The second carbon film should have a surface roughness ≤3 nm, uniform deposition, and high hardness to withstand high lateral stress.

[0096] The second carbon film layer is a composite carbon film layer formed by stacking at least one layer of graphite-like amorphous carbon film and at least one layer of diamond-like amorphous carbon film in the thickness direction. The thickness of each graphite-like amorphous carbon film layer is preferably 10-20 nm, with a surface roughness ≤3 nm; the thickness of each diamond-like amorphous carbon film layer is 10-30 nm, with a surface roughness ≤3 nm. The total thickness of the composite carbon film layer is ≤150 nm. If the composite carbon film layer is too thick, the overall stress of the carbon film layer will be too high.

[0097] The carbon-coated optical fiber of this invention includes carbon-coated single-mode optical fiber and carbon-coated multimode optical fiber. After being placed in a hydrogen environment at 85°C and 11 atm for 7 days, the carbon-coated single-mode optical fiber has an additional attenuation of <0.2dB / km at a wavelength of 1240nm, and the carbon-coated multimode optical fiber has an additional attenuation of <0.2dB / km at a wavelength of 850nm.

[0098] This invention provides a high-temperature resistant carbon-coated optical fiber and its preparation system and method. The prepared optical fiber carbon film has a multi-layer structure. The inner layer is mainly composed of a graphite-like amorphous carbon film, which is preheated to provide the heat required for the reaction. The outer layer is mainly composed of a diamond-like amorphous carbon film. The preparation method involves adding an induction coil around the reaction area of ​​the carbon coating reaction chamber. The deposited carbon film is used as a heating element, and induction heating is used to provide heat for the subsequent deposition reaction to generate a diamond-like amorphous carbon film (or a combination of graphite-like amorphous carbon film and diamond-like amorphous carbon film). Finally, the temperature of the curing area is controlled by an improved multi-level coil design to cure the thermosetting coating, thus preparing the high-temperature resistant carbon-coated optical fiber.

[0099] To better understand the preparation method, preparation system, and product of the present invention, the following embodiments are provided:

[0100] If the temperature of the optical fiber surface reaction zone in the second carbon-coated reaction chamber is controlled to be 800~1100℃ by the parameters of the induced current, a new layer of graphite-like amorphous carbon film can be formed on the first layer of graphite-like amorphous carbon film.

[0101] By controlling the temperature of the optical fiber surface reaction zone within the second carbon-coated reaction chamber to be greater than 1100℃ (preferably 1100~1300℃) using parameters of the induced current, a diamond-like amorphous carbon film is obtained.

[0102] The optical fiber is heated by utilizing the residual heat of the drawing furnace (approximately 2000℃) or by using a heating device to heat the optical fiber to 800~1100℃, so that the temperature of the optical fiber entering the first carbon coating reaction chamber is 800~1100℃.

[0103] Example 1

[0104] This embodiment utilizes Figure 2 The high-temperature resistant carbon-coated optical fiber fabrication system shown above produces high-temperature resistant carbon-coated optical fibers, as follows: Figure 7As shown. In this embodiment, the core layer 10 is a G652D single-mode optical fiber with a diameter of 9 μm, and the cladding 20 has a diameter of 125 μm. The raw material gas in both reaction chambers is a mixture of acetylene and helium, with an acetylene concentration of 10%~30%. The total flow rate of the raw material gas in both carbon-coated reaction chambers (i.e., the mixed gas feed rate) is 0.5-1 L / min, and the exhaust rate must be 0.5-1 L / min higher than the feed rate to maintain stable airflow within the chambers. The fiber drawing speed is 40~80 m / min. The optical fiber is heated to 900~1000℃ using a heating device before entering the first carbon-coated reaction chamber. The temperature of the reaction zone on the surface of the optical fiber in the first carbon-coated reaction chamber is maintained at 900~1000℃, thereby forming a graphite-like amorphous carbon film on the cladding. The induction coil used in the second carbon coating reaction chamber 2 has a rated output power of 2kW, an alternating current frequency of 18kHz, and a rated input current of 3A, resulting in a reaction zone temperature on the fiber surface within the second carbon coating reaction chamber exceeding 1100℃. This forms a diamond-like amorphous carbon film on the first graphite-like amorphous carbon film. The graphite-like amorphous carbon film deposited in the first carbon coating reaction chamber 1 has a thickness of 20~40nm, while the diamond-like amorphous carbon film deposited in the second carbon coating reaction chamber 2 has a thickness of 30~50nm. After passing through the first and second carbon coating reaction chambers, a carbon coating layer 30 is formed. Subsequently, the fiber is coated with polyimide paint and then enters a curing device. The curing temperature of the polyimide paint in the curing device is controlled to be 80~350℃ by the parameters of the induction coil current, thereby forming a resin coating layer 40 on the surface of the carbon coating layer 30. The resin coating layer has a thickness of 15μm.

[0105] The carbon-coated polyimide single-mode fiber prepared in this embodiment exhibits an attenuation of 0.462 dB / km at 1310 nm and 0.295 dB / km at 1550 nm. Its tensile strength (F15%) is 3.53 GPa, (F50%) is 3.56 GPa, and its nd value is 105. Under a hydrogen atmosphere of 85°C and 11 atm for 7 days, the additional attenuation at 1240 nm is <0.2 dB / km. The carbon-coated fiber obtained in this embodiment demonstrates excellent hydrogen loss resistance, high mechanical strength, and good consistency.

[0106] Example 2

[0107] This embodiment adopts Figure 3 The high-temperature resistant carbon-coated optical fiber fabrication system shown above produces high-temperature resistant carbon-coated optical fibers, as follows: Figure 8As shown. In this embodiment, the core layer 10 is a GI50 multimode optical fiber with a diameter of 50 μm, and the cladding 20 has a diameter of 125 μm. The raw material gas in the three reaction chambers is a mixture of acetylene and nitrogen, with an acetylene concentration of 30%~50%. The feed rate of the mixed gas in the three reaction chambers is 0.5-1 L / min, and the exhaust rate needs to be 0.5-1 L / min higher than the feed rate to maintain stable airflow within the chambers. The drawing speed is 80~150 m / min. The optical fiber is heated to 900~1000℃ using a heating device before entering the first carbon coating reaction chamber 1. The temperature of the reaction zone on the surface of the optical fiber in the first carbon coating reaction chamber is maintained at 900~1000℃, thereby forming a graphite-like amorphous carbon film on the cladding. The first carbon-coated reaction chamber 2 has an induction coil with a rated output power of 2kW, an alternating current frequency of 18Hz, and a rated input current of 3A. This results in a reaction zone temperature of 900~1000℃ on the fiber surface within the second carbon-coated reaction chamber 2, thereby forming another layer of graphite-like amorphous carbon film on the first layer of graphite-like amorphous carbon film. The second carbon-coated reaction chamber 2 uses an induction coil with a rated output power of 3kW, an alternating current frequency of 18Hz, and a rated input current of 3A. This results in a reaction zone temperature greater than 1100℃ on the fiber surface within the second carbon-coated reaction chamber 2, thereby forming a diamond-like amorphous carbon film on this second layer of graphite-like amorphous carbon film. The graphite-like amorphous carbon film deposited in the first carbon-coated reaction chamber 1 has a thickness of 20~40nm, the graphite-like amorphous carbon film deposited in the first carbon-coated reaction chamber 2 has a thickness of 20~30nm, and the diamond-like amorphous carbon film deposited in the second carbon-coated reaction chamber 2 has a thickness of 30~50nm. After passing through the first carbon coating reaction chamber 1 and two second carbon coating reaction chambers 2, a carbon coating layer 30 is formed. After the carbon film is deposited, the optical fiber is coated with a thermosetting high-temperature resistant polyester coating for the first time and then enters the first curing device. The curing temperature of the polyester coating in the first curing device is controlled at 200~350℃ by the parameter of the induction coil current, thereby forming a resin inner coating layer 50 on the surface of the carbon coating layer 30. Then, the optical fiber is coated with a thermosetting high-temperature resistant polyester coating for the second time and then enters the second curing device. The curing temperature of the polyester coating in the second curing device is controlled at 200~350℃ by the parameter of the induction coil current, thereby forming a resin outer coating layer 60 on the surface of the resin inner coating layer 50.

[0108] The carbon-coated high-temperature resistant multimode fiber prepared in this embodiment exhibits an attenuation of 2.46 dB / km at 850 nm and 0.68 dB / km at 1300 nm; its F15% tensile strength is 3.45 GPa; its F50% tensile strength is 3.53 GPa; its nd value is 135; and after being stored in a hydrogen atmosphere at 85°C and 11 atm for 7 days, the additional attenuation at 850 nm is <0.2 dB / km. The carbon-coated fiber obtained in this embodiment demonstrates excellent hydrogen loss resistance, high mechanical strength, and good consistency.

[0109] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. A high-temperature resistant carbon-coated optical fiber, characterized in that, It includes a core layer, a cladding layer, a carbon coating layer, and a resin coating layer arranged sequentially from the inside out; The carbon coating layer includes a first carbon film layer and a second carbon film layer; the second carbon film layer is formed by induction heating. The first carbon film layer is a graphite-like amorphous carbon film; the percentage of sp2 bonds in the carbon atoms of the first carbon film layer is over 95%, three of the four electrons outside the carbon atom form chemical bonds with adjacent atoms in the plane, and the fourth electron forms a weaker bond through van der Waals forces, forming a graphite-like layered structure. The layers are connected by van der Waals forces, which can achieve slip; and the first carbon film layer forms SI-C bonds with the cladding layer, thus making the structure from the cladding layer to the carbon layer a gradual transition. The second carbon film layer is a diamond-like amorphous carbon film, or a graphite-like amorphous carbon film, or the second carbon film layer is a combined carbon film layer formed by stacking at least one graphite-like amorphous carbon film and at least one diamond-like amorphous carbon film in the thickness direction; the percentage of sp3 bonds in the carbon atoms of the diamond-like amorphous carbon film is more than 95%, and the four electrons outside the nucleus of the carbon atom form chemical bonds with the valence electrons of the adjacent atoms to form a diamond-like structure.

2. The high-temperature resistant carbon-coated optical fiber as described in claim 1, characterized in that, The carbon-coated optical fiber includes carbon-coated single-mode optical fiber and carbon-coated multimode optical fiber. After being placed in a hydrogen environment at 85°C and 11 atm for 7 days, the carbon-coated single-mode optical fiber has an additional attenuation of <0.2dB / km at a wavelength of 1240nm, and the carbon-coated multimode optical fiber has an additional attenuation of <0.2dB / km at a wavelength of 850nm.

3. A method for preparing high-temperature resistant carbon-coated optical fiber, characterized in that, Includes the following steps: S1, after heating the optical fiber, place it in the first carbon coating reaction chamber for carbon film deposition, so that a first carbon film layer is formed on the surface of the optical fiber. The first carbon film layer is a graphite-like amorphous carbon film. The temperature of the optical fiber entering the first carbon coating reaction chamber is controlled to be 800~1100℃, so that the first carbon film layer is a graphite-like amorphous carbon film. In the first carbon film layer, the percentage of sp2 bonds in the carbon atoms is over 95%. Three of the four electrons outside the carbon atom's nucleus form chemical bonds with adjacent atoms in the plane, while the fourth electron forms a weaker bond through van der Waals forces, forming a graphite-like layered structure. The layers are connected by van der Waals forces, enabling slip. Furthermore, the first carbon film layer and the cladding layer form SI-C bonds, resulting in a gradual transition from the cladding layer to the carbon layer. S2, the optical fiber with the first carbon film layer deposited on its surface is placed in the second carbon coating reaction chamber for carbon film deposition, so that a second carbon film layer is formed on the surface of the optical fiber. The second carbon film layer is a graphite-like amorphous carbon film or a diamond-like amorphous carbon film, or the second carbon film layer is a combined carbon film layer formed by stacking at least one graphite-like amorphous carbon film and at least one diamond-like amorphous carbon film in the thickness direction. The second carbon-coated reaction chamber has a first induction coil on its outer periphery, which controls the temperature of the optical fiber surface reaction zone inside the second carbon-coated reaction chamber. The temperature of the optical fiber entering the second carbon coating reaction chamber is controlled to be 800~1100℃, so that the second carbon film layer is a graphite-like amorphous carbon film; or, the temperature of the optical fiber entering the second carbon coating reaction chamber is controlled to be greater than 1100℃, so that the second carbon film layer is a diamond-like amorphous carbon film. The percentage of sp3 bonds in the carbon atoms of the diamond-like amorphous carbon film is over 95%, and all four electrons outside the nucleus of the carbon atom form chemical bonds with the valence electrons of the adjacent atoms, forming a diamond-like structure. S3, after coating the surface of the optical fiber with the second carbon film layer with a thermosetting coating, the fiber is placed in a curing device for thermosetting, thereby obtaining a high-temperature resistant carbon-coated optical fiber; Both the first carbon coating reaction chamber and the second carbon coating reaction chamber include a deposition chamber and a sealing chamber located at both ends of the deposition chamber along its axial direction. The sealing chamber is provided with a protective gas inlet, through which protective gas is continuously introduced during the reaction process.

4. The method for preparing high-temperature resistant carbon-coated optical fiber as described in claim 3, characterized in that, The curing device is equipped with a second induction coil on its outer periphery, which controls the curing temperature of the thermosetting coating inside the curing device.

5. The method for preparing high-temperature resistant carbon-coated optical fiber as described in claim 3 or 4, characterized in that, The raw material gases in the first carbon coating reaction chamber and the second carbon coating reaction chamber include hydrocarbon gases and protective gases, with hydrocarbon gases accounting for 15% to 75% of the raw material gases; the feed rate of the raw material gases is 250 ml / min to 2 L / min, the exhaust rate is 0.5-1 L / min higher than the feed rate, and the wire drawing speed is 40 to 250 m / min.

6. The method for preparing high-temperature resistant carbon-coated optical fiber as described in claim 4, characterized in that, In step S3, the spacing between each turn of the second induction coil gradually decreases from the fiber optic inlet end to the fiber optic outlet end of the curing device.

7. A system for preparing high-temperature resistant carbon-coated optical fibers, applied to the method for preparing high-temperature resistant carbon-coated optical fibers according to any one of claims 3-6, characterized in that, It includes a wire drawing furnace, a first carbon coating reaction chamber, at least one second carbon coating reaction chamber, and at least one set of resin coating and curing devices arranged sequentially; wherein, The drawing furnace is used to heat and draw optical fiber preforms to obtain optical fibers; at the same time, it can use the residual heat to heat the optical fibers. The first carbon coating reaction chamber is the reaction chamber for forming the first carbon film layer; The second carbon coating reaction chamber is a reaction chamber for forming the second carbon film layer, and a first induction coil is provided on its outer periphery; The resin coating and curing apparatus includes a resin coating device and a curing device; the resin coating device is used to coat a thermosetting coating; the curing device is used to cure the thermosetting coating.

8. The fabrication system for high-temperature resistant carbon-coated optical fiber according to claim 7, characterized in that, The curing device is equipped with a second induction coil on its outer periphery.

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