Optical fiber capillary drawing apparatus, method and system

Abstract

The application provides a fiber capillary drawing device, method and system. The drawing device comprises a feeding assembly, a graphene heating element and a traction assembly which are sequentially arranged along the vertical direction of a glass mother tube; the graphene heating element heats the glass mother tube to form a melting zone; the air pressure control mechanism comprises a ventilation assembly and a ceramic air pressure adjusting element, the ventilation assembly is connected to a through cavity, and the ceramic air pressure adjusting element is annularly arranged in the melting zone to form an annular air cavity; the inner circumferential surface of the ceramic air pressure adjusting element is annularly provided with ventilation micropores which are directed towards the glass mother tube and are connected to the annular air cavity; when the inner diameter of the glass mother tube is too large, the ceramic air pressure adjusting element continuously introduces gas to extrude the outer circumferential surface of the melting zone to adjust the internal and external pressure difference of the melting zone. The drawing device provided above can quickly rebuild the internal and external pressure difference balance and significantly improve the consistency and yield by arranging the ceramic air pressure adjusting element on the outer circumferential surface of the melting zone and forming the annular air cavity, thereby establishing a circumferential uniform and adjustable equivalent external pressure field in the near field of the forming point.

Description

Technical Field

[0001] This application relates to the field of optical fiber capillary technology, and in particular to a method and apparatus for drawing optical fiber capillaries. Background Technology

[0002] Fiber optic capillaries are widely used in fiber optic communication, sensing, microstructured fibers, and fiber lasers. Their outer diameter, inner diameter, and micropore integrity directly determine device performance and yield. Existing processes mostly rely on drawing towers to heat and soften the glass mother tube before stretching it into shape. The finished product size and hole structure are highly sensitive to the process parameters of the drawing process (heating position / temperature field, mother rod falling speed, drawing speed, auxiliary air pressure, etc.).

[0003] Existing control strategies typically rely on preset, fixed parameters based on ideal equipment conditions, maintaining them constant. The target outer diameter and inner diameter can be estimated based on mass conservation. However, under prolonged high-temperature operation, the heating furnace body and insulation structure inevitably experience thermal deformation and temperature field drift. This causes the center of the effective heating zone (softening point) to shift, altering the heating range and viscous rheological state of the molten zone. Consequently, the actual descent velocity of the main tube deviates from the preset value, disrupting the original internal and external pressure differential balance. The direct consequence is outer diameter fluctuation; when material transport and thermal history are mismatched, surface tension dominates the evolution of the inner diameter, easily leading to inner diameter shrinkage or even closure, resulting in scrap.

[0004] To suppress fluctuations, common practices include fine-tuning the main circuit internal pressure or the overall heating power. However, these two channels are far from the forming point and have large time delays, making them prone to overshoot. Consequently, the adjustment of the inner and outer diameters is easily intertwined: increasing pressure to adjust the inner diameter may induce outer diameter drift, and fine-tuning the traction speed, in turn, changes the force on the inner cavity, making stable convergence difficult. Therefore, an adaptive closed-loop wire drawing control device is needed to maintain forming stability under dynamic disturbances and achieve high consistency and high yield. Summary of the Invention

[0005] In view of this, it is necessary to provide a method and apparatus for drawing optical fiber capillaries to solve the above problems.

[0006] Embodiments of this application provide a method and apparatus for drawing optical fiber capillaries, used to draw a glass mother tube to generate an optical fiber capillary, comprising:

[0007] The glass mother tube has a through cavity along its axis, and a feeding assembly, a graphene heating element, and a traction assembly are sequentially inserted vertically.

[0008] The graphene heating element is heated to 1990℃~2010℃ to heat the glass mother tube, and the glass mother tube forms a molten zone. The traction component pulls the glass mother tube to stretch the molten zone to generate an optical fiber capillary.

[0009] The air pressure control mechanism includes a ventilation component and a ceramic air pressure regulator. The ventilation component is connected to the ventilation cavity and continuously introduces gas at a pressure of 0.8 kPa to 1.1 kPa. The ceramic air pressure regulator is arranged in a ring around the melting zone and forms an annular air cavity between the ceramic component and the melting zone.

[0010] The inner circumferential surface of the ceramic gas pressure regulating component is provided with a ventilation micro-hole facing the glass mother tube and communicating with the annular gas cavity. When the inner diameter of the glass mother tube is too large, the ceramic gas pressure regulating component continuously introduces gas to squeeze the outer circumferential surface of the melting zone, adjusts the pressure difference between the inside and outside of the melting zone, and controls the inner diameter of the optical fiber capillary to be 58μm~62μm.

[0011] In at least one embodiment of this application, the ceramic air pressure regulating component includes a first regulating part and a second regulating part. The first regulating part is arranged in a ring shape and has a first air cavity. The second regulating part is arranged around the inner circumferential surface of the first regulating part. The second regulating part is fixedly connected to the first regulating part and surrounds the first regulating part to form a second air cavity.

[0012] The ventilation micropore includes a first micropore and a second micropore. The first micropore is disposed in the first adjustment part and connects the first air chamber and the second air chamber. The second micropore is disposed in the second adjustment part. The diameter of the first micropore is larger than the diameter of the second micropore.

[0013] In at least one embodiment of this application, the first micropores are equidistantly arranged in an annular ring on the first adjustment part, and the second micropores are equidistantly arranged in an annular ring on the second adjustment part.

[0014] In at least one embodiment of this application, the first micropore includes a first opening and a second opening disposed opposite to each other, the second opening being located on the side of the first adjustment portion closer to the second adjustment portion;

[0015] Viewed along the axial direction of the first micropore, the diameter of the first opening is denoted as a, and the diameter of the second opening is denoted as b, satisfying 1.5a≤b≤3a.

[0016] In at least one embodiment of this application, the second adjustment part includes a first diffusion layer, a gas equalization layer and a second diffusion layer arranged sequentially along the extension direction of the glass mother tube. The first diffusion layer and the second diffusion layer are both disposed on the first adjustment part. The second micropore is formed on the gas equalization layer. The side of the gas equalization layer near the glass mother tube is parallel to the outer peripheral surface of the glass mother tube.

[0017] In at least one embodiment of this application, when viewed along the direction from the first adjustment portion toward the second adjustment portion, the projection of the first micropore along its central axis toward the first diffusion layer and the second diffusion layer, and offset from the gas equalization layer.

[0018] In at least one embodiment of this application, the second adjustment part further includes an arc-shaped part, the first diffusion layer and the second diffusion layer are symmetrically disposed on both sides of the gas equalization layer, and the arc-shaped part is disposed at the connection end between the first diffusion layer and the second diffusion layer and the first adjustment part.

[0019] In at least one embodiment of this application, the first diffusion layer, the gas equalization layer, and the second diffusion layer are integrally formed.

[0020] A method for drawing an optical fiber capillary, applied to an optical fiber capillary drawing apparatus as described above, the drawing method comprising the following steps:

[0021] Collect various process control parameters and establish a process model based on these parameters. Each process parameter includes:

[0022] The falling speed of the glass mother tube, the traction speed of the traction assembly, the inflation pressure and adjustment pressure of the air pressure control mechanism, and the product parameters.

[0023] The product parameters and the remaining process parameters are input into the process model to generate a sensitivity matrix;

[0024] The actual falling speed of the main tube in the drawing zone is obtained, and the determination threshold of the adjustment mode is calculated based on the sensitivity matrix;

[0025] Determine whether the threshold is met. If so, trigger the adjustment mode, input the actual falling speed and the target size of the product into the process model, calculate the auxiliary adjustment air pressure of the air pressure control mechanism, and suppress the inner hole contraction or closure.

[0026] The actual falling speed is combined with the auxiliary road regulating air pressure input to the process model to calculate the traction speed of the wire drawing module and control the outer diameter of the main tube;

[0027] Based on the adjusted auxiliary road regulating air pressure and the traction speed, the main traction tube is continuously tractioned to generate the optical fiber capillary.

[0028] A fiber capillary drawing system is applied to a fiber capillary drawing device as described above.

[0029] The aforementioned fiber capillary drawing device establishes a uniform and adjustable equivalent external pressure field near the forming point by setting a ceramic gas pressure regulating component on the outer periphery of the molten zone to form an annular gas cavity and arranging ventilation micropores on the inner circumferential surface. This allows for the local and rapid reconstruction of the internal and external pressure difference balance when the forming point shifts due to furnace temperature drift, prioritizing the stabilization of the inner hole size. The external pressure channel has a short path and minimal overshoot, and the traction speed of the traction component controls the outer diameter of the glass mother tube. This provides an execution basis for "inner-to-outer" size decoupling control, reduces the mutual entanglement between the inner and outer diameters, facilitates convergence, and effectively suppresses inner hole shrinkage and closure caused by surface tension imbalance. This enhances the feasibility and long-term robustness of the device, thereby maintaining forming stability under dynamic disturbances and significantly improving consistency and yield. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a fiber capillary drawing device according to one embodiment of this application.

[0031] Figure 2 for Figure 1 A perspective view of the ceramic air pressure regulating component of the fiber capillary drawing device.

[0032] Figure 3 for Figure 2 A cross-sectional view of the ceramic air pressure regulating component.

[0033] Figure 4 for Figure 3 Enlarged view of part A.

[0034] Figure 5 for Figure 2 A frontal cross-sectional view of the ceramic air pressure regulator.

[0035] Figure 6 for Figure 5 Enlarged view of part B.

[0036] Figure 7 This is a flowchart of a fiber capillary drawing method according to an embodiment of this application.

[0037] Explanation of main component symbols

[0038] 100. A fiber capillary drawing device; 10. Glass mother tube; 20. Graphene heating element; 30. Traction assembly; 40. Air pressure regulation mechanism; 41. Ventilation assembly; 42. Ceramic air pressure regulating element; 421. First adjustment part; 422. First air cavity; 423. First micropore; 423a. First opening; 423b. Second opening; 424. Second adjustment part; 424a. First diffusion layer; 424b. Gas equalization layer; 424c. Second diffusion layer; 425. Second air cavity; 426. Second micropore; 427. Arc-shaped part; 43. Annular air cavity; 200. A fiber capillary drawing method. Detailed Implementation

[0039] The embodiments of this application will now be described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0040] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have an intervening component. When a component is considered to be "placed" on another component, it can be directly placed on the other component or may also have an intervening component. The terms "top," "bottom," "upper," "lower," "left," "right," "front," "back," and similar expressions used in this article are for illustrative purposes only.

[0041] The embodiments of this application provide a method and apparatus for drawing optical fiber capillaries, used to draw an optical fiber capillary by pulling a glass mother tube, including a through cavity opened along the axis of the glass mother tube, and a feeding component, a graphene heating element and a drawing component sequentially inserted in the vertical direction.

[0042] The graphene heating element is heated to 1990℃~2010℃ to heat the glass mother tube, and the glass mother tube forms a molten zone. The traction component pulls the glass mother tube to stretch the molten zone to generate an optical fiber capillary.

[0043] The air pressure control mechanism includes a ventilation component and a ceramic air pressure regulator. The ventilation component is connected to the cavity and continuously introduces gas at a pressure of 0.8 kPa to 1.1 kPa. The ceramic air pressure regulator is arranged in a ring around the melting zone and forms an annular air cavity between the ceramic component and the melting zone.

[0044] The inner circumferential surface of the ceramic gas pressure regulating component is provided with a ventilation micro-hole facing the glass mother tube and communicating with the annular gas cavity. When the inner diameter of the glass mother tube is too large, the ceramic gas pressure regulating component continuously introduces gas to squeeze the outer circumferential surface of the melting zone, adjusts the pressure difference between the inside and outside of the melting zone, and controls the inner diameter of the optical fiber capillary to be 58μm~62μm.

[0045] The aforementioned fiber capillary drawing device establishes a uniform and adjustable equivalent external pressure field near the forming point by setting a ceramic gas pressure regulating component on the outer periphery of the molten zone to form an annular gas cavity and arranging ventilation micropores on the inner circumferential surface. This allows for the local and rapid reconstruction of the internal and external pressure difference balance when the forming point shifts due to furnace temperature drift, prioritizing the stabilization of the inner hole size. The external pressure channel has a short path and minimal overshoot, and the traction speed of the traction component controls the outer diameter of the glass mother tube. This provides an execution basis for "inner-to-outer" size decoupling control, reduces the mutual entanglement between the inner and outer diameters, facilitates convergence, and effectively suppresses inner hole shrinkage and closure caused by surface tension imbalance. This enhances the feasibility and long-term robustness of the device, thereby maintaining forming stability under dynamic disturbances and significantly improving consistency and yield.

[0046] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0047] Please see Figures 1-7 This application provides an embodiment of an optical fiber capillary drawing device 100. Specifically, in this embodiment, it should be noted that the optical fiber capillary drawing device employs a vertically arranged feeding assembly, a graphene heating element 20, and a traction assembly 30. The glass mother tube 10 has a through cavity along its axis. The ventilation assembly 41 communicates with this cavity and continuously provides an internal cavity pressure of 0.8 kPa to 1.1 kPa as the main support pressure throughout the drawing process. The operating temperature of the graphene heating element 20 is set in the range of 1990℃ to 2010℃, so that the mother tube forms a stable melting zone in the heating section. The traction assembly 30 cooperates with the feeding assembly to continuously stretch and shape the mother tube below the melting zone.

[0048] To establish a uniform and controllable peripheral pressure environment near the forming point, this embodiment coaxially mounts a ceramic pressure regulator 42 around the outer periphery of the molten zone, defining an annular gas cavity 43 between the ceramic pressure regulator 42 and the molten zone. Ventilation micropores are equidistantly arranged circumferentially on the inner circumferential surface of the ceramic pressure regulator 42, each micropore communicating with the annular gas cavity 43 and facing the outer surface of the glass mother tube 10. When the inner diameter of the product is detected or confirmed to be too large during production, gas is continuously supplied to the annular gas cavity 43 through the ceramic pressure regulator 42. The ventilation micropores distribute the incoming gas circumferentially into a uniform external pressure film, generating a stable extrusion effect on the outer periphery of the molten zone. This locally adjusts the internal and external pressure difference of the molten zone at the forming point, gradually reducing the inner diameter and stabilizing it within the target range of 58μm to 62μm. The above structure and operating conditions are only described for this embodiment to ensure a repeatable internal and external pressure difference adjustment window and inner hole stabilization conditions are obtained near the forming point under typical wire drawing speeds and feeding rates.

[0049] The technical solution implemented in this embodiment can quickly construct a uniform circumferential equivalent external pressure in the near field of the molten zone without changing the baseline of the main road internal pressure and the traction cycle, thereby prioritizing the stabilization of the inner diameter: when the inner diameter is too large, the equivalent external pressure on the outer periphery is uniformly applied in the circumferential direction through the annular air cavity 43 and the ventilation micropores, which reduces the net outward driving force of the molten glass wall, and the inner hole gradually shrinks and enters a narrow tolerance zone of 58μm to 62μm; since the external pressure is applied close to the forming point, the air path is short, and the response is fast, the inner diameter correction process is mild and controllable, avoiding the time delay and overshoot that may be caused by remote adjustment (such as simply increasing the main road pressure or heating).

[0050] Meanwhile, the uniform distribution of external pressure suppresses stripes and lateral disturbances caused by local jetting, which is beneficial to improving the roundness and dimensional consistency of the inner hole. Therefore, in actual continuous production, even if the heating position slowly shifts due to temperature drift, this embodiment can still maintain an effective balance of the pressure difference between the inside and outside of the forming point through continuous adjustment of the equivalent external pressure on the outer periphery. While ensuring that the outer diameter is kept stable by the traction cycle, it achieves rapid convergence and long-term stable control of the inner diameter, reducing the risk of inner hole shrinkage, pore closure, and dimensional deviations, and improving product consistency and yield.

[0051] Furthermore, in this embodiment, the graphene heating element 20 heats the glass mother tube 10 to 1990℃~2010℃ to form a molten zone; a ceramic gas pressure regulating element 42 is coaxially arranged on the outer periphery of this molten zone, defining an annular gas cavity 43 between the two. The ceramic element is preferably made of high-temperature stable ceramic (such as alumina ≥95% or silicon nitride), with an inner diameter coaxial with the outer diameter of the mother tube ≤0.2mm, and an axial position such that the effective action zone of the annular gas cavity 43 covers a range of 3–8 mm above and below the forming point to ensure uniform action on the near field of the forming point.

[0052] The ventilation component 41 is connected to the main pipe cavity to form the main internal pressure, and dry gas (such as N2) at 0.8 kPa to 1.1 kPa (gauge pressure) is continuously introduced during production. The auxiliary gas supply enters the outer periphery of the melting zone through a short path via a proportional valve → buffer chamber (which can be the upstream chamber of the regulating component) → annular gas chamber 43 → inner circumferential micropores, realizing local external pressure regulation.

[0053] Furthermore, in this embodiment, it should be noted that a high-precision vision sensor is installed near the molten end to monitor the falling speed of the main tube in the melting zone in real time. The sensor obtains the real-time falling speed by tracking the displacement of the main tube's edge / feature point. The control unit compares the falling speed with the preset nominal speed initially calibrated by the equipment and sets a dead zone and dwell time to avoid misjudgment due to jitter. When the detected speed is lower than the preset speed and continues to exceed the set dwell time, it is determined that the adjustment mode is entered.

[0054] In one specific embodiment, if the descent speed of the main tube slows down while the traction cycle remains unchanged, the following chain effect occurs: the volume of glass entering the molten zone per unit time decreases, while traction continues, resulting in an increased equivalent draw ratio and a thinner tube wall. Thinner tube walls reduce the "circumferential load-bearing capacity" against outward bulging under the same internal pressure. Due to slower feeding, the same voxel spends a longer time in the high-temperature zone, resulting in more thorough heating and further reduced viscosity. The lower the viscosity, the more pronounced the "blowing effect" of the internal pressure on the orifice wall. While the main circuit internal pressure remains constant (e.g., 0.8–1.1 kPa), the thinner and softer glass wall weakens its resistance to internal pressure; in the balance of "internal pressure—external pressure—surface tension," the inner orifice is more easily "blown up," resulting in a larger inner diameter.

[0055] Furthermore, the control unit first calculates and issues a new setting for the auxiliary air pressure. Through the annular air chamber 43 and the micro-pore array, a uniform circumferential external pressure is formed on the outer periphery of the molten zone to reduce the pressure difference between the inside and outside and suppress the inner hole inflation, so that the inner diameter falls back to the target range. If necessary, the traction speed is slightly corrected to restore the outer diameter to stability.

[0056] In one specific embodiment, the ceramic gas pressure regulating component 42 adopts a double-layer coaxial annular structure, including a first regulating part 421 and a second regulating part 424. The first regulating part 421 is arranged in an annular shape, and a first gas cavity 422 is formed circumferentially inside it; the second regulating part 424 is arranged around the inner circumferential surface of the first regulating part 421 and is fixedly connected to the first regulating part 421, and the two together form a second gas cavity 425 located on the inner side and close to the melting zone. In order to achieve graded pressure equalization and orderly release, this embodiment divides the venting microholes into two levels: the first microhole 423 set in the first regulating part 421 is used for conduction and throttling between the first gas cavity 422 and the second gas cavity 425, and the second microhole 426 set in the second regulating part 424 is used to uniformly release the gas in the second gas cavity 425 to the non-contact annular gap between the regulating component and the outer wall of the main tube (i.e., the annular air gap on the outer periphery of the melting zone).

[0057] To achieve stable pressure drop distribution and a smooth transition between dynamic and static pressure, the diameter of the first micropore 423 is larger than that of the second micropore 426. Gas from the supply end is first buffered in the first gas chamber 422, then passes through the first micropore 423 to form a primary pressure drop and initial diffusion. After entering the second gas chamber 425, it passes through the smaller-diameter second micropore 426 to complete a secondary pressure drop and refine the distribution, ultimately forming a circumferentially uniform, low-velocity static pressure film within the annular gap. This structure establishes a controllable equivalent external pressure field near the forming point without contacting the molten outer wall or forming a directional jet scour.

[0058] Furthermore, implementing the technical solution of this embodiment has the following technical effects: First, the tiered release of pressure energy through two-stage gas chambers and two-stage micropores dissipates pressure energy in sequence: the first micropore 423 with a larger aperture undertakes the main pressure drop and flow shaping, while the second micropore 426 with a smaller aperture completes fine pressure equalization at the end, thereby obtaining a circumferentially consistent and less pulsating static pressure film within the annular gap, significantly reducing the risk of stripes and lateral disturbances common in external blowing schemes; Second, the second gas chamber 425, as a near-field pressure equalization chamber close to the molten zone, can quickly establish the target external pressure within a small volume, with fast response and small overshoot, which is beneficial for micro- and continuous closed-loop correction of the internal and external pressure difference.

[0059] Furthermore, the graded pore size provides reliable anti-backflow and anti-clogging capabilities: the first micropore 423 is larger, has strong dirt-holding capacity, and is easy to clean; the second micropore 426 is smaller, more numerous, and evenly distributed. Even if individual pores are weakened by dust or condensation, the overall pressure equalization effect can still be maintained. In addition, the double-layer ceramic structure isolates the high-temperature surface from the gas supply surface. Combined with the low Reynolds number release of the second micropore 426, it can effectively prevent directional jet from scouring the molten outer wall, protect the flatness of the forming interface, and improve the roundness and dimensional consistency of the inner hole. In summary, this embodiment achieves near-field, gentle, and uniform application of equivalent external pressure to the outer periphery of the molten zone through a graded pressure equalization path of "first gas chamber 422—first micropore 423—second gas chamber 425—second micropore 426—annular gap". This provides a linear and predictable execution end for subsequent small-step pressure adjustment based on forming deviations, thereby prioritizing the stabilization of the inner diameter and reducing the risk of over-adjustment and oscillation without interfering with the outer diameter mass conservation control.

[0060] In one specific embodiment, the ventilation micro-holes are arranged in an annular equidistant pattern. The first micro-hole 423 is arranged in a closed annular shape with equal angular intervals along the circumference of the first adjusting part 421, used to uniformly introduce gas from the first air chamber 422 into the second air chamber 425. Similarly, the second micro-hole 426 is arranged in a closed annular shape with equal angular intervals along the circumference of the second adjusting part 424, used to uniformly release gas from the second air chamber 425 to the non-contact annular gap between the adjusting component and the outer wall of the main tube. The annular equidistant arrangement of the first and second micro-holes 426 is achieved within the same coaxial system, preferably ensuring the coaxiality and end-face perpendicularity of the adjusting component and the main tube, to reduce circumferential pressure difference caused by assembly eccentricity.

[0061] To balance manufacturing and pressure equalization, the number of first micropores 423 can be relatively small, but their diameter can be relatively large to facilitate primary diffusion. The number of second micropores 426 can be relatively large, but their diameter can be relatively small to facilitate uniform distribution at the end. The circumferential equidistant spacing of the two stages of micropores can significantly reduce flow concentration and dynamic pressure jet in a certain angular region, ensuring that the circumferential pressure field is fully "flattened" before entering the annular gap. In actual assembly, equidistant and concentric degrees can be ensured by positioning with reference holes and indexing machining, and the consistency of circumferential spacing can be confirmed by measuring tools or optical projection, thereby improving the consistency and reproducibility of repeated assembly.

[0062] Furthermore, the annular equidistant arrangement of the first and second micropores 426 balances the release process from the two-stage gas chambers to the annular gap in the angular direction, significantly suppressing defects caused by circumferential unevenness such as "stripes," "lateral disturbances," and "local bulges / depressions," thus improving the smoothness of the molten outer wall interface and the roundness of the inner hole. Secondly, the equidistant arrangement reduces the phase difference and gradient of the gas in the circumferential propagation, reducing the risk of standing waves / acoustic pulsations being amplified in small-volume cavities, making the external pressure film closer to the static pressure field, thereby exhibiting a more linear response and smaller overshoot during small-step pressure regulation. Thirdly, the equidistant annular geometry aligns with the assembly of minor eccentricities and thermal expansion. The system exhibits better robustness against disturbances such as cold contraction. Even if individual holes experience slight degradation due to contamination or wear, the overall circumferential pressure equalization capability can be maintained stable through the "majority hole" averaging effect. Fourth, the clearly defined division of labor between the "first micro-hole 423 (primary diffusion) - second micro-hole 426 (end uniform distribution)" and the equidistant ring layout helps to achieve higher angular uniformity without increasing the gas supply pressure. This reduces the peak-valley difference requirement for external peripheral pressure from the source, ultimately achieving a gentle and uniform application of the equivalent external pressure to the molten zone. This facilitates the rapid and predictable pullback of the inner diameter and its stabilization within the target range during subsequent closed-loop control.

[0063] In one specific embodiment, the first micropore 423 is a staged release orifice connecting the first air chamber 422 and the second air chamber 425, with a first opening 423a and a second opening 423b at its two ends; wherein, the second opening 423b is located on the side of the first adjusting part 421 closer to the second adjusting part 424 (i.e., the end closer to the second air chamber 425). Viewed axially along the first micropore 423, the diameter of the first opening 423a is denoted as a, and the diameter of the second opening 423b is denoted as b, satisfying 1.5a≤b≤3a. Thus, the first micropore 423 forms an expanding (divergent) flow channel in the direction from the first air chamber 422 to the second air chamber 425: the front section uses a smaller cross-section a to initially limit and shape the upstream flow, and the rear section uses a larger cross-section b to diffuse and reduce the velocity of the flow, thereby completing a first-stage pressure drop and a smooth transition from dynamic pressure to static pressure before entering the second air chamber 425.

[0064] To reduce the risk of eddies and howling, the first and second openings 423b preferably adopt rounded / chamfered transitions, and the roughness and coaxiality of the micro-holes are controlled. The ratio of b / a is controlled at 1.5 to 3 times, which can provide sufficient diffusion angle to suppress jet pressure, while taking into account the strength of the ceramic wall thickness and the positioning accuracy of the micro-hole processing, avoiding structural weakness caused by excessive expansion or local jetting and uneven pressure in the two cavities caused by insufficient expansion.

[0065] Furthermore, implementing the technical solution of this embodiment yields the following technical effects specific to this embodiment: First, the divergent first micro-orifice 423 enables the upstream gas to undergo significant energy dissipation and deceleration before entering the second gas chamber 425, effectively weakening the jet impact and providing the second gas chamber 425 with a more uniform incoming gas close to static pressure, reducing the risk of circumferential non-uniformity and streaks from the source; Second, utilizing the diffusion geometry of a→b to achieve a predictable first-stage pressure drop, the subsequent end-stage uniform distribution performed by the second micro-orifice 426 only requires handling a small-amplitude pressure equalization refinement, resulting in a more linear system response and less overshoot; Third, the smaller upstream opening a acts as a flow limiter and anti-backflow mechanism, while the larger downstream opening b enhances the discharge capacity, maintaining stable chamber pressure under a wider range of gas supply variations, improving robustness to operating condition fluctuations and thermal breathing; Fourth, the divergent flow channel and rounded corner transition together reduce whistling and localized erosion, delaying the wear of the micro-orifice edge under long-term operating conditions of high temperature and low flow rate, improving lifespan and maintainability; Fifth, b / a The ratio is controlled between 1.5 and 3, ensuring sufficient ceramic wall thickness while meeting the requirements for pressure equalization and energy dissipation, balancing strength and processing yield, and facilitating large-scale manufacturing and repeated assembly. In summary, this embodiment, through the geometry of the first micropore 423 with "small-aperture forming, large dispersion, and first-stage pressure drop," ensures that the second gas chamber 425 obtains smooth and stable gas supply conditions, laying the foundation for the subsequent establishment of a circumferentially uniform, low-speed static pressure film in the annular gap, thereby achieving the gentle and controllable application of the equivalent external pressure on the outer periphery of the molten zone.

[0066] In one specific embodiment, the second adjustment section 424 is configured as a three-layer stacked structure along the extending direction (axial direction) of the glass mother tube 10, consisting of a first diffusion layer 424a, a gas equalization layer 424b, and a second diffusion layer 424c. The first diffusion layer 424a and the second diffusion layer 424c are both disposed on the first adjustment section 421 (which may be an annular shallow cavity / microgroove opened on the two opposing end faces of the inner circumference of the first adjustment section 421 or a porous ceramic / sintered metal thin ring), used for axial and circumferential pre-diffusion / post-rectification of the gas from upstream. The gas equalization layer 424b, located in the middle, is a coaxial annular cavity, with its inner annular surface facing the mother tube 10 on the side closest to the mother tube. This inner annular surface remains parallel to the outer circumferential surface of the mother tube within the working gap, thereby defining a stable non-contact annular gap. To achieve uniform distribution at the end, the second micropore 426 is formed on the gas equalization layer 424b (i.e., formed on the inner annular surface or the surface layer connected to it), so that the gas in the gas equalization layer 424b is released to the non-contact annular gap in a multi-point, small-hole, low-speed manner.

[0067] The resulting structural relationship is as follows: first diffusion layer 424a (upstream side) → equalization layer 424b (intermediate layer, with second micropores 426 and communicating with the annular gap) → second diffusion layer 424c (downstream side, suppressing backflow and vortex). These three layers, together with the first regulating part 421 / second regulating part 424, form a near-field, graded, and controllable release-pressure equalization-rectification path. The axial and radial geometric relationship ensures that the inner annular surface of the equalization layer 424b does not contact the outer wall of the parent tube and the gap is constant, avoiding mechanical disturbance or directional jet scouring of the forming interface.

[0068] Furthermore, the second micropore 426 is directly arranged in the gas equalization layer 424b, so that the gas completes the final circumferential pressure equalization in the small volume cavity before entering the annular gap, and is released in the form of low Reynolds number through multiple micropores, significantly weakening the dynamic pressure component and avoiding stripes and lateral disturbances caused by directional jet flow. The first / second diffusion layers 424c on the upper and lower sides of the gas equalization layer 424b perform pre-diffusion / post-rectification of the upstream incoming gas and downstream return flow, respectively, reducing the axial pressure gradient and vortex intensity in the cavity, suppressing the amplification of "thermal breathing" and gas supply pulsation in the small cavity, and making the pressure equalization closer to the static pressure field. The inner annular surface of the gas equalization layer 424b is parallel to and non-contact with the outer circumferential surface of the parent tube, so that the annular gap thickness is stable and the boundary conditions are consistent. Combined with the uniform distribution of the ends of the second micropore 426, a circumferentially consistent, low-speed and smooth external pressure film can be formed in the annular gap, which is conducive to the gentle adjustment of the internal and external pressure difference in the near field at the forming point and prioritizes the stabilization of the inner diameter.

[0069] Furthermore, the small volume and short path of the equalization layer 424b, combined with the buffering and rectification of the upper and lower diffusion layers, transforms the step pressure of the auxiliary path into a gradual change in cavity pressure, thus exhibiting dynamic characteristics of small overshoot and fast convergence in closed-loop pressure regulation. The second micropore 426 is located on the surface of the equalization layer 424b, with a small diameter and a large number of pores. Even if individual pores are attenuated due to dust or thermal deposition, they can still maintain uniform distribution through the averaging effect of the majority of pores. The upper and lower diffusion layers perform the "front-end" function of particle interception and flow shaping, further enhancing the anti-clogging and anti-fluctuation capabilities.

[0070] In one specific embodiment, when viewed from the first adjustment part 421 toward the second adjustment part 424, the axis of the first micropore 423 is not directly aligned with the gas equalization layer 424b. Instead, the projection of its axis is directed toward the first diffusion layer 424a and the second diffusion layer 424c located on the upper and lower sides of the gas equalization layer 424b, and is axially offset from the gas equalization layer 424b. In other words, the airflow from the first air cavity 422, guided through the first micropore 423, does not directly impact the working surface of the gas equalization layer 424b. Instead, it preferentially "sweeps" towards the diffusion layer regions above and below the gas equalization layer 424b, and then, after being buffered and shaped by the volume of the diffusion layers, enters the gas equalization layer 424b.

[0071] This geometric relationship, through minute axial misalignment and directional control, allows the micro-orifice jet to undergo dynamic pressure clipping and circumferential pre-diffusion before entering the gas equalization layer 424b, suppressing local erosion, streaks, and high-frequency pulsations within the gas equalization layer 424b at the source. To ensure the aforementioned directional and misalignment effects, the first micro-orifice 423 should have its axial deviation angle and axial coordinate tolerance controlled during manufacturing, ensuring its projection stably falls within the effective flow-receiving zone of the diffusion layer, rather than falling into the central working surface of the gas equalization layer 424b.

[0072] Furthermore, the jet from the first micro-orifice 423 first "contacts" with the upper and lower diffusion layers, completing the first stage of energy dissipation and lateral broadening within the diffusion layers. By the time it enters the gas equalization layer 424b, it is already approaching a low-velocity, broad-spectrum incoming gas. The gas equalization layer 424b thus operates closer to static pressure, reducing angular peak-to-valley differences and local vortices. The axial projection points towards the diffusion layer and is offset from the gas equalization layer 424b, ensuring that the dynamic pressure pulsations of the micro-orifice jet are absorbed / rectified by the diffusion layer before being fed into the gas equalization layer 424b. During closed-loop pressure regulation, this manifests as small overshoot and short steady-state time. The gas equalization layer 424b does not bear direct jet flow; the annular gap side receives a uniform, low Reynolds number external pressure film, reducing the forming interface stripes and lateral disturbances caused by directional scouring, which helps maintain the roundness and dimensional stability of the inner hole. Even if the flow rate of individual first micropores 423 is too high, its projection still falls on the diffusion layer rather than the gas equalization layer 424b. Abnormal dynamic pressure is "peak-suppressed" in the diffusion layer, and the system is less sensitive to minor deviations in processing / assembly and fluctuations in gas supply.

[0073] In one specific embodiment, the axial projection of the first micropore 423 points towards the diffusion layer. The gas ejected from the micropore first acts on the receiving surface of the first diffusion layer 424a, where it undergoes lateral widening and dynamic pressure reduction. Subsequently, the gas enters the intermediate gas equalization layer 424b through the channel of the diffusion layer, where circumferential static pressure equalization is achieved. Then, the gas is released into the non-contact annular gap by the second micropore 426 disposed on the gas equalization layer 424b in a multi-point, low-flow, and low-speed manner. The arc-shaped portion 427 is only disposed at the connection end between the first adjustment portion 421 and the diffusion layer, and at the connection end between the diffusion layer and its adjacent structure. Its function is to eliminate sharp angles and steps, provide a smooth transition, and prevent local separation, backflow vortices, and howling caused by the jet or secondary backflow of the first micropore 423 impacting sharp corners. The arc-shaped portion 427 does not serve as a flow channel and does not undertake the function of "introducing gas into the gas equalization layer 424b".

[0074] Specifically, the sequence of first micropore 423 → first diffusion layer 424a → gas equalization layer 424b → second micropore 426 → annular gap remains pure; the arc-shaped portion 427 only undergoes geometric rounding and rectification transitions to avoid being misunderstood as a flow guiding component, reducing design coupling and control uncertainties. The jet from the first micropore 423 no longer collides with sharp angles, and the rounded corners reduce the probability of boundary layer separation; in conjunction with the symmetrical diffusion layer, it can symmetrically absorb pulsations on both sides of the gas equalization layer 424b, reducing local vortex intensity and noise within the cavity. The jet first completes energy dissipation and lateral broadening in the first diffusion layer 424a, and when it enters the gas equalization layer 424b, it is already close to low-speed, broad-spectrum incoming gas; the gas equalization layer 424b is therefore closer to the static pressure working state, and the angular consistency of the evenly distributed ends of the second micropore 426 is better.

[0075] Furthermore, since the dynamic pressure is reduced in the diffusion layer and equalized in the gas equalization layer 424b, the small-step pressure regulation in the auxiliary path is transformed into smooth cavity pressure changes; the arc-shaped transition further reduces geometric excitation points, resulting in smaller overshoot and faster steady-state operation in the closed loop. The surface of the gas equalization layer 424b is not exposed to direct sunlight; a low Reynolds number static pressure film is obtained within the annular gap, which minimizes disturbance to the molten outer wall and helps maintain the roundness and dimensional stability of the inner hole. The arc-shaped section 427 avoids sharp corner erosion and particle accumulation, improving long-term durability and maintainability.

[0076] In one specific embodiment, the first diffusion layer 424a, the gas equalization layer 424b, and the second diffusion layer 424c are integrally formed.

[0077] Specifically, the integrated molding process avoids assembly seams and coating interfaces between the diffusion layer and the gas equalization layer 424b, reducing microleakage and bypass flow, and ensuring that the intracavity pressure drop occurs as designed along the "diffusion-gas equalization-re-diffusion" path, resulting in more stable pressure equalization quality. All three layers share the same reference, and the axial height difference and annular gap parallelism are guaranteed by the same processing, significantly reducing circumferential pressure difference and the risk of "stripes," making the annular gap external pressure film closer to an isocircular static pressure field. Interlayer connections and redundant cavities are eliminated; after the auxiliary gas pressure step, the near-field cavity pressure build-up time is shortened, and the annular gap static pressure film forms faster, facilitating online closed-loop micro-pressure regulation. The integrated microstructure dimensions exhibit less fluctuation in batches, the relative geometric stability of the second micropore 426 and the gas equalization layer 424b, and the higher angular consistency and long-term repeatability of the uniformly distributed ends facilitate quality control in large-scale production.

[0078] A fiber capillary drawing method 200, applied to a fiber capillary drawing apparatus 100 as described above, the drawing method comprising the steps of:

[0079] S10 collects various process control parameters and establishes a process model based on these parameters. Each of the process parameters includes:

[0080] The falling speed of the glass mother tube 10, the traction speed of the traction component 30, the inflation pressure and adjustment pressure of the air pressure control mechanism 40, and the product parameters.

[0081] S20 inputs the product parameters and the remaining process parameters into the process model to generate a sensitivity matrix;

[0082] S30 obtains the actual falling speed of the mother tube in the drawing zone and calculates the determination threshold of the adjustment mode based on the sensitivity matrix;

[0083] S40 determines whether the threshold is met. If so, the adjustment mode is triggered. The actual falling speed is combined with the target size of the product and input into the process model to calculate the auxiliary adjustment air pressure of the air pressure control mechanism 40 to suppress the inner hole contraction or closure.

[0084] S50 combines the actual falling speed with the auxiliary road regulating air pressure input to the process model to calculate the traction speed of the wire drawing module and control the outer diameter of the main tube;

[0085] S60 continuously tractions the main tube to generate the optical fiber capillary based on the adjusted auxiliary road regulating air pressure and the traction speed.

[0086] Specifically, this method is designed for continuous fiber capillary drawing. Its core idea is to first sense the actual descent speed of the main tube in the fusion zone in real time. Once a deviation from the nominal operating conditions is detected, two levels of adaptive closed-loop adjustment are performed, prioritizing stabilizing the inner diameter before the outer diameter. Based on the real-time speed, the auxiliary external pressure (equivalent external pressure applied by the annular pressure equalization mechanism) is first adjusted to establish a uniform and gentle external pressure field in the near field of the forming point, prioritizing the pulling of the inner diameter back to the target zone to avoid shrinkage, bulging, or pore closure. After the first stage is completed, the traction speed is then fine-tuned in small steps to bring the outer diameter back to its nominal size and stabilize it under mass conservation constraints.

[0087] Furthermore, when the equipment is initially stable, data on the main pipe's descent velocity, traction velocity, main road internal pressure, auxiliary road external pressure, and corresponding outer and inner diameters are collected step-by-step around the nominal point. Small-scale orthogonal or single-factor experiments (e.g., slight upward or downward adjustments to parameters) are preferred to ensure that only one quantity is changed each time, while the others remain unchanged, facilitating subsequent inference of "which change led to which dimensional response." Near the nominal point, a concise first-order approximation model describes the correspondence between "velocity / pressure—size." The model does not aim for global accuracy, but only requires predictable "direction" and "magnitude" within a small perturbation range.

[0088] Based on the above experimental data, following the method of "changing a little and observing the change," the strength of the impact of each input on the dimensions is directly quantified in words. For example: "When the main pipe's descent speed increases slightly, the inner diameter tends to decrease; when the traction speed increases slightly, the outer diameter decreases significantly, and the inner diameter decreases slightly; when the pressure inside the main line increases slightly, the inner diameter increases; when the pressure outside the auxiliary line increases slightly, the inner diameter decreases, but the impact on the outer diameter is minimal." This information of "direction + relative strength" can serve as an engineering expression of sensitivity, providing a basis for subsequent adjustments. The "nominal point" refers to the benchmark operating point determined during the design / debugging phase of the process or control system.

[0089] Furthermore, a vision sensor is placed near the molten end to continuously read the actual falling speed, and simple smoothing and outlier suppression are performed to avoid accidental noise triggering of false judgments. The product tolerance of the inner diameter is used as the basic constraint (e.g., requiring stability of 58-62 μm); referring to the "direction and strength" of the aforementioned sensitivity, the "maximum allowable deviation of the inner diameter" is converted into the "maximum allowable change in falling speed"; based on the converted theoretical value, a safety factor (e.g., 70-80%) is multiplied, and a dwell time (e.g., triggering is only considered if the limit is exceeded for two or three consecutive seconds) and a dead zone (e.g., triggering is not considered if the threshold is reached 60-70%) are set, thereby obtaining a judgment threshold that is both sensitive and resistant to jitter.

[0090] When the actual falling speed exceeds the threshold and continues to exceed the dwell time, the system enters adjustment mode. If it lingers at the threshold for an extended period, the system may also enter a slight adjustment phase to prevent slow drift accumulation. Based on the "speed deviation" and "target inner diameter," the process model provides a new auxiliary path external pressure setting. During execution, small steps are used (e.g., increasing or decreasing by 0.02–0.05 kPa per step), with intervals of waiting (e.g., waiting 8–10 seconds to allow the molten glass to complete its delayed response) until the inner diameter stabilizes. The auxiliary path external pressure varies within the equipment's safe range, and the differential pressure with the main path internal pressure is maintained within an empirically usable window to avoid bulging or hole collapse. With the inner diameter stable, the outer diameter is restored to its nominal value. Under the constraint of "mass conservation," the model provides small-step corrections to the traction speed. During execution, a limited slope is used (e.g., each step is only 0.1–0.2% of the nominal traction speed), with each step held for 5–8 seconds, and the online outer diameter value is observed.

[0091] A fiber capillary drawing system is provided, which is applied to a fiber capillary drawing device 100 as described above. This embodiment includes all the features of the above embodiments, and therefore has all the beneficial effects of the above embodiments, which will not be repeated here.

[0092] The above description is merely an embodiment of this application. It should be noted that those skilled in the art can make improvements without departing from the inventive concept of this application, but these improvements all fall within the protection scope of this application.

Claims

1. A fiber optic capillary drawing device for drawing a glass mother tube to form a fiber optic capillary, characterized in that, include: The glass mother tube has a through cavity along its axis, and a feeding assembly, a graphene heating element, and a traction assembly are sequentially inserted vertically. The graphene heating element is heated to 1990℃~2010℃ to heat the glass mother tube, and the glass mother tube forms a molten zone. The traction component pulls the glass mother tube to stretch the molten zone to generate an optical fiber capillary. The air pressure control mechanism includes a ventilation component and a ceramic air pressure regulator. The ventilation component is connected to the ventilation cavity and continuously introduces gas at a pressure of 0.8 kPa to 1.1 kPa. The ceramic air pressure regulator is arranged in a ring around the melting zone and forms an annular air cavity between the ceramic component and the melting zone. The inner circumferential surface of the ceramic gas pressure regulating component is provided with a ventilation micro-hole facing the glass mother tube and communicating with the annular gas cavity. When the inner diameter of the glass mother tube is too large, the ceramic gas pressure regulating component continuously introduces gas to squeeze the outer circumferential surface of the molten zone, adjusts the pressure difference between the inside and outside of the molten zone, and controls the inner diameter of the optical fiber capillary to be 58μm~62μm. The ceramic air pressure regulating component includes a first regulating part and a second regulating part. The first regulating part is arranged in a ring shape and has a first air cavity. The second regulating part is arranged around the inner circumferential surface of the first regulating part. The second regulating part is fixedly connected to the first regulating part and surrounds the first regulating part to form a second air cavity. The ventilation micropore includes a first micropore and a second micropore. The first micropore is disposed in the first adjustment part and connects the first air chamber and the second air chamber. The second micropore is disposed in the second adjustment part. The diameter of the first micropore is larger than the diameter of the second micropore. The second adjustment section includes a first diffusion layer, a gas equalization layer and a second diffusion layer arranged sequentially along the extension direction of the glass mother tube. The first diffusion layer and the second diffusion layer are both disposed on the first adjustment section. The second micropore is formed on the gas equalization layer. The side of the gas equalization layer near the glass mother tube is parallel to the outer peripheral surface of the glass mother tube.

2. The fiber capillary drawing device according to claim 1, characterized in that, The first micropores are equidistantly arranged in an annular ring on the first adjustment part, and the second micropores are equidistantly arranged in an annular ring on the second adjustment part.

3. The fiber capillary drawing device according to claim 2, characterized in that, The first micropore includes a first opening and a second opening disposed opposite to each other, the second opening being located on the side of the first adjustment portion closer to the second adjustment portion; Viewed along the axial direction of the first micropore, the diameter of the first opening is denoted as a, and the diameter of the second opening is denoted as b, satisfying 1.5a≤b≤3a.

4. The fiber capillary drawing device according to claim 1, characterized in that, When viewed along the direction from the first adjustment section toward the second adjustment section, the projection of the first micropore along its central axis is toward the first diffusion layer and the second diffusion layer, and is offset from the gas equalization layer.

5. The fiber capillary drawing device according to claim 1, characterized in that, The second adjustment part further includes an arc-shaped part, the first diffusion layer and the second diffusion layer are symmetrically disposed on both sides of the gas equalization layer, and the arc-shaped part is disposed at the connection end between the first diffusion layer and the second diffusion layer and the first adjustment part.

6. The fiber capillary drawing device according to claim 1, characterized in that, The first diffusion layer, the gas equalization layer, and the second diffusion layer are integrally formed.

7. A method for drawing optical fiber capillaries, characterized in that, An optical fiber capillary drawing apparatus is applied to an optical fiber capillary as described in any one of claims 1-6, the drawing method comprising the steps of: Collect various process control parameters and establish a process model based on these parameters. Each process parameter includes: The falling speed of the glass mother tube, the traction speed of the traction assembly, the inflation pressure and adjustment pressure of the air pressure control mechanism, and the product parameters. The product parameters and the remaining process parameters are input into the process model to generate a sensitivity matrix; The actual falling speed of the main tube in the drawing zone is obtained, and the determination threshold of the adjustment mode is calculated based on the sensitivity matrix; Determine whether the threshold is met. If so, trigger the adjustment mode, input the actual falling speed and the target size of the product into the process model, calculate the auxiliary adjustment air pressure of the air pressure control mechanism, and suppress the inner hole contraction or closure. The actual falling speed is combined with the auxiliary road regulating air pressure input to the process model to calculate the traction speed of the wire drawing module and control the outer diameter of the main tube; Based on the adjusted auxiliary road regulating air pressure and the traction speed, the main traction tube is continuously tractioned to generate the optical fiber capillary.

8. A fiber capillary drawing system, characterized in that, The drawing apparatus for an optical fiber capillary as described in any one of claims 1-6 or the drawing method as described in claim 7.

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