Method for producing optical fiber

Abstract

A method for producing an optical fiber according to the present invention includes: melting a glass preform in a heating furnace and drawing out a glass fiber; coating the glass fiber with a resin layer to form an optical fiber; changing the travel direction of the optical fiber by a roller disposed below the heating furnace; and taking off the optical fiber. When the surface of the roller with which the optical fiber comes into contact is taken to be the travel surface of the roller, when viewed from a direction orthogonal to the rotation axis of the roller, a groove is formed in the travel surface of the roller. At least the central part of the groove is formed so as to form a curved surface. The width of the curved surface along the rotation axis direction is 2 mm or more.

Description

Optical fiber manufacturing method

[0001] This disclosure relates to a method for manufacturing an optical fiber. This application claims priority to Japanese Patent Application No. 2024-018604, filed February 9, 2024, and incorporates the entire contents of said application by reference.

[0002] Patent Document 1 discloses an optical fiber manufacturing apparatus.

[0003] Japanese Patent Application Publication No. 2021-175685

[0004] An object of the present disclosure is to provide a method for manufacturing an optical fiber that is less susceptible to unintended twisting.

[0005] A method for manufacturing an optical fiber according to one aspect of the present disclosure includes melting a glass preform in a heating furnace and drawing out a glass fiber, coating the glass fiber with a resin layer to form an optical fiber, changing the running direction of the optical fiber using a roller arranged below the heating furnace, and drawing out the optical fiber, wherein when the surface of the roller that contacts the optical fiber is the running surface of the roller, a groove is formed in the running surface of the roller when viewed from a direction perpendicular to the rotation axis of the roller, and at least a central portion of the groove is formed to be a curved surface, and the width of the curved surface along the rotation axis direction is 2 mm or more.

[0006] FIG. 1 is a schematic diagram of an optical fiber manufacturing apparatus according to the present embodiment. FIG. 2 is a partial enlarged view of a directly below roller according to the present embodiment. FIG. 3 illustrates an optical fiber running on the running surface of a directly below roller according to the present embodiment. FIG. 4 illustrates an optical fiber running on the running surface of a directly below roller according to a first comparative example. FIG. 5 illustrates an optical fiber running on the running surface of a directly below roller according to a second comparative example. FIG. 6 is a partial enlarged view of a directly below roller according to a modified example of the present embodiment. FIG. 7 illustrates an optical fiber running on the running surface of a directly below roller according to a modified example of the present embodiment. FIG. 8 illustrates an optical fiber running on the running surface of a directly below roller according to a modified example of the present embodiment.

[0007] (Problem to be Solved by the Invention) In the optical fiber manufacturing apparatus of Patent Document 1, guide rollers having V-shaped running surfaces are provided immediately below the heating furnace and the die.

[0008] When optical fibers are manufactured using guide rollers with V-shaped running surfaces, the optical fibers may be twisted unintentionally as they roll along the slope of the V-shape of the guide rollers. The twisting of the optical fibers may result in an excessive load being applied to the optical fibers.

[0009] (Effects of the Invention) According to the present disclosure, a method for manufacturing an optical fiber that is less likely to develop unintended twists can be provided.

[0010] (Description of Embodiments of the Present Disclosure) First, embodiments of the present disclosure will be described. (1) A method for manufacturing an optical fiber according to one aspect of the present disclosure includes melting a glass preform in a heating furnace and drawing out a glass fiber, coating the glass fiber with a resin layer to form an optical fiber, changing the running direction of the optical fiber using a roller disposed below the heating furnace, and drawing out the optical fiber. When the surface of the roller that contacts the optical fiber is defined as the running surface of the roller, a groove is formed on the running surface of the roller when viewed from a direction perpendicular to the rotation axis of the roller, and at least a central portion of the groove is curved, and the width of the curved surface along the rotation axis is 2 mm or more. According to the above manufacturing method, when the optical fiber is drawn out while coming into contact with the curved surface of the running surface of the roller, it is less likely to be displaced in a direction intersecting the tension of the optical fiber compared to when the running surface is flat or V-shaped. This makes it less likely for the optical fiber to roll on the running surface, making it less likely for unintended twisting to occur in the optical fiber.

[0011] (2) In the method for manufacturing an optical fiber according to (1), the curved surface including the central portion may have a semicircular shape when viewed from a direction perpendicular to the rotation axis. According to the manufacturing method, even if any part of the traveling surface contacts the optical fiber, the traveling surface is curved, so that the optical fiber is less likely to be displaced in a direction intersecting the tension of the optical fiber.

[0012] (3) In the optical fiber manufacturing method according to (1), when viewed from a direction perpendicular to the rotation axis, the running surface may include two first flat portions connected to the curved surface to form continuous inclined surfaces on both sides of the curved surface in the direction of the rotation axis, and two second flat portions connected to the two first flat portions and rising in a direction along the radial direction of the roller. According to the manufacturing method, when the optical fiber runs near the center of the running surface, the optical fiber comes into contact with the curved surface, making it less likely to be displaced in a direction intersecting the tension of the optical fiber. When the optical fiber runs on the first flat portion of the running surface, the optical fiber is more likely to be displaced toward the center of the running surface due to the tension. As a result, the optical fiber spends a longer time running near the center during optical fiber manufacturing, making it less likely to develop unintended twists in the optical fiber.

[0013] (4) In the optical fiber manufacturing method according to any one of (1) to (3), when viewed from a direction perpendicular to the rotation axis of the roller, the curved surface may be arc-shaped, and the radius of curvature of the curved surface may be 2.0 mm or more and 10.0 mm or less. According to the manufacturing method, since the radius of curvature of the curved surface is 2.0 mm or more, it is possible to form a groove with a sufficient width for the optical fiber. Furthermore, since the radius of curvature of the curved surface is 10.0 mm or more, the arc-shaped running surface is likely to have the effect of making the optical fiber less likely to displace in a direction intersecting the tension.

[0014] (Details of the embodiments of the present disclosure) Specific examples of the method for manufacturing an optical fiber according to the embodiments of the present disclosure will be described below with reference to the drawings. Note 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.

[0015] In the description of this embodiment, the symbol U shown in the drawings indicates an upward direction, the symbol D indicates a downward direction, the symbol L indicates a leftward direction, the symbol R indicates a rightward direction, the symbol F indicates a forward direction, and the symbol B indicates a backward direction.

[0016] 1 is a schematic diagram of an optical fiber manufacturing apparatus 1 according to this embodiment. The manufacturing apparatus 1 illustrated in FIG. 1 includes a heating furnace 2, a cooling device 3, a coating unit 4, a direct below roller 5, a capstan 6, and a take-up bobbin 7.

[0017] The heating furnace 2 is disposed at the most upstream side of the manufacturing apparatus 1. The heating furnace 2 melts the glass preform G for the optical fiber G2, and enables the drawn glass fiber G1 to be drawn out.

[0018] The heating furnace 2 includes a heating element 21. The heating element 21 is provided so as to surround the glass base material G. The region surrounded by the heating element 21 is a heating region capable of softening the glass base material G.

[0019] The glass preform G is fed into the heating furnace 2 so that the lower end portion of the glass preform G is positioned in the heating region formed by the heating element 21. The glass preform G is stretched downward to reduce its diameter, and a glass fiber G1, which is an optical fiber before being coated with resin, is formed.

[0020] A cooling device 3 is provided below the heating furnace 2. The cooling device 3 cools the glass fiber G1 drawn out from the heating furnace 2. The cooling device 3 may cool the glass fiber G1, for example, by sending a cooling gas such as helium gas into the internal space of a cylindrical housing.

[0021] A coating unit 4 is provided below the cooling device 3. The coating unit 4 coats the glass fiber G1 with a resin layer to form the optical fiber G2.

[0022] The coating unit 4 has an application section 41 that applies resin to the glass fiber G1 and a curing section 42 that cures the applied resin. The application section 41 applies, for example, ultraviolet-curable resin to the glass fiber G1. If the applied resin is ultraviolet-curable resin, the curing section 42 irradiates the resin applied by the application section 41 with ultraviolet light to cure the resin. The glass fiber G1 that has passed through the application section 41 and the curing section 42 is coated on its outer periphery with a resin layer, thereby forming the optical fiber G2.

[0023] Below the coating unit 4, there are provided directly below rollers 5 (rollers that change the running direction of the optical fiber drawn vertically downward). That is, the directly below rollers 5 are disposed below the heating furnace 2. The running direction of the optical fiber G2 can be changed by the directly below rollers 5. In the example shown in FIG. 1 , the optical fiber G2 upstream of the directly below rollers 5 is fed downward, while the optical fiber G2 downstream of the directly below rollers 5 is fed rightward.

[0024] The capstan 6 takes up the optical fiber G2. The optical fiber G2 is taken up by the capstan 6 and then wound up by the take-up bobbin 7.

[0025] Fig. 2 is a partially enlarged view of the direct below roller 5 according to this embodiment. Fig. 2 is a view of the direct below roller 5 illustrated in Fig. 1 as viewed from below. The direction viewed from below is an example of a direction perpendicular to the rotation axis 51 of the direct below roller 5. As illustrated in Fig. 2, the direct below roller 5 includes a rotation axis 51 and a roller body 52. ​​In the direct below roller 5, the disk-shaped roller body 52 rotates around the rotation axis 51. The rotation axis 51 is supported to be swingable so as to allow for some fluctuation in the posture of the direct below roller 5.

[0026] A running surface 53 is formed on the roller body 52. ​​The running surface 53 is a surface with which the optical fiber G2 comes into contact at the directly below roller 5. The running surface 53 is formed circumferentially along the outer edge of the roller body 52. ​​As the optical fiber G2 runs on the running surface 53, the directly below roller 5 rotates around the rotation axis 51.

[0027] The running surface 53 is a groove formed around the entire radial outer edge of the roller body 52. ​​In other words, when viewed from below, which is a direction perpendicular to the rotation axis 51 of the direct-below roller 5, the running surface 53 of the direct-below roller 5 is formed so that the central portion O of the running surface 53 is concave. Furthermore, at least the central portion O of the running surface 53 is formed so as to be curved. Furthermore, the width B1 of the curved surface in the direction of the rotation axis Ax is 2 mm or more. The radius of curvature of the curved surface may be 2.0 mm or more and 10.0 mm or less.

[0028] In the running surface 53 according to the present embodiment, the curved surface including the central portion O is semicircular when viewed from a direction perpendicular to the rotation axis 51 of the direct-below roller 5. For example, when viewed from a direction perpendicular to the rotation axis 51 of the direct-below roller 5, the running surface 53 is formed to be a semicircle having a diameter defined by a front first end 531 and a rear second end 532 in the rotation axis direction Ax of the running surface 53.

[0029] Next, a description will be given of the behavior of the optical fiber G2 running on the running surface 53 of the directly below roller 5 according to this embodiment. Fig. 3 illustrates an example of the optical fiber G2 running on the running surface 53 of the directly below roller 5 according to this embodiment.

[0030] The optical fiber G2 traveling on the traveling surface 53 is taken up by the capstan 6, and therefore the optical fiber G2 is subjected to a force by the tension T that presses it against the peripheral surface of the roller toward the rotation shaft 51. The optical fiber in contact with the peripheral surface of the roller moves gradually from the position where it first contacts the roller to the position where it leaves the roller, moving to the deepest position on the peripheral surface of the roller as it moves. At this time, the optical fiber rolls on the peripheral surface of the roller, causing a twist in the optical fiber.

[0031] 3, the optical fiber G2 in contact with the curved surface of the running surface 53 is unlikely to move toward the center O because the inclination of the contact surface is small. As a result, the optical fiber G2 is unlikely to roll on the running surface 53 and become twisted during the manufacturing of the optical fiber G2.

[0032] 4 illustrates an optical fiber G2 running on the running surface 53A of the direct-below roller 5A according to a first comparative example. The running surface 53A of the direct-below roller 5A is formed so that the central portion OA is located at the valley where two inclined surfaces meet. The running surface 53A differs from the running surface 53 of the direct-below roller 5 according to this embodiment in that it is a V-shaped running surface formed by two inclined straight lines in cross section. The shape of the running surface 53A according to the first comparative example is referred to as a "V-shaped running surface."

[0033] At this time, if the optical fiber G2 travels at a position deviated from the center portion OA toward the first end portion 531A, the optical fiber will move toward the center portion OA (indicated by the white arrow D1) along the inclined travel surface 53A as it travels on the rollers. As a result, the optical fiber G2 may roll on the travel surface 53A and become twisted during the manufacturing of the optical fiber G2.

[0034] 5 illustrates an optical fiber G2 running on the running surface 53B of a direct-below roller 5B according to a second comparative example. The running surface 53B of the direct-below roller 5B differs from the running surface 53 of the direct-below roller 5 according to this embodiment in that it is formed as a single flat surface in cross section. Therefore, the central portion O of the running surface 53B does not have a recessed shape. The shape of the running surface 53B according to the second comparative example is referred to as a "flat groove-shaped running surface."

[0035] 5 shows a case where the rotation axis of the roller directly below the optical fiber G2 is slightly tilted and not perpendicular to the plane including the path line of the optical fiber G2. When the optical fiber G2 travels at a position deviated from the center portion OB toward the first end 531B, the optical fiber G2 is displaced toward the first end 531B (indicated by the white arrow D2) along the tilted traveling surface 53B. This can cause the optical fiber G2 to roll on the traveling surface 53B and become twisted during the manufacturing of the optical fiber G2.

[0036] In the direct below roller 5 according to this embodiment, the central portion O of the running surface 53 is curved. According to the manufacturing method according to this embodiment, when the optical fiber G2 is pulled up while contacting the curved surface of the running surface 53 of the direct below roller 5, the optical fiber G2 is less likely to roll on the running surface 53 than when it is in contact with a V-shaped running surface or a flat groove-shaped running surface. This makes it less likely that unintended twisting will occur in the optical fiber G2.

[0037] When the direct below roller 5 according to this embodiment is viewed from a direction perpendicular to the rotation axis 51, the curved surface including the central portion O is semicircular. Therefore, no matter what part of the running surface 53 the optical fiber G2 comes into contact with, the running surface 53 is curved. As a result, the optical fiber G2 is less likely to be displaced in a direction intersecting the tension T of the optical fiber G2.

[0038] Next, a manufacturing method and a direct below roller 15 according to a modification of this embodiment will be described. Fig. 6 is a partially enlarged view of the direct below roller 15 according to the modification of this embodiment. The running surface 153 of the direct below roller 15 according to the modification is different from the running surface 53 of the direct below roller 5 according to this embodiment in that it is formed by a combination of a curved surface and a flat surface.

[0039] The running surface 153 includes a curved surface portion 154 , a first flat surface portion 155 , and a second flat surface portion 156 .

[0040] The curved surface portion 154 is formed as a curved surface that includes at least the central portion O of the running surface 153. The width B2 of the curved surface portion 154 (the width of the curved surface in the rotation axis direction Ax) is 2 mm or more.

[0041] Two first flat portions 155 are formed on the running surface 153. The first flat portions 155 are continuously connected to the curved surface of the curved surface portion 154 on both sides (the front end and the rear end) in the direction along the rotation axis Ax. Here, "connected to form a continuous inclined surface" means that the ends of the connected surfaces have the same gradient.

[0042] Two second flat portions 156 are formed on the running surface 153. The second flat portions 156 are connected to the two first flat portions 155 and are formed so as to rise in a direction along the radial direction of the directly below roller 15.

[0043] 7 and 8 show an example of the optical fiber G2 running on the running surface 153 of the direct below roller 15 according to a modified example of this embodiment. As shown in Fig. 7 and 8, when the optical fiber G2 runs on the curved surface portion 154, the optical fiber G2 is unlikely to be displaced in the direction of the first end portion 1531 or the direction of the central portion O. This makes it difficult for the optical fiber G2 to roll and twist on the running surface 153 during the manufacturing of the optical fiber G2.

[0044] In this way, according to the manufacturing method using the modified direct below roller 15, when the optical fiber G2 runs near the center O of the running surface 153, the optical fiber G2 comes into contact with the curved surface, and therefore the optical fiber G2 is less likely to displace to the deepest position of the groove.

[0045] 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.

[0046] REFERENCE SIGNS LIST 1 Manufacturing device 2 Heating furnace 3 Cooling device 4 Coating unit 5, 5A, 5B, 15 Directly below roller 6 Capstan 7 Take-up bobbin 21 Heating element 41 Coating section 42 Hardening section 51 Rotating shaft 52 Roller body 53, 53A, 53B, 153 Running surface 154 Curved surface section 155 First flat section 156 Second flat section 531, 531A, 531B, 1531 First end section 532 Second end section G Glass base material G1 Glass fiber G2 Optical fiber O, OA, OB Center section T Tension

Claims

1. A method for manufacturing an optical fiber, comprising: melting a glass base material in a heating furnace and drawing out a glass fiber; coating the glass fiber with a resin layer to form an optical fiber; changing the running direction of the optical fiber by a roller arranged below the heating furnace; and drawing out the optical fiber, wherein, when the surface of the roller that comes into contact with the optical fiber is the running surface of the roller, a groove is formed on the running surface of the roller when viewed from a direction perpendicular to the rotation axis of the roller, at least a central portion of the groove is formed to be a curved surface, and the width of the curved surface along the rotation axis direction is 2 mm or more.

2. The method for manufacturing an optical fiber according to claim 1, wherein the curved surface including the central portion has a semicircular shape when viewed from a direction perpendicular to the rotation axis.

3. The method for manufacturing optical fiber according to claim 1, wherein, when viewed from a direction perpendicular to the rotation axis, the running surface comprises: two first flat portions connected to the curved surface so as to form a continuous inclined surface on both sides in the direction along the rotation axis; and two second flat portions connected to the two first flat portions and rising in a direction along the radial direction of the roller.

4. A method for manufacturing an optical fiber according to any one of claims 1 to 3, wherein, when viewed from a direction perpendicular to the rotation axis of the roller, the curved surface has an arc shape, and the radius of curvature of the curved surface is 2.0 mm or more and 10.0 mm or less.

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