Optical fiber preform laser heating furnace and processing method

Abstract

The application belongs to the technical field of optical fiber preform manufacturing, and discloses an optical fiber preform laser heating furnace and a processing method. The optical fiber preform laser heating furnace comprises a furnace body, a rod, a laser emitter, a water cooling device, a visual control device, an air extraction device and a control system. The rod is arranged in the furnace body, and the extension direction of the furnace body is parallel to the extension direction of the rod. The emission end of the laser emitter is arranged in the furnace body. The water cooling device is arranged in the furnace body. The detection end of the visual control device is arranged in the furnace body. The air extraction device is connected with the furnace body and used for extracting waste gas in the furnace body. The laser emitter and the visual control device are both connected with the control system. In this way, the surface cleanliness and uniformity of the optical fiber preform can be improved.

Description

Technical Field

[0001] This invention relates to the field of optical fiber preform technology, and in particular to an optical fiber preform laser heating furnace and processing method. Background Technology

[0002] In-tube vapor deposition is a process that deposits vapor on the inner wall of a high-purity glass tube to form a multilayered loose layer of doped or undoped silica. After deposition, the high-purity glass tube is a composite hollow glass tube with a certain thickness. The hollow glass tube after deposition needs to be melted at high temperature to make a solid optical fiber preform.

[0003] In related technologies, the melting and shrinking process of optical fiber preforms typically uses a graphite resistance furnace as the heating equipment. Power is supplied to the graphite heater through heating electrodes, and the high resistance of graphite generates heat. The heat is then transferred to the outer graphite core cylinder in the form of radiation and thermal conduction. Finally, the incandescent graphite core cylinder locally surrounds and heats the inner liner tube, causing the glass tube to soften, melt, and eventually collapse into a solid optical fiber preform at high temperature.

[0004] However, graphite materials undergo oxidation and sublimation when used in high-temperature environments above 1600℃ for extended periods. The resulting micron-sized graphite dust, distributed within the thermal field, easily adheres to the surface of the optical fiber preform. If these carbonaceous contaminants are not thoroughly removed in subsequent processes, they will form defect sources during optical fiber drawing, leading to decreased fiber strength and increased optical transmission attenuation. Furthermore, since graphite is a consumable material, the diameter of the graphite heater changes with the usage cycle, causing the thermal field distribution to drift. Additionally, the graphite resistance furnace uses contact heating, which limits energy density and creates a large temperature gradient, easily causing uneven heating of the hollow tube blank in the circumferential or axial direction. This results in central aperture drift or excessive ellipticity in the optical fiber preform during the melting process, affecting the geometric uniformity of the preform and consequently impacting the consistency of the optical fiber's optical performance. Summary of the Invention

[0005] The purpose of this invention is to provide a laser heating furnace and processing method for optical fiber preforms to solve the problems of low surface cleanliness and poor uniformity in the optical fiber preform melting process.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, a laser heating furnace for fiber optic preforms includes: a furnace body and a preform, the preform being disposed within the furnace body, the extension direction of the furnace body being parallel to the extension direction of the preform; a laser emitter, the emitting end of which is disposed inside the furnace body; a water cooling device, the water cooling device being disposed inside the furnace body; a vision control device, the detection end of which is disposed inside the furnace body; an exhaust device, the exhaust device being connected to the furnace body for extracting waste gas from inside the furnace body; and a control system, wherein both the laser emitter and the vision control device are connected to the control system.

[0007] Preferably, the water cooling device includes a plurality of water cooling pipes, which are arranged at intervals along the height direction of the furnace body and surround the inner wall of the furnace body.

[0008] Preferably, the optical fiber preform laser heating furnace further includes a heat dissipation partition, on which multiple heat dissipation grooves are formed.

[0009] Preferably, the bottom of the furnace body is provided with an air extraction port, and the air extraction device is disposed at the air extraction port.

[0010] Preferably, the furnace body has receiving holes at both ends along its length for the rod to pass through, and the rod has an air inlet and an air outlet at both ends, with the air outlet connected to a vacuum pump.

[0011] Preferably, the optical fiber preform laser heating furnace further includes a temperature measuring instrument, the detection end of which is located inside the furnace body, and the temperature measuring instrument is connected to the control system.

[0012] Preferably, the furnace body includes a hinged furnace cover and a furnace body, and the laser emitter, the vision control device, and the temperature measuring instrument are all located on the furnace cover.

[0013] Secondly, a processing method is applied to the laser heating furnace for fiber preforms as described above, the processing method comprising: S1. Turn on the water cooling device, the vision control device, and the air extraction device; S2. Place the rod inside the furnace body and set the laser emitter's spot shape to a rectangular spot; S3. Start the laser emitter to heat the rod. The vision control device tests the outer diameter of the rod and adjusts the power of the laser emitter according to the test results until the process requirements are met and the optical fiber preform is obtained. S4. Stop heating and remove after cooling; S5. Process and encapsulate the outer surface of the preform.

[0014] Preferably, in step S3, the heating time of the rod is in the range of 500 minutes to 1000 minutes, the heating temperature gradient of the rod increases, and the heating temperature range is 1000℃ to 1800℃.

[0015] Preferably, in step S4, the cooling time of the optical fiber preform ranges from 30 minutes to 100 minutes.

[0016] The beneficial effects of this invention are: The fiber optic preform laser heating furnace provided by this invention includes a furnace body, a preform, a laser emitter, a water cooling device, a vision control device, an exhaust device, and a control system. The preform is disposed inside the furnace body, and the extension direction of the furnace body is parallel to the extension direction of the preform. The emitting end of the laser emitter is disposed inside the furnace body. The water cooling device is disposed inside the furnace body. The detection end of the vision control device is disposed inside the furnace body. The exhaust device is connected to the furnace body and is used to extract the waste gas inside the furnace body. Both the laser emitter and the vision control device are connected to the control system.

[0017] In this way, the laser emitter can make the high-temperature field more stable and uniform, achieving uniform heating of the rod. Combined with the vision control device, it can avoid radial temperature difference caused by wear of heating elements or spot deviation, avoid rod ellipticity deviation and stress concentration caused by local overheating or heating dead zone, improve the uniformity of optical fiber preforms, and improve the surface cleanliness of optical fiber preforms because no additional dust pollution source is generated during laser heating. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the first structure of the laser heating furnace for optical fiber preforms in one embodiment of the present invention; Figure 2 This is a schematic diagram of the second structure of the laser heating furnace for optical fiber preforms in one embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a water-cooled pipe in one embodiment of the present invention.

[0019] In the picture: 1. Furnace body; 11. Exhaust port; 12. Accommodation hole; 13. Furnace cover; 14. Furnace body; 2. Bar stock; 21. Inlet end; 22. Outlet end; 3. Laser emitter; 4. Water cooling pipe; 5. Vision control device; 6. Heat dissipation baffle; 61. Heat dissipation groove; 7. Temperature measuring instrument. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0023] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0024] See Figures 1 to 3 This invention provides a laser heating furnace for optical fiber preforms, comprising a furnace body 1, a preform 2, a laser emitter 3, a water cooling device, a vision control device 5, an exhaust device, and a control system. The preform 2 is disposed within the furnace body 1, and the extension direction of the furnace body 1 is parallel to the extension direction of the preform 2. The emitting end of the laser emitter 3 is disposed inside the furnace body 1. The water cooling device is disposed inside the furnace body 1. The detection end of the vision control device 5 is disposed inside the furnace body 1. The exhaust device is connected to the furnace body 1 and is used to extract waste gas from inside the furnace body 1. Both the laser emitter 3 and the vision control device 5 are connected to the control system.

[0025] In this embodiment, the furnace body 1 is a rectangular structure extending horizontally. The laser emitter 3 is a 10.6μm wavelength carbon dioxide laser with a continuously adjustable output power range of 1-10kW and an output power fluctuation of ≤±1%. A laser resonant cavity is used in conjunction with beam homogenization technology. Multiple laser emitters 3 are arranged at intervals along the length of the furnace body 1. Each laser emitter 3 is connected to an optical conversion lens (not shown in the figure) to convert a circular light spot into a rectangular light spot, which is then projected onto the rod 2 for heating. A water-cooling device controls the temperature inside the furnace body 1. The visual control device 5 is a CCD (Charge-coupled Device). The device (photosensitive coupling assembly) is a vision device with a repeatability accuracy of ±1μm, capable of detecting the outer diameter of the rod 2. The laser emitter 3 and the vision control device 5 are connected through the control system. The vision control device 5 can capture the outer diameter profile and aperture changes of the molten rod 2 in real time and send control signals to the laser emitter 3. Based on the visual feedback data, the control system dynamically corrects the laser power and residence time through an algorithm model to achieve fully automated and micron-level precision control of the melting and shrinking process. The air extraction device can promptly remove the volatile silica inside the furnace 1 during the melting process.

[0026] In this way, the laser emitter 3 can make the high temperature field more stable and uniform, achieving uniform heating of the outer peripheral surface of the rod 2. Combined with the vision control device 5, it can avoid radial temperature difference caused by wear of heating elements or spot deviation, avoid ellipticity deviation and stress concentration of the rod 2 caused by local overheating or heating dead zone, and improve the uniformity of the optical fiber preform. Since no additional dust pollution source is generated during the laser heating process, the laser heating furnace for optical fiber preform can improve the surface cleanliness of the optical fiber preform, thereby improving the yield of the optical fiber preform.

[0027] It should be noted that the vision control device 5 transmits the outer diameter profile and outer diameter change of the rod 2 to the control system, and the control system dynamically adjusts the power and dwell time of the laser emitter 3 through algorithms. These are all existing technologies and will not be elaborated here.

[0028] See Figure 2 and Figure 3 In some embodiments, the water cooling device includes a plurality of water cooling pipes 4, which are arranged at intervals along the height direction of the furnace body 1 and surround the inner wall of the furnace body 1. In this embodiment, five water cooling pipes 4 are provided, and the five water cooling pipes 4 are arranged at equal intervals.

[0029] In this way, the water-cooling pipe 4 can provide circumferential cooling of the rod 2, making the thermal field inside the furnace more uniform and stable, avoiding temperature differences in the circumferential or axial direction of the rod 2 caused by uneven heat dissipation, improving the uniformity of the optical fiber preform in the melting process, and the fully enclosed water-cooling device can provide continuous heat insulation protection for the furnace body 1, preventing the furnace body 1 from overheating and extending the service life of the optical fiber preform laser heating furnace.

[0030] It is understandable that the water cooling pipe 4 can also be in the shape of a snake, a labyrinth, etc., to extend the flow path of the coolant in the water cooling pipe 4. The number, shape and setting position of the water cooling pipe 4 can be adjusted according to actual needs, and will not be listed in detail here.

[0031] See Figure 2 In some embodiments, the optical fiber preform laser heating furnace also includes a heat dissipation partition 6, on which a plurality of heat dissipation grooves 61 are formed.

[0032] In this embodiment, the heat dissipation baffle 6 is disposed at the bottom of the furnace body 1, and multiple square heat dissipation slots 61 are distributed in an array on the heat dissipation baffle 6 to improve the heat dissipation efficiency of the heat dissipation baffle 6 and to cooperate with the water cooling device to prevent heat from accumulating inside the furnace body 1.

[0033] In this way, the heat dissipation baffle 6 can absorb the heat accumulated at the bottom of the furnace and transfer it to the water cooling device, avoiding local overheating and deformation of the bottom of the furnace. This helps to maintain a uniform temperature in the laser heating furnace for optical fiber preforms under high-temperature conditions, and improves the stability of laser melting and the uniformity of optical fiber preforms.

[0034] See Figure 3 In some embodiments, the bottom of the furnace body 1 is provided with an exhaust port 11, and an exhaust device is provided at the exhaust port 11.

[0035] In this embodiment, the exhaust port 11 is a round hole. The exhaust device is used to extract the waste gas generated inside the furnace body 1 when the molten bar 2 is melted. The exhaust port 11 is located below the heat dissipation baffle 6.

[0036] In this way, the waste gas can be prevented from being retained, diffused and redeposited on the surface of the rod 2 inside the furnace body 1 during the melting process, thus improving the cleanliness of the surface of the optical fiber preform. The exhaust port 11 is set at the bottom of the furnace body 1, which can form a top-down exhaust path with the laser heating zone at the top, thus avoiding the accumulation of waste gas in dead corners at the bottom of the rod 2 and avoiding affecting the temperature uniformity inside the furnace body 1.

[0037] It is understandable that the air extraction device can be an air pump, and the location of the air extraction device and the air extraction port 11 can be adjusted according to actual needs, which will not be elaborated here.

[0038] See Figure 1 and Figure 2In some embodiments, the furnace body 1 has receiving holes 12 at both ends along its length for the rod 2 to pass through. The rod 2 has an air inlet end 21 and an air outlet end 22 at both ends, and the air outlet end 22 is connected to a vacuum pump (not shown in the figure).

[0039] In this embodiment, the rod 2 is horizontally inserted into the furnace body 1. The diameter of the receiving hole 12 is larger than the outer diameter of the rod 2. The air inlet end 21 and the air outlet end 22 of the rod 2 are respectively located on the outer sides of both ends of the furnace body 1. The air inlet end 21 is located on the left side of the furnace body 1, and the air outlet end 22 is located on the right side of the furnace body 1.

[0040] In this way, the rod 2 is inserted into the furnace body 1 and heated by the laser emitter 3, which can realize non-contact melting of the rod 2. The energy density is high and the controllability is strong. By introducing gas into the rod 2, the uniformity of the pore size of the rod 2 can be controlled, which is beneficial to improving the yield of optical fiber preforms and avoiding excessive ellipticity.

[0041] See Figure 1 and Figure 2 In some embodiments, the fiber optic preform laser heating furnace further includes a temperature measuring instrument 7, the detection end of which is located inside the furnace body 1, and the temperature measuring instrument 7 is connected to the control system. Further, in some embodiments, the furnace body 1 includes a hinged furnace cover 13 and a furnace body 14, with the laser emitter 3, vision control device 5, and temperature measuring instrument 7 all located on the furnace cover 13.

[0042] In this embodiment, the temperature measuring instrument 7 is a high-temperature resistant colorimetric / radiation thermometer with a temperature measurement range that can cover the temperature range inside the furnace body 1. The closed-loop control accuracy is ±0.5℃. The temperature measuring instrument 7 can monitor the ambient temperature inside the furnace body 1 in real time. The temperature measuring instrument 7 is connected to the control system, enabling the control system to send control signals to the laser emitter 3 based on the temperature signal inside the furnace body 1 and the outer diameter of the rod 2, thereby controlling the power of the laser emitter 3 and keeping the quartz glass in the optimal viscous flow range to effectively suppress crystallization.

[0043] In this way, the control system can integrate the temperature signal and the outer diameter signal of the rod 2 monitored by the vision control device 5 to adjust the power of the laser emitter 3, improve the performance consistency and uniformity of the optical fiber preform, and avoid aperture changes caused by uneven heating. The laser emitter 3, vision control device 5, and temperature measuring instrument 7 are centrally installed on the furnace cover 13, which facilitates the monitoring of the rod 2. The rod 2 can be loaded and unloaded and maintained by flipping and opening, which improves the reliability of the laser heating furnace for optical fiber preforms.

[0044] It is understandable that the positions of the laser emitter 3, the vision control device 5, and the temperature measuring instrument 7 can be adjusted according to actual needs, which will not be elaborated here.

[0045] See Figures 1 to 3 The present invention also provides a processing method applied to the laser heating furnace for optical fiber preforms as described in the above embodiments. The processing method includes: S1. Turn on the water cooling device, vision control device 5 and air extraction device; S2. Place the rod 2 inside the furnace body 1 and set the shape of the laser emitter 3 to a rectangular spot. S3. Start the laser emitter 3 to heat the rod 2. The vision control device 5 tests the outer diameter of the rod 2 and adjusts the power of the laser emitter 3 according to the test results until the process requirements are met and the optical fiber preform is produced. S4. Stop heating and remove after cooling; S5. Process and encapsulate the outer surface of the preform.

[0046] In this embodiment, in step S1, after turning on the water cooling device and the air extraction device, the water flow rate of the water cooling device is adjusted to 1L-10L, the air extraction pressure of the air extraction device is adjusted to -10Pa-40Pa, and the temperature measuring instrument 7 is turned on to monitor the temperature inside the furnace body 1.

[0047] In this way, the furnace body 1 can meet the process requirements before the rod 2 is put in, and the rod 2 can be monitored by the visual control device 5 and the temperature measuring instrument 7 throughout the melting process, and the laser power can be adjusted in time to ensure that the rod 2 is heated evenly and improve the surface cleanliness and uniformity of the optical fiber preform.

[0048] See Figure 1 In some embodiments, in step S3, the heating time of the bar 2 ranges from 500 minutes to 1000 minutes, and the heating temperature gradient of the bar 2 increases, with a heating temperature range of 1000℃ to 1800℃.

[0049] In this embodiment, the heating time of the bar 2 can be any value between 500 minutes and 1000 minutes or any two values, such as 500 minutes, 600 minutes, 700 minutes, 800 minutes, 900 minutes, and 1000 minutes; the heating temperature can be any value between 1000℃ and 1800℃ or any two values, such as 1000℃, 1200℃, 1400℃, 1600℃, and 1800℃; the heating temperature gradient range of the bar 2 is 0.1℃ / s to 3℃ / s, and the heating temperature gradient of the bar 2 can be any value between 0.1 and 3 or any two values, such as 0.1℃ / s, 0.5℃ / s, 1℃ / s, 2℃ / s, and 3℃ / s.

[0050] In this way, gradient heating can ensure that the inner and outer layers of the rod 2 are fully heated and melted at each temperature step, avoiding uneven heating of the rod 2 in certain areas and improving the uniformity and consistency of the optical fiber preform.

[0051] In some embodiments, in step S4, the cooling time of the optical fiber preform ranges from 30 minutes to 100 minutes.

[0052] In this embodiment, the cooling time of the optical fiber preform can be any value between 30 minutes and 100 minutes or any range between two values, such as 30 minutes, 50 minutes, 70 minutes, 90 minutes, 100 minutes, etc.

[0053] In this way, after the laser heating is stopped, the optical fiber preform is slowly cooled down by the water cooling device, thereby slowly releasing thermal stress and preventing cracks and splits in the optical fiber preform due to a sudden drop in temperature, thus improving the performance of the optical fiber preform.

[0054] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A laser heating furnace for optical fiber preforms, characterized in that, include: A furnace body (1) and a bar (2), wherein the bar (2) is disposed inside the furnace body (1), and the extension direction of the furnace body (1) is parallel to the extension direction of the bar (2); A laser emitter (3), the emitting end of which is located inside the furnace body (1); A water-cooling device is installed inside the furnace body (1); A vision control device (5), wherein the detection end of the vision control device (5) is located inside the furnace body (1); An exhaust device is connected to the furnace body (1) and is used to extract the exhaust gas inside the furnace body (1); The control system is connected to both the laser emitter (3) and the vision control device (5).

2. The optical fiber preform laser heating furnace according to claim 1, characterized in that, The water cooling device includes multiple water cooling pipes (4), which are arranged at intervals along the height direction of the furnace body (1) and surround the inner wall of the furnace body (1).

3. The optical fiber preform laser heating furnace according to claim 1, characterized in that, The optical fiber preform laser heating furnace also includes a heat dissipation partition (6), on which a plurality of heat dissipation grooves (61) are provided.

4. The optical fiber preform laser heating furnace according to claim 1, characterized in that, The furnace body (1) has an exhaust port (11) at the bottom, and the exhaust device is located at the exhaust port (11).

5. The optical fiber preform laser heating furnace according to claim 1, characterized in that, The furnace body (1) has accommodating holes (12) at both ends along its length for the rod (2) to pass through. The rod (2) has an air inlet (21) and an air outlet (22) at both ends, and the air outlet (22) is connected to a vacuum pump.

6. The optical fiber preform laser heating furnace according to claim 1, characterized in that, The optical fiber preform laser heating furnace also includes a temperature measuring instrument (7), the detection end of which is located inside the furnace body (1), and the temperature measuring instrument (7) is connected to the control system.

7. The optical fiber preform laser heating furnace according to claim 6, characterized in that, The furnace body (1) includes a hinged furnace cover (13) and a furnace body (14), and the laser emitter (3), the vision control device (5), and the temperature measuring instrument (7) are all located on the furnace cover (13).

8. A processing method, characterized in that, The processing method, applied to the laser heating furnace for fiber preforms as described in any one of claims 1-7, comprises: S1. Turn on the water cooling device, the vision control device (5) and the air extraction device; S2. Place the rod (2) inside the furnace body (1) and set the laser emitter (3) to a rectangular spot shape; S3. Start the laser emitter (3) to heat the rod (2), and the vision control device (5) performs an outer diameter test on the rod (2) and adjusts the power of the laser emitter (3) according to the test results until the process requirements are met and the optical fiber preform is obtained. S4. Stop heating and remove after cooling; S5. Process and encapsulate the outer surface of the preform.

9. The processing method according to claim 8, characterized in that, In step S3, the heating time of the rod (2) is in the range of 500 minutes to 1000 minutes, and the heating temperature gradient of the rod (2) increases, with the heating temperature range being 1000℃ to 1800℃.

10. The processing method according to claim 8, characterized in that, In step S4, the cooling time of the optical fiber preform ranges from 30 minutes to 100 minutes.

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