High temperature-resistant carbon-coated optical fiber, preparation method therefor, and preparation system thereof

Abstract

Disclosed is a high temperature-resistant carbon-coated optical fiber, characterized in that said optical fiber comprises a core layer, a cladding layer, a carbon coating layer, and a resin coating layer which are sequentially arranged from the inside to the outside; the carbon coating layer comprises 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 the second carbon film layer is a composite 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. Also disclosed are a corresponding preparation method and system, which solve the problem that optical fiber on which a layer of carbon film has been deposited cannot be preheated during traditional cold-wall chemical vapor deposition. The graphite-like amorphous carbon film deposited on the inner layer of the optical fiber of the present invention can be tightly bonded to the optical fiber and has good sealing performance, while the diamond-like amorphous carbon film deposited on the outer layer has high mechanical strength and good wear resistance, which can provide good protection for the optical fiber.

Description

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

[0001] The present invention belongs to the technical field of optical fiber manufacturing, and in particular relates to a high-temperature resistant carbon-coated optical fiber and a preparation method and a preparation system thereof. Background Art

[0002] Carbon-coated optical fiber, also known as carbon-sealed optical fiber or carbon-coated optical fiber, has a thin layer of carbon film on the surface of the glass fiber. This film provides 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, and 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 isolate water molecules or smaller hydrogen molecules from diffusing. Water molecules can accelerate crack propagation on the glass fiber surface, and hydrogen molecules invading the core layer can cause a significant increase in optical loss. Carbon-coated optical fiber can effectively solve these problems.

[0003] The preparation of carbon-coated optical fiber requires the deposition of a carbon film several tens of nanometers thick on the cladding surface before applying conventional optical fiber coatings. This carbon film is prepared using vapor deposition, where carbon and other elements are deposited on the surface of the bare optical fiber to form an amorphous carbon film. Based on the principle of deposition, these methods can be categorized as physical vapor deposition (PVD) and chemical vapor deposition (CVD). Common methods include magnetron sputtering, plasma-enhanced chemical vapor deposition, and thermal chemical vapor deposition. Currently, the mainstream carbon film deposition method is thermal chemical vapor deposition, which utilizes a heat source to cause gaseous raw material molecules to undergo a chemical reaction in the gas phase or at the gas-solid interface, thereby depositing the carbon film on the bare optical fiber.

[0004] During the deposition of carbon films, heat for the activation reaction is generally provided in two ways: one is to introduce hydrocarbons or other raw gas into the reaction chamber to heat the reaction chamber, causing the raw gas to undergo a thermal decomposition reaction 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. The carbon film is deposited on the surface of the optical fiber cladding as well as on the reaction chamber wall. After the reaction has been carried out for a period of time, accumulation is likely to occur, affecting the continuation of the reaction.

[0005] The other method is to introduce raw gas into the reaction chamber without heating the chamber. Instead, the optical fiber is heated by preheating or directional heating, so that the gas is first adsorbed on the surface of the optical fiber and then undergoes a pyrolysis reaction. This method is called cold-wall chemical vapor deposition. Cold-wall chemical vapor deposition only reacts on the surface of the optical fiber cladding, with few by-products. In theory, it is easy to produce long sections of carbon-coated optical fiber with high-quality carbon film. However, during cold-wall chemical vapor deposition, the temperature of the preheated optical fiber drops rapidly, making it difficult to control the reaction temperature. At the same time, since the carbon film will oxidize after heating, this deposition method can only produce a single layer of carbon film, resulting in a single carbon film structure. Therefore, the carbon-coated optical fiber formed has poor resistance to mechanical damage and cannot meet the needs of use in harsh environments of special applications. Summary of the Invention

[0006] In response to one or more of the above-mentioned defects or improvement needs in the prior art, the present invention provides a method, system and product for preparing high-temperature resistant carbon-coated optical fibers, which solves the problem that traditional cold-wall chemical vapor deposition cannot preheat an optical fiber with a layer of carbon film deposited thereon. In addition, the graphite-like amorphous carbon film deposited on the inner layer of the optical fiber can be tightly bonded to the optical fiber and has good sealing properties. The diamond-like amorphous carbon film deposited on the outer layer has high mechanical strength and good wear resistance, and can play a good protective role throughout the entire life cycle of the optical fiber.

[0007] To achieve the above object, according to a first aspect of the present invention, there is provided a high temperature resistant carbon coated optical fiber comprising a core layer, a cladding layer, a carbon coating layer and a resin coating layer arranged in sequence 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 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.

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

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

[0013] S1, heating the optical fiber and placing it in a first carbon coating reaction chamber to deposit a carbon film, so that a first carbon film layer is formed on the surface of the optical fiber, wherein the first carbon film layer is a graphite-like amorphous carbon film;

[0014] S2, placing the optical fiber with the first carbon film layer deposited on the surface in a second carbon coating reaction chamber to perform carbon film deposition, so that a second carbon film layer is formed on the surface of the optical fiber, wherein 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 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 a thickness direction;

[0015] Wherein, a first induction coil is provided on the periphery of the second carbon-coated reaction chamber, and the temperature of the optical fiber surface reaction zone in the second carbon-coated reaction chamber is controlled by the first induction coil;

[0016] S3, coating the surface of the optical fiber deposited with the second carbon film layer with a heat-curing coating and placing it in a curing device for heat curing, thereby obtaining 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 periphery of the curing device, and the curing temperature of the heat-curing 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° C., 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° C., so that the second carbon film layer is 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 gas of the first carbon-coated reaction chamber and the second carbon-coated reaction chamber includes hydrocarbon gas and protective gas, and the proportion of hydrocarbon gas in the raw gas is 15%~75%; the feed rate of the raw gas is 250ml / min~2L / min, the exhaust rate is 0.5-1L / min higher than the feed rate, and the drawing speed is 40~250m / 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 optical fiber inlet end to the optical fiber outlet end of the curing device.

[0023] According to a third aspect of the present invention, a system for preparing a high-temperature resistant carbon-coated optical fiber is provided, which is applied to the method for preparing a high-temperature resistant carbon-coated optical fiber, 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 curing devices arranged in sequence; wherein,

[0024] The drawing furnace is used to heat the optical fiber preform and draw it to obtain an optical fiber; at the same time, the residual heat can be used to heat the optical fiber;

[0025] The first carbon coating reaction chamber is a 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 the periphery of the reaction chamber;

[0027] The resin coating and curing device comprises a resin coating device and a curing device; the resin coating device is used for coating a heat-curing coating; and the curing device is used for curing the heat-curing coating.

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

[0029] In general, the above technical solutions conceived by the present 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 carbon coating layer of a multi-layer composite structure, in which the carbon layers and the carbon layers and the cladding are tightly bonded. The innermost graphite-like amorphous carbon film is mainly composed of a relatively high content of SP2 bonds, which has good sealing and ductility, can reduce the corrosion effect of hydrogen and water vapor on the optical fiber, and can prevent the expansion of microcracks on the cladding surface, thereby 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 compound bond makes the carbon film have a relatively high hardness and good mechanical strength, which can improve the ability of the optical fiber cladding and the graphite-like amorphous carbon film to resist mechanical damage, and can significantly improve the service life of the high-temperature resistant carbon-coated optical fiber in harsh high-temperature environments.

[0031] (2) The preparation method of the high-temperature resistant carbon-coated optical fiber of the present invention first draws the preform into an optical fiber, then deposits a carbon film on the surface of the optical fiber cladding by conventional cold-wall chemical vapor deposition, and then deposits one or more carbon films by induction heating. The deposition reaction is activated by induction heating, and finally a heat-curing coating is applied and thermally cured by induction heating. The carbon film is directly used as a heat source for subsequent deposition or curing, thus solving the problem that conventional cold-wall chemical vapor deposition cannot preheat an optical fiber with a layer of carbon film deposited on it. The inner layer of the carbon coating is mainly a graphite-like amorphous carbon film, which forms an SI-C bond with the optical fiber, forming a tight bond with good sealing. At the same time, the SI-C bond makes 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 life cycle of the optical fiber.

[0032] (3) The method for preparing high-temperature resistant carbon-coated optical fiber of the present invention uses the deposition area as the heat source, which has the advantages of fewer by-products than traditional cold-wall chemical vapor deposition and can easily produce long optical fiber segments. Furthermore, the present invention utilizes a carbon film as the heat source, resulting in a fast heating rate, high heating efficiency, and easy control while consuming little energy.

[0033] (4) The preparation method of the high-temperature resistant carbon-coated optical fiber of the present invention cures the heat-curing coating by induction heating. The heat curing process is carried out from the inside out, with high curing quality, and is not prone to problems such as bubbling, which can improve the coating curing quality.

[0034] (5) In the preparation system of the high-temperature resistant carbon-coated optical fiber of the present invention, the induction coil is located outside the corresponding reaction chamber, which can prevent contamination and avoid the problem of a large amount of carbon film and by-products being deposited on the coil due to being set inside, thereby affecting the induction heating effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a flow chart of a method for preparing a high-temperature resistant carbon-coated optical fiber according to an embodiment of the present invention;

[0036] FIG2 is a schematic structural diagram of a system for preparing a high-temperature resistant carbon-coated optical fiber according to an embodiment of the present invention;

[0037] FIG3 is a schematic diagram of the structure of a preparation system for a high-temperature resistant carbon-coated optical fiber according to another embodiment of the present invention;

[0038] FIG4 is a schematic structural diagram of a first carbon coating reaction chamber involved in a system for preparing a high-temperature resistant carbon-coated optical fiber according to an embodiment of the present invention;

[0039] FIG5 is a schematic structural diagram of a second carbon coating reaction chamber involved in a system for preparing a high-temperature resistant carbon-coated optical fiber according to an embodiment of the present invention;

[0040] FIG6 is a schematic structural diagram of a curing device involved in a system for preparing a high-temperature resistant carbon-coated optical fiber according to an embodiment of the present invention;

[0041] FIG7 is a schematic diagram of the structure of a high-temperature resistant carbon-coated optical fiber prepared in Example 1 of the present invention;

[0042] FIG8 is a schematic diagram of the structure of a high-temperature resistant carbon-coated optical fiber prepared in Example 2 of the present invention.

[0043] In all the 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 rod;

[0044] 11 - first deposition chamber, 12 - first sealed chamber; 21 - second deposition chamber, 22 - second sealed chamber, 23 - first induction coil; 41 - curing chamber, 42 - second induction coil;

[0045] 10-core layer, 20-cladding layer, 30-carbon coating layer, 40-resin coating layer, 50-resin inner coating layer, 60-resin outer coating layer; Modes for Carrying Out the Invention

[0046] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present 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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0049] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0050] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0051] As shown in FIG1 , the method for preparing a high-temperature resistant carbon-coated optical fiber according to an embodiment of the present invention includes carbon film deposition and high-temperature resistant coating application and curing, specifically comprising the following steps:

[0052] (1) setting a first carbon coating reaction chamber; heating the optical fiber, and then performing carbon film deposition 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 described herein comprises a core layer and an outer cladding layer. The optical fiber is obtained by heating and drawing a preform rod in a drawing furnace. In this step, the fiber is heated using residual heat from the drawing furnace (approximately 2000°C) or by using a heating device to heat the fiber to a temperature of 800-1100°C. This ensures that the fiber enters the first carbon coating reaction chamber at a temperature of 800-1100°C. Once in the first carbon coating reaction chamber, the raw gas reacts on the surface of the fiber cladding to form a carbon film, which serves as 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 is deposited evenly, so that the first carbon film layer has good sealing performance, small stress on the optical fiber cladding, and thus little impact on the optical fiber strength.

[0055] In a preferred embodiment, the raw material gas includes a hydrocarbon gas and a protective gas. The hydrocarbon gas includes but is not limited to benzene, methane, acetylene, etc., and the protective gas is an inert gas or nitrogen. The hydrocarbon gas and the protective gas are mixed in a certain proportion to form a raw material gas, which is passed into the first carbon coating reaction chamber. The specific ratio and flow rate of the hydrocarbon gas and the protective gas depend on the specific process conditions and the designed deposition thickness. The proportion of hydrocarbon gas in the raw material gas is preferably between 15% and 75%, and the total flow rate of the raw material gas (i.e., the feed rate of the raw material gas) is preferably between 250ml / min and 2L / min. The exhaust speed needs to be 0.5-1L / min greater than the feed rate, and the drawing speed is 40~250m / 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℃, thereby forming a graphite-like amorphous carbon film. The carbon atoms of the carbon film are mainly SP2 hybrid structures. Three of the four electrons outside the carbon atom nucleus form chemical bonds with adjacent atoms in the plane, and the fourth electron produces a weaker bond through van der Waals force, eventually forming a dense graphite-like layered structure. The percentage of SP2 bonds in the carbon atoms in the graphite-like layered structure is more than 95%. The layers are connected by van der Waals force, which can achieve a certain degree of slip. At the same time, the inner layer of carbon film is bonded to the silicon on the surface of the cladding 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 comes from the reaction of C and Si at high temperature, which occurs at the same time as the deposition of the graphite-like carbon layer.

[0057] (2) providing at least one second carbon coating reaction chamber, the periphery of which is provided with a first induction coil; utilizing the first induction coil to heat the optical fiber coated with the first carbon film layer in the corresponding second carbon coating reaction chamber, performing 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 induced electrothermal effect to provide heat for the deposition reaction. Specifically, an induction coil is provided on the periphery of 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. Under the action of the alternating magnetic field, the first carbon film layer generates an induced potential, eddy currents are formed in the carbon film, and high temperature is generated, which triggers the reaction and deposition of raw materials around the carbon film to form a second carbon film layer.

[0059] In a preferred embodiment, the raw material gas includes a hydrocarbon gas and a protective gas. The hydrocarbon gas includes, but is not limited to, hydrocarbon gases such as benzene, methane, and acetylene; the protective gas includes an inert gas or nitrogen. The hydrocarbon gas and the protective gas are mixed in a certain proportion to form a raw material gas, which is introduced into the second carbon coating reaction chamber. The specific ratio and flow rate of the hydrocarbon gas and the protective gas depend on the specific process conditions and the designed deposition thickness. The volume proportion of the hydrocarbon gas in the raw material gas is preferably between 15% and 75%, and the total flow rate of the raw material gas (i.e., the feed rate of the raw material gas) is preferably between 250 ml / min and 2 L / min. The exhaust speed needs to be 0.5-1 L / min greater than the feed rate, and the 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 optical fiber surface reaction zone in the second carbon coating reaction chamber is controlled to be greater than 1100°C (preferably 1100-1300°C) by the parameters of the induction current, a layer of diamond-like amorphous carbon film is obtained, in which the carbon atoms mainly form an SP3 hybrid structure, the percentage of SP3 bonds in the carbon atoms is greater than 95%, and the four electrons outside the carbon atom nucleus form chemical bonds with the valence electrons of adjacent atoms, ultimately forming a diamond-like structure. Therefore, the structure has high hardness and good wear resistance, which 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, greatly improving 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 coating reaction chamber is controlled to 800-1100°C by adjusting 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] As you can understand, 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 in the graphite-like amorphous carbon film. Therefore, a first carbon film layer (the first carbon film layer) must be deposited. Only with this carbon film on the outside of the optical fiber can the electromagnetic induction principle be used to generate heat for subsequent deposition.

[0063] It should be noted that, as needed, a single deposition or multiple depositions can be performed outside the first carbon film layer to form a second carbon film layer, i.e., 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 composite 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. In other words, the diamond-like amorphous carbon film can be applied solely to the first carbon film layer, or two carbon films in different arrangements and combinations can be applied to the first carbon film layer. Compared to applying only the diamond-like amorphous carbon film, applying two carbon films in different arrangements and combinations to the first carbon film layer can, to a certain extent, avoid the problem of excessively thick diamond-like amorphous carbon film, which can lead to high stress and increased impact on optical fiber strength.

[0064] If the second carbon film formed by the above method is a diamond-like amorphous carbon film, the thickness of the second carbon film is 20 to 60 nm, and the surface roughness of the second carbon film is ≤ 3 nm. The carbon film is deposited uniformly and has a high hardness, capable of withstanding high lateral stress.

[0065] If the second carbon film formed by the above method is a graphite-like amorphous carbon film, the thickness of the second carbon film is 10-30 nm, and the surface roughness of the second carbon film is ≤3 nm. The carbon film is deposited evenly 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 graphite-like amorphous carbon film and at least one diamond-like amorphous carbon film in the thickness direction, the thickness of each graphite-like amorphous carbon film layer is 10-20 nm, and the surface roughness is ≤3 nm; the thickness of each diamond-like amorphous carbon film layer is 10-30 nm, and the surface roughness is ≤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 carbon film layer will experience significant stress.

[0067] Preferably, a corresponding second carbon coating reaction chamber is provided for each deposition, and the carbon film deposited in each reaction chamber corresponds to one layer. By setting up multiple depositions, on the one hand, the thickness can be conveniently and quickly controlled by adjusting the current size as needed. The alternating current size will affect the size 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, a faster drawing speed can be achieved through multiple depositions (the faster the speed, the thinner the single deposition thickness under the same conditions). On the other hand, better optical fiber performance can also be achieved by designing a carbon film structure with different layers. Each layer can form a different amorphous state through different temperature control. The heating temperature for forming a graphite-like amorphous carbon film is 800~1100℃, and the heating temperature for forming a diamond-like amorphous carbon film is greater than 1100℃. Because of the different temperatures, the way atoms are arranged and combined during chemical reactions is different (each carbon atom in graphite-like carbon film has three electrons that form covalent bonds with the electrons of other carbon atoms, while each carbon atom in diamond-like carbon film has four outer electrons that form covalent bonds with the outer electrons of other carbon atoms), thus forming different amorphous states. Graphite-like amorphous carbon films are mainly based on graphite structure, so their properties are similar to those of graphite. Diamond-like amorphous carbon films are mainly based on diamond structure, so their properties are relatively close to those of diamond, thereby being able to achieve different functional orientations.

[0068] For example, the two-layer structure of graphite-like inner layer and diamond-like outer layer of carbon film can not only achieve good sealing but also ensure the mechanical properties of the carbon film; while the continuous multilayer structure of graphite-like + diamond-like + graphite-like + diamond-like can increase the sealing and mechanical properties of the carbon film layer while maintaining the ductility of the carbon film.

[0069] In addition, the graphite-like amorphous carbon film has a better heating effect, and the conductivity of the diamond-like amorphous carbon film is poorer than that of the graphite-like amorphous carbon film, and the induced heating effect is poorer. Therefore, when the diamond-like carbon film is deposited outside the diamond-like carbon film, the heat is mainly generated by the first deposited graphite-like amorphous carbon film.

[0070] (3) providing a curing device with a second induction coil provided on its periphery; coating a heat-curing coating on the surface of the second carbon film layer, and causing the heat-curing coating to be heat-cured from the inside out in the curing device through the second induction coil, and performing at least one coating and curing process of the heat-curing coating 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° C. by controlling the parameters of the induced current to obtain 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 dip coating using a coating cup. The curing device is preferably a glass chamber. The carbon-coated optical fiber passes through the coating cup filled with polyimide and then enters the glass chamber, where the thermosetting coating is cured in an atmosphere of protective gas (inert gas or nitrogen). A second induction coil is coaxially positioned around the glass chamber. During the curing process, an alternating current is passed through the coil, generating an alternating magnetic field around the induction coil. This alternating magnetic field induces an electromotive force in the carbon film (primarily graphite-like amorphous carbon film), forming eddy currents within the carbon film, generating high temperatures and initiating the curing of the polyimide surrounding the carbon film.

[0073] The present invention uses induction heating to cure heat-curing coatings. The heat curing process operates from the inside out, resulting in high-quality curing and less prone to blistering and other issues, improving the quality of the coating. The induction heating curing process offers precise temperature control, rapid heating, and uniform heating. It also facilitates the rational configuration of different curing processes, improving the drawing speed of the heat-curing coating.

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

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

[0076] The carbon-coated optical fiber formed by the above preparation method, after being placed in a hydrogen environment at 85°C and 11atm for 7 days, has an additional attenuation of less than 0.2dB / km for the carbon-coated single-mode optical fiber at a wavelength of 1240nm, and an additional attenuation of less than 0.2dB / km for the carbon-coated multimode optical fiber at a wavelength of 850nm.

[0077] The method for preparing a high-temperature resistant carbon-coated optical fiber of the present invention first draws a preform into an optical fiber, then deposits a layer of carbon film on the surface of the optical fiber cladding by conventional cold-wall chemical vapor deposition, and then deposits one or more carbon films by induction heating, activates the deposition reaction by induction heating, and finally applies a heat-curing coating, which is thermally cured by induction heating, with the carbon film directly serving as a heat source for subsequent deposition or curing. The present invention solves the problem that conventional cold-wall chemical vapor deposition cannot preheat an optical fiber on which a layer of carbon film is deposited. The heat source of the present invention is the deposition area, which has the advantages of fewer by-products than conventional cold-wall chemical vapor deposition and is easy to produce long sections of optical fiber. In addition, the present invention utilizes a carbon film as a heat source, which has a fast heating speed, high heating efficiency, and is easy to control while consuming low energy.

[0078] The high-temperature resistant carbon-coated optical fiber obtained by the preparation method of the high-temperature resistant carbon-coated optical fiber of the present invention has a first-deposited carbon film and a later-deposited carbon film, both of which are amorphous carbon films, but have slightly different structural components. The inner layer is mainly a graphite-like amorphous carbon film, which forms an SI-C bond with the optical fiber, and has a tight bond and a good sealing effect. At the same time, the SI-C bond makes the structure from 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, can protect the sealing effect of the graphite-like amorphous carbon film, and has certain wear resistance, and can play a good protective role throughout the life cycle of the optical fiber.

[0079] Furthermore, as shown in Figures 2 to 5, embodiments of the present invention provide a system for preparing a high-temperature-resistant carbon-coated optical fiber, 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 in sequence. The resin coating and curing devices include a resin coating device and a curing device.

[0080] In the first embodiment of the present invention, as shown in Figure 2, the high-temperature resistant 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-coated reaction chamber 1 is a reaction chamber for forming the first carbon film layer. The first carbon-coated reaction chamber 1 is preferably a glass circular tube structure, including a first deposition chamber 11 and a first sealed chamber 12, wherein the first sealed chamber 12 is provided at both axial ends of the first deposition chamber 11. A protective gas inlet is provided on the first sealed chamber 12. During the reaction process, 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, thereby achieving the purpose of gas sealing. Preferably, the first carbon-coated reaction chamber 1 has an inner diameter of 20-40 mm and a length of 300-400 mm. The inner diameter of the first sealed chamber 12 is the same as that of the first deposition chamber 11, and the length of the first sealed chamber 12 is preferably 20-40 mm. Corresponding optical fiber passage holes are provided at both axial ends of the first deposition chamber 11 for optical fiber entry and exit, and the diameter of the optical fiber passage hole 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 one end of the first deposition chamber 11 near the optical fiber entrance, and the raw material gas outlet is located at one end of the first deposition chamber 11 near the optical fiber exit. In the first deposition chamber 11, the raw material gas enters the chamber through the raw material gas inlet, is subsequently decomposed at high temperature to form a carbon film, and is deposited on the optical fiber. Other products are then discharged through the raw material gas outlet.

[0083] The first carbon coating reaction chamber 1 is close to 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 react in the first carbon coating reaction chamber 1 to form a 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, so that the residual heat of the drawing furnace 6 can be used for heating, and the optical fiber heating furnace 5 can also be used for heating to provide heat for the deposition reaction and control the temperature of the optical fiber bare fiber.

[0084] The second carbon-coated reaction chamber 2 is a reaction chamber for forming a second carbon film layer. The first carbon-coated reaction chamber 2 is preferably a glass circular tube structure, including a second deposition chamber 21 and a second sealed chamber 22, wherein the second sealed chamber 22 is provided at both axial ends of the second deposition chamber 21. A protective gas inlet is provided on the second deposition chamber 21. 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, thereby achieving the purpose of gas sealing. A first induction coil 23 is provided coaxially with the second deposition chamber 21 on the periphery. Compared with the first carbon-coated reaction chamber 1, an induction coil is additionally provided on the periphery of the reaction area of ​​the second carbon-coated reaction chamber 2. The induction coil is coaxially arranged with the reaction chamber, and the end of the induction coil is connected to an alternating current to provide heat for the deposition reaction through the induced electrothermal effect.

[0085] Preferably, the first carbon-coated reaction chamber 2 has an inner diameter of 20-40 mm and a length of 300-400 mm. The inner diameter of the second sealed chamber 22 is the same as that of the second deposition chamber 21, and the length of the second sealed chamber 22 is preferably 20-40 mm. Optical fiber holes are provided at both axial ends of the second deposition chamber 21 for optical fiber entry and exit, and the diameter of the optical fiber holes is preferably 5-15 mm.

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

[0087] The resin coating device 3 is preferably a coating cup filled with 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] Curing device 4 is a resin curing device. Its main structure consists of a curing chamber 41, preferably a glass tube. Both ends of the curing chamber 41 are open axially. An exhaust port is located near the axial end of the curing chamber 41, which is connected to the exhaust device. A second induction coil 42 is coaxially positioned 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. Heat induced in the carbon film (primarily a graphite-like amorphous carbon film) heats and cures the coating. Exhaust gases generated during curing (such as solvent volatilized during the polyimide curing process) are discharged through the exhaust port. The inner diameter of the curing chamber 4 is preferably 100-200 mm, and the length is preferably 500-1500 mm.

[0089] Preferably, the inner diameter of the second induction coil 42 (the radial distance between the induction coil and the curing device) is 130-230 mm, slightly larger than the outer diameter of the curing device to ensure effective heating. The diameter of the second induction coil 42 (the diameter of the wire used) is preferably 1-4 mm. The spacing between the second induction coils 42 decreases from top to bottom (from the optical fiber input end to the optical fiber output end of the curing device), from 50 mm to 10 mm. This gradual decrease in spacing is intended to ensure a relatively uniform temperature within the curing device cavity. Heat within the curing cavity tends to rush upward. If the coil spacing is uniform, the temperature above the curing tube will be significantly higher than that below. Excessively high temperatures can cause the polyimide solvent to boil, leading to bubbles in the high-temperature-resistant coating. Excessively low temperatures will not achieve a satisfactory curing effect.

[0090] In addition, the first induction coil outside the second carbon-coated reaction chamber 2 and the second induction coil outside the curing device 4 of the present invention are located outside the corresponding reaction chamber, which can prevent contamination and avoid the problem of more carbon film and by-products being deposited on the coils due to being set inside, thereby affecting the induction heating effect.

[0091] In a second embodiment of the present invention, as shown in FIG3 , a system for preparing a high-temperature-resistant carbon-coated optical fiber comprises, in sequence, 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. This embodiment differs from the first embodiment in that it includes two second carbon coating reaction chambers 2.

[0092] It can be understood that the high-temperature resistant carbon-coated optical fiber preparation system shown in Figures 2 and 3 of the present invention includes one second carbon-coated reaction chamber 2 and two second carbon-coated reaction chambers 2, respectively, that is, one and two induction coil heating carbon film depositions are performed respectively. When multiple carbon film depositions are required, the number of second carbon-coated reaction chambers 2 can be increased accordingly according to the number of carbon film depositions.

[0093] Furthermore, an embodiment of the present invention also provides a high-temperature resistant carbon-coated optical fiber prepared by the above-mentioned preparation method, comprising a core layer, a cladding layer, a carbon coating layer, and a resin coating layer arranged in sequence from the inside to the outside. The deposition process of the carbon coating layer belongs to the cold-wall chemical vapor deposition method, and is formed by multiple depositions of nano-scale carbon films; the inner layer of the carbon coating layer is the first carbon coating layer, and the outer layer is the second carbon coating layer, and 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 the second carbon film layer is a graphite-like amorphous carbon film, or 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 resin coating layer is a heat-curing coating layer, preferably a polyimide, and the resin coating layer is formed by one or more coatings and curing processes of the heat-curing 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 sensed, resulting in inefficient carbon film deposition or curing of the thermally cured coating. If the first carbon film layer is too thick, stress within the first carbon film layer is high. A thickness of 30-40 nm is further preferred. The surface roughness of the first carbon film layer is ≤ 3 nm, ensuring uniform carbon film deposition. This ensures good sealing performance and minimizes stress on the optical fiber cladding, thereby minimizing the impact on optical fiber strength.

[0095] If the second carbon film layer is only a diamond-like amorphous carbon film, the thickness of the second carbon film layer is 20-60nm, and the surface roughness of the second carbon film layer is ≤3nm. The carbon film is deposited evenly, has high hardness, and can withstand high lateral stress. If the diamond-like amorphous carbon film of the second carbon film layer is too thin, the mechanical protection of the carbon film is poor; if the diamond-like amorphous carbon film of the second carbon film layer is too thick, the stress in the diamond-like amorphous carbon film of the second carbon film layer is large. The surface roughness of the diamond-like amorphous carbon film of the second carbon film layer is ≤3nm, the carbon film is deposited evenly, has high hardness, and can withstand high lateral stress.

[0096] If the second carbon film layer is a composite 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, each graphite-like amorphous carbon film layer preferably has a thickness of 10-20 nm and a surface roughness of 3 nm or less; each diamond-like amorphous carbon film layer preferably has a thickness of 10-30 nm and a surface roughness of 3 nm or less. The total thickness of the composite carbon film layer is ≤150 nm. If the composite carbon film layer is too thick, the overall carbon film layer will experience significant stress.

[0097] The carbon-coated optical fibers of the embodiments of the present invention include carbon-coated single-mode optical fibers and carbon-coated multimode optical fibers. After being stored in a hydrogen environment at 85°C and 11 atm for 7 days, the additional attenuation of the carbon-coated single-mode optical fibers at a wavelength of 1240 nm is less than 0.2 dB / km, and the additional attenuation of the carbon-coated multimode optical fibers at a wavelength of 850 nm is less than 0.2 dB / km.

[0098] The present invention provides a high-temperature resistant carbon-coated optical fiber and a preparation system and method thereof. The prepared optical fiber carbon film has a multi-layer structure, wherein the main component of the inner layer is a graphite-like amorphous carbon film, and preheating is used to provide the heat required for the reaction. The main component of the outer layer is a diamond-like amorphous carbon film, and the preparation method is as follows: an induction coil is added to the periphery of the reaction area of ​​the carbon coating reaction chamber, and the deposited carbon film is used as a heating element. Induction heating is used to provide heat for the subsequent deposition reaction to generate a diamond-like amorphous carbon film (or a combined carbon film of a graphite-like amorphous carbon film and a diamond-like amorphous carbon film). Finally, an improved multi-stage coil design is used to control the temperature of the curing area to cure the heat-curing coating, thereby preparing the high-temperature resistant carbon-coated optical fiber.

[0099] To better understand the preparation methods, preparation systems, and products of the embodiments of the present invention, the following examples are provided:

[0100] If the temperature of the optical fiber surface reaction zone in the second carbon coating reaction chamber is controlled to be 800-1100° C. by adjusting 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] The temperature of the optical fiber surface reaction zone in the second carbon coating reaction chamber is controlled to be greater than 1100°C (preferably 1100-1300°C) by the parameters of the induced current to obtain a layer of diamond-like amorphous carbon film.

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

[0103] Example 1

[0104] This example utilizes the high-temperature-resistant carbon-coated optical fiber preparation system shown in Figure 2. The resulting high-temperature-resistant carbon-coated optical fiber is shown in Figure 7. The core layer 10 drawn in this example is a G652D single-mode optical fiber with a core diameter of 9 μm and a cladding diameter of 125 μm. The feed gases in both reaction chambers are a mixture of acetylene and helium, with an acetylene concentration of 10% to 30%. The total feed gas flow rate (i.e., the mixed gas feed rate) in both carbon-coated reaction chambers is 0.5-1 L / min. The exhaust rate must be 0.5-1 L / min greater than the feed rate to maintain stable airflow within the chambers. The drawing speed is 40-80 m / min. The optical fiber is heated to 900-1000°C using a heating device before entering the first carbon-coated reaction chamber. The surface reaction zone of the optical fiber within the first carbon-coated reaction chamber maintains a temperature of 900-1000°C, 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. This causes the temperature of the reaction zone on the optical fiber surface within the second carbon coating reaction chamber to exceed 1100°C, thereby forming 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 1 and 2, a carbon coating layer 30 is formed. Subsequently, the optical fiber is coated with polyimide coating and enters a curing device. The curing temperature of the polyimide coating in the curing device is controlled by the parameters of the induction coil current to be between 80°C and 350°C, 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 optical fiber prepared in this example exhibited an attenuation of 0.462 dB / km at 1310 nm and 0.295 dB / km at 1550 nm, an F15% tensile strength of 3.53 GPa, an F50% tensile strength of 3.56 GPa, and an ND value of 105. After seven days at 85°C and 11 atm of hydrogen, the additional attenuation at 1240 nm was less than 0.2 dB / km. The carbon-coated optical fiber obtained in this example exhibited excellent hydrogen damage resistance, high mechanical strength, and good consistency.

[0106] Example 2

[0107] This embodiment uses the high-temperature carbon-coated optical fiber preparation system shown in Figure 3. The resulting high-temperature carbon-coated optical fiber is shown in Figure 8. The core layer 10 drawn in this embodiment is a GI50 multimode optical fiber with a core layer 10 diameter of 50 μm and a cladding 20 diameter of 125 μm. The feed gas in the three reaction chambers is a mixture of acetylene and nitrogen with an acetylene concentration of 30% to 50%. The feed rate of the mixed gas in the three reaction chambers is 0.5-1 L / min. The exhaust rate must be 0.5-1 L / min higher than the feed rate to maintain stable airflow in the chamber. The drawing speed is 80-150 m / min. The optical fiber is heated to 900-1000°C using a heating device before entering the first carbon coating reaction chamber 1. The surface reaction zone of the optical fiber in the first carbon coating reaction chamber is kept at a temperature of 900-1000°C, thereby forming a layer of graphite-like amorphous carbon film on the cladding. The induction coil in the first second carbon coating reaction chamber 2 has a rated output power of 2kW, an alternating current frequency of 18Hz, and a rated input current of 3A. This results in a temperature of 900-1000°C on the surface reaction zone of the optical fiber in the second carbon coating reaction chamber 2, thereby forming another layer of graphite-like amorphous carbon film on the first layer. The induction coil in the second second carbon coating reaction chamber 2 has a rated output power of 3kW, an alternating current frequency of 18Hz, and a rated input current of 3A. This results in a temperature of greater than 1100°C on the surface reaction zone of the optical fiber in reaction chamber 3, thereby forming a diamond-like amorphous carbon film on the other layer of graphite-like amorphous carbon film. The thickness of the graphite-like amorphous carbon film deposited in the first carbon coating reaction chamber 1 is 20-40nm, the thickness of the graphite-like amorphous carbon film deposited in the first second carbon coating reaction chamber 2 is 20-30nm, and the thickness of the diamond-like amorphous carbon film deposited in the second second carbon coating reaction chamber 2 is 30-50nm. After passing through the first carbon coating reaction chamber 1 and the 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 heat-cured 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 to be 200~350℃ by the parameters of the induction coil current, thereby forming a layer of resin inner coating 50 on the surface of the carbon coating layer 30. Then, the optical fiber is coated with a heat-cured 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 to be 200~350℃ by the parameters of the induction coil current, thereby forming a resin outer coating 60 on the surface of the resin inner coating 50.

[0108] The carbon-coated, high-temperature-resistant multimode optical fiber prepared in this example exhibits an attenuation of 2.46 dB / km at a wavelength of 850 nm, an attenuation of 0.68 dB / km at a wavelength of 1300 nm, an F15% tensile strength of 3.45 GPa, an F50% tensile strength of 3.53 GPa, and an ND value of 135. After aging for 7 days in a hydrogen environment at 85°C and 11 atm, the additional attenuation at a wavelength of 850 nm is less than 0.2 dB / km. The carbon-coated optical fiber obtained in this example exhibits excellent hydrogen damage resistance, high mechanical strength, and good consistency.

[0109] It will be easily understood by those skilled in the art 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 in 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 which are sequentially arranged from the inside to the outside; 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 the second carbon film layer is a composite carbon film layer formed by laminating at least one graphite-like amorphous carbon film and at least one diamond-like amorphous carbon film in the thickness direction.

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

3. A method for preparing a high-temperature resistant carbon-coated optical fiber, characterized in that, It includes the following steps: S1, Heat the optical fiber and 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, and the first carbon film layer is a graphite-like amorphous carbon film; S2, Place the optical fiber with the first carbon film layer deposited on its surface 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, and 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 composite carbon film layer formed by laminating at least one graphite-like amorphous carbon film and at least one diamond-like amorphous carbon film in the thickness direction; Among them, a first induction coil is provided on the outer periphery of the second carbon coating reaction chamber, and the temperature of the reaction zone on the surface of the optical fiber in the second carbon coating reaction chamber is controlled by the first induction coil; S3, Coat the surface of the optical fiber with the second carbon film layer with a thermosetting coating and place it in a curing device for thermosetting, so as to obtain a high-temperature resistant carbon-coated optical fiber.

4. The preparation method of the high-temperature resistant carbon-coated optical fiber according to claim 3, characterized in that, 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.

5. The preparation method of the high-temperature resistant carbon-coated optical fiber according to claim 3, characterized in that, In step S1, control the temperature of the optical fiber entering the first carbon coating reaction chamber to be 800 - 1100 °C, so that the first carbon film layer is a graphite-like amorphous carbon film.

6. The method for preparing a high-temperature resistant carbon-coated optical fiber according to claim 3, wherein, In step S2, control the temperature of the optical fiber entering the second carbon coating reaction chamber to be 800 - 1100 °C, so that the second carbon film layer is a graphite-like amorphous carbon film; or, In step S2, control the temperature of the optical fiber entering the second carbon coating reaction chamber to be greater than 1100 °C, so that the second carbon film layer is a diamond-like amorphous carbon film.

7. The method for preparing the high-temperature resistant carbon-coated optical fiber according to any one of claims 3-6, characterized in that, The raw material gases of the first carbon coating reaction chamber and the second carbon coating reaction chamber include hydrocarbon gases and protective gases. The volume ratio of hydrocarbon gases in the raw material gases is 15% - 75%; the feeding speed of the raw material gases is 250 ml / min - 2 L / min, the exhaust speed is 0.5 - 1 L / min greater than the feeding speed, and the drawing speed is 40 - 250 m / min.

8. The method for preparing a high-temperature resistant carbon-coated optical fiber according to any one of claims 3-6, characterized in that, In step S3, the distance between each turn of the second induction coil gradually decreases from the optical fiber inlet end to the optical fiber outlet end of the curing device.

9. A preparation system for high-temperature resistant carbon-coated optical fibers, which is applied to the preparation method of the high-temperature resistant carbon-coated optical fibers described in any one of claims 3-8, and is characterized in that, It includes 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 curing devices arranged in sequence; among them, The drawing furnace is used to heat and draw an optical fiber preform to obtain an optical fiber; at the same time, it can heat the optical fiber using its residual heat; The first carbon coating reaction chamber is the reaction chamber for forming the first carbon film layer; The second carbon coating reaction chamber is the 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 device includes a resin coating device and a curing device; the resin coating device is used for coating a thermosetting coating; the curing device is used for curing the thermosetting coating.

10. The preparation system of the high-temperature resistant carbon-coated optical fiber according to claim 9, characterized in that, A second induction coil is provided on the outer periphery of the curing device.

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