System and method for producing optical fiber preform

Abstract

The present disclosure provides a lathe system for producing an optical fiber preform, the lathe system comprising: a rotating fishing rod; a burner box configured to deposit soot containing silica on the rotary fishing rod; a hood configured to direct an airflow within the lathe system through an exhaust; and a perforated floor configured to exhaust air within the lathe system as a plurality of air jets from a bottom of the lathe system to a top of the lathe system.

Description

[0001] This application claims the priority benefit of Dutch Patent Application No. 2033604, filed on November 23, 2022, which claims the priority benefit of U.S. Provisional Application No. 63 / 421,257, filed on November 1, 2022. The content of the U.S. Provisional Application is hereby incorporated by reference in its entirety. Technical Field

[0002] The present disclosure generally relates to systems and methods for producing optical fiber preforms. Specifically, the present disclosure relates to a lathe system for producing optical fiber preforms and methods of using the same. Background Art

[0003] Optical fibers play an increasingly important role in the field of communication and operate by propagating light beams. Generally, an optical fiber includes a core and a cladding. The core is used to propagate light, while the cladding is used to confine the light within the core by reflection.

[0004] During the optical fiber manufacturing process, optical fibers are drawn from a large-diameter glass structure called a preform. Conventional processes for manufacturing preforms include outside vapor deposition (OVD), in which glass particles are deposited on a glass mandrel. As the glass mandrel rotates, the glass particles can be deposited in multiple layers. Summary of the Invention

[0005] Embodiments of the present disclosure relate to a lathe system for producing an optical fiber preform from glass particles. Within the lathe system, the glass particles are deposited on a rotating bait rod to form the preform. The lathe system is specifically designed to regulate and control the airflow within the system to efficiently and cost-effectively remove any contaminants that may contaminate the formed preform and cause deformation of the formed preform. Thus, the lathe system according to embodiments of the present disclosure includes a specific hood and perforated bottom plate design and other components to provide a uniform airflow within the system. This uniform airflow removes contaminants within the lathe system without contaminating the formed preform.

[0006] Aspects of the present disclosure relate to a lathe system for producing an optical fiber preform, the lathe system including: a rotating bait rod; a burner box configured to deposit silica-containing soot on the rotating bait rod; a hood configured to direct the airflow within the lathe system through an exhaust device; and a perforated bottom plate configured to discharge air within the lathe system as a plurality of air jets from the bottom of the lathe system to the top of the lathe system.

[0007] Aspects of the present disclosure relate to a lathe system for producing an optical fiber preform, the lathe system including a rotating mandrel; a burner box configured to deposit silica-containing soot on the rotating mandrel; and a perforated bottom plate including a plurality of holes. For each horizontal cross-section between the mandrel and the perforated bottom plate, the lathe system has a uniformity index between about 0.75 and about 1.0, the uniformity index being calculated by the following equation

[0008]

[0009] where UI is the uniformity index of the horizontal cross-section, Vi is the vertical velocity of air (m / s) at point i in the horizontal cross-section, Vmean is the average velocity of air (m / s) within the horizontal cross-section, dS is the horizontal cross-sectional integral, and S is the area of the horizontal cross-section (m 2 ).

[0010] A method for producing an optical fiber preform, the method including: depositing silica-containing soot on a rotating mandrel disposed within a housing; directing air within the housing to an exhaust device such that the air flows within the housing in a uniform flow direction; and removing air from the housing through the exhaust device. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram of an exemplary lathe system for producing an optical fiber preform in accordance with an embodiment of the present disclosure;

[0012] Figure 2 is of a burner of a lathe system in accordance with an embodiment of the present disclosure Figure 1 where the burner deposits silica-containing soot to form an optical fiber preform;

[0013] Figure 3A is a top-down schematic view showing a burner moving along a track of a lathe system in accordance with an embodiment of the present disclosure Figure 1 ;

[0014] Figure 3B is a top-down schematic view showing a burner moving along a track of a lathe system in accordance with an embodiment of the present disclosure Figure 1 ;

[0015] Figure 4A and 4B show burners of a lathe system in accordance with an embodiment of the present disclosure Figure 1 in a first position and a second position, respectively;

[0016] Figure 5A show a burner of a lathe system in accordance with an embodiment of the present disclosure Figure 1Perspective view of the cover of the lathe system;

[0017] Figure 5B Showing according to an embodiment of the present disclosure Figure 1 Partial cross-sectional perspective view of the cover of the lathe system;

[0018] Figure 5C Showing according to an embodiment of the present disclosure Figure 1 Perspective view of the front end portion of the cover of the lathe system;

[0019] Figure 6A Showing according to an embodiment of the present disclosure Figure 1 Perspective view of the perforated bottom plate of the lathe system;

[0020] Figure 6B Showing according to an embodiment of the present disclosure Figure 6A Enlarged view of a part of the perforated bottom plate;

[0021] Figure 6C Showing according to an embodiment of the present disclosure Figure 6A Graph of pressure drop vs. porosity of the perforated bottom plate;

[0022] Figure 6D Comparing the flow rates of air discharged from perforated bottom plates with different porosities according to an embodiment of the present disclosure Figure 6A of the perforated bottom plate;

[0023] Figure 6E is according to an embodiment of the present disclosure Figure 6A Graph of the minimum spacing between adjacent holes vs. hole diameter of the perforated bottom plate;

[0024] Figure 6F is according to an embodiment of the present disclosure from Figure 6A Graph of the jet convergence distance of air discharged from the holes of the perforated bottom plate;

[0025] Figure 6G is with Figure 6A Graph of the jet convergence distance varying with the minimum spacing between adjacent holes and hole diameter of the perforated bottom plate;

[0026] Figure 7 is according to an embodiment of the present disclosure Figure 1 Schematic diagram of the burner of the lathe system;

[0027] Figure 8A Showing according to an embodiment of the present disclosure Figure 1 Airflow within the lathe system;

[0028] Figure 8B Showing the airflow within the system when using a bottom plate with open slots; and

[0029] Figure 8C A bottom plate with an open slot is shown. DETAILED DESCRIPTION

[0030] Additional features and advantages of the present disclosure will be elucidated in the following detailed description, and those skilled in the art will understand or recognize these features and advantages from the description or by practicing the present disclosure described in the following description, claims, and drawings.

[0031] As used herein, when used in a list of two or more items, the term "and / or" means that any one of the listed items can be taken alone, or any combination of two or more of the listed items can be taken. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B, and C.

[0032] In this document, relational terms such as first and second, top and bottom, etc. are only used to distinguish one entity or action from another entity or action, and do not necessarily require or imply any actual such relationship or order between these entities or actions.

[0033] Those of ordinary skill in the art should understand that the described disclosure and the construction of other components are not limited to any specific material. Unless otherwise described herein, other exemplary embodiments of the disclosure herein can be formed of various materials.

[0034] It is also worth noting that the construction and arrangement of the elements of the present disclosure as shown in the exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in the present disclosure, those skilled in the art who review the present disclosure will easily understand that many modifications can be made (e.g., changes in the size, dimensions, structure, shape, and ratio of various elements, parameter values, installation arrangements, material uses, colors, orientations, etc.) without substantially departing from the novel teachings and advantages of the subject matter described herein. For example, elements shown as integrally formed can be constructed of multiple parts, or elements shown as multiple parts can be integrally formed, the operation of the interfaces can be reversed or otherwise changed, the structure of the system, and / or the length or width of the parts, or connectors, or other elements can be changed, and the nature or number of adjustment positions provided between the elements can be changed. It should be noted that the elements and / or components of the system can be constructed of any of a variety of materials in any of a variety of colors, textures, and combinations that provide sufficient strength or durability. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. Other alternatives, modifications, changes, and omissions can be made in the design, operating conditions, and arrangements of the required and other exemplary embodiments without departing from the spirit of the present disclosure.

[0035] Reference will now be made in detail to the exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Where appropriate, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

[0036] Now referring Figure 1 to, an exemplary lathe system 10 for producing a soot preform 20 is shown. The soot preform 10 advantageously includes reduced or no contaminants when produced by the system 10. As discussed further below, the system 10 deposits silica-containing soot on a rotating mandrel to produce the soot preform 20. Specific adjustments are made to the airflow within the system 10 to evenly distribute the silica-containing soot on the rotating mandrel. The components of the system 10 are disposed within an outer housing 30. The soot preform 20 can be a precursor for an optical fiber. However, in other embodiments, it is also contemplated that the soot preform 20 is a precursor for, for example, a mirror or a photomask.

[0037] Silica-containing soot is formed by the combustion of a glass precursor, which can include, for example, silicon carbide (SiC), silicon monoxide (SiO), silicon nitride (Si 3 N 4 ), silicon tetrabromide (SiBr 4 ), silicon tetrachloride (SiCl 4 ), silicon tetraiodide (SiT 4 ), and silicon dioxide (SiO 2 ). The glass precursor can additionally contain one or more dopants, such as germanium or fluorine, or other modifiers and / or additives. The glass precursor can be stored in a reservoir 40 in vapor form. A gas coupler 45 connects the reservoir 40 to a burner box 50 such that the vaporous glass precursor flows from the reservoir 40 to the burner box 50. In an embodiment, the vaporous glass precursor is conveyed within the gas coupler 45 by a carrier gas. When the vaporous glass precursor reaches the burner box 50, the vaporous glass precursor combines with a fuel and oxygen mixture and burns through the flame 54 of a burner 55 to produce silica-containing soot. More specifically, the glass precursor forms silica-containing soot when burned through the burner 55. The silica-containing soot flows from the burner 55 and then deposits onto the rotating mandrel 60 to form the soot preform 20. As discussed further below, the airflow within the system 10 aids in directly depositing the silica-containing soot onto the rotating mandrel 60. The silica-containing soot is deposited on the mandrel 60 in multiple layers. It should also be noted that in some embodiments, the rotating mandrel 60 can be a rotating glass core rod.

[0038] Also as Figure 1As shown, support fixtures 62 at both ends of fishing rod 60 support the fishing rod while allowing the fishing rod 60 to rotate. The support fixtures 62 also prevent radial movement of the fishing rod 60 relative to the housing 30 (i.e., in and out Figure 1 of the page). In some embodiments, the support fixture 62 includes a V-block fixture. At least one end of the fishing rod 60 is connected to a motor 64 to provide rotational movement of the fishing rod 60, as indicated by Figure 1 arrow A in. The motor 64 causes the fishing rod 60 to rotate about an axis parallel to the longitudinal length of the fishing rod 64. The rotational speed of the fishing rod 60 can be about 55 radians per second (rad / s) or less, or about 50 rad / s or less, or about 45 rad / s or less, or about 40 rad / s or less, or about 35 rad / s or less, or about 30 rad / s or less, or about 25 rad / s or less, or about 20 rad / s or less, or about 15 rad / s or less, or about 12 rad / s or less, or about 10 rad / s or less. Additionally or alternatively, the fishing rod 60 can have a rotational speed of about 10 rad / s or greater, or about 12 rad / s or greater, or about 15 rad / s or greater, or about 20 rad / s or greater, or about 25 rad / s or greater, or about 30 rad / s or greater, or about 35 rad / s or greater, or about 40 rad / s or greater, or about 45 rad / s or greater, or about 50 rad / s or greater. In some embodiments, the rotational speed is in the range of about 10 rad / s to about 35 rad / s, or about 12 rad / s to about 32 rad / s, or about 16 rad / s to about 28 rad / s.

[0039] Furthermore, in some embodiments, the support fixture 62 is connected to a frame that provides translational movement of the fishing rod 60 relative to the burner box 50 (i.e., Figure 1 left and right movement in). In other embodiments, the fishing rod 60 remains stationary along the translational axis and the burner box 50 moves relative to the fishing rod 60. In still other embodiments, both the fishing rod 60 and the burner box 50 move simultaneously.

[0040] The fishing rod 60 must be of sufficient size to withstand the weight of the deposited silica-containing soot while being light enough to rotate by the motor 64. In an embodiment, the fishing rod 60 is a tubular structure with an inner diameter of about 4 mm to about 10 mm, or about 5 mm to about 8 mm, or about 6 mm to about 7 mm. The outer diameter of the fishing rod 60 is about 12 mm or greater, or about 13 mm or greater, or about 14 mm or greater, or about 15 mm or greater, or in the range of about 12 mm to about 30 mm, or about 14 mm to about 25 mm, or about 15 mm to about 20 mm. The fishing rod 60 can be made of, for example, aluminum.

[0041] As discussed above, the vaporous glass precursor is burned in the flame 54 to produce silica-containing soot, and then the silica-containing soot is deposited on the fishing rod 60 to form the soot preform 20. Thus, also as Figure 1 shown, the fishing rod 60 is very close to the flame 54, such that the fishing rod 60 must be able to withstand high temperatures up to 1000 °C from the flame 54. Materials sufficient to withstand such high temperatures include, for example, alumina (Al 2 O 3 ), silicon nitride (Si 3 N 4 ), silicon carbide (SiC), and silica (SiO 2 ). The fishing rod 60 can be formed of one or more of these materials.

[0042] As discussed above, the burner box 50 includes burners 55, each of which generates a flame 54. Thus, the burner box 50 forms an outer housing that houses each burner 55. Although Figure 1 two burners 55 are shown within the burner box 50, it should be noted that more or fewer burners 55 can be used. For example, the burner box 50 can include 1, 3, 4, 5, or more burners 55. Additionally, the system 10 can include more than one burner box 50, each burner box having one or more burners 55. In some embodiments, the system 10 can include a first burner box 50 and a second burner box 50 such that the first burner box 50 includes a different number of burners 55 than the second burner box 50.

[0043] As Figure 1 shown, the burner box 50 can be traversed along the longitudinal length of the fishing rod 60 to uniformly deposit the silica-containing soot along the length of the fishing rod 60. Additionally, because the fishing rod 60 rotates relative to the burner box 50 (as shown by arrow A), the silica-containing soot is deposited uniformly not only along the length of the fishing rod 60 but also along the radial perimeter of the fishing rod 60. The burner box 50 traverses along the length of the fishing rod 60 while the fishing rod 60 rotates in order to deposit the silica-containing soot as a layer on the fishing rod 60. More specifically, the first traverse of the burner box 50 along the fishing rod 60 produces a first layer of soot on the fishing rod 60, and the second traverse of the burner 60 along the fishing rod 60 produces a second layer of soot on the fishing rod 60.

[0044] It should also be noted that the burner box 50 can be traversed transversely along the length of the fishing rod 60 while the fishing rod 60 rotates to heat the deposited silica-containing soot. Thus, the flame 54 can only heat the soot preform 20 deposited on the fishing rod 60 without depositing new silica-containing soot. This can help to completely fuse the deposited silica-containing soot or help to straighten or elongate the soot preform 20.

[0045] In an embodiment, the burner box 50 traverses back and forth along the longitudinal length of the fishing rod 60 (as shown by arrow B). Additionally, in an embodiment, the burner box 50 traverses along the fishing rod 60 at a speed of about 10 mm / s to about 70 mm / s, or about 15 mm / s to about 65 mm / s, or about 20 mm / s to about 60 mm / s, or about 25 mm / s to about 55 mm / s, or about 30 mm / s to about 50 mm / s, or about 35 mm / s to about 45 mm / s. The speed of the burner box 50 in combination with the speed of the fishing rod 60 (as discussed above) causes the silica-containing soot to be deposited uniformly and evenly on the fishing rod 60. Specifically, the combination of the traversing speed of the burner box 50 and the rotational speed of the fishing rod 60 allows the silica-containing soot to be fixedly deposited on the fishing rod 60 such that most of the silica-containing soot firmly adheres to the fishing rod 60 (rather than floating around inside the housing 30). In some exemplary embodiments, the burner box 50 traverses at a speed of about 20 mm / s to about 60 mm / s and the fishing rod 60 rotates at a speed of about 12 rad / s to about 32 rad / s. In still other exemplary embodiments, the burner box 50 traverses at a speed of about 40 mm / s and the fishing rod 60 rotates at a speed of about 25 rad / s.

[0046] It should also be noted that the burner box 50 traverses along an axis parallel to the longitudinal axis of the fishing rod 60 and passing through the centerline of the fishing rod 60. This helps to ensure that the silica-containing soot is deposited uniformly and evenly onto the fishing rod 60. As Figure 1 shown, the burner box 50 moves along the track 57 to traverse along the length of the fishing rod 60. The length of the track 57 can be longer than the length of the fishing rod 60. A motor (not shown) can be used to move the burner box 50 along the track 57.

[0047] When the burner box 50 is translated only backward and forward along the length of the fishing rod (as shown by arrow B), it may cause the resulting soot preform to not be cylindrical in shape. More specifically, the resulting soot preform may become tapered at one end, such that the tapered end has a smaller diameter than its opposite end, thereby forming a carrot-like shape. Such a carrot-like shape has non-uniform optical properties along its length. For example, the resulting preform will have a reduced mode field diameter uniformity. In other instances, the resulting soot preform may become tapered at both ends, such that the ends are tapered relative to the center, middle portion of the preform. Now refer to Figure 2 , as an example of the conventional movement of the burner box 50, the burner first travels along the length of the soot preform 20 in the direction of arrow X to the first end 22 of the preform. Before reaching the first end 22, the flame 54 applies heat and deposits silica-containing soot onto at least position 26 of the soot preform 20. When the burner box 50 reaches the end 22 of the soot preform 20, the burner box turns and then travels towards the second end 24 of the soot preform 20 in the direction of arrow Y. Thus, at the turning point at the first end 22, the burner 54 changes direction and then applies heat and deposits silica-containing soot onto position 26 of the soot preform 20 again. However, position 26 may not have been fully cooled from its first heat application (when the burner box 50 was traveling in the direction of arrow X) to this second heat application (when the burner box 50 is traveling in the direction of arrow Y). Thus, position 26 may receive the second heat application while still hot after the first heat application. However, position 28 of the soot preform 20 is positioned further away from the turning position at the first end 22 such that position 28 is fully cooled before it receives its second heat application. This may cause the silica-containing soot deposited at positions 26 and 28 of the soot preform 20 to have unequal densities, resulting in the soot preform 20 having a non-uniform (e.g., carrot-like) shape. Thus, for example, the shape of the soot preform 20 may not be completely cylindrical, and in fact, the end 22 of the preform may be tapered.

[0048] To counteract the non-uniform heating of the flame 54 disclosed above, in the embodiments disclosed herein, the burner box 50 may be moved along an off-line return route positioned away from the soot preform 20. The track 57 may extend in length such that the burner box 50 moves along the off-line return route. Figure 1 is a cross-sectional side view of the system 10, where the off-line return route is not shown from the side view. Figure 3A is a top view of a portion of the system 10 in an embodiment that includes the off-line return route. As Figure 3AAs shown, the track 57 has a first route 58 for depositing silica-containing soot on the fishing rod tube 60. In addition, the track 57 has a second route 59 for the offline return of the burner box 50. The first route 58 passes through the center line of the fishing rod tube 60 parallel to the longitudinal axis of the fishing rod tube 60. The second route 59 is laterally offset from the fishing rod tube 60 such that the second route 59 is positioned relatively further away from the fishing rod tube 60 than the first route 58. The second route 59 is positioned away from the fishing rod tube 60 and spaced apart from the fishing rod tube by a sufficient distance such that when the burner box 50 travels along the second route 59, the fishing rod tube 60 and the silica-containing soot deposited thereon are not affected by the flame 54.

[0049] In an embodiment, the second route 59 is spaced apart from the first route 58 by a distance of about 75 mm or greater, or about 80 mm or greater, or about 85 mm or greater, or about 90 mm or greater, or about 100 mm or greater, or about 105 mm or greater, or about 110 mm or greater, or about 115 mm or greater. In some embodiments, the second route 59 is spaced apart from the first route 58 by a distance of about 75 mm to about 115 mm, or about 80 mm to about 110 mm, or about 85 mm to about 105 mm, or about 90 mm to about 100 mm, or about 95 mm to about 105 mm. It should be noted that the distance between the first route 59 and the second route 58 may depend on the size of the preform 20 and the size of the flame 54.

[0050] Although Figure 3A The first route 58 and the second route 59 of the track 57 are shown as forming a rectangular configuration, but it is also contemplated that the routes may form different configurations. For example, in some embodiments, the second route 59 of the track 57 may include an arcuate shape that curves outwardly away from the fishing rod tube 60. It should also be noted that the track length of the second route 59 is longer than the track length of the first route 58.

[0051] During the process of depositing silica-containing soot on the fishing rod blank 60, the burner box 50 moves along both the first path 58 and the second path 59. However, it should be noted that the burner box 50 deposits silica-containing soot on the fishing rod blank 60 only on the first path 58 (not on the second path 59). The burner box 50 can move along the first path 58 at a relatively slower speed compared to when it moves along the second path 59. However, the speed at which the burner box 50 moves along the second path 59 should allow sufficient time for the silica-containing soot on the fishing rod blank 60 to cool completely before the burner box 50 makes another deposition pass along the fishing rod blank 60. This allows the silica-containing soot to be deposited on the fishing rod blank 60 with a uniform density, thereby producing a symmetric and homogeneous cylindrical preform. Arrow 58' shows the relatively slower speed of the burner box 50 along the first path 58, and arrow 59' shows the relatively faster speed of the burner box 50 along the second path 59.

[0052] As discussed above, the burner box 50 can move along the first path 58 at an average speed of about 10 mm / s to about 70 mm / s, or about 15 mm / s to about 65 mm / s, or about 20 mm / s to about 60 mm / s, or about 25 mm / s to about 55 mm / s, or about 30 mm / s to about 50 mm / s, or about 35 mm / s to about 45 mm / s. The burner box 50 can move along the second path 59 at an average speed of about 0.25 m / s to about 2.00 m / s, or about 0.50 m / s to about 1.50 m / s, or about 0.75 m / s to about 1.25 m / s, or about 0.75 m / s to about 1.00 m / s. In other embodiments, the burner box 50 can move along the second path 59 at an average speed greater than 2.00 m / s.

[0053] The offline return path of the track 57 also provides a service stop during which the burner box 50 can remain stationary for a period of time while one or more process conditions can be inspected or repaired. More specifically, the burner box 50 can move to the second path 59 and remain stationary for a period of time to inspect or repair one or more process conditions. This allows the process conditions to be inspected or repaired without the need to extinguish the flame 54. For example, the burner box 50 can move onto the second path 59 to stabilize the flow conditions of the glass precursor.

[0054] Figure 3B A second embodiment of the offline return path of the track 57 is shown, where the burner box 50 travels along the first path 58 and the second path 59 as discussed above. However, in this embodiment, the system 10 includes side burners 52 that apply heat to the ends 22, 24 of the soot preform 20 to densify the soot at these ends, which helps reduce cracking of the soot.

[0055] In some embodiments, the burner box 50 may rotate toward and away from the centerline of the fishing rod 60. More specifically, referring to Figure 4A , the burner 55 is shown in a first position, where the central axis CA of the cross-section of the burner B is positioned along the same central axis CA of the cross-section of the fishing rod 60 R (i.e., the axis passing through the centerline of the fishing rod 60). In the first position of the burner 55, the flame 54 is directed toward the fishing rod 60 and the soot preform 20. Further, as Figure 4B shown, the burner 55 may rotate away from the central axis CA of the fishing rod 60 R to a second position. In the second position of the burner 55, the flame 54 is directed away from the fishing rod 60 and the soot preform 20. Thus, in the second position, the central axis CA of the burner 55 B forms a non-zero angle θ R with the central axis CA of the fishing rod 60 CA . In an embodiment, the angle θ CA is about 180 degrees or less, or about 145 degrees or less, or about 120 degrees or less, or about 100 degrees or less, or about 90 degrees or less, or about 60 degrees or less, or about 45 degrees or less. Additionally or alternatively, the angle θ CA is about 20 degrees or greater, or about 30 degrees or greater, or about 45 degrees or greater, or about 60 degrees or greater, or about 90 degrees or greater, or about 100 degrees or greater, or about 120 degrees or greater, or about 145 degrees or greater, or about 180 degrees or greater. It should be noted that in the first position, the angle θ CA is about 0 degrees (+ / -5 degrees).

[0056] In some embodiments, the burner box 50 may move up and down relative to the fishing rod 60. Referring to Figure 1 , the burner box 50 may move toward and away from the soot preform 20 and the fishing rod 60, as shown by the arrow C, to adjust the heating of the soot preform 20 by the flame 54. A linear actuator or any other well-known component may be used to move the burner box 50 up and down. In an embodiment, the linear actuator is attached to a wheel that moves along a track 57. Thus, when the burner box 50 moves up and down relative to the soot preform 20 and the fishing rod 60, the burner box also moves up and down relative to the track 57.

[0057] As discussed above, the burner 55 of the burner box 50 discharges a fuel and oxygen mixture that forms a flame 54. Then, the glass precursor (from reservoir 40) is burned through the flame 54 to form silica-containing soot. In some embodiments, the fuel used to form the flame 54 is methane fuel, and the combustion of the glass precursor by the flame 54 is illustrated by:

[0058] SiCl 4 +O 2 →SiO 2 +Cl 2

[0059] Thus, the combustion process forms chlorine gas. In addition, the combustion of methane fuel produces water:

[0060] CH 4 +O 2 →H 2 O+CO+O 2

[0061] Then, the water can react with the chlorine gas produced above to form hydrochloric acid (HCl), as shown below, and the hydrochloric acid will corrode the components of the system 10. The gas flow within the system 10 must be regulated to quickly and efficiently discharge the hydrochloric acid from the system 10.

[0062] 2Cl 2 +2H 2 O→4HCl+O 2

[0063] In addition to removing hydrochloric acid from the system 10, the gas flow within the system 10 must also be regulated to remove any loose soot particles that are not firmly adhered to the fishing rod 60. In a conventional lathe system, loose soot particles would, for example, adhere to the sidewalls of the system. After a period of time, the loose soot particles would detach from the sidewalls and fall. If the loose soot particles land on the soot preform rotating on the fishing rod, the loose soot particles will contaminate the preform, causing defects in the preform. Such defects will result in an increase in the attenuation of the drawn optical fiber.

[0064] Referring again to Figure 1 , the gas flow within the system 10 near the fishing rod 60 must have sufficient velocity to carry the hydrochloric acid, loose soot particles, and any other floating contaminants in the housing 30 upward and away from the soot preform 20. In addition, in order to carry the contaminants upward and away from the soot preform 20, the gas flow must not flow in a recirculation pattern. As Figure 1 shown, the upper portion of the housing 30 includes a hood 70 that provides the required gas flow within the housing 30 and the velocity of the gas flow is sufficient to carry the contaminants upward and away from the soot preform 20.

[0065] Figure 1 Shows a cross-sectional view of the cover 70. Figure 5A Shows a perspective view of the cover 70, Figure 5B shows a partially cut-away perspective view of the cover 70, and Figure 5C shows a perspective view of the front end portion of the cover 70. As Figure 1 and 5A shown in -5C, the cover 70 includes a body 72 that is connected to a manifold 74 and an exhaust device 76. The body 72 of the cover 70 is connected and fixed to the wall 33 of the housing 30. The cover 70 provides an exhaust system that continuously removes contaminants from the housing 30. Specifically, the exhaust device 76 is connected to a pressure source 79 ( Figure 1 ), which draws the air within the housing 30, along with any contaminants, upward within the housing 30 and within the cover 70 and through the exhaust device 76. The pressure source 79 can supply a negative pressure to draw the air and contaminants upward within the system 10. The air and contaminants are then removed from the housing 30 through the exhaust device 76. In an embodiment, the air can be filtered and recycled within the housing 30. The air within the housing 30 can be filtered air, such as HEPA filtered air. It should also be noted that the housing 30, the cover 70, and the pressure source 79 form a pollution mitigation system.

[0066] The body 72 of the cover 70 includes side walls 71 that are angled relative to the wall 33 of the housing 30 and the bottom surface 78 of the cover 70. As Figure 5C shown, the side walls 71 each make an angle θ with an axis parallel to the bottom surface 78 of the cover 70 H . In an embodiment, the angle θ H is an acute angle. In some exemplary embodiments, the angle θ H is from about 20° to about 40°, or from about 30° to about 38°, or from about 35° to about 40°. At both ends of the side walls 71, end walls 77 are connected to the side walls 71. The plane of the end walls 77 can be perpendicular to the plane of the wall 33.

[0067] The length L of the cover 70 H can be from about 2 m to about 4 m, or from about 2.5 m to about 3.5 m, or from about 2.7 m to about 3.3 m, or from about 3 m to about 3.3 m. The length L H can be the length of the body 72 and the length of the manifold 74. It should be noted that the length L Hshould be longer than the length of the fishing rod 60. As disclosed herein, the particular shape of the manifold 74 allows air and contaminants within the housing 30 to be uniformly drawn across the entire area of the housing 30 (such that, for example, air and contaminants at the center of the housing 30 are not drawn with a greater force than air and contaminants at the left and right sides of the housing 30). The cylindrical shape of the manifold 74 helps to provide such uniform air draw. Additionally, the slot 75 between the manifold 74 and the body 72 also helps to provide such uniform air draw. The slot 75 provides a minimum diameter within the shroud 70 such that the airflow is restricted at the slot 75. Thus, the slot 75 is a narrowed orifice within the shroud. The slot 75 may have a width W of from about 10 mm to about 50 mm, or from about 12 mm to about 40 mm, or from about 15 mm to about 38 mm, or from about 22 mm to about 35 mm, or from about 25 mm to about 30 mm. S . In some embodiments, the width W S varies along the length of the shroud 70. For example, the ends of the slot 75 (closer to the end wall 77) may have a greater width W than the central portion of the slot 75. S . The ends of the slot 75 may have a width W of from about 22 mm to about 28 mm, or from about 24 mm to about 26 mm, or about 25 mm, or about 26 mm. S , and the central portion of the slot 75 may have a width W of from about 20 mm to about 26 mm, or from about 22 mm to about 24 mm, or about 22 mm, or about 23 mm. S . The varying width W of the slot 75 s helps to provide uniform air draw within the system 10. It should also be noted that the length of the slot 75 is equal to the length L of the shroud 70. H .

[0068] The exhaust device 76 must be of sufficient size to exhaust air from the housing 30. In an embodiment, the exhaust device 76 has a diameter of from about 150 mm to about 350 mm, or from about 175 mm to about 325 mm, or from about 200 mm to about 300 mm, or from about 225 mm to about 275 mm, or from about 250 mm to about 260 mm.

[0069] Referring again to Figure 1 , air within the housing 30 is drawn upward by the pressure source 79 and through the exhaust device 76. The design of the shroud 70 is such that air within the housing 30 flows uniformly as it is drawn into the exhaust device 76 by the pressure source 79. Figure 1 The arrows D in Figure 1As shown by arrow D therein, air flows upward through hood 70 rather than circulating (similar to a vortex) within housing 30. Thus, air flows in a pattern that is free of recirculation (or substantially free of recirculation). This uniform airflow into exhaust device 76 allows any hydrochloric acid, loose soot particles, and other contaminants within housing 30 to be quickly removed before they can cause any contamination to soot preform 20 or any corrosion to system 10. Any lateral flow air within housing 30 (e.g., perpendicular to arrow D) or recirculating air within housing 30 can cause floating contaminants within housing 30 to move laterally and contact soot preform 20 rather than flowing directly upward and out through exhaust device 76.

[0070] It should also be noted that the air must flow in such a uniform manner so as to maximize the amount of silica-containing soot that adheres to fishing wire rod 60 when dispensed from burner box 50. Any significant turbulence or eddies in the airflow can cause the silica-containing soot to be blown off fishing wire rod 60. Silica-containing soot that was previously adhered to fishing wire rod 60 (or adhered to soot preform 20 disposed on fishing wire rod 60) but before complete fusion may be knocked off and removed from fishing wire rod 60 due to such turbulent airflow. If the knocked-off silica-containing soot moves around housing 30 (e.g., due to lateral flow or recirculating air within housing 30) and re-attaches to soot preform 20 rather than flowing directly upward into exhaust device 76, this will contaminate soot preform 20 and cause defects in the soot preform, which may increase the attenuation of the optical fiber drawn from soot preform 20.

[0071] As discussed above, in order to direct any loose soot particles or other contaminants upward away from the soot preform 20, the airflow within the housing 30 must be without recirculation (or substantially without recirculation). However, the airflow must also move at a sufficient velocity to carry such loose soot particles and contaminants upward. If the airflow does not move at a sufficiently fast velocity, the loose soot particles and contaminants will fall downward due to gravity rather than being lifted upward with the airflow. In an embodiment, air flows at a velocity of at least about 0.05 m / s, or at least about 0.08 m / s, or at least about 0.10 m / s, or at least about 0.12 m / s, or at least about 0.15 m / s, or at least about 0.18 m / s, or at least about 0.20 m / s, or at least about 0.22 m / s, or at least about 0.25 m / s, or at least about 0.28 m / s, or at least about 0.30 m / s. Additionally or alternatively, air flows at a velocity of about 1.50 m / s or less, or about 1.25 m / s or less, or about 1.00 m / s or less, or about 0.80 m / s or less, or about 0.75 m / s or less, or about 0.60 m / s or less, or about 0.50 m / s or less, or about 0.40 m / s or less. In some embodiments, air flows at a velocity of about 0.10 m / s to about 1.50 m / s, or about 0.20 m / s to about 1.00 m / s, or about 0.25 m / s to about 1.00 m / s, or about 0.30 m / s to about 0.80 m / s.

[0072] The uniformity of the airflow within the housing 30 is represented by the uniformity index of the air, which is calculated by the following equation:

[0073]

[0074] where UI is the uniformity index of the horizontal cross-section, Vi is the vertical velocity of the air at point i in the horizontal cross-section (m / s), Vmean is the average velocity of the air within the horizontal cross-section (m / s), dS is the horizontal cross-sectional area integral, and S is the area of the horizontal cross-section (m 2 ). The uniformity index can be up to 1.0. In an embodiment, for each horizontal cross-section between the fishing rod 60 (or the soot preform 20) and the perforated bottom plate 80 (discussed below) of the system 10, the uniformity index within the housing 30 is between about 0.75 and about 1.0, or between about 0.80 and about 1.0, or between about 0.85 and about 1.0, or between about 0.90 and about 1.0, or between about 0.92 and about 1.0, or between about 0.94 and about 1.0, or between about 0.95 and about 1.0, or between about 0.96 and about 1.0, or between about 0.98 and about 1.0, or between about 0.99 and about 1.0.

[0075] Another important aspect of the uniform flow within the housing 30 is to prevent cold spots and / or hot spots in certain portions of the housing 30. Turbulent and circulating airflows can cause local cold spots and / or hot spots in the airflow, which in turn can create local cold spots and / or hot spots on the soot preform 20. Such local cold spots and / or hot spots on the soot preform 20 can affect the soot density at these cold / hot spots, thereby forming a non-uniform preform.

[0076] The inner surface of the heatable housing 30 can be heated to prevent loose soot particles and other contaminants from adhering to the surface. For example, the inner surfaces of the heatable shroud 70, such as the inner surfaces of the sidewall 71 and the end wall 77, can be heated. In some embodiments, the inner surface of the wall 33 is heated together with the inner surface of the shroud 70. Heating the inner surfaces reduces corrosion of these surfaces, including corrosion caused by hydrochloric acid or other contaminants. In an embodiment, the inner surfaces are heated to a temperature that is substantially matched to the temperature of the loose soot particles and contaminants. This reduces any temperature difference between the loose soot particles / contaminants and the inner surface of the housing 30. It should be noted that when the loose soot particles / contaminants and the inner surface of the housing 30 are at substantially the same temperature, the loose soot particles / contaminants tend not to stick to the inner surface of the housing. In an embodiment, the inner surfaces are heated to a temperature of about 100°C to about 200°C, or about 110°C to about 190°C, or about 120°C to about 180°C, or about 130°C to about 170°C, or about 140°C to about 160°C, or about 120°C to about 150°C, or about 135°C to about 145°C, or about 135°C, or about 140°C, or about 145°C, or about 150°C. For example, a heating pad is used to heat the inner surfaces.

[0077] Referring again to Figure 1 , the system 10 further includes a perforated bottom plate 80 to condition the air as it flows into the housing 30. An inlet 90 is formed in the housing 30 to introduce air into the interior of the housing 30. The air initially flows uniformly into the bottom 32 of the interior of the housing 30, as shown by the streamline D'. In an embodiment, the air flows into the bottom 32 through the inlet 90 at a flow rate of about 10,000 standard liters per minute (SLPM) to about 30,000 SLPM, or about 13,000 SLPM to about 28,000 SLPM, or about 15,000 SLPM to about 25,000 SLPM. Then, the air diffuses and fills the space of the bottom 32, as shown by the streamline D". As Figure 1 shown, the air flows in a non-uniform direction as it diffuses and fills the space of the bottom 32. Next, the air is directed upward into the top 34 of the interior of the housing 30 by an air jet formed by the perforated bottom plate 80. It should be noted that the perforated bottom plate 80 provides a separator between the bottom 32 and the top 34 of the housing 30. Figure 6AAn exemplary embodiment of a perforated bottom plate 80 is shown, where the bottom plate includes a plurality of holes 82. Each hole 82 is an orifice or a small hole that forms an opening from the top surface to the bottom surface of the perforated bottom plate 80. It should be noted that as also Figure 6A shown, the perforated bottom plate 80 is connected to the burner box 50 ( Figure 6A only the burner box 50 without the burner 55 is shown in

[0078] and a spring 86, as further discussed below.

[0079] The orifice formed by the hole 82 can be cylindrical. In other embodiments, the orifice at least includes a taper. For example, the inner wall of the orifice can taper at the central portion of the orifice such that the central portion has a smaller diameter than the ends of the orifice.

[0080] The orifice formed by the hole 82 can also have a length of about 0.05 mm to about 1.00 mm, or about 0.10 mm to about 0.90 mm, or about 0.20 mm to about 0.80 mm, or about 0.30 mm to about 0.70 mm, or about 0.40 mm to about 0.60 mm, or about 0.10 mm to about 0.30 mm, or about 0.15 mm to about 0.25 mm, or about 0.15 mm to about 0.20 mm. In an embodiment, the length can be about 0.16 mm, 0.18 mm, 0.20 mm or about 0.24 mm. It should be noted that the length of the orifice of the hole 82 is also the same as the thickness (from the top surface to the bottom surface) of the perforated bottom plate 80.

[0081] Figure 6B An enlarged view of a portion of the perforated bottom plate 80 is shown. As Figure 6B shown, each hole 82 has a diameter D H , which can range from about 5 mm to about 50 mm, or about 10 mm to about 40 mm, or about 15 mm to about 35 mm, or about 20 mm to about 30 mm. Adjacent holes 82 can be spaced apart from each other by a minimum distance d of about 5 mm to about 100 mm, or about 10 mm to about 90 mm, or about 15 mm to about 80 mm, or about 20 mm to about 70 mm, or about 30 mm to about 60 mm, or about 40 mm to about 50 mm H . It should be noted that one or more holes 82 can have a different diameter D from one or more other holes 82H In addition, the first set of adjacent holes 82 may be spaced from each other by a minimum distance d H1 and the second set of adjacent holes 82 may be spaced from each other by a minimum distance d H2 such that d H1 is not equal to d H2 . Thus, not all of the holes 82 need to have the same size and be spaced the same distance apart. It should also be noted that although Figure 6A and 6B show the holes 82 as being circular, the holes 82 may include other shapes such as oval, square, rectangular, etc.

[0082] The relationship between the hole diameter D H and the hole pitch d H must be controlled in order to provide the desired jet flow from the holes 82. A combination of an overly large hole diameter and a small spacing between adjacent holes can result in non-uniform air flow from the holes 82. Conversely, a combination of an overly small hole diameter and a large spacing between adjacent holes can result in jets that are too large and reach the soot preform 20, creating defects in the preform. The relationship between the hole diameter D H and the hole pitch d H in the perforated bottom plate 80 is shown by the following equation:

[0083]

[0084] where DH is the average hole diameter (the average diameter D H ) of all the holes 82, dH is the average minimum distance between adjacent holes (the average minimum distance d H ) of all the holes 82, and OA% is the open area ratio in the perforated bottom plate 80 (the percentage of the area of the perforated bottom plate 80 that includes the open holes compared to the area of the perforated bottom plate 80 including the material of the bottom plate itself). It should be noted that OA% represents the porosity of the perforated bottom plate 80.

[0085] Figure 6C Shows a graph of OA% (calculated using the above equation) versus the pressure drop of the air when the air flows through the holes 82. In Figure 6C the graph, air initially flows into the bottom 32 through the inlet 90 at a flow rate of 22,653 SLPM. As Figure 6CAs shown, too low an OA% creates too high a pressure drop across hole 82. For example, an OA% of about 5% creates a pressure drop of about 85 Pascals. Such a high pressure drop across hole 82 was found to cause air to be discharged from hole 82 at too great a rate, such that the air would reach the soot preform 20 on the fishing rod 60. Further, too high an OA% was found to result in too much open space in the perforated base plate 80, such that air would flow non-uniformly through hole 82. In an embodiment, an OA% greater than about 5% to less than about 33%, or about 6% to about 32%, or about 9% to about 30% creates an optimal air flow from hole 82.

[0086] Figure 6D Compare the flow rate of air discharged from hole 82 when the perforated base plate 80 with an OA% of 50% is compared to a perforated base plate with an OA% of 30. As Figure 6D shown, the air discharged from the base plate with an OA% of 50% has a much higher flow rate than the air discharged from the base plate with an OA% of 30%. The high rate created by 50% OA% can cause the jet stream to reach the preform 20 rather than dissipate before the preform. In contrast, the air discharged from the base plate with an OA% of 30% is very uniform and has an acceptable flow rate.

[0087] Figure 6E Further shows the hole diameter D H and the minimum spacing d between adjacent holes H The relationship between them is shown. The hole diameter D H and the minimum spacing d H Each of them must be within a specific range in order to maintain the OA% within the preferred range (as disclosed above). As Figure 6E shown, when the OA% is outside the preferred range, the pressure drop across hole 82 is too high, or the air flow is non-uniform when discharging from hole 82.

[0088] Figure 6F Shows the air flow discharged from hole 82 as a jet. Specifically, air is discharged from hole 82 at a relatively fast rate, but not so fast that the air jet itself contacts the growing soot preform 20 on the fishing rod 60. In fact, the air jet dissipates and converges well before reaching the growing soot preform 20. Thus, only passive air reaches the growing soot preform 20, thereby not causing any defects in the preform. As Figure 6F shown, in this embodiment, the air jet dissipates and converges at a distance of about 0.3 m from hole 82. Figure 6F The position of each hole 82 is indicated. It should also be noted that the air between holes 82 experiences a small amount of turbulence, as Figure 6F shown. However, any non-uniform air flow from this turbulence also dissipates before the 0.3 m convergence distance.

[0089] Figure 6G shows the resulting jet convergence distance (in mm) varying with the hole diameter D H and the minimum distance d between the holes H Specifically, as discussed above with reference to 6E, the hole diameter D H and the minimum distance d H are within a specific range that is acceptable in order to maintain the OA% within a preferred range. For the hole diameter D H and the minimum distance d H within these acceptable ranges, then it is determined what range provides the required jet convergence distance to avoid air flow recirculation within the system. When the hole diameter D H and the minimum distance d H are both too high, the air discharged from the holes 82 has too high a velocity, such that the air easily recirculates within the housing 30 towards the fishing rod 60 rather than flowing upward. Thus, the hole diameter D H and the minimum distance d H should be balanced to provide sufficient jet convergence distance. In the Figure 6G embodiment, the portion within region Y is determined to have excessive recirculating air flow, while the portion within region Z is determined to have acceptable air flow.

[0090] As discussed above, an OA% of less than about 5%, or less than about 6%, or less than about 9% results in an excessive pressure drop across the holes 82. Thus, the air is discharged from the holes at too high a rate such that the air jets reach the soot preform 20. Also as discussed above, this may cause defects in the soot preform 20. Thus, the air jets discharged from the holes 82 should dissipate and converge before reaching the soot preform 20 such that only passively flowing air (rather than the directed air within the air jets) reaches the soot preform 20. In an embodiment, the air jets should converge at a distance of about 0.300 m or less from the outlet of the holes 82 in order to prevent the air jets from reaching the soot preform 20. In some specific embodiments, the air jets should converge at a distance of about 0.275 m or less, or about 0.250 m or less, or about 0.225 m or less, or about 0.200 m or less, or about 0.175 m or less, or about 0.150 m or less from the outlet of the holes 82.

[0091] Referring again to Figure 1 , the burner box 50 can also help to provide a uniform air flow within the system 10. Air can flow from the bottom 32 to the top 34 of the housing 30 through the burner box 50. Figure 7 shows a more detailed view of the burner box 50 according to some embodiments. As Figure 7As shown, air can flow through inlet 105 and enter the body 107 of burner box 50. The air flowing into inlet 105 can be air from the bottom 32 of housing 30. In some embodiments, inlet 105 can be an amplifier that uses compressed air to increase the flow rate of air through body 107. In an embodiment, air flows into inlet 105 and through body 107 at a flow rate of about 2,000 SLPM to about 5,000 SLPM, or about 2,500 SLPM to about 4,500 SLPM, or about 3,000 SLPM to about 4,000 SLPM, or about 3,500 to about 4,000 SLPM. It should be noted that the flow rate of air flowing through inlet 90 of housing 30 is faster than the flow rate of air flowing through inlet 105 and flowing within body 107.

[0092] Inside body 107, the air can cool the internal components of burner box 50 to prevent the internal components from overheating. Then, the air leaves burner box 50 through outlet 120 after flowing through circuit 110. As Figure 7 shown, circuit 110 includes a series of perforated plates, specifically first perforated plate 112 and second perforated plate 114. Each perforated plate 112, 114 includes a plurality of holes 115 having a diameter of about 3.0 mm to about 5.0 mm, or about 3.5 mm to about 4.5 mm, or about 4.0 mm to about 5.0 mm, or about 4.5 mm to about 5.0 mm, or about 4.7 mm to about 5.0 mm. Additionally, each hole 115 can be spaced from an adjacent hole by a minimum distance of about 50 mm to about 75 mm, or about 55 mm to about 70 mm, or about 60 mm to about 65, or about 62 mm to about 65 mm, or about 62 mm to about 70 mm. Thus, the perforations of plates 112, 114 can have an open area percentage OA% (using the equation mentioned above) of about 30% to about 80%, or about 35% to about 75%, or about 40% to about 70%, or about 45% to about 65%, or about 50% to about 60%, or about 51% to about 55%.

[0093] The holes 115 in the perforated plates 112, 114 are each an orifice or a small hole that forms an opening from the top surface to the bottom surface of the plate, similar to the holes 82 in the perforated bottom plate 80. Each plate 112, 114 may have a thickness of about 0.50 mm to about 2.00 mm, or about 0.75 mm to about 1.75 mm, or about 1.00 mm to about 1.500 mm, or about 1.00 mm to about 1.60 mm, or about 1.50 mm to about 2.00 mm, or about 1.60 mm to about 2.00 mm. This air flow within the body 107 of the burner box 50 passes through the holes 115 in each perforated plate 112, 114 to evenly distribute the air flow around the burner 55 and the flame 54. The air should ideally be uniform and without recirculation when flowing around the flame 54. Otherwise, this may cause the flame to move to one side or the other. In some embodiments, the air flow "hugs" the flame 54 when passing through the outlet 120, and thus supports the flame 54 when the air flows through the outlet 120. This helps to provide a uniform and straight flame that is directed upward within the housing 30. As Figure 7 shown, the outlet 120 of the burner box 50 radially surrounds the burner 55.

[0094] Figure 8A shows the air flow within the housing 30 according to an embodiment of the present disclosure when using the shroud 70 and the perforated bottom plate 80 with holes 82. As Figure 8A shown, the air flows upward in a uniform manner within the housing 30 with very little recirculation. In contrast, Figure 8B shows the air flow within the housing when using a similar shroud but without a perforated bottom plate. Figure 8B The bottom plate in Figure 8C has open slots 90 to discharge air instead of having perforations. Such an open slot bottom plate design is also shown in Figure 8B . As Figure 8A shown, the air within this comparative example experiences a large amount of recirculation and does not flow upward in a uniform manner. It should be noted that due to the unique bottom plate and shroud design of the embodiments of the present disclosure, Figure 8A only about 0.5% of the pollutants are retained in the system of Figure 8B . Therefore, about 95.5% of the pollutants are removed from the system of Figure 7 B. However, in contrast, in the system of

[0095] with an open slot bottom plate design, about 9% of the pollutants are retained. Therefore, only about 91% of the pollutants are removed from the system of Figure 6A, the perforated bottom plate 80 is directly attached to the burner box 50 and the spring 86. The perforated bottom plate 80 can be conveyed backward and forward between the ends 87, 89 of the bottom plate. Since the perforated bottom plate 80 is directly attached to the burner box 50, when the perforated bottom plate 80 is conveyed between the ends 87, 89, this also causes the burner box 50 to move backward and forward between the ends 87, 89. It should be noted that this conveying movement of the burner box 50 can be supplementary to or alternative to the movement of the burner box 50 along the track 57 (as shown by the arrow B in Figure 1 ). The spring 86 maintains a tight tension on the perforated bottom plate 80, so that the perforated bottom plate 80 remains flat and taut, even when the perforated bottom plate 80 is conveyed between the ends 87, 89. The spring 86 can be adjusted to provide the required amount of tension on the perforated bottom plate 80.

[0096] The perforated bottom plate 80 can also be configured as a heat shield to block the radiation and heat from the top 34 from reaching the bottom 32 of the housing 30. In an embodiment, the bottom 32 can include, for example, devices and electronics for one or more settings of the monitoring and control system 10. These devices and electronics need to be protected from overheating and the temperature of these components needs to be maintained at a relatively cool temperature. The heat and radiation from the flame 54 and the heated wall of the shroud 70 in the top 34 may diverge outward within the housing 30 and cause the devices and electronics in the bottom 32 to overheat. Therefore, the perforated bottom plate 80 can be made of a material that blocks this heat and radiation from reaching the bottom 32. In an embodiment, the perforated bottom plate 80 can reflect the heat and radiation, so that the heat and radiation are confined within the top 34. In some embodiments, the perforated bottom plate 80 is capable of reflecting and blocking the heat and radiation within the top 34, such that the bottom 32 is cooler than the top 34 by about 40 °C or more, or about 45 °C or more, or about 50 °C or more, or about 55 °C or more, or about 60 °C or more, or about 65 °C or more. For example, the top 34 is maintained at a temperature of about 75 °C, while the bottom 32 is maintained at a temperature of about 25 °C because the perforated bottom plate 80 forms a partition between these two parts.

[0097] To block the heat and radiation within the top 34, the perforated bottom plate 80 can be made of, for example, a metal (such as stainless steel) or a polymer (such as polytetrafluoroethylene (PTFE)). The perforated bottom plate 80 can also be made of a corrosion-resistant material. In some embodiments, the perforated bottom plate includes a coating, such as a corrosion-resistant coating. In an embodiment, the coating is Dursan.

[0098] The perforated bottom plate 80 should be corrosion-resistant and anti-fragmentation, and at the same time have sufficient strength. Specifically, the perforated bottom plate 80 should have sufficient strength to capture the fishing line 60 when the fishing rod 60 happens to loosen and fall. The perforated bottom plate should be able to absorb the falling force from the fishing rod 60 without breaking itself. In addition, the material of the perforated bottom plate should be able to withstand the internal temperature within the housing 30, which can be as high as about 200 °C, or about 250 °C, or about 300 °C.

[0099] After the formation of the soot preform 20 is completed, the fishing rod 60 can be removed, and the remaining soot preform 20 can be folded and conveyed to the drawing tower. Then, at the drawing tower, the preform is drawn into an optical fiber.

[0100] As discussed above, the system 10 includes several innovative components that work together to generate the required air flow within the system, so as to efficiently and quickly remove loose soot contaminants from the system, including removing loose soot particles and hydrochloric acid. For example, the hood 70 and the perforated bottom plate 80 work together to direct the air flow at the required flow rate in order to remove contaminants from the system. In addition, the burner box 50 and the track 57 allow the soot preform to be formed in a uniform and homogeneous manner. The innovative components disclosed herein extend the life of the system 10 and reduce the time and energy required for cleaning the system. The innovative components disclosed herein also help to produce a uniform and non-deformed soot preform.

[0101] Although various embodiments have been described herein, these embodiments are presented by way of example only and not by way of limitation. Obviously, based on the teachings and guidance presented herein, there may be adaptations and modifications within the meaning and scope of the equivalents of the disclosed embodiments. Therefore, those skilled in the art will understand that various changes in form and detail can be made to the embodiments disclosed herein without departing from the spirit and scope of the present disclosure. The elements of the embodiments presented herein are not necessarily mutually exclusive, but may be interchangeable to meet various needs as will be understood by those skilled in the art.

[0102] It should be understood that the idioms or terms herein are for the purpose of description rather than limitation. The breadth and scope of the present disclosure should not be limited by any of the exemplary embodiments described above, but should be defined only in accordance with the appended claims and their equivalents.

Claims

1. A lathe system for producing an optical fiber preform, the lathe system comprising: a rotating mandrel; a burner box configured to deposit silica-containing soot on the rotating mandrel; a hood configured to direct the airflow within the lathe system through an exhaust device; and a perforated bottom plate configured to discharge the air within the lathe system as a plurality of air jets from the bottom of the lathe system to the top of the lathe system.

2. The lathe system according to claim 1, wherein the perforated bottom plate comprises a plurality of holes, each hole configured to discharge the air as an air jet.

3. The lathe system according to claim 2, wherein each of the holes has a diameter of about 5 mm to about 50 mm.

4. The lathe system according to claim 3, wherein each of the holes has a diameter of about 10 mm to about 40 mm.

5. The lathe system according to claim 2 or claim 3, wherein the minimum distance between adjacent holes is about 5 mm to about 100 mm.

6. The lathe system according to claim 5, wherein the minimum distance between adjacent holes is about 10 mm to about 90 mm.

7. The lathe system according to any one of claims 2 to 6, wherein the perforated bottom plate has an open area ratio greater than about 5% and less than about 33%, the open area ratio being provided by the following equation: where OA% is the open area ratio of the perforated bottom plate, DH is the average diameter of the holes in the perforated bottom plate, and dH is the average minimum distance between adjacent holes in the perforated bottom plate.

8. The lathe system according to claim 7, wherein the open area ratio of the perforated bottom plate is between about 9% and about 30%.

9. The lathe system according to any one of claims 1 to 8, wherein for each horizontal cross-section between the mandrel and the perforated bottom plate, the lathe system has a uniformity index between about 0.75 and about 1.0, the uniformity index being calculated by the following equation: where UI is the uniformity index of the horizontal cross-section, Vi is the vertical velocity (m / s) of the air at point i in the horizontal cross-section, Vmean is the average velocity (m / s) of the air within the horizontal cross-section, dS is the horizontal cross-sectional integral, and S is the area (m 2 ) 10. The lathe system according to claim 9, wherein the uniformity index is between about 0.80 and about 1.

0.

11. The lathe system according to any one of claims 1 to 10, wherein the perforated bottom plate is made of a corrosion-resistant material.

12. The lathe system according to any one of claims 1 to 11, the lathe system further comprising a track along which the burner box moves to deposit the silica-containing soot on the rotating mandrel.

13. The lathe system according to claim 12, wherein the track comprises a first path parallel to the longitudinal axis of the rotating mandrel and a second path laterally offset from the rotating mandrel.

14. The lathe system according to any one of claims 1 to 13, wherein the hood comprises angled side walls heated to a temperature of about 100°C to about 200°C.

15. The lathe system according to any one of claims 1 to 14, wherein the hood includes angled sidewalls connected to a manifold, the manifold is connected to an exhaust device, and a slot is positioned between the manifold and the exhaust device.

16. The lathe system according to claim 15, wherein the slot has a width of from about 10 mm to about 50 mm.

17. The lathe system according to claim 16, wherein the ends of the slot have a greater width than the central portion of the slot.

18. The lathe system according to any one of claims 1 to 17, wherein the hood has a length of from about 2 m to about 4.

19. The lathe system according to any one of claims 1 to 18, wherein the burner box includes an inlet through which air flows into the burner box and an outlet through which air flows out of the burner box, the outlet surrounding a burner that generates a flame.

20. The lathe system according to claim 19, wherein the burner box further includes a first perforated plate and a second perforated plate, each of the first perforated plate and the second perforated plate including a plurality of holes.

21. The lathe system according to claim 20, wherein each of the plurality of holes has a diameter of from about 3.0 mm to about 5.0 mm.

22. The lathe system according to claim 20, wherein each of the plurality of holes is spaced apart from an adjacent hole by a minimum distance of from about 50 mm to about 75 mm.

23. A lathe system for producing an optical fiber preform, the lathe system comprising: a rotating mandrel; a burner box configured to deposit silica-containing soot on the rotating mandrel; and a perforated bottom plate including a plurality of holes, wherein for each horizontal cross-section between the mandrel and the perforated bottom plate, the lathe system has a uniformity index between about 0.75 and about 1.0, the uniformity index being calculated by the following equation: where UI is the uniformity index of the horizontal cross-section, Vi is the vertical velocity (m / s) of the air at point i in the horizontal cross-section, Vmean is the average velocity (m / s) of the air within the horizontal cross-section, dS is the horizontal cross-sectional integral, and S is the area (m 2 ) 24. The lathe system according to claim 23, wherein the uniformity index is between about 0.80 and about 1.

0.

25. The lathe system according to claim 24, wherein the uniformity index is between about 0.85 and about 1.

0.

26. The lathe system according to any one of claims 23 to 25, wherein each of the holes has a diameter of from about 5 mm to about 50 mm.

27. The lathe system according to any one of claims 23 to 26, wherein the minimum distance between adjacent holes is from about 5 mm to about 100 mm.

28. A method for producing an optical fiber preform, the method comprising: depositing silica-containing soot on a rotating mandrel disposed within a housing; directing air within the housing to an exhaust device such that the air flows within the housing in a uniform flow direction; and removing the air from the housing through the exhaust device.

29. The method according to claim 28, wherein the uniform air flows at a velocity of at least about 0.05 m / s.

30. The method according to claim 28 or claim 29, wherein the uniform air flows at a flow rate of at least about 0.10 m / s.

31. The method according to any one of claims 28 to 30, wherein the air flows within the lathe system, and for each horizontal cross-section, the lathe system has a uniformity index between about 0.75 and about 1.0, and the uniformity index is calculated by the following equation: where UI is the uniformity index of the horizontal cross-section, Vi is the vertical velocity (m / s) of the air at point i in the horizontal cross-section, Vmean is the average velocity (m / s) of the air within the horizontal cross-section, dS is the horizontal cross-sectional integral, and S is the area (m 2 ) 32. The method according to any one of claims 28 to 31, wherein the housing includes a bottom and a top, and the air flows in the top of the housing in the uniform flow direction.

33. The method according to claim 32, the method further comprising discharging the air from the bottom of the housing to the top through a plurality of air jets.

34. The method according to claim 33, wherein the air jets do not reach the silica-containing soot deposited on the rotating fishing rod.

35. The method according to claim 33 or claim 34, wherein the air jets converge at a distance of about 0.300 m or less from the outlet of the air jets.

36. The method according to any one of claims 33 to 35, wherein the air jets are formed through a plurality of holes in a perforated bottom plate that separates the top of the housing from the bottom.

37. The method according to any one of claims 28 to 36, the method further comprising heating the inner wall of the hood to a temperature of about 100 °C to about 200 °C.

38. The method according to any one of claims 28 to 37, the method further comprising heating the inner wall of the hood to a temperature substantially matching the temperature of the loose soot particles and / or contaminants in the housing.

39. The method according to any one of claims 28 to 38, the method further comprising depositing the silica-containing soot on the rotating fishing rod with a burner box that generates a flame.

40. The method according to claim 39, the method further comprising traversing the burner box along the longitudinal length of the rotating fishing rod.

41. The method according to claim 39 or claim 40, the method further comprising moving the burner box up and down relative to the rotating fishing rod.

42. The method according to claim 38, the method further comprising moving the burner box along a first path and a second path, and the burner box deposits the silica-containing soot only on the first path and not on the second path.

43. The method according to claim 42, wherein the burner box moves at a relatively faster speed on the second path than on the first path.

44. The method according to claim 43, wherein the burner box moves at a speed of about 10 mm / s to about 70 mm / s on the first path.

45. The method according to claim 39, the method further comprising rotating the burner of the burner box between a first position and a second position, wherein when in the first position, the central axis of the burner is positioned along the same axis as the central axis of the rotary fishing rod, and in the second position, the central axis of the burner forms a non-zero angle with the central axis of the rotary fishing rod.

46. The method according to any one of claims 28 to 45, the method further comprising causing air to flow through an inlet of the burner box and out through an outlet of the burner box, the outlet surrounding the flame.

47. The method according to any one of claims 28 to 46, wherein air flows within the burner box at a flow rate of from about 2,000 SLPM to about 5,000 SLPM.

48. The method according to any one of claims 28 to 47, the method further comprising removing contaminants containing loose soot particles in the housing through the exhaust device.

49. The method according to claim 48, wherein the contaminants flow within the housing along with a uniform air flow.

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