Method for manufacturing optical fiber

Abstract

A method for manufacturing an optical fiber by drawing while feeding a glass base material comprising a core rod and a clad tube into which the core rod is inserted into a heating furnace, the method comprising joining a quartz tube to the upper end of the clad tube, and drawing the glass base material while feeding the glass base material to the heating furnace. The core rod and the cladding tube are made to communicate with the internal space of the quartz tube, the gap and the internal space of the quartz tube are made to be in a vacuum state in a state that the upper part of the quartz tube is gripped by a metal gripping member, and the length of the quartz tube is more than 250 mm and less than 1250 mm. And a heat insulation plate is arranged below the holding part and at a distance of more than 10 mm from the holding part.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing optical fibers.

[0002] This application claims priority based on Japanese Patent Application No. 2023-175739, filed on October 11, 2023, and incorporates all the contents set forth in that application. Background Technology

[0003] Patent Document 1 discloses a method for manufacturing optical fibers while the quartz tube and the glass matrix are bonded together. The optical fiber is manufactured by drawing the glass matrix into a thinner diameter by melting and reducing its diameter in a heating furnace.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-173895 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] In Patent Document 1, a dummy quartz tube and a clamping quartz tube are installed on the upper part of the optical fiber mother material, and a vacuum cover is installed on the upper part of the quartz tube.

[0009] However, during the drawing of optical fiber preforms, the radiant heat from the drawing furnace can affect the upper part of the preforms, which can sometimes cause the holding components that hold the quartz tube to be overheated and damaged or deteriorated.

[0010] The purpose of this disclosure is to provide a method for manufacturing optical fibers that improves the durability of the holding components.

[0011] Solutions for solving technical problems

[0012] One aspect of this disclosure relates to a method for manufacturing optical fibers by drawing a glass matrix while feeding it into a heating furnace. The glass matrix has a core rod and a cladding tube into which the core rod is inserted. The manufacturing method includes joining a quartz tube to the upper end of the cladding tube, such that the gap between the core rod and the cladding tube communicates with the internal space of the quartz tube. With the upper part of the quartz tube held by a metal holding member, the hollow portion and the internal space are made into a vacuum state. The length of the quartz tube is 250 mm or more and 1250 mm or less. A heat insulation plate is provided below the holding member and at a distance of 10 mm or more from the holding member.

[0013] Invention Effects

[0014] According to this disclosure, a method for manufacturing an optical fiber that improves the durability of the gripping component can be provided. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the optical fiber manufacturing apparatus according to this embodiment.

[0016] Figure 2 This is a top view of the holding components and the heat insulation panel.

[0017] Figure 3 The graph shows the relationship between the length of the quartz tube and the temperature of the holding component for Examples 1 to 4, 8 and 9 in Table 1. Detailed Implementation

[0018] (Description of embodiments of this disclosure)

[0019] First, the implementation aspects of this disclosure will be described.

[0020] (1) One aspect of the present disclosure relates to a method for manufacturing optical fibers by drawing a glass matrix while feeding it into a heating furnace. The glass matrix has a core rod and a cladding tube into which the core rod is inserted. The manufacturing method includes joining a quartz tube to the upper end of the cladding tube, such that the gap between the core rod and the cladding tube is in communication with the internal space of the quartz tube. With the upper part of the quartz tube held by a metal holding member, the hollow part and the internal space are made into a vacuum state. The length of the quartz tube is 250 mm or more and 1250 mm or less. A heat insulation plate is provided below the holding member and at a distance of 10 mm or more from the holding member.

[0021] According to the aforementioned optical fiber manufacturing method, the quartz tube is 250 mm or more and 1250 mm or less in length, and the optical fiber is manufactured with a heat insulation plate placed between the midpoint of the quartz tube and the holding component. This allows for the manufacture of the optical fiber while preventing the metal holding component from becoming excessively hot. Consequently, the durability of the holding component can be improved.

[0022] (2) Alternatively, in the optical fiber manufacturing method mentioned in (1) above, the heat insulation plate is displaced in such a way that the distance between the heat insulation plate and the holding member remains unchanged as the holding member is displaced.

[0023] According to the above structure, even if the metal holding component is displaced, the distance between the heat insulation plate and the holding component remains unchanged. Therefore, even if the holding component approaches the heating furnace as the optical fiber manufacturing progresses and the glass matrix descends, the heat insulation effect on the holding component can still be obtained.

[0024] (3) Alternatively, in the optical fiber manufacturing method involved in (1) or (2) above, the glass matrix is ​​arranged to be fed to the heating furnace by a feeder, and the heat insulation plate is installed on at least one of the movable part of the feeder and the holding part.

[0025] According to the above structure, the glass substrate is conveyed toward the heating furnace by a feeder, and the heat insulation plate and the holding component are also conveyed toward the heating furnace at the same speed along with the glass substrate. Therefore, even if the holding component is close to the heating furnace, the heat insulation plate is also close to the heating furnace to the same extent, so even if the manufacturing of optical fibers progresses, a roughly equivalent heat insulation effect can be expected.

[0026] (4) Alternatively, in any of the fiber manufacturing methods described in (1) to (3) above, the outer edge of the heat insulation plate is located outside the holding member when viewed from above.

[0027] According to the above structure, when viewed from the heating furnace, the holding component is covered by a heat insulation plate, so the holding component is not easily exposed to heat from the heating furnace.

[0028] (5) Alternatively, in any of the fiber manufacturing methods mentioned in (1) to (4) above, the heat insulation plate is a metal plate.

[0029] Based on the above structure, the reflectivity of the heat insulation board is high enough that the heat insulation board itself does not easily store heat and is not likely to become a heat source for overheating the holding components.

[0030] (6) Alternatively, in any of the fiber manufacturing methods described in (1) to (4) above, at least a portion of the heat insulation plate is made of carbon.

[0031] According to the above structure, at least a portion of the insulation board is made of carbon, which improves the durability of the insulation board.

[0032] (Details of the embodiments described in this disclosure)

[0033] Hereinafter, specific examples of the optical fiber manufacturing method according to embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to these examples, but is defined by the claims and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0034] Furthermore, in the description of this embodiment, for ease of explanation, the terms "vertical direction," "left-right direction," and "front-back direction" will be appropriately mentioned. Here, "vertical direction" includes both "up" and "down." "Left-right direction" includes both "left" and "right." In the figures shown below, reference numeral U indicates the up direction. Reference numeral D indicates the down direction. Reference numeral L indicates the left direction. Reference numeral R indicates the right direction.

[0035] (Manufacturing equipment)

[0036] Figure 1 This is a schematic diagram of the optical fiber manufacturing apparatus 1 according to this embodiment. Figure 1 The illustrated manufacturing apparatus 1 is configured to manufacture optical fibers by drawing glass matrix G into fibers while feeding it into a heating furnace H. The heating furnace H is configured to melt the glass matrix using a heater or the like.

[0037] The glass matrix G has a core rod G1. The core rod G1 is formed of quartz glass. The core rod G1 forms the core of the optical fiber.

[0038] The glass substrate G has a cladding tube G2. The cladding tube G2 is formed of quartz glass. A core rod G1 is inserted into the cladding tube G2. A gap S1 is formed between the cladding tube G2 and the core rod G1. The cladding tube G2 forms a cladding portion surrounding the core of the optical fiber. The core rod G1 and the cladding tube G2 are configured such that at least one of them contains a refractive index modifier, and the refractive index of the light from the core rod G1 is higher than that from the cladding tube G2.

[0039] A quartz tube 10 is attached to the upper end of the cladding tube G2. The internal space S2 of the quartz tube 10 communicates with the gap S1 between the cladding tube G2 and the mandrel G1. The quartz tube 10 is, for example, formed of quartz glass. The length Ld of the quartz tube 10 is 250 mm or more and 1250 mm or less.

[0040] The holding member 20 holds the upper part of the quartz tube 10. The holding member 20 is made of metal. The holding member 20 is separated into upper and lower parts and is held by clamping the upper part of the quartz tube 10 with fasteners such as bolts. On the holding member 20, a pipe (not shown) for evacuating the gap S1 between the mandrel G1 and the cladding tube G2 and the quartz tube 10 S2 is connected to the exhaust pipe 21.

[0041] A cover 22 is provided on the holding member 20. The cover 22 is fixed to the feeder. The cover 22 is fastened to the holding member 20 by bolts. A recess is provided on the side of the glass substrate G or the quartz tube 10. By hanging the holding member 20 in the recess, the glass substrate G and the quartz tube 10 are suspended.

[0042] The glass substrate G, quartz tube 10, and holding component 20 are displaced by a feeder. The feeder is configured to gradually feed the glass substrate G, quartz tube 10, and holding component 20 to the heating furnace by gradually lowering them as the optical fiber manufacturing progresses. The feeder has a movable part 30 that moves together with the glass substrate G.

[0043] A heat insulation plate 40 is provided in the manufacturing apparatus 1. The heat insulation plate 40 is a disc-shaped plate with a hole formed in the center for the quartz tube 10 to pass through. The diameter of the heat insulation plate 40 is larger than the diameter of the holding member 20 when viewed from above or below. The heat insulation plate 40 is arranged with its lower surface facing the heating furnace H. The heat insulation plate 40 is suspended from a support member.

[0044] The heat insulation plate 40 is located below the holding member 20 and at a distance of 10 mm or more from the holding member 20. In other words, the distance Ls between the heat insulation plate 40 and the holding member 20 is 10 mm or more. In this embodiment, the heat insulation plate 40 is mounted on the movable part 30. The heat insulation plate 40 is in contact with the quartz tube 10. A small gap may also be provided between the heat insulation plate 40 and the quartz tube 10.

[0045] Figure 2 This is a top view of the holding component 20 and the heat insulation plate 40. Figure 2 This is a cross-sectional view after being cut along a horizontal section that makes the cross-section of the quartz tube 10 visible. For example... Figure 2 As illustrated, the heat insulation plate 40 is preferably configured such that its outer edge is outside the holding member 20 when viewed from above. Therefore, when viewed from the perspective of the heating furnace H, the holding member 20 is covered by the heat insulation plate 40.

[0046] Preferably, the heat insulation plate 40 is formed of a material with high heat resistance. Specifically, the heat insulation plate 40 preferably has a heat resistance of 150°C or higher, and more preferably has a heat resistance of 300°C or higher. The heat insulation plate 40 may also be a metal plate such as stainless steel (SUS) or iron. Preferably, the metal plate is mirror-polished. Stainless steel (SUS) and iron have high mechanical strength and excellent machinability. Therefore, the heat insulation plate 40 can be configured to be water-cooled or to have a heat dissipation mechanism, thereby improving heat dissipation performance.

[0047] Next, the manufacturing method of the optical fiber using manufacturing apparatus 1 will be described.

[0048] Glass substrate G is fed to heating furnace H by a feeder with quartz tube 10 installed on it and holding member 20 installed on the upper part of quartz tube 10. For this purpose, glass substrate G, quartz tube 10 and holding member 20 move toward heating furnace H at the same speed.

[0049] The heat insulation plate 40 is mounted on the movable part 30, which is fixed to the feeder. If the feeder moves downward, the heat insulation plate 40 moves toward the heating furnace H at the same speed as the glass substrate G, the quartz tube 10, and the holding member 20. Thus, the heat insulation plate 40 moves together with the glass substrate G in a manner that keeps the distance Ls between the heat insulation plate 40 and the holding member 20 constant, as the holding member 20 moves.

[0050] The heat insulation plate 40 prevents the heat from the heating furnace H from directly radiating to the holding component 20. As a result, the holding component 20 is less likely to become excessively hot during the manufacturing of optical fibers.

[0051] Since the holding member 20 is made of metal, it is prone to deterioration due to heat damage if it becomes excessively hot. According to the aforementioned optical fiber manufacturing method, the quartz tube 10 is 250 mm or more and 1250 mm or less in length, and the optical fiber is manufactured with a heat insulation plate 40 installed at a distance of 10 mm or more between the quartz tube 10 and the holding member 20. Because the holding member 20 is not directly exposed to heat from the heating furnace H, optical fiber can be manufactured while preventing the metal holding member 20 from becoming excessively hot. This improves the durability of the holding member 20.

[0052] According to the above-described optical fiber manufacturing method, the heat insulation plate 40 is installed on the movable part 30 of the feeder, and thus, as the holding member 20 is displaced, the distance Ls between the heat insulation plate 40 and the holding member 20 remains constant. Therefore, even if the holding member 20 approaches the heating furnace H, the heat insulation plate 40 also approaches the heating furnace H to the same extent, so even if the manufacturing of the optical fiber progresses, a substantially equivalent heat insulation effect can be expected.

[0053] If the heat insulation board 40 is made of metal, it has excellent workability.

[0054] At least a portion of the heat insulation panel 40 may also be made of carbon. Carbon has high heat resistance and is not prone to thermal expansion, so even if the temperature changes repeatedly during and after optical fiber manufacturing, the heat insulation panel 40 is not prone to deformation, thus improving its durability.

[0055] Next, the verification results for the length of the quartz tube are explained. Table 1 shows the temperature of the holding member corresponding to the length of the quartz tube when the lower end of the quartz tube is at a specified distance from the upper end of the heating furnace (the temperature when the lower end of the dummy tube is at a specified distance from the upper end of the heating furnace). Examples 1 to 4 and Example 8 show the results with the heat insulation plate installed. Examples 5 to 7 show the results without the heat insulation plate installed. In all examples, the distance Ls from the holding member to the heat insulation plate is 10 mm, and the heat insulation plate is made of stainless steel.

[0056] [Table 1]

[0057] [Table 1]

[0058] Ld[mm] Insulation board Temperature of the holding component [°C] Example 1 1250 have 60 Example 2 1000 have 68 Example 3 750 have 75 Example 4 250 have 130 Example 5 1000 none 161 Example 6 1250 none 154 Example 7 1500 none 139 Example 8 100 have 165 Example 9 500 have 93

[0059] As illustrated in Table 1, the longer the length Ld of the quartz tube, the lower the temperature of the holding component is suppressed. Furthermore, as shown in Examples 1 and 6, and Examples 2 and 5, even with the same quartz tube length, the temperature of the holding component decreases when a heat insulation plate is provided.

[0060] According to the results, the temperature of the holding component decreases when a heat insulation plate is installed, and the temperature of the holding component also decreases when the length of the quartz tube Ld is longer. However, in the same optical fiber manufacturing apparatus, if the length of the quartz tube is increased, the length of the glass matrix becomes shorter. Since the manufacturing cost of optical fiber decreases as the amount of fiber that can be drawn in one pass increases, the longer the glass matrix and the shorter the length of the quartz tube Ld, the better. In order to balance preventing the temperature of the holding component from rising too high and reducing the manufacturing cost of optical fiber, the length of the quartz tube Ld is preferably 250 mm or more and 1250 mm or less.

[0061] Figure 3 This is a graph showing the relationship between the length Ld of the quartz tube and the temperature of the holding component, referring to Examples 1 to 4, 8, and 9 in Table 1. Examples 1 to 4, 8, and 9 are all examples with heat insulation plates installed. Figure 3 As illustrated, it can be seen that the longer the length Ld of the quartz tube, the lower the temperature of the holding component.

[0062] Here, when the length Ld of the quartz tube is 100mm or more and 500mm or less, the temperature inclination of the holding component is more abrupt than when the length Ld of the quartz tube is 500mm or more and 1250mm or less. Therefore, when the length Ld of the quartz tube is 100mm or more and 500mm or less, the temperature of the holding component is less likely to rise due to the presence of a heat insulation plate, thus proving effective.

[0063] The present disclosure has been described in detail above with reference to specific embodiments, but various changes or modifications can be made without departing from the spirit and scope of the present disclosure, which will be apparent to those skilled in the art. Furthermore, the number, position, shape, etc., of the constituent components described above are not limited to the above embodiments, and can be changed to preferred numbers, positions, shapes, etc., for implementing the present disclosure.

[0064] As in Figure 1As illustrated by the dashed line, the heat insulation plate 40 can also be configured to be mounted on the holding member 20 instead of being mounted on the movable part 30. In this case, the heat insulation plate 40 can also be configured, similar to this embodiment, to move together with the glass matrix G in such a way that the distance Ls between the heat insulation plate 40 and the holding member 20 remains unchanged.

[0065] In this embodiment, a method for manufacturing a multi-core optical fiber is illustrated, but it can also be a method for manufacturing a single-core optical fiber with one core.

[0066] Explanation of reference numerals in the attached figures

[0067] 1 Manufacturing apparatus

[0068] 10 Quartz Tubes

[0069] 20 Holding components

[0070] 21 Exhaust pipe

[0071] 22 cover

[0072] 30 movable parts

[0073] 40 heat insulation board

[0074] G Glass matrix

[0075] G1 Chip

[0076] G2 cladding tube

[0077] H heating furnace

[0078] S1 gap

[0079] S2 interior space.

Claims

1. A method for manufacturing optical fiber, comprising drawing an optical fiber while feeding a glass matrix into a heating furnace. The glass matrix has a core rod and a cladding tube into which the core rod is inserted. The manufacturing method includes: The upper end of the quartz tube is joined to the cladding tube, while the gap between the mandrel and the cladding tube communicates with the internal space of the quartz tube. With the upper part of the quartz tube held by a metal gripping component, the gap and the internal space of the quartz tube are made into a vacuum state. The length of the quartz tube is more than 250 mm and less than 1250 mm. A heat insulation plate is provided at a location below the gripping component and at a distance of more than 10 mm from the gripping component.

2. The method for manufacturing optical fiber according to claim 1, wherein, The heat insulation plate is displaced in a manner that keeps the distance between the heat insulation plate and the holding member constant as the holding member is displaced.

3. The method for manufacturing optical fiber according to claim 1 or 2, wherein, The glass matrix is ​​configured to be fed to the heating furnace via a feeder. The heat insulation plate is installed on at least one of the movable part of the feeder and the holding part.

4. The method for manufacturing an optical fiber according to any one of claims 1 to 3, wherein, When viewed from above, the outer edge of the heat insulation plate is located outside the holding member.

5. The method for manufacturing an optical fiber according to any one of claims 1 to 4, wherein, The insulation board is a metal plate.

6. The method for manufacturing an optical fiber according to any one of claims 1 to 4, wherein, At least a portion of the heat insulation panel is made of carbon.

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