An annealing apparatus and method for ultra-low-loss optical fibers

Abstract

This invention discloses an annealing apparatus and method for ultra-low loss optical fibers. The annealing apparatus includes: a fiber preform heating system, an optical fiber annealing system, a swirl-type air intake system, a fish-mouth stacked ceramic tube system, a coating system, and a take-up system. The fiber preform heating system, optical fiber annealing system, swirl-type air intake system, coating system, and take-up system are arranged sequentially along the fiber entry direction. The fish-mouth stacked ceramic tube system is located within the optical fiber annealing system. This invention optimizes the airflow path in the annealing area through the fish-mouth stacked ceramic tube design, enabling the airflow to be evenly distributed in multiple directions, thereby achieving a more uniform temperature distribution and improving the mechanical and optical properties of the optical fiber. The swirl-type air intake method causes the incoming airflow to rotate, enhancing gas mixing and flow rate control, ensuring stable airflow during the annealing process, reducing unnecessary fluctuations, and improving optical fiber quality. It also improves the flexibility and adaptability of the annealing equipment to meet different production needs.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber manufacturing technology, specifically relating to an annealing apparatus and method for ultra-low loss optical fiber. Background Technology

[0002] Optical fiber communication technology is a crucial component of modern communication technology. Due to its advantages such as high transmission rate, large capacity, and low loss, it has been widely applied in many fields, including communication networks, data transmission, and fiber optic sensing. The manufacturing technology of optical fibers directly affects the performance and reliability of optical fiber communication systems. Annealing, as a key step in optical fiber manufacturing, eliminates internal stress and improves the mechanical and optical properties of the fiber. Particularly for ultra-low loss fibers, the quality of the annealing process directly affects the fiber's attenuation characteristics and the protection of its large effective area.

[0003] In the fiber optic annealing process, temperature field control and gas intake control are two key factors affecting the annealing effect. However, existing fiber optic annealing equipment has limitations in temperature field control and gas intake control, mainly in the following aspects:

[0004] (1) Uneven temperature distribution: Existing annealing equipment is difficult to achieve a uniform temperature distribution in a high-temperature environment, which makes it easy for ultra-low loss optical fibers to have uneven annealing during the annealing process, thereby affecting the effectiveness of optical fiber annealing and the mechanical and optical properties of the optical fiber.

[0005] (3) Unstable airflow control or no active airflow: The airflow control system of the existing annealing equipment is not well designed, the airflow path is complex, and the airflow cannot be stably controlled. This will lead to poor gas mixing effect and uneven flow rate during the annealing process, as well as unnecessary fluctuations, which will affect the stability and accuracy of the annealing process.

[0006] (3) Inability to effectively control the uniformity of fiber diameter: When processing ultra-low loss optical fibers, existing annealing equipment is difficult to meet the high requirements of temperature control accuracy and airflow purity. At the same time, the absence of airflow or discrete airflow cannot achieve the high-precision diameter uniformity requirement, which makes it difficult to maintain the large effective area of ​​ultra-low loss optical fibers.

[0007] Patent application number IN202417014031 discloses a method for manufacturing optical fibers in an optical fiber production system. By controlling outlet nozzles of different sizes, the airflow entering the annealing furnace can be controlled, thereby producing optical fibers with low fiber attenuation. However, the airflow stability of the microenvironment during optical fiber annealing is difficult to maintain in this patent, which can easily cause fiber disturbance and affect the uniformity of fiber diameter.

[0008] Chinese patent application number CN211999466U provides an optical fiber annealing furnace, focusing on precise control of the annealing process to improve optical fiber quality. However, while this patent provides stable energy through precise instrument control, it cannot effectively guarantee the temperature field uniformity of the microenvironment during optical fiber annealing.

[0009] The invention patent with application number WO2019153473A1 provides an optical fiber stretching and annealing equipment. This equipment integrates optical fiber stretching and annealing processes, which improves the structural performance of optical fibers. However, it does not take into account the higher activity of ash due to gas expansion at high temperatures, making it difficult to guarantee the cleanliness of the annealing microenvironment. Summary of the Invention

[0010] To address the technical problems existing in the prior art, the present invention aims to provide an annealing apparatus and method for ultra-low loss optical fibers.

[0011] To achieve the above objectives and technical effects, the technical solution adopted by this invention is as follows:

[0012] An annealing apparatus for ultra-low loss optical fiber, comprising:

[0013] Optical rod heating system, used to heat and melt optical rods and draw them into optical fibers;

[0014] Fiber annealing system, used to anneal drawn optical fibers;

[0015] A swirling air intake system is used to create a stable rotating airflow within the annealing region;

[0016] Fish-mouth stacked ceramic tube system is used to ensure uniform airflow distribution within the annealing zone;

[0017] Coating systems are used to add protective materials to the surface of optical fibers;

[0018] The take-up system is used to ensure the tension stability of the optical fiber during the drawing and coating process and to take the optical fiber back up.

[0019] The optical rod heating system, optical fiber annealing system, spiral air intake system, coating system, and take-up system are arranged sequentially along the optical fiber entry direction, and the fish-mouth stacked ceramic tube system is located within the optical fiber annealing system.

[0020] Furthermore, the light rod heating system includes:

[0021] Optical rods, as precursor materials for optical fibers, need to be heated and melted at high temperatures;

[0022] An optical fiber drawing furnace is used to heat an optical rod, causing it to form a cone and be drawn into an optical fiber of a fixed size.

[0023] Optical fiber is formed by melting an optical rod and then drawing it to the required diameter in an optical fiber drawing furnace. During the drawing process, the optical fiber maintains a uniform speed and direction to ensure the consistency of the optical fiber diameter.

[0024] Furthermore, the fiber optic annealing system includes:

[0025] Annealing furnace;

[0026] Heating coils are installed inside the annealing furnace.

[0027] A quartz barrel is placed inside an annealing furnace, and a heating coil is wound around the quartz barrel;

[0028] Metal retaining rings are installed at the inlet end of the annealing furnace to secure the fish-mouth stacked ceramic tube system;

[0029] The lower tray is located at the outlet end of the annealing furnace, facilitating the disassembly and installation of internal components of the annealing furnace.

[0030] Furthermore, the total height of the heating coil is 1500-3000mm, the inner diameter is 45-70mm, and the number of turns is 7-15. Cooling water is circulated inside the heating coil to prevent coil deformation and ensure uniform heating.

[0031] Furthermore, the outer diameter of the quartz barrel is 43-70mm and the inner diameter is 40-65mm. During the assembly of the heating coil and the quartz barrel, the distance between the two ends of the quartz barrel and the heating coil is controlled within the range of 1-3mm to ensure uniform heating.

[0032] Furthermore, the swirl-type air intake system is located at the outlet end of the fiber optic annealing system, with an outer diameter of 40–80 mm and an inner diameter of 18–32 mm. The swirl-type air intake system includes:

[0033] The intake pipe is used to provide a channel for gas flow, with a diameter of 4-8 mm;

[0034] Gas one-way throttle valve;

[0035] Proportional control valve;

[0036] Gas source storage tank;

[0037] The angle between the air intake pipe and the normal is 20-60°, and the angle between the air intake pipe and the lower wall is 20-45°. A one-way gas throttle valve and a proportional regulating valve are installed on the pipeline between the air intake pipe and the gas source storage tank.

[0038] Furthermore, the system comprises several fish-mouth stacked ceramic tubes, which are connected together from bottom to top by fish-mouth stacked ceramic tube connecting rings. The lower fish-mouth stacked ceramic tubes extend upwards by 5 to 15 mm, and the total length of all fish-mouth stacked ceramic tubes after successful connection is 1600 to 3100 mm.

[0039] Furthermore, the maximum outer diameter of the fish-mouth stacked ceramic tube is 30-48 mm, and the size decreases by 0.6-0.8 times from bottom to top.

[0040] Furthermore, the maximum inner diameter of the fish-mouth stacked ceramic tube is 18.5 to 29.6 mm, decreasing in size by 0.6 to 0.8 times from bottom to top, with the minimum inner diameter being 0.618 times the maximum inner diameter.

[0041] This invention also discloses an annealing method for ultra-low loss optical fiber, which uses an annealing apparatus for ultra-low loss optical fiber as described above, and includes the following steps:

[0042] 1) Complete the installation of the optical rod heating system, optical fiber annealing system, spiral inlet air intake system, fish-mouth stacked ceramic tube system, coating system and take-up system;

[0043] 2) The optical fiber preform enters the optical fiber drawing furnace and is heated and melted under high temperature conditions; the molten optical fiber preform is drawn along the optical fiber drawing direction in the optical fiber drawing furnace to form an optical fiber of the required diameter;

[0044] 3) The optical fiber obtained in step 2) is annealed in an annealing furnace.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] 1) By using a fish-mouth stacked ceramic tube design, the airflow path in the annealing area is optimized, enabling the airflow to be evenly distributed in multiple directions, thereby achieving a more uniform temperature distribution and improving the mechanical and optical properties of the optical fiber.

[0047] 2) Enhanced airflow stability control: By using a swirling air intake method, the incoming airflow is made to rotate, which enhances the gas mixing effect and flow rate control, ensures stable airflow during the annealing process, reduces unnecessary fluctuations, and improves optical fiber quality;

[0048] 3) Enhanced adaptability: Provide annealing apparatus and methods suitable for optical fibers with high diameter uniformity requirements, improve the flexibility and adaptability of annealing equipment, and meet different production needs. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0050] Figure 2This is a schematic diagram of the vortex-type air intake system of the present invention;

[0051] Figure 3 This is a potential gas movement path diagram for the present invention;

[0052] Figure 4 This is a diagram showing the dimensional changes of the fish-mouth stacked ceramic tube of the present invention;

[0053] Figure 5 This is a schematic diagram of the connection of the fish-mouth stacked ceramic tube of the present invention. Detailed Implementation

[0054] The present invention will now be described in detail so that its advantages and features can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0055] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0056] like Figure 1-5 As shown, the present invention discloses an annealing device for ultra-low loss optical fiber, including an optical rod heating system 1, an optical fiber annealing system 2, a spiral inlet air intake system 3, a fish-mouth stacked ceramic tube system 4, a coating system 5, and a take-up system 6. Through the cooperation between the above systems, the quality and efficiency of optical fiber production can be effectively improved.

[0057] The main function of the optical fiber heating system 1 is to heat and melt the optical fiber and draw it into an optical fiber. The specific structure and technical implementation scheme are as follows:

[0058] Optical rod 11, as the precursor material for optical fiber, needs to be heated and melted at high temperature;

[0059] The fiber drawing furnace 12 primarily heats the optical rod 11, shaping it into a cone and allowing it to be drawn into an optical fiber of a fixed size. The fiber drawing furnace 12 uses heating elements to reach a high temperature, melting the optical rod 11.

[0060] Optical fiber 13 is formed by melting optical rod 11 and drawing it to the required diameter through optical fiber drawing furnace 12;

[0061] During the traction process, the fiber 13 needs to maintain a uniform speed and direction to ensure the consistency of the fiber diameter.

[0062] The main function of the fiber annealing system 2 is to anneal the drawn fiber 13 to eliminate internal stress, lower the hypothetical temperature, promote the relaxation of the fiber molecular structure, and improve the optical and mechanical properties of the fiber. The specific structure and technical implementation scheme are as follows:

[0063] The outer wall 21 of the annealing furnace is made of high-temperature resistant material, which can withstand high-temperature environments. Existing conventional products can be used.

[0064] Heating coil 22 is placed inside the annealing furnace. The total height of the coil is 1500-3000 mm, the inner diameter is 45-70 mm, and the number of turns is 7-15. Cooling water is circulated inside the heating coil 22 to prevent the coil from deforming and to ensure uniform heating.

[0065] Quartz barrel 23 is placed inside the annealing furnace. A heating coil 22 with an outer diameter of 43-70 mm and an inner diameter of 40-65 mm is wound on the quartz barrel 23 to transfer heat. During the assembly of the heating coil 22 and the quartz barrel 23, the distance between the two ends of the quartz barrel 23 and the heating coil 22 is controlled within the range of 1-3 mm to ensure uniform heating.

[0066] Metal retaining ring 24 is set at the inlet end of the annealing furnace to fix the fish-mouth stacked ceramic tube 4. The inner diameter of the retaining ring is rotatable and telescopic to precisely control the fish-mouth stacked ceramic tube 4 to be centered.

[0067] The lower tray 25 is located at the outlet end of the annealing furnace, which facilitates the disassembly and installation of internal components of the annealing furnace, and makes maintenance and replacement easier.

[0068] The design of the swirl-type intake system 3 enables the airflow to form a stable swirling motion in the annealing region, that is, to form a stable swirling airflow in the annealing region. The outer diameter 31 of the swirl-type intake system 3 is 40-80 mm, the wall thickness is 15-30 mm, the inner diameter 32 is 18-32 mm, and the wall thickness is 15-30 mm. The swirl-type intake system 3 includes:

[0069] The intake pipe 33 is used to provide a channel for gas flow, and has a diameter of 4 to 8 mm;

[0070] The air intake direction 34 is used to allow gas to enter the device from the air intake pipe 33;

[0071] In the top view, the angle 35 formed by the intake pipe 33 and the normal is 20-60°.

[0072] In the top view, the angle 36 formed by the air intake pipe 33 and the lower wall is 20-45°.

[0073] Gas one-way throttle valve 37;

[0074] Proportional regulating valve 38;

[0075] Gas source storage tank 39;

[0076] The potential movement path 310 of the gas entering the channel allows the airflow to form a stable rotational motion after entering the device, which helps maintain the consistency of the fiber diameter.

[0077] A gas one-way throttle valve 37 and a proportional regulating valve 38 are installed on the pipeline between the air intake pipe 33 and the gas source storage tank 39. The gas one-way throttle valve 37 and the proportional regulating valve 38 are arranged in order of proximity to the terminal gas outlet. The function of the gas one-way throttle valve 37 is to stabilize the downstream airflow, and the function of the proportional regulating valve 38 is to provide a stable airflow input.

[0078] The design of the fish-mouth stacked ceramic tube system 4 enables a more uniform airflow distribution within the annealing region, effectively preventing fiber quality issues caused by excessive temperature gradients. The specific structure and technical implementation scheme are as follows:

[0079] The fish-mouth stacked ceramic tube has a maximum outer diameter of 41A-41D, with the inner diameter of 41A ranging from 30 to 48 mm. From 41A to 41D, the inner diameter decreases by 0.6 to 0.8 times. The minimum inner diameter is 42A-42D, with the inner diameter of 42A ranging from 18.5 to 29.6 mm. From 42A to 42D, the inner diameter decreases by 0.6 to 0.8 times, and the minimum inner diameter is 0.618 times the maximum inner diameter.

[0080] Fish-mouth stacked ceramic tube connecting ring 43 is used to connect adjacent fish-mouth stacked ceramic tubes. After all fish-mouth stacked ceramic tubes are successfully connected, the total length is 1600-3100mm, and the lower fish-mouth stacked ceramic tube will extend upwards by 5-15mm.

[0081] The connection between the fish-mouth stacked ceramic tube 4 and the fish-mouth stacked ceramic tube connecting ring 43 relies on gravity to bond together, allowing for expansion movement under high temperature conditions.

[0082] There is a gap between the combination of the quartz barrel 23 and the fish-mouth stacked ceramic tube 4, which is filled with soft, elastic graphite felt to increase the heat preservation effect.

[0083] The coating system 5 is used to add protective material to the surface of the optical fiber and improve the mechanical strength and abrasion resistance of the fiber through a curing process. The specific structure and technical implementation are as follows:

[0084] Coating device: When the optical fiber passes through the coating device, a protective material will be evenly coated on its surface. Existing conventional products can be used.

[0085] Curing device: The protective material is quickly cured by ultraviolet light or heat curing to form a strong protective layer. Existing conventional products can be used.

[0086] The take-up system 6 is used to ensure that the optical fiber maintains stable tension during the drawing and coating process, and to collect the optical fiber into the storage device. The specific structure and technical implementation are as follows:

[0087] A tension controller is used to maintain a stable tension of optical fiber 13 during the drawing process; existing conventional products can be used.

[0088] A collection device is used to collect the drawn and coated optical fiber 13 onto a storage reel or take-up reel for easy subsequent transportation and use. Existing conventional products can be used.

[0089] This invention also discloses an annealing method for ultra-low loss optical fiber, which uses an annealing apparatus for ultra-low loss optical fiber as described above, and includes the following steps:

[0090] 1) Complete the installation of the optical fiber heating system 1, optical fiber annealing system 2, swirl-type air intake system 3, fish-mouth stacked ceramic tube system 4, coating system 5, and take-up system 6; wind the heating coil 22 around the outer wall of the quartz barrel 23 and place the whole assembly inside the annealing furnace; connect several fish-mouth stacked ceramic tubes 4 from bottom to top using fish-mouth stacked ceramic tube connecting rings 43 and place them inside the quartz barrel 23; fix the fish-mouth stacked ceramic tubes 4 with metal retaining rings 24 to complete the assembly of the optical fiber annealing system 2 and the fish-mouth stacked ceramic tubes 4. Sequentially install the swirl-type air intake system 3, coating system 5, and take-up system 6 at the outlet of the annealing furnace to perform the annealing process;

[0091] 2) The optical rod 11 enters the optical fiber drawing furnace 12 and is heated and melted under high temperature conditions; the molten optical rod 11 is drawn and stretched along the optical fiber drawing direction 14 using the optical fiber drawing furnace 12 to form an optical fiber 13 of the required diameter;

[0092] 3) The optical fiber 13 obtained in step 2) is put into the annealing furnace for annealing treatment.

[0093] Any parts or structures not specifically described in this invention can be made using existing technologies or products, and will not be elaborated upon here.

[0094] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An annealing apparatus for ultra-low-loss optical fibers, characterized in that, include: Optical rod heating system, used to heat and melt optical rods and draw them into optical fibers; Fiber annealing system, used to anneal drawn optical fibers; A swirling air intake system is used to create a stable rotating airflow within the annealing region; Fish-mouth stacked ceramic tube system is used to ensure uniform airflow distribution within the annealing zone; Coating systems are used to add protective materials to the surface of optical fibers; The take-up system is used to ensure the tension stability of the optical fiber during the drawing and coating process and to take the optical fiber back up. The optical rod heating system, optical fiber annealing system, spiral air intake system, coating system, and take-up system are arranged sequentially along the optical fiber entry direction, and the fish-mouth stacked ceramic tube system is arranged inside the optical fiber annealing system. The fish-mouth stacked ceramic tube system consists of several fish-mouth stacked ceramic tubes, which are connected together from bottom to top by fish-mouth stacked ceramic tube connecting rings. The lower fish-mouth stacked ceramic tubes extend upwards by 5~15mm. The total length of all fish-mouth stacked ceramic tubes after successful connection is 1600~3100mm. The maximum outer diameter of the fish-mouth stacked ceramic tube is 30~48mm, and the size decreases by 0.6~0.8 times from bottom to top; The maximum inner diameter of the fish-mouth stacked ceramic tube is 18.5~29.6mm, and the size decreases by 0.6~0.8 times from bottom to top, with the minimum inner diameter being 0.618 times the maximum inner diameter. The swirl-type air intake system is located at the outlet end of the fiber optic annealing system, with an outer diameter of 40-80 mm and an inner diameter of 18-32 mm. The swirl-type air intake system includes: The intake pipe is used to provide a channel for gas flow, with a diameter of 4~8mm; Gas one-way throttle valve; Proportional control valve; Gas source storage tank; The angle between the air intake pipe and the normal is 20~60°, and the angle between the air intake pipe and the lower wall is 20~45°. A one-way gas throttle valve and a proportional regulating valve are installed on the pipeline between the air intake pipe and the gas source storage tank.

2. The apparatus for annealing an ultra-low-loss optical fiber according to claim 1, wherein The light rod heating system includes: Optical rods, as precursor materials for optical fibers, need to be heated and melted at high temperatures; An optical fiber drawing furnace is used to heat an optical rod, causing it to form a cone and be drawn into an optical fiber of a fixed size. Optical fiber is formed by melting an optical rod and then drawing it to the required diameter in an optical fiber drawing furnace. During the drawing process, the optical fiber maintains a uniform speed and direction to ensure the consistency of the optical fiber diameter.

3. The apparatus of claim 1, wherein the apparatus is configured to anneal the optical fiber at a temperature of about 1000 °C to about 1200 °C. The fiber optic annealing system includes: Annealing furnace; Heating coils are installed inside the annealing furnace. A quartz barrel is placed inside an annealing furnace, and a heating coil is wound around the quartz barrel; Metal retaining rings are installed at the inlet end of the annealing furnace to secure the fish-mouth stacked ceramic tube system; The lower tray is located at the outlet end of the annealing furnace, facilitating the disassembly and installation of internal components of the annealing furnace.

4. The annealing apparatus for ultra-low loss optical fiber according to claim 3, characterized in that, The total height of the heating coil is 1500~3000mm, the inner diameter is 45~70mm, and the number of turns is 7~15. Cooling water is circulated inside the heating coil to prevent coil deformation and ensure uniform heating.

5. The annealing apparatus for ultra-low loss optical fiber according to claim 3, characterized in that, The outer diameter of the quartz barrel is 43~70mm and the inner diameter is 40~65mm. During the assembly of the heating coil and the quartz barrel, the distance between the two ends of the quartz barrel and the heating coil is controlled within the range of 1~3mm to ensure uniform heating.

6. An annealing method for ultra-low loss optical fiber, characterized in that, Annealing is performed using the annealing apparatus for ultra-low loss optical fiber as described in any one of claims 1-5, comprising the following steps: 1) Complete the installation of the optical rod heating system, optical fiber annealing system, spiral inlet air intake system, fish-mouth stacked ceramic tube system, coating system and take-up system; 2) The optical fiber preform enters the optical fiber drawing furnace and is heated and melted under high temperature conditions; the molten optical fiber preform is drawn along the optical fiber drawing direction in the optical fiber drawing furnace to form an optical fiber of the required diameter; 3) The optical fiber obtained in step 2) is annealed in an annealing furnace.

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