Carbon coating optical fiber containing compact carbon layer and preparation method

Abstract

The invention provides a carbon coating optical fiber containing a compact carbon layer and a preparation method, and relates to the technical field of optical fibers, and the carbon coating optical fiber is characterized in that an optical fiber core rod is arranged in an outer structure cladding, and an air layer is formed between the inner wall of the outer structure cladding and the outer wall of the optical fiber core rod; and at least one carbon coating is formed between the air layer and the outer wall of the optical fiber core rod and / or between the inner wall of the outer structure cladding and the air layer. Mixing a carbon-containing gas source and an inert gas source, and injecting the mixture into an air layer of the optical fiber preform through a gas injection device at the tail end of the optical fiber preform; the optical fiber preform injected with the mixed gas is input into a high-temperature heating furnace, the mixed gas is subjected to high-temperature cracking to form a carbon coating, and meanwhile, the optical fiber preform is fused and drawn into filaments to obtain the carbon-coated optical fiber. The device has the beneficial effects that the effect of preventing mechanical damage is enhanced; the carbon element of the carbon coating does not pollute an external coating layer; an additional gas cracking reaction furnace is not needed, energy is saved, carbon powder cannot be accumulated in the cracking reaction furnace, and therefore the preparation length of the optical fiber is not limited.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fibers, and in particular to a carbon-coated optical fiber containing a dense carbon layer and a preparation method thereof. Background Art

[0002] Optical fibers are known as one of the top ten inventions that have changed the world. Since the 1970s, they have rapidly penetrated into application fields such as communication, sensing, and lasers due to their advantages of light weight, low cost, large transmission capacity, low transmission loss, good confidentiality, and strong anti-interference ability. However, in some harsh environments, such as submarine optical cables and ocean exploration systems, oil exploration, etc., although the coatings composed of original components such as silicone rubber, polyurethane, or acrylate on optical fibers can protect the optical fibers, they cannot prevent the influence of moisture and hydrogen on the mechanical strength and optical performance of the optical fibers, resulting in a significant reduction in the working life of ordinary optical fibers under wet or small bending radius conditions. Optical fibers with a carbon film coated on the surface of quartz optical fibers are called carbon-coated optical fibers (CCF: Carbon Coated Fiber). Its mechanism is to use a dense film layer of carbon to isolate the surface of the optical fiber from the outside world, so as to improve the mechanical fatigue loss of the optical fiber and the loss increase of hydrogen molecules. CCF is a kind of hermetic coated fiber (HCF).

[0003] Carbon hermetic coated optical fiber is simply called carbon-coated optical fiber. During the drawing process of this optical fiber, a carbon film with a nanoscale thickness is formed on the surface of the optical fiber with a quartz cladding through a special process. Although the carbon film is thin, its structure is dense, it has a blocking effect on moisture and hydrogen, and has a small shrinkage on the surface of the optical fiber, and its chemical properties are stable. It can effectively prevent the expansion of microcracks on the surface of the optical fiber, delay the fatigue process of mechanical strength, and reduce the dense carbon film.

[0004] The traditional carbon coating process is to coat carbon on the outer surface of the optical fiber to play a role in protecting the optical fiber. However, the carbon coating layer in the traditional carbon-coated optical fiber is itself thin and brittle, and the protection effect is limited when the optical fiber is mechanically damaged. Therefore, a polymer needs to be coated on the outside to form an external coating layer, but this will cause the external coating layer to be in direct contact with the carbon coating layer, polluting the coating system of the external coating layer.

[0005] Furthermore, this traditional process requires the optical fiber to pass through a gas cracking reaction furnace, and elemental carbon is deposited on the surface of the optical fiber through gas or liquid vapor cracking. At present, there are few units with domestic coating optical fiber production processes, and it can no longer meet the application requirements of hydrogen resistance and temperature resistance in the ocean, exploration, etc. Moreover, the carbon-coated optical fiber has the problem that the preparation length is limited by the dust in the cracking furnace, resulting in a short single production length. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a carbon-coated optical fiber containing a dense carbon layer, including:

[0007] An outer structure cladding, in which an optical fiber core rod is provided, and an air layer is formed between the inner wall of the outer structure cladding and the outer wall of the optical fiber core rod;

[0008] At least one carbon coating layer is formed between the air layer and the outer wall of the optical fiber core rod, and / or between the inner wall of the outer structure cladding and the air layer.

[0009] Preferably, a support tube, or a support rod, or a support arm is provided between the inner wall of the outer structure cladding and the outer wall of the optical fiber core rod, so that a gap filled with air is formed between the inner wall of the outer structure cladding and the outer wall of the optical fiber core rod, thereby forming the air layer.

[0010] Preferably, the number of the support tube, or the support rod, or the support arm is at least one.

[0011] Preferably, the diameter range of the optical fiber core rod is 5 to 800 micrometers.

[0012] Preferably, the diameter range of the outer structure cladding is 15 to 1500 micrometers.

[0013] Preferably, the thickness dimension range of the air layer is 1 to 100 micrometers.

[0014] Preferably, the thickness dimension range of the carbon coating layer is 10 to 2000 nanometers.

[0015] Preferably, the optical fiber core rod is an optical fiber waveguide structure.

[0016] Preferably, the material of the optical fiber core rod is germanium-doped quartz, or fluorine-doped quartz, or rare-earth-doped quartz, or soft glass material, or chalcogenide glass material.

[0017] The present invention also provides a method for preparing a carbon-coated optical fiber for preparing the above-mentioned carbon-coated optical fiber, including:

[0018] Step S1: Mix a carbon-containing gas source and an inert gas source, and then inject the mixture into the air layer of the optical fiber preform through an air injection device at the tail end of the optical fiber preform;

[0019] Step S2: Input the optical fiber preform injected with the mixed gas into a high-temperature heating furnace, the mixed gas is pyrolyzed at high temperature to form the carbon coating layer, and at the same time the optical fiber preform is melted and drawn into a wire to obtain the carbon-coated optical fiber.

[0020] The above technical solution has the following advantages or beneficial effects:

[0021] 1. By first providing an outer structure cladding outside the optical fiber core rod, compared with the traditional structure of a carbon coating layer plus an outer coating layer, the effect of protecting the optical fiber from mechanical damage is enhanced;

[0022] 2. A carbon coating is formed on the inner wall of the outer structural cladding, such that the outer coating on the outer wall of the outer structural cladding is not in direct contact with the carbon coating, and the carbon element of the carbon coating will not contaminate the coating system of the outer coating.

[0023] 3. In the process of preparing the optical fiber of the present invention, the cracking process of gas or liquid vapor occurs directly in the structure of the optical fiber preform, and the heat is directly provided by the high-temperature furnace for optical fiber drawing. No additional gas cracking reactor is required, saving energy and preventing carbon powder from accumulating in the cracking reactor, thereby not restricting the length of optical fiber preparation. Description of the Drawings

[0024] Figure 1 In a preferred embodiment of the present invention, it is a schematic structural diagram of a carbon-coated optical fiber with a dense carbon layer.

[0025] Figure 2 In a preferred embodiment of the present invention, it is a schematic diagram of the device for preparing the carbon-coated optical fiber. Detailed Description of the Invention

[0026] The present invention will be described in detail below with reference to the drawings and specific embodiments. The present invention is not limited to this embodiment, and other embodiments may also fall within the scope of the present invention as long as they conform to the gist of the present invention.

[0027] In a preferred embodiment of the present invention, in view of the above problems existing in the prior art, a carbon-coated optical fiber with a dense carbon layer is provided, as Figure 1 shown, including:

[0028] An outer structural cladding 1, in which an optical fiber core rod 2 is provided, and an air layer 3 is formed between the inner wall of the outer structural cladding 1 and the outer wall of the optical fiber core rod 2;

[0029] At least one carbon coating 4 is formed between the air layer 3 and the outer wall of the optical fiber core rod 2, and / or between the inner wall of the outer structural cladding 1 and the air layer 3.

[0030] Specifically, in this embodiment, through the optical fiber structure design, at least one carbon coating 4 is formed, which provides stronger protection for the optical fiber. In traditional carbon-coated optical fibers, the carbon coating itself is thin and brittle and cannot protect the optical fiber from mechanical damage. Therefore, a polymer layer needs to be coated on the outside. Of course, a standard acrylate coating can also be used, and a polyimide coating can also be used for high temperature applications. For general manufacturing processes, the carbon coating requires high speed, while the polymer coating requires low speed.

[0031] In this embodiment, a layer of outer structural cladding 1 is first provided outside the optical fiber core rod 2, and then a carbon coating 4 is formed on the inner wall of the outer structural cladding 1, so that the outer coating layer on the outer wall of the outer structural cladding 1 does not directly contact the carbon coating 4, and the carbon element in the carbon coating 4 will not contaminate the coating system of the outer coating layer. There are more choices for the type of the outer coating layer, such as polyimide, acrylic resin, silica gel, metal (gold, aluminum, copper, tin, etc.); there are more choices for the outer material coating process, and thermal curing, light curing, molten metal coating, magnetron sputtering, etc. can be selected.

[0032] In a preferred embodiment of the present invention, a support member 5 is provided between the inner wall of the outer structural cladding 1 and the outer wall of the optical fiber core rod 2. A support tube, or a support rod, or a support arm can be used, so that an air-filled gap is formed between the inner wall of the outer structural cladding 1 and the outer wall of the optical fiber core rod 2, and then an air layer 3 is formed.

[0033] Specifically, in this embodiment, the support tube 5 "suspends" the optical fiber core rod 2 region in the center of the outer structural cladding 1 region of the optical fiber, forming an air layer 3.

[0034] In a preferred embodiment of the present invention, the number of the support tube, or the support rod, or the support arm is at least one.

[0035] Specifically, in this embodiment, the number of the support tube or the support rod can be 1, 2, 3 or more. Since more support tubes will affect the attachment area of the carbon coating and the hydrogen barrier performance of the carbon coating, support tubes or support rods with a smaller number are preferred.

[0036] The support tube can be replaced with a support wall, and the number of the support walls can also be 1, 2, 3 or more.

[0037] In a preferred embodiment of the present invention, the diameter range of the optical fiber core rod 2 is 5 to 800 microns.

[0038] In a preferred embodiment of the present invention, the diameter range of the outer structural cladding 1 is 15 to 1500 microns.

[0039] In a preferred embodiment of the present invention, the thickness dimension range of the air layer 3 is 1 to 100 microns.

[0040] In a preferred embodiment of the present invention, the thickness dimension range of the carbon coating 4 is 10 to 2000 nanometers.

[0041] Specifically, the sizes and thicknesses of the optical fiber core rod 2, the outer structural cladding 1, the air layer 3 and the carbon coating 4 in this embodiment are all in the micron or nanometer range, so that the diameter of the prepared optical fiber meets the usage requirements of most scenarios.

[0042] In a preferred embodiment of the present invention, the optical fiber core rod 2 is an optical fiber waveguide structure.

[0043] Specifically, in this embodiment, the optical fiber core rod 2 can not only adopt a solid optical fiber core rod, but also adopt the structures of communication optical fibers, active optical fibers, single-mode optical fibers, multi-mode optical fibers, graded-index multi-mode optical fibers, large-mode area optical fibers, multi-core optical fibers, imaging optical fibers, anti-resonant optical fibers, and various microstructured optical fibers, including hollow optical fibers, refractive-index guiding photonic crystal optical fibers, large-mode area microstructured optical fibers, etc. The internal coating method of the carbon-coated optical fiber of the present invention is suitable for all optical fibers with microstructures and various types of optical fibers.

[0044] In a preferred embodiment of the present invention, the material of the optical fiber core rod 2 is germanium-doped quartz, or fluorine-doped quartz, or rare-earth-doped quartz, or soft glass material, or chalcogenide glass material.

[0045] The present invention also provides a preparation method of a carbon-coated optical fiber for preparing the above-mentioned carbon-coated optical fiber, including:

[0046] Step S1: Mix a carbon-containing gas source and an inert gas source, and then inject them into the air layer of the optical fiber preform through an air injection device at the tail end of the optical fiber preform;

[0047] Step S2: Input the optical fiber preform injected with the mixed gas into a high-temperature heating furnace. The mixed gas pyrolyzes at high temperature to form a carbon coating, and at the same time, the optical fiber preform melts and is drawn into a wire to obtain a carbon-coated optical fiber.

[0048] Specifically, as Figure 2 shown is the device for preparing the carbon-coated optical fiber in this embodiment. The preparation methods of the various layers of the optical fiber can be: the stacking method, the extrusion method, the punching method, etc., which are conventional means in the industry for preparing microstructured optical fibers. Figure 2 not shown in Figure 2 This mainly shows the process preparation flow and method of introducing special gases into the air layer or air voids of the microstructured optical fiber and forming a carbon coating.

[0049] First, in Figure 2 , (1) is a carbon-containing gas source (i.e., the gas source to be pyrolyzed, including but not limited to carbon-containing element gases such as acetylene and methane); (2) is an inert gas source: including but not limited to inert protective gases that are not easily reactive such as nitrogen and argon;

[0050] Subsequently, gas premixing is performed at (3). The gas to be pyrolyzed and the inert gas are premixed in a certain proportion; depending on the carbon content of the gas to be pyrolyzed, the premixing ratio with the inert gas source is different; different optical fiber preparation parameters result in different premixing ratios; different optical fiber structures also result in different premixing ratios. Taking acetylene and argon as an example, when preparing the optical fiber in Figure 1 , when the optical fiber preparation speed is 100 m / min, the relatively optimized premixing ratio of acetylene and argon is 2:1

[0051] According to different process parameters, the premixing ratio range of the gas to be cracked and other gases is (1:99) to (99:1);

[0052] Next, Figure 2 In (4) is an air injection device at the tail end of the optical fiber preform, and the mixed gas is introduced into the air layer (air holes or air voids) in the optical fiber preform with a certain microstructure in (5);

[0053] Figure 2 In (6) is a high-temperature heating furnace, whose main function is to melt and draw the optical fiber preform into filaments, and also plays the function of high-temperature cracking of the carbon element-containing gas in the present invention to form a carbon coating inside the optical fiber structure; finally, a finished optical fiber with a carbon coating inside in (7) is obtained, and subsequent external coating of the optical fiber can be carried out by various coating methods to form an external coating layer.

[0054] The main innovation of the preparation method of the optical fiber in the present invention lies in depositing a carbon coating inside the microstructure optical fiber. During the process of directly melting and drawing the optical fiber preform into filaments, the mixed gas to be cracked and the inert gas are heated by a high-temperature heating furnace to undergo cracking to form a carbon coating. The cracking process of the gas or liquid vapor directly occurs in the optical fiber preform structure, and the heat is directly provided by the optical fiber drawing furnace, without the need for an additional gas cracking reaction furnace. It saves energy, and carbon powder will not accumulate in the cracking reaction furnace, thus not limiting the length of optical fiber preparation.

[0055] The above are only preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention accordingly. For those skilled in the art, it should be realized that all equivalent replacements and obvious changes made by using the content of this specification and the drawings should be included in the protection scope of the present invention.

Claims

1. A carbon-coated optical fiber with a dense carbon layer, characterized in that, Comprising: An outer structural cladding, in which an optical fiber core rod is provided, and an air layer is formed between the inner wall of the outer structural cladding and the outer wall of the optical fiber core rod; At least one carbon coating layer, formed between the air layer and the outer wall of the optical fiber core rod, and / or between the inner wall of the outer structural cladding and the air layer.

2. The carbon-coated optical fiber according to claim 1, wherein, A support tube, or a support rod, or a support arm is provided between the inner wall of the outer structural cladding and the outer wall of the optical fiber core rod, so that an air-filled gap is formed between the inner wall of the outer structural cladding and the outer wall of the optical fiber core rod, thereby forming the air layer.

3. The carbon-coated optical fiber according to claim 2, wherein The number of the support tube, or the support rod, or the support arm is at least one.

4. The carbon-coated optical fiber according to claim 1, wherein The diameter range of the optical fiber core rod is 5 to 800 microns.

5. The carbon-coated optical fiber according to claim 1, wherein The diameter range of the outer structural cladding is 15 to 1500 microns.

6. The carbon-coated optical fiber according to claim 1, wherein The thickness dimension range of the air layer is 1 to 100 microns.

7. The carbon-coated optical fiber according to claim 1, characterized in that The thickness dimension range of the carbon coating layer is 10 to 2000 nanometers.

8. The carbon-coated optical fiber according to claim 1, wherein The optical fiber core rod is an optical fiber waveguide structure.

9. The carbon-coated optical fiber according to claim 1, wherein The material of the optical fiber core rod is germanium-doped quartz, or fluorine-doped quartz, or rare-earth-doped quartz, or soft glass material, or chalcogenide glass material.

10. A method for preparing a carbon-coated optical fiber, characterized in that, For preparing the carbon-coated optical fiber as described in any one of claims 1-9, comprising: Step S1, mixing a carbon-containing gas source and an inert gas source, and then injecting the mixture into the air layer of the optical fiber preform through an air injection device at the tail end of the optical fiber preform; Step S2, inputting the optical fiber preform injected with the mixed gas into a high-temperature heating furnace, the mixed gas pyrolyzes at high temperature to form the carbon coating layer, and at the same time the optical fiber preform melts and is drawn into a wire to obtain the carbon-coated optical fiber.

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