Method for manufacturing optical fiber

Abstract

A method for manufacturing an optical fiber (G3), in which an optical fiber (G3) including a glass fiber (G1) is manufactured using a fiber drawing furnace (120) that heats and softens a glass base material (G) and a slow cooling furnace (130) that is disposed downstream of the fiber drawing furnace (120) and that slowly cools the glass fiber (G1) drawn by the fiber drawing furnace (120), a fiber drawing termination step (S200) having: a fiber downstream side cutting step (S210) in which the fiber is cut downstream side; cutting the glass fiber (G1) at a position closer to the downstream side than the slow cooling furnace (130); a cooling step (S220) in which, after the fiber-downstream-side cutting step (S210), the temperature inside the slow cooling furnace (130) is reduced to or below the slow cooling point of the glass fiber (G1); and a fiber removal step (S250) of removing the glass fiber (G1) from the slow cooling furnace (130) after the cooling step (S220).

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing an optical fiber.

[0002] This application claims the priority based on Japanese application No. 2022-099385 for which it applied on June 21, 2022, and cites all the contents described in the said Japanese application. Background Art

[0003] As a method for manufacturing an optical fiber from a glass base material, there is known a method for manufacturing an optical fiber using a drawing furnace for heating a glass base material to soften it and a slow cooling furnace arranged below the drawing furnace for slowly cooling the glass fiber drawn by the drawing furnace (for example, refer to Patent Document 1).

[0004] In such an optical fiber manufacturing apparatus, when the manufacturing of the optical fiber is completed, the process shifts from a drawing step for manufacturing the optical fiber to a drawing termination step for terminating the manufacturing of the optical fiber.

[0005] In the drawing finalization step, the glass fiber, which is an intermediate product during optical fiber production, is removed from the optical fiber production apparatus upstream of the annealing furnace while the temperature of the annealing furnace is set to the same level as in the drawing step.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2010-168247 Summary of the invention

[0009] The optical fiber manufacturing method disclosed in the present invention uses a drawing furnace for heating a glass base material to soften it and a slow cooling furnace arranged at a position downstream of the drawing furnace and for slowly cooling the glass fiber drawn by the drawing furnace to manufacture an optical fiber containing the glass fiber. The optical fiber manufacturing method comprises: a drawing step for manufacturing the optical fiber; and a drawing termination step for terminating the manufacture of the optical fiber, the drawing termination step comprising: a fiber downstream side cutting step for cutting the glass fiber at a position downstream of the slow cooling furnace; a cooling step for cooling the internal temperature of the slow cooling furnace to below the slow cooling point of the glass fiber after the fiber downstream side cutting step; and a fiber removal step for removing the glass fiber from the slow cooling furnace after the cooling step. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram of an optical fiber manufacturing device according to one aspect of the present disclosure.

[0011] Figure 2 is a flow chart of a method for manufacturing an optical fiber according to one aspect of the present disclosure.

[0012] Figure 3 yes Figure 2 Flow chart of the wire drawing finishing process shown.

[0013] Figure 4A This is a diagram for explaining the cutting of glass fibers on the downstream side of the slow cooling furnace.

[0014] Figure 4B This is a diagram for explaining the cutting of glass fibers on the upstream side of the slow cooling furnace.

[0015] Figure 4C This is a diagram for explaining the state in which marking is performed on the upstream end of the glass fiber.

[0016] Figure 4D is a picture of glass fiber being removed from a slow cooling furnace.

[0017] Figure 5A It is a diagram for explaining a state in which the upstream end portion of the glass fiber in a modified example is marked.

[0018] Figure 5B This is a diagram for explaining the cutting of glass fibers on the upstream side of the slow cooling furnace in a modified example. DETAILED DESCRIPTION

[0019] [Technical Problems to be Solved by the Present Disclosure]

[0020] In the above-mentioned conventional drawing termination process, glass fibers sometimes remain in the slow cooling furnace, requiring regular cleaning of the slow cooling furnace, or sometimes the glass fibers being drawn come into contact with the glass fibers remaining in the slow cooling furnace and break during the next optical fiber manufacturing.

[0021] Therefore, the present disclosure solves the above-mentioned problems of the prior art, that is, an object of the present disclosure is to provide a method for manufacturing an optical fiber in which a glass fiber sheet is not easily attached to the inner surface of a slow cooling furnace in a drawing and finishing step.

[0022] [Effects of the present disclosure]

[0023] According to the above, in the wire drawing finalization step, it is possible to prevent the glass fiber pieces from being easily left in the slow cooling furnace.

[0024] [Description of Embodiments of the Present Disclosure]

[0025] First, embodiments of the present disclosure will be listed and described.

[0026] The optical fiber manufacturing method (1) disclosed in the present invention uses a drawing furnace for heating a glass matrix to soften it and a slow cooling furnace arranged at a position downstream of the drawing furnace and for slowly cooling the glass fiber drawn by the drawing furnace to manufacture an optical fiber containing the glass fiber. The optical fiber manufacturing method comprises: a drawing step for manufacturing the optical fiber; and a drawing termination step for terminating the manufacture of the optical fiber, the drawing termination step comprising: a fiber downstream side cutting step for cutting the glass fiber at a position downstream of the slow cooling furnace; a cooling step for cooling the internal temperature of the slow cooling furnace to below the slow cooling point of the glass fiber after the fiber downstream side cutting step; and a fiber removal step for removing the glass fiber from the slow cooling furnace after the cooling step.

[0027] According to the manufacturing method of the optical fiber constructed in this way, since the drawing termination process has a cooling step, the glass fiber is removed from the slow cooling furnace when the internal temperature of the slow cooling furnace is cooled to below the slow cooling point of the glass fiber and the viscosity of the glass fiber is reduced. Therefore, when the glass fiber is removed from the slow cooling furnace, the glass fiber is not easy to adhere to the inner surface of the slow cooling furnace, which can reduce the cleaning frequency of the slow cooling furnace or prevent the optical fiber from breaking during the drawing process.

[0028] Here, the slow cooling point of glass (i.e., glass fiber and glass matrix) is the point where the viscosity of the glass is 10 12 The temperature of [Pa·s] is a temperature at which the strain inside the glass can be removed in about 15 minutes.

[0029] Furthermore, in a temperature range where the surface temperature of the glass fiber is higher than the annealing point of the glass, the viscous flow on the surface of the glass fiber increases. Therefore, when the glass fiber contacts the inside of the annealing furnace, it is believed that the surface shape of the glass fiber changes and it is easy to adhere to the inside of the annealing furnace.

[0030] Therefore, by setting the surface temperature of the glass fiber to a temperature range not higher than the annealing point of the glass, the viscous flow of the glass fiber becomes extremely slow, and it is considered that even if the glass fiber contacts the inside of the annealing furnace, it is unlikely to adhere.

[0031] Therefore, after the internal temperature of the slow cooling furnace is lowered to below the slow cooling point of the glass fiber, the glass fiber is removed from the slow cooling furnace.

[0032] (2) In the above-mentioned method for producing an optical fiber, in the fiber removing step, the glass fiber is pulled out from below the slow cooling furnace and removed from the slow cooling furnace.

[0033] As a result, the length of the glass fiber that may touch the slow cooling furnace when the glass fiber is pulled out from the slow cooling furnace is shortened compared to the case where the glass fiber is pulled out from above the slow cooling furnace and removed from the slow cooling furnace. Therefore, when the glass fiber is removed from the slow cooling furnace, it is possible to make the glass fiber less likely to adhere to the inner surface of the slow cooling furnace.

[0034] In addition, since the direction in which the glass fiber is pulled out from the slow cooling furnace is opposite to the flow direction of the rising air flow generated inside the slow cooling furnace, when the glass fiber is removed from the slow cooling furnace, the posture of the glass fiber is stabilized by the rising air flow, which can make it more difficult for the glass fiber to adhere to the inner surface of the slow cooling furnace.

[0035] (3) In the above-mentioned optical fiber manufacturing method, the drawing termination step includes a fiber upstream side cutting step of cutting the glass fiber at a position upstream of the slow cooling furnace after the temperature reduction step and before the fiber removal step.

[0036] Thus, when the glass fiber is removed from the annealing furnace, the tip of the glass fiber extending from the glass matrix is ​​located upstream of the annealing furnace, so that when the production of the optical fiber is completed, the glass fiber can be reliably prevented from remaining on the inner surface of the annealing furnace.

[0037] (4) In the above-mentioned method for manufacturing an optical fiber, the drawing termination process includes a marking step of marking the glass fiber at a position upstream of the slow cooling furnace after the fiber downstream side cutting step and before the fiber upstream side cutting step, and in the fiber upstream side cutting step, the marked portion of the glass fiber is cut.

[0038] Thus, when the glass fiber is pulled out from the slow cooling furnace, by confirming whether there is a mark on the rear end side of the pulled glass fiber, it is known whether the glass fiber is cut during the process of pulling the glass fiber out from the slow cooling furnace, so it is easy to confirm whether the glass fiber is pulled out from the slow cooling furnace without any residue.

[0039] (5) In the above-mentioned method for producing an optical fiber, the drawing and terminating step includes, after the fiber upstream side cutting step, a marking step of marking the upstream end portion of the glass fiber separated from the glass base material.

[0040] Thus, when the glass fiber is pulled out from the slow cooling furnace, by confirming whether there is a mark on the rear end side of the pulled glass fiber, it is known whether the glass fiber is cut during the process of pulling the glass fiber out from the slow cooling furnace, so it is easy to confirm whether the glass fiber is pulled out from the slow cooling furnace without any residue.

[0041] (6) In the above-mentioned method for producing an optical fiber, the marking is a coating material applied to the upstream end of the glass fiber.

[0042] Therefore, compared with the case where a tape is attached to the upstream end of the glass fiber as a mark on the upstream end of the glass fiber, the outer diameter of the glass fiber is less likely to increase, so the glass fiber is less likely to be entangled when removing the glass fiber from the slow cooling furnace, and the glass fiber can be easily removed from the slow cooling furnace.

[0043] [Details of the embodiments of the present disclosure]

[0044] Hereinafter, a specific example of the method for producing an optical fiber according to the present disclosure will be described.

[0045] First, using FIG. 100 as an example of an optical fiber manufacturing apparatus 100, Figure 1 The optical fiber manufacturing apparatus 100 will be described.

[0046] <1. Configuration of Optical Fiber Manufacturing Apparatus>

[0047] like Figure 1 As shown, the optical fiber manufacturing device 100 comprises, in order from the most upstream, a base material feeding unit 110 for holding the upper part of the glass base material G; a drawing furnace 120 for heating the glass base material G to soften it; a slow cooling furnace 130 for slowly cooling the glass fiber G1 drawn by the drawing furnace 120; a forced cooling unit 140 for forcedly cooling the glass fiber G1 that has passed through the slow cooling furnace 130; a resin coating mold 150 for coating the glass fiber G1 that has passed through the forced cooling unit 140 with an ultraviolet curing resin (hereinafter referred to as UV (UltraViolet) curing resin) to generate a resin-coated fiber G2; a UV curing furnace 160 for curing the UV curing resin coated on the surface of the resin-coated fiber G2 to generate an optical fiber G3; and a roller 170 directly below for converting the traveling direction of the optical fiber G3 toward the bobbin B wound around the optical fiber G3.

[0048] like Figure 1 As shown, the optical fiber manufacturing device 100 also includes: a fiber cutting unit 180, which cuts the glass fiber G1 on the upstream side or downstream side of the slow cooling furnace 130; a fiber holding unit 190, which holds the glass fiber G1 on the downstream side of the drawing furnace 120 and the upstream side of the slow cooling furnace 130; and a controller (not shown) that controls the various elements of the optical fiber manufacturing device 100.

[0049] like Figure 1 As shown, the base material feeding unit 110 holds the upper portion of the glass base material G and can freely raise or lower the glass base material G relative to the wire drawing furnace 120 .

[0050] The wire drawing furnace 120 includes a cylindrical furnace core tube 121 into which the glass base material G is supplied, a heating element 122 surrounding the furnace core tube 121 , and a gas supply unit 123 for supplying an inert gas into the furnace core tube 121 .

[0051] The heating element 122 may be a resistance furnace or an induction furnace.

[0052] The slow cooling furnace 130 includes a cylindrical furnace core tube 131 into which the glass base material G is supplied, a heating element 132 surrounding the furnace core tube 131 , and a shutter 133 for opening and closing the furnace core tube 131 .

[0053] The heating element 132 may be a resistance furnace or an induction furnace, similarly to the heating element 122 of the wire drawing furnace 120 .

[0054] In addition, when a slow cooling furnace is provided downstream of the drawing furnace, the glass fiber is not cooled suddenly to room temperature but is gradually cooled to room temperature in stages, thereby reducing the Rayleigh scattering intensity and the transmission loss of the optical fiber.

[0055] The forced cooling unit 140 is supplied with a cooling gas such as helium from a gas supply source (not shown), and the glass fiber G1 drawn from the glass base material G is forcibly cooled by the cooling gas.

[0056] The resin coating mold 150 stores a UV curing resin for protecting glass fibers.

[0057] The UV curing furnace 160 includes: a cylindrical quartz tube; a light source disposed outside the quartz tube; and a reflector for focusing ultraviolet rays irradiated from the light source onto the resin-coated fibers G2.

[0058] The directly below roller 170 is disposed directly below the drawing furnace 120 , and the traveling direction of the optical fiber G3 is changed from the vertical direction to, for example, obliquely upward.

[0059] <2. Manufacturing of optical fiber by optical fiber manufacturing apparatus>

[0060] Next, based on Figure 1 to Figure 4D The method for manufacturing an optical fiber using the optical fiber manufacturing apparatus 100 will be described in detail.

[0061] Figure 2 is a flow chart of a method for manufacturing an optical fiber according to one aspect of the present disclosure, Figure 3 yes Figure 2 The flowchart of the wire drawing finishing process is shown in FIG. Figure 4A This is a diagram for explaining the cutting of glass fibers on the downstream side of the slow cooling furnace. Figure 4B This is a diagram for explaining the cutting of glass fibers on the upstream side of the slow cooling furnace. Figure 4C is a diagram for explaining the condition of marking the upstream end of the glass fiber. Figure 4D is a picture of glass fiber being removed from a slow cooling furnace.

[0062] like Figure 2As shown, the optical fiber manufacturing method performed by the optical fiber manufacturing apparatus 100 is composed of a drawing step S100 for manufacturing the optical fiber G3 and a drawing termination step S200 for terminating the manufacturing of the optical fiber G3 following the drawing step S100.

[0063] <2.1. Wire drawing process>

[0064] First, refer to Figure 1 The wire drawing step S100 will be described.

[0065] In the wire drawing step S100 , the glass base material G is fed into the furnace core tube 121 of the wire drawing furnace 120 by the base material feeding unit 110 .

[0066] Then, when the lower end portion of the glass base material G is softened by heating the furnace core tube 121 with the heating element 122 and is drawn downward, the glass fiber G1 constituting the optical fiber G3 is formed.

[0067] The glass fiber G1 is an optical waveguide having a core portion and a cladding portion and an outer diameter of, for example, 125 μm.

[0068] Then, the glass fiber G1 drawn from the glass matrix G passes through the slow cooling furnace 130 having a lower temperature (eg, 1200 degrees) than the drawing furnace 120 , so that the surface temperature of the glass fiber G1 gradually decreases.

[0069] Then, after the glass fiber G1 is gradually cooled in the slow cooling furnace 130 , it passes through the forced cooling unit 140 , so that the surface temperature of the glass fiber G1 drops to about room temperature.

[0070] The glass fiber G1 cooled to about room temperature passes through the resin coating die 150 , whereby UV curing resin is coated around the glass fiber G1 to form a resin-coated fiber G2 .

[0071] The fiber G2 coated with resin passes through the UV curing furnace 160, and the UV curing resin coated on the surface of the glass fiber G1 is cured by irradiating ultraviolet rays in the UV curing furnace 160, thereby generating the optical fiber G3.

[0072] Then, the optical fiber G3 whose traveling direction is changed by the directly below roller 170 is wound around the bobbin B.

[0073] <2.2. Wire drawing finalization process>

[0074] Next, refer to Figure 1 , Figure 3 , Figure 4A to Figure 4D The wire drawing finishing step S200 will be described.

[0075] like Figure 3As shown, the wire drawing finishing process S200 includes: a fiber downstream side cutting step S210, a temperature reduction step S220, a fiber upstream side cutting step S230, a marking step S240 and a fiber removing step S250.

[0076] The fiber downstream cutting step S210 is a step of cutting the glass fiber G1 downstream of the slow cooling furnace 130 and upstream of the resin coating die 150 .

[0077] Then, in the fiber downstream cutting step S210, as shown in FIG. Figure 4A As shown, the glass fiber G1 is cut by the fiber cutting unit 180 on the downstream side of the slow cooling furnace 130 and on the upstream side of the resin coating die 150 .

[0078] The temperature reduction step S220 is performed after the fiber downstream cutting step S210.

[0079] Furthermore, in the temperature reduction step S220 , the internal temperature of the slow cooling furnace 130 is reduced to a temperature lower than the slow cooling point of the glass base material G (eg, lower than 1000 degrees).

[0080] The fiber upstream side cutting step S230 is performed after the temperature lowering step S220.

[0081] Furthermore, in the fiber upstream cutting step S230, Figure 4B As shown, the glass fiber G1 is cut by the fiber cutting unit 180 on the upstream side of the fiber holding unit 190 while the glass fiber G1 is held by the fiber holding unit 190 downstream of the drawing furnace 120 and upstream of the slow cooling furnace 130 .

[0082] Therefore, when the glass fiber G1 is removed from the slow cooling furnace 130, the front end of the glass fiber G1 extending from the glass matrix G is located upstream of the slow cooling furnace 130, so when the manufacture of the optical fiber G3 is completed, the glass fiber G1 can be reliably prevented from remaining on the inner surface of the slow cooling furnace 130.

[0083] The marking step S240 is performed after the fiber upstream cutting step S230.

[0084] Furthermore, in the marking step S240, if Figure 4C As shown, the upstream end G4a of the glass fiber G4 separated from the glass matrix G is marked (coated with white paint P).

[0085] Therefore, when the glass fiber G4 separated from the glass matrix G is pulled out from the slow cooling furnace 130, by confirming whether there is a mark on the rear end side of the pulled glass fiber G4, it is known whether the glass fiber G4 is cut in the process of pulling out the glass fiber G4 from the slow cooling furnace 130, so it is easy to confirm whether the glass fiber G4 is pulled out from the slow cooling furnace 130 without any residue.

[0086] In addition, as compared with the case where a tape is attached to the upstream end G4a of the glass fiber G4 as the marking on the upstream end of the glass fiber G4 separated from the glass matrix G, the outer diameter of the glass fiber G4 is not easy to increase. Therefore, when the glass fiber G4 separated from the glass matrix G is removed from the slow cooling furnace 130, the glass fiber G4 becomes less likely to be entangled, and the glass fiber G4 can be easily removed from the slow cooling furnace 130.

[0087] The fiber removal step S250 is performed after the marking step S240.

[0088] Furthermore, in the fiber removal step S250, Figure 4D As shown, the glass fiber G4 separated from the glass matrix G is pulled out from the bottom of the slow cooling furnace 130 and removed from the slow cooling furnace 130 .

[0089] In the wire drawing termination process S200 performed in this way, the internal temperature of the slow cooling furnace 130 is cooled to below the slow cooling point of the glass fiber G1, and the glass fiber G1 is removed from the slow cooling furnace 130 in a state where the viscosity of the glass fiber G1 is reduced. Therefore, when the glass fiber G1 is removed from the slow cooling furnace 130, the glass fiber G1 is not easy to adhere to the inner surface of the slow cooling furnace 130, which can reduce the cleaning frequency of the slow cooling furnace 130, or can prevent the optical fiber G3 from breaking during the wire drawing process.

[0090] In addition, when the glass fiber G4 separated from the glass matrix G is pulled out from the slow cooling furnace 130, the length of the glass fiber G4 that has the possibility of touching the slow cooling furnace 130 is shortened compared to the case where the glass fiber G4 is pulled out from the top of the slow cooling furnace 130 and removed from the slow cooling furnace 130. Therefore, when the glass fiber G4 separated from the glass matrix G is removed from the slow cooling furnace, it is possible to make the glass fiber G4 less likely to adhere to the inner surface of the slow cooling furnace 130.

[0091] In addition, since the direction in which the glass fiber G4 separated from the glass matrix G is pulled out of the slow cooling furnace is in opposite directions to the flow direction A of the rising airflow generated inside the slow cooling furnace 130, when the glass fiber G4 separated from the glass matrix G is removed from the slow cooling furnace 130, the posture of the glass fiber G4 is stabilized due to the rising airflow, which can make it further difficult for the glass fiber G4 to adhere to the inner surface of the slow cooling furnace 130.

[0092] [Modifications]

[0093] As mentioned above, although embodiment of this disclosure was described, this disclosure is not limited to the above content.

[0094] In addition, the elements included in the above-described embodiments can be combined as long as it is technically possible, and the elements obtained by combining these elements are also included in the scope of the present invention as long as they include the characteristics of the present invention.

[0095] For example, in the above-described embodiment, the slow cooling furnace 130 includes one furnace core tube 131 and one heating element 132 , but may be composed of a plurality of furnace core tubes and heating elements.

[0096] When the slow cooling furnace is composed of a plurality of furnace core tubes and a heating element, it is preferable to gradually lower the temperature of the heating element from the upstream to the downstream.

[0097] For example, the fiber cutting unit 180 in the above-described embodiment may be any cutting unit such as a knife or scissors as long as it can cut the glass fiber G1.

[0098] In the above embodiment, the fiber cutting unit 180 cuts the glass fiber G1 , but the glass fiber G1 may be cut in any manner, such as by an operator, and is not limited to the fiber cutting unit 180 of the optical fiber manufacturing apparatus 100 .

[0099] For example, the fiber holding unit 190 in the above-described embodiment may be any fiber holding unit as long as it can hold the glass fiber G1.

[0100] In the above-mentioned embodiment, the fiber holding unit 190 holds the glass fiber G1 , but the glass fiber G1 may be held in any manner, such as by an operator, and is not limited to the fiber holding unit 190 of the optical fiber manufacturing apparatus 100 .

[0101] For example, in the above-described embodiment, the white paint P is applied to the glass fiber G1 as a mark, but the color of the paint applied to the glass fiber G1 is not limited to white.

[0102] In addition, marking of the glass fiber G1 is not limited to coating with paint, and may be, for example, affixing with a tape.

[0103] For example, in the above-mentioned embodiment, the temperature reduction step S220 is performed after the fiber downstream side cutting step S210, but the timing of performing the temperature reduction step is not limited thereto, and for example, it may be performed before the fiber downstream side cutting step S210.

[0104] For example, in the above-mentioned embodiment, the internal temperature of the slow cooling furnace is cooled to below the slow cooling point of the glass fiber in the temperature reduction step S220, but the internal temperature of the slow cooling furnace may be cooled to below the strain point of the glass fiber.

[0105] Here, the strain point of glass refers to the point at which the viscosity of glass becomes 10 13.5 The temperature [Pa·s] at which virtually no viscous flow occurs and below which strain in the glass cannot be removed.

[0106] Therefore, when the surface temperature of the glass fiber is within the temperature range between the strain point and the annealing point of the glass, although viscous flow occurs, it is very slow. Therefore, as with the case below the strain point temperature, it is believed that the glass fiber is not likely to adhere even if it contacts the inside of the annealing furnace.

[0107] In addition, it is considered that in the temperature range where the surface temperature of the glass fiber is equal to or lower than the strain point of the glass, even if the glass fiber is in contact with the inside of the slow cooling furnace, it does not adhere to the glass fiber as in the case where the glass fiber is in contact with a solid.

[0108] Therefore, by lowering the internal temperature of the slow cooling furnace to a temperature below the strain point of the glass fiber, it is possible to more reliably prevent the glass fiber from being easily attached to the inner surface of the slow cooling furnace.

[0109] For example, in the above-mentioned embodiment, the marking step S240 is performed after the fiber upstream side cutting step S230, but the execution timing of the marking step is not limited to this. For example, it can also be performed after the fiber downstream side cutting step S210 and before the fiber upstream side cutting step S230.

[0110] In this case, after the fiber downstream cutting step S210 is performed, Figure 5A As shown, perform the marking step, such as Figure 5B As shown, in the fiber upstream side cutting step S230, the marked portion of the glass fiber G1 is cut.

[0111] Furthermore, when the marking step is performed after the fiber cutting step S210 on the downstream side and before the fiber cutting step S230 on the upstream side, the marking step may be performed after the temperature lowering step S220 or after the marking step.

[0112] For example, in the fiber removal step S250 of the above-mentioned embodiment, the glass fiber G4 separated from the glass matrix G is pulled out from the bottom of the slow cooling furnace 130 and removed from the slow cooling furnace 130, but the glass fiber G4 separated from the glass matrix G can also be pulled out from the top of the slow cooling furnace 130 and removed from the slow cooling furnace 130.

[0113] Description of Reference Numerals

[0114] 100: Optical fiber manufacturing device

[0115] 110: Base material feeding unit

[0116] 120: Wire drawing furnace

[0117] 121: Furnace core tube

[0118] 122: Heater

[0119] 123: Gas supply unit

[0120] 130: Slow cooling furnace

[0121] 131: Furnace core tube

[0122] 132: Heater

[0123] 133: Gate

[0124] 140: Forced cooling unit

[0125] 150: Resin coated mold

[0126] 160: UV curing oven

[0127] 170: Directly below the roller

[0128] 180: Fiber cutting unit

[0129] 190: Fiber holding unit

[0130] B: Bobbin

[0131] G: Glass base material

[0132] G1: Fiberglass

[0133] G2: Resin coated fiber

[0134] G3: Fiber Optic

[0135] G4: Glass fiber separated from glass matrix

[0136] G4a: Upstream end of the glass fiber separated from the glass matrix

[0137] P: White paint

[0138] A: The direction of the updraft.

Claims

1. A method for manufacturing an optical fiber, comprising: using a drawing furnace for heating a glass base material to soften it and a slow cooling furnace arranged at a downstream side of the drawing furnace for slowly cooling the glass fiber drawn by the drawing furnace to manufacture an optical fiber including the glass fiber, the method comprising: A drawing process for manufacturing the optical fiber; and The drawing and termination process terminates the manufacturing of the optical fiber. The wire drawing finishing process comprises: A fiber downstream cutting step of cutting the glass fiber at a position downstream of the slow cooling furnace; A temperature reduction step, after the fiber downstream side cutting step, reducing the internal temperature of the slow cooling furnace to below the slow cooling point of the glass fiber; as well as A fiber removing step is performed to remove the glass fiber from the slow cooling furnace after the temperature lowering step.

2. The method for manufacturing an optical fiber according to claim 1, wherein: In the fiber removal step, the glass fibers are pulled out from below the slow cooling furnace and removed from the slow cooling furnace.

3. The method for manufacturing an optical fiber according to claim 2, wherein: The wire drawing finishing step includes a fiber upstream side cutting step of cutting the glass fiber at a position upstream of the slow cooling furnace after the temperature lowering step and before the fiber removing step.

4. The method for manufacturing an optical fiber according to claim 3, wherein: The wire drawing finishing step includes a marking step of marking the glass fiber at a position upstream of the slow cooling furnace after the fiber downstream cutting step and before the fiber upstream cutting step. In the fiber upstream cutting step, the marked portion of the glass fiber is cut.

5. The method for manufacturing an optical fiber according to claim 3, wherein: The wire drawing finishing step includes, after the fiber upstream side cutting step, a marking step of marking an upstream end portion of the glass fiber separated from the glass base material.

6. The method for manufacturing an optical fiber according to claim 4 or 5, wherein: The marking is performed by applying a coating to the upstream end of the glass fiber.

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