Method of manufacturing optical fiber

Abstract

To provide a method for manufacturing an optical fiber in which variation in the outer diameter of the optical fiber is further reduced.SOLUTION: A method of manufacturing an optical fiber includes connecting a dummy rod to an upper end of a glass preform having a reduced diameter portion at an upper portion thereof, heating and melting the glass preform in a drawing furnace to draw an optical fiber, arranging a cap member so as to surround an outer periphery of the reduced diameter portion of the glass preform, arranging the cap member so that an upper end of the cap member is close to a lower end of the dummy rod, arranging a partition member having an opening portion inside the cap member, and drawing the optical fiber in a state where the reduced diameter portion is inserted into the opening portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to methods for manufacturing optical fibers. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing an optical fiber. Patent Document 1 discloses that in the process of drawing a glass preform having a diameter-reduced portion, the volume of space inside the drawing furnace increases due to the diameter-reduced portion, which changes significantly in diameter, and this changes the flow of inert gas inside the drawing furnace, causing fluctuations in the outer diameter of the optical fiber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-088463 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, a cap member is provided to cover the outer periphery of the tapered portion of the glass preform in order to reduce fluctuations in the outer diameter of the optical fiber. However, the internal space of the cap member is relatively large, and inert gas may flow into the space between the cap member and the tapered portion, causing the tapered portion to disrupt the air flow inside the cap member. As a result, the flow of inert gas inside the drawing furnace changes, which can cause fluctuations in the outer diameter of the optical fiber.

[0005] An object of the present disclosure is to provide a method for manufacturing an optical fiber that further reduces variations in the outer diameter of the optical fiber. [Means for solving the problem]

[0006] The manufacturing method disclosed herein is a method for manufacturing an optical fiber in which a dummy rod is connected to the upper end of a glass base material having a tapered portion at the top, and the glass base material is heated and melted in a drawing furnace to draw an optical fiber, wherein a cap member is arranged to surround the outer periphery of the tapered portion of the glass base material, the cap member is arranged so that the upper end of the cap member is close to the lower end of the dummy rod, a partition member having an opening is arranged inside the cap member, and the optical fiber is drawn with the tapered portion inserted into the opening. [Effects of the Invention]

[0007] The present disclosure provides a method for manufacturing an optical fiber that further reduces variations in the outer diameter of the optical fiber. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view illustrating a wire drawing apparatus according to the present embodiment. [Figure 2] FIG. 2 is a perspective view illustrating a partition member of the drawing device. [Figure 3] 3 is a cross-sectional view of the cap member taken along the line III-III in FIG. [Figure 4] FIG. 4 is a cross-sectional view illustrating the flow of inert gas in a drawing apparatus according to a comparative example. [Figure 5] FIG. 5 is a cross-sectional view illustrating the flow of inert gas in the drawing apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Description of one embodiment of the present disclosure) First, embodiments of the present disclosure will be listed and described. (1) A method for manufacturing an optical fiber according to one aspect of the present disclosure includes connecting a dummy rod to the upper end of a glass base material having a tapered portion at the top, heating and melting the glass base material in a drawing furnace to draw an optical fiber, and arranging a cap member to surround the outer periphery of the tapered portion of the glass base material, arranging the cap member so that the upper end of the cap member is close to the lower end of the dummy rod, arranging a partition member having an opening inside the cap member, and inserting the tapered portion into the opening, and drawing the optical fiber.

[0010] According to the present disclosure, a partition member having an opening is disposed inside a cap member, and an optical fiber is drawn with a tapered portion inserted through the opening. Even if inert gas flows into the space between the cap member and the tapered portion, the flow of inert gas is blocked by the partition member, and the flow rate of the air flowing inside the cap member is low. Therefore, even as drawing progresses, the flow of inert gas inside the drawing furnace is less likely to change, further reducing fluctuations in the outer diameter of the optical fiber.

[0011] (2) In the above (1), the inner diameter of the opening of the partition member may be smaller than the maximum outer diameter of the reduced diameter portion.

[0012] According to the present disclosure, the inner diameter of the opening of the partition member is smaller than the maximum outer diameter of the reduced diameter portion, making it easy to place the partition member on the reduced diameter portion.

[0013] (3) In the above (1) or (2), the partition member may contain at least one of carbon, ceramics, and quartz glass.

[0014] According to the present disclosure, since the partition member is formed of a heat-resistant material, the partition member is less likely to deform even when heated in a drawing furnace.

[0015] (4) In any of (1) to (3) above, in a cross section perpendicular to the longitudinal direction of the glass base material, the cross-sectional area of ​​the glass base material and the partition member may be 83% or more of the cross-sectional area of ​​the interior of the cap member.

[0016] According to the present disclosure, the cross-sectional area of ​​the glass base material and the partition member is 83% or more of the cross-sectional area of ​​the interior of the cap member, so the space between the cap member and the partition member is narrow and the flow rate of the inert gas flowing inside the cap member can be reduced.

[0017] (5) In any one of the above (1) to (4), the partition member may be disposed at a position between 0 mm and 120 mm from the lower end of the cap member in the longitudinal direction of the glass base material.

[0018] According to the present disclosure, the partition member is positioned at a position between 0 mm and 120 mm from the lower end of the cap member, making it difficult for inert gas to flow into the space between the cap member and the reduced diameter portion, and even if it does flow in, the flow rate of the inert gas can be reduced.

[0019] (Details of one embodiment of the present disclosure) A specific example of a method for manufacturing a glass base material according to an embodiment of the present disclosure will be described with reference to the drawings. It should be noted that the present disclosure is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0020] (Glass base material drawing equipment) First, with reference to FIGS. 1 and 2, a drawing apparatus 1 used in the manufacturing method of a glass preform G according to this embodiment will be described. The drawing apparatus 1 is part of a manufacturing apparatus for manufacturing an optical fiber. FIG. 1 is a cross-sectional view illustrating the drawing apparatus 1. As illustrated in FIG. 1, the drawing apparatus 1 has a drawing furnace 10. A heating element 11 is provided in the drawing furnace 10 so as to surround the glass preform G. The drawing apparatus 1 is configured to generate heat from the heating element 11, heat and melt the glass preform G in the drawing furnace 10, and draw an optical fiber. Furthermore, a gas supply device (not shown) that supplies an inert gas into the drawing furnace 10 is connected to the drawing furnace 10.

[0021] In this embodiment, the main component of the glass base material G is quartz. The outer shape of the glass base material G in a cross section perpendicular to the longitudinal direction D1 of the glass base material G is circular.

[0022] The upper end G11 of the glass base material G is connected to the lower end G01 of the dummy rod G0. The upper end G11 of the glass base material G and the lower end G01 of the dummy rod G0 may be connected directly or indirectly. For example, a separate member may connect the glass base material G and the dummy rod G0 between the upper end G11 and the lower end G01. In this way, the glass base material G is supported by the dummy rod G0 and suspended within the drawing furnace 10.

[0023] The glass base material G has a main body portion G12, a tapered portion G13, and a reduced diameter portion G14. The diameter of the main body portion G12 is constant along the longitudinal direction D1 of the glass base material G. The tapered portion G13 is located between the main body portion G12 and the reduced diameter portion G14. The diameter of the tapered portion G13 gradually increases from the reduced diameter portion G14 toward the main body portion G12 along the longitudinal direction D1. Not only the reduced diameter portion G14 but also the tapered portion G13 are part of the reduced diameter portion described in the claims.

[0024] The reduced diameter portion G14 is located at the upper portion of the glass preform G, above the tapered portion G13. The reduced diameter portion G14 has an intermediate portion G15. The diameter of the reduced diameter portion G14 gradually increases from the upper end portion G11 of the glass preform G toward the intermediate portion G15 along the longitudinal direction D1, and is maximum at the intermediate portion G15. In other words, the maximum outer diameter of the reduced diameter portion G14 is the diameter of the reduced diameter portion G14 at the intermediate portion G15. Furthermore, the diameter of the reduced diameter portion G14 gradually decreases from the intermediate portion G15 toward the tapered portion G13. The maximum outer diameter of the reduced diameter portion G14 is smaller than the diameter of the main body portion G12.

[0025] Within the drawing furnace 10, a cap member 20 is arranged to surround the outer periphery of the reduced diameter portion G14 of the glass preform G. The cap member 20 is a cylindrical member. The cap member 20 has a disk-shaped lid with a hole formed in the center at the upper end for inserting a dummy rod G0. The lower end of the cap member 20 is open. At least the reduced diameter portion G14 is housed within the cap member 20. A portion of the tapered portion G13 may also be housed within the cap member 20. The cap member 20 is arranged so that the upper end 21 of the cap member 20 is close to the lower end G01 of the dummy rod G0. If the lower end 22 of the cap member 20 is close to the glass preform G, it becomes difficult for an inert gas to enter between the lower end 22 of the cap member 20 and the glass preform G.

[0026] The cap member 20 has a circular outer shape in a cross section perpendicular to the longitudinal direction D1 of the glass base material G. The diameter of the cap member 20 is constant along the longitudinal direction D1 of the glass base material G. The diameter of the cap member 20 is equal to or smaller than the diameter of the main body portion G12 of the glass base material G and is larger than the maximum outer diameter of the tapered portion G14. The cap member 20 includes at least one of carbon, ceramics, and quartz glass.

[0027] A partition member 30 is disposed inside the cap member 20. More specifically, the length L between the lower end 32 of the partition member 30 and the lower end 22 of the cap member 20 is 0 mm or more and 120 mm or less. In other words, the partition member 30 is disposed at a position 0 mm or more and 120 mm or less from the lower end 22 of the cap member 20 in the longitudinal direction D1 of the glass preform G. The partition member 30 includes at least one of carbon, ceramics, and quartz glass.

[0028] The partition member 30 has an opening 31 through which the reduced diameter portion G14 of the glass preform G is inserted. Fig. 2 is a perspective view illustrating the partition member 30. As illustrated in Fig. 2, the outer shape of the partition member 30 is ring-shaped in a cross section perpendicular to the longitudinal direction D1 of the glass preform G. The inner diameter D31 of the opening 31 is smaller than the maximum outer diameter of the reduced diameter portion G14, in other words, the diameter of the reduced diameter portion G14 in the intermediate portion G15.

[0029] If the clearance between the inner surface 23 of the cap member 20 and the outer surface 33 of the partition member 30 is small, the inert gas is blocked by the partition member 30 and does not easily pass through the clearance (FIG. 1). Fig. 3 is a cross-sectional view of the cap member 20 taken along the line III-III in Fig. 1. As illustrated in Fig. 3, in a cross section perpendicular to the longitudinal direction D1 of the glass base material G, the cross-sectional areas of the glass base material G and the partition member 30 are 83% or more of the cross-sectional area of ​​the interior of the cap member 20.

[0030] Next, the flow of inert gas during the manufacture of optical fiber will be described with reference to FIGS. 4 and 5. FIG. 4 is a cross-sectional view illustrating the flow of inert gas in a drawing apparatus Z according to a comparative example. As illustrated in FIG. 4, in the drawing apparatus Z according to the comparative example, unlike the drawing apparatus 1 according to the present embodiment, the partition member 30 is not disposed inside the cap member 20. FIG. 5 is a cross-sectional view illustrating the flow of inert gas in the drawing apparatus 1 according to the present embodiment. In the configurations shown in FIGS. 4 and 5, the same components as those shown in FIG. 1 are designated by the same reference numerals, and their description will be omitted. In addition, for the sake of explanation, the flow of inert gas is illustrated by arrows in FIGS. 4 and 5.

[0031] 4 and 5, the optical fiber manufacturing method involves first connecting a dummy rod G0 to the upper end G11 of a glass preform G, and suspending the glass preform G in a drawing furnace 10. Furthermore, a cap member 20 is placed in the drawing furnace 10 so as to surround the outer periphery of the reduced diameter portion G14 of the glass preform G. At this time, the cap member 20 is placed in the drawing furnace 10 so that the upper end 21 of the cap member 20 is close to the lower end G01 of the dummy rod G0. After placing the cap member 20, an inert gas is supplied into the drawing furnace 10, and the heating element 11 is heated to heat and melt the glass preform G in the drawing furnace 10, thereby drawing an optical fiber.

[0032] As the drawing progresses, the glass preform G descends in the longitudinal direction D1 within the drawing furnace 10. Because the diameter of the main body G12 of the glass preform G is constant in the longitudinal direction D1, even when the main body G12 descends into the drawing furnace 10, the spatial volume within the drawing furnace 10 does not change, and the flow of inert gas within the drawing furnace 10 is not easily disturbed. On the other hand, the diameter of the tapered portion G13 of the glass preform G and the maximum outer diameter of the tapered portion G14 are smaller than the diameter of the main body G12. Therefore, when the tapered portion G13 and the tapered portion G14 descend into the drawing furnace 10, the spatial volume within the drawing furnace 10 increases, and the flow of inert gas within the drawing furnace 10 is likely to change. When the flow of inert gas changes, the outer diameter of the optical fiber is likely to fluctuate.

[0033] 4, in the drawing apparatus Z according to the comparative example, the cap member 20 is disposed so as to cover the outer periphery of the reduced diameter portion G14 of the glass preform G. Because the diameter of the cap member 20 is constant in the longitudinal direction D1, the spatial volume within the drawing furnace 10 is unlikely to change. Therefore, even if the tapered portion G13 and the reduced diameter portion G14 descend into the drawing furnace 10, the flow of the inert gas flowing within the drawing furnace 10 is unlikely to be disturbed.

[0034] However, inert gas may flow in between the lower end 22 of the cap member 20 and the glass preform G. The internal space of the cap member 20 is relatively large, and the diameters of the tapered portion G13 and the reduced diameter portion G14 are not constant in the longitudinal direction D1. This makes it easy for the flow of inert gas to become turbulent inside the cap member 20. Furthermore, if the flow rate of inert gas flowing into the cap member 20 is high, the inert gas may flow from the upper end 21 of the cap member 20 along the dummy rod G0 and outward from the drawing furnace 10. In this way, the turbulence of the inert gas inside the cap member 20 or the outflow from the cap member 20 may change the flow of inert gas inside the drawing furnace 10, causing fluctuations in the outer diameter of the optical fiber.

[0035] On the other hand, as illustrated in FIG. 5, in the drawing apparatus 1 according to this embodiment, a cap member 20 is disposed in a drawing furnace 10, and a partition member 30 is disposed inside the cap member 20.

[0036] Furthermore, in this embodiment, the optical fiber is drawn with the reduced diameter portion G14 inserted through the opening 31 of the partition member 30. Even if inert gas flows in between the lower end 22 of the cap member 20 and the glass preform G, the flow of inert gas is blocked by the partition member 30. Therefore, the flow of inert gas inside the cap member 20 is less likely to be disturbed. Furthermore, the flow rate of inert gas flowing into the cap member 20 is also low. Therefore, even as drawing progresses, the flow of inert gas inside the drawing furnace 10 is less likely to change, further reducing fluctuations in the outer diameter of the optical fiber.

[0037] In this embodiment, the inner diameter of the opening 31 of the partition member 30 is smaller than the maximum outer diameter of the reduced diameter portion G14, which makes it easier to place the partition member 30 on the reduced diameter portion G14, improving workability.

[0038] The partition member 30 contains at least one of carbon, ceramics, and quartz glass. Because the partition member 30 is made of such a heat-resistant material, it is less likely to deform even when heated in the drawing furnace 10. Therefore, the flow of the inert gas is less likely to change, and fluctuations in the outer diameter of the optical fiber are further reduced.

[0039] Since the cross-sectional area of ​​the glass preform G and the partition member 30 is 83% or more of the cross-sectional area of ​​the interior of the cap member 20, the space between the inner surface 23 of the cap member 20 and the outer surface 33 of the partition member 30 is narrow. This allows the flow rate of the inert gas flowing into the cap member 20 to be reduced, thereby further reducing the fluctuation in the outer diameter of the optical fiber.

[0040] Since the partition member 30 is disposed at a position between 0 mm and 120 mm from the lower end 22 of the cap member 20, the inert gas is less likely to flow into the space between the cap member 20 and the reduced diameter portion G14, and even if the inert gas does flow in, the flow rate of the inert gas can be reduced, thereby further reducing the fluctuation in the outer diameter of the optical fiber.

[0041] Although the present disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to the number, position, shape, etc. that are suitable for implementing the present disclosure.

[0042] Although the glass base material G of this embodiment has a tapered portion G14, the glass base material G may have only a main portion G12 and a tapered portion G13 without having the tapered portion G14. In this case, the partition member 30 is placed on the tapered portion G13.

[0043] The partition member 30 of this embodiment is placed on the reduced diameter portion G14 and disposed inside the cap member 20. In other words, the cap member 20 and the partition member 30 are disposed by different actions, but the arrangement of the partition member 30 is not limited to this. The partition member 30 may be disposed on the inner surface 23 of the cap member 20. For example, the partition member 30 may be erected in a convex shape from the inner surface 23 of the cap member 20 toward the glass preform G. In this case, the partition member 30 is disposed at the same time as the cap member 20 is disposed. If the clearance between the opening 31 of the partition member 30 and the reduced diameter portion G14 of the glass preform G is small, the inert gas is blocked by the partition member 30, making it difficult for the inert gas to pass through the clearance. Even in such a case, the outer diameter fluctuation of the glass fiber can be reduced.

[0044] In this embodiment, the outer shape of the partition member 30 in the cross section perpendicular to the longitudinal direction D1 of the glass preform G is ring-shaped, but the outer shape of the partition member 30 is not limited to a ring shape. For example, the outer shape of the partition member 30 may be rectangular with a circular opening 31 in the center. Even with such a shape, the inert gas is blocked by the partition member 30, so that fluctuations in the outer diameter of the glass fiber can be reduced. [Explanation of symbols]

[0045] 1, Z drawing device 10 Wire drawing furnace 11 Heating element G0 Dummy Rod G01 Lower end G Glass base material G11 Upper end G12 main body G13 tapered section G14 Reduced diameter part G15 middle part 20 Cap member 21 Upper end 22 Lower end 23 Inner 30 Partition member 31 Opening 32 Lower end 33 Exterior D31 inner diameter D1 Longitudinal direction

Claims

1. 1. A method for manufacturing an optical fiber, comprising: connecting a dummy rod to an upper end of a glass preform having a tapered portion at an upper portion thereof; and heating and melting the glass preform in a drawing furnace to draw an optical fiber, a cap member is disposed so as to surround the outer periphery of the reduced diameter portion of the glass base material; The cap member is positioned so that the upper end of the cap member is adjacent to the lower end of the dummy rod; A method for manufacturing an optical fiber, comprising: disposing a partition member having an opening inside the cap member; and drawing the optical fiber in a state in which the reduced diameter portion is inserted into the opening.

2. The method for manufacturing an optical fiber according to claim 1 , wherein the inner diameter of the opening of the partition member is smaller than the maximum outer diameter of the tapered portion.

3. 2. The method for producing an optical fiber according to claim 1, wherein the partition member includes at least one of carbon, ceramics, and silica glass.

4. 4. The method for manufacturing an optical fiber according to claim 1, wherein in a cross section perpendicular to the longitudinal direction of the glass base material, a cross-sectional area of ​​the glass base material and the partition member is 83% or more of a cross-sectional area of ​​the interior of the cap member.

5. 4. The method for manufacturing an optical fiber according to claim 1, wherein the partition member is disposed at a position not less than 0 mm and not more than 120 mm from a lower end of the cap member in the longitudinal direction of the glass preform.

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