Method for manufacturing optical fibers, and apparatus for manufacturing optical fibers

Abstract

To provide a method of manufacturing an optical fiber which efficiently cools a wiredrawn optical fiber bare wire.SOLUTION: A method of manufacturing an optical fiber includes the steps of: melting an optical fiber base material and wiredrawing an optical fiber bare wire; changing a travel direction of the optical fiber bare wire by at least one non-contact guide while cooling the optical fiber bare wire; and coating the optical fiber bare wire with a resin to make an optical fiber element wire. In the step of cooling, gas is ejected from the inside of the non-contact guide toward the optical fiber element wire. The gas is dry air the dew point of which is controlled at 0°C or lower.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a method for manufacturing an optical fiber. In this method for manufacturing an optical fiber, the traveling direction of an optical fiber bare wire obtained by melting and drawing an optical fiber preform is changed by a direction changer, and the path length of the optical fiber bare wire is adjusted. Then, by adjusting this path length, the temperature of the optical fiber bare wire to be resin-coated is adjusted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method for manufacturing an optical fiber described in Patent Document 1, the path length of the optical fiber is increased by moving the traveling direction of the optical fiber bare wire in the horizontal direction, and thereby, the time for which the optical fiber bare wire touches the cooling gas atmosphere is increased to perform cooling. However, since cooling is performed by passing the optical fiber bare wire through the cooling gas atmosphere, it takes time to cool the optical fiber bare wire. Therefore, a method and an apparatus for manufacturing an optical fiber that can more efficiently cool the optical fiber bare wire are desired.

[0005] The present disclosure Without disconnection, aims to provide a method and an apparatus for manufacturing an optical fiber that can efficiently cool an optical fiber bare wire.

Means for Solving the Problems

[0006] This disclosure provides a method for manufacturing an optical fiber. This method for manufacturing an optical fiber comprises the steps of: melting an optical fiber matrix to draw a bare optical fiber; cooling the bare optical fiber while changing the direction of travel of the bare optical fiber using at least one non-contact guide; and coating the bare optical fiber with resin to form an optical fiber strand. In the cooling step, gas is ejected from inside the non-contact guide toward the bare optical fiber. The gas is dry air with a dew point controlled to be 0°C or lower.

[0007] This disclosure provides an apparatus for manufacturing optical fibers. The apparatus comprises a melting device, a cooling device, a supply device, and a coating device. The melting device melts optical fiber matrix to draw bare optical fiber wires from the optical fiber matrix. The cooling device cools the bare optical fiber wires. The supply device supplies gas to the cooling device. The coating device coats the bare optical fiber wires with resin to form optical fiber strands. The cooling device has at least three non-contact guides. Each of the non-contact guides is configured to eject gas from the inside out to change the direction of travel of the bare optical fiber wires in a non-contact manner. The gas supplied from the supply device to the non-contact guides is dry air with a dew point controlled to be 0°C or below. [Effects of the Invention]

[0008] According to this disclosure, Without disconnection, This allows for efficient cooling of bare optical fibers. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram of an optical fiber manufacturing apparatus according to one embodiment. [Figure 2] Figure 2 is a perspective view showing a non-contact guide. [Figure 3] Figure 3 is an enlarged cross-sectional view of the guide area of ​​the non-contact guide shown in Figure 2. [Figure 4] Figure 4 is a cross-sectional view of the non-contact guide shown in Figure 2, cut along the IV-IV line. [Modes for carrying out the invention]

[0010] [Description of Embodiments in this Disclosure] First, the contents of the embodiments of this disclosure will be listed and explained. One embodiment of a method for manufacturing an optical fiber comprises the steps of: melting an optical fiber base material to draw a bare optical fiber; cooling the bare optical fiber while changing the direction of travel of the bare optical fiber with at least one non-contact guide; and coating the bare optical fiber with resin to form an optical fiber strand. In the cooling step, gas is ejected from the inside of the non-contact guide toward the bare optical fiber. The gas is dry air with a dew point controlled to be 0°C or lower.

[0011] In this optical fiber manufacturing method, a gas (dry air) is ejected from inside a non-contact guide that changes the direction of the optical fiber without contact, toward the optical fiber. In this case, since the dry air is blown directly onto the optical fiber in an area close to the optical fiber, the optical fiber can be efficiently cooled. The non-contact guide, which changes the direction of the optical fiber without touching it by ejecting dry air, has a part (for example, a groove) that receives and guides the optical fiber. When the direction of the optical fiber is changed, the ejected dry air is rapidly released from the narrow guide part to a wide area along the entire portion of the non-contact guide. At this time, a localized temperature drop occurs due to the effect of adiabatic expansion, causing condensation of the dry air, and there is a risk that this condensation may come into contact with the optical fiber and cause it to break. However, in the manufacturing method according to one embodiment of this disclosure, the dew point of the dry air is controlled to be 0°C or lower, so such condensation is prevented. Therefore, this manufacturing method makes it possible to efficiently cool the optical fiber without causing it to break due to condensation. Note that dry air is not limited to air; any gas will suffice. Dry air could, for example, be nitrogen.

[0012] As one embodiment of the above optical fiber manufacturing method, in the cooling step, dry air may be supplied to the non-contact guide via a gas filter with a filtration accuracy of 0.03 μm or less. In this case, since impurities are removed from the dry air blown directly onto the bare optical fiber from the non-contact guide, it is possible to prevent the bare optical fiber from breaking due to collisions with impurities contained in the dry air. This makes it possible to efficiently cool the bare optical fiber without causing it to break.

[0013] In one embodiment of the above optical fiber manufacturing method, during the cooling process, the amount of dry air supplied to the non-contact guide may be adjusted by an on-off valve without metal sliding parts. In this case, dust generation (such as metal powder) from the on-off valve that adjusts the amount of dry air supplied to the non-contact guide can be reduced, thereby preventing the breakage of the bare optical fiber due to dust generation. As an on-off valve without metal sliding parts, for example, an air-operated valve can be used. A solenoid valve can be used to control the opening and closing of the air-operated valve.

[0014] Furthermore, an optical fiber manufacturing apparatus according to one embodiment comprises a melting apparatus, a cooling apparatus, a supply apparatus, and a coating apparatus. The melting apparatus melts the optical fiber base material to draw bare optical fiber wires from it. The cooling apparatus cools the bare optical fiber wires. The supply apparatus supplies gas to the cooling apparatus. The coating apparatus coats the bare optical fiber wires with resin to form optical fiber strands. The cooling apparatus has at least three non-contact guides. Each of the non-contact guides is configured to eject gas from the inside out to change the direction of travel of the bare optical fiber wires in a non-contact manner. The gas supplied from the supply apparatus to the non-contact guides is dry air with a dew point controlled to be 0°C or below.

[0015] In this optical fiber manufacturing apparatus, a gas (dry air) is ejected from inside a non-contact guide that changes the direction of the bare optical fiber without contact, toward the bare optical fiber. In this case, since the dry air is blown directly onto the bare optical fiber in an area close to the bare optical fiber, the bare optical fiber can be efficiently cooled. Furthermore, the non-contact guide that changes the direction of the bare optical fiber without touching it by ejecting dry air has a part that receives and guides the bare optical fiber (for example, a groove), and when the direction of the bare optical fiber is changed, the ejected dry air is rapidly released from the narrow guide part to a wide area along the entire portion of the non-contact guide. At this time, due to the effect of adiabatic expansion, a localized temperature drop occurs, causing condensation of the dry air, and there is a risk that this condensation will come into contact with the bare optical fiber and cause it to break. However, in the manufacturing apparatus according to one embodiment of this disclosure, the dew point of the dry air is controlled to be 0°C or lower, so such condensation is prevented. Therefore, this manufacturing method makes it possible to efficiently cool the bare optical fiber without causing it to break due to condensation.

[0016] In one embodiment, the optical fiber manufacturing apparatus may further include a filter positioned between the non-contact guide and the supply device. The filter may be a gas filter with a filtration accuracy of 0.03 μm or less. In this case, since impurities are removed by the filter from the dry air blown directly onto the bare optical fiber from the non-contact guide, it is possible to prevent the bare optical fiber from breaking due to collisions with impurities contained in the dry air. This makes it possible to efficiently cool the bare optical fiber without causing it to break.

[0017] As one embodiment, the above-described optical fiber manufacturing apparatus may further include an opening / closing valve that is disposed between the non-contact guide and the supply device and adjusts the supply amount of the dry air supplied to the non-contact guide. The opening / closing valve may be an opening / closing valve that does not have a metal sliding part. In this case, it is possible to reduce the generation of dust (such as metal powder) from the opening / closing valve that adjusts the supply amount of the dry air to the non-contact guide, and prevent the disconnection of the optical fiber bare wire due to the generated dust. Note that, as the opening / closing valve that does not have a metal sliding part, for example, an air-operated valve or the like can be used. A solenoid valve can be used for the opening / closing control of the air-operated valve.

[0018] [Details of Embodiments of the Present Disclosure] Specific examples of the optical fiber manufacturing method and the optical fiber manufacturing apparatus according to the present disclosure will be described below with reference to the drawings. In the following description, the same reference numerals will be used for the same elements or elements having the same function, and duplicate descriptions will be omitted. Note that the present invention is not limited to these examples, and is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0019] Referring to FIG. 1, the optical fiber manufacturing method and the optical fiber manufacturing apparatus according to one embodiment will be described. FIG. 1 is a schematic view of an optical fiber manufacturing apparatus 1 according to one embodiment. As shown in FIG. 1, the manufacturing apparatus 1 is an apparatus that heats and melts an optical fiber preform Fa to draw an optical fiber bare wire Fb, and manufactures an optical fiber element wire Fc by providing a coating resin on the outer periphery of the optical fiber bare wire Fb. The manufacturing apparatus 1 includes a drawing furnace 2 (melting device), a cooling device 3, a coating unit 4 (coating device), a curing unit 5, a directly-below roller 6, a traction roller 7, and a winding unit 8 in order along the passage path of the optical fiber bare wire Fb and the optical fiber element wire Fc. The manufacturing apparatus 1 further includes a gas supply device 10, a control device 11, a filter 12, and an opening / closing valve 13.

[0020] The drawing furnace 2 forms an optical fiber bare wire Fb by heating and melting an optical fiber base material Fa and drawing it along the vertical direction (direction X shown in FIG. 1). The drawing furnace 2 has a heater located around the optical fiber base material Fa. The optical fiber base material Fa is a glass body (preform) containing, for example, quartz glass. The optical fiber bare wire Fb is a glass wire containing, for example, a core and a cladding covering the outer periphery of the core. The drawing furnace 2 performs drawing after heating and softening the lower end of the optical fiber base material Fa by the heater. The drawn optical fiber bare wire Fb is sent to the cooling device 3.

[0021] The cooling device 3 cools the optical fiber bare wire Fb. The cooling device 3 has, for example, an internal space S surrounded by a housing 3a, and the optical fiber bare wire Fb passes through the internal space S. The outer wall constituting the housing 3a of the cooling device 3 may be made of transparent glass or resin so that the inside of the cooling device 3 can be confirmed.

[0022] The optical fiber bare wire Fb passes through the internal space S while meandering with its traveling direction changed by a plurality of non-contact guides 20. The optical fiber bare wire Fb passes between each non-contact guide 20 in a direction inclined with respect to the directions X and Y. In the present embodiment, the height direction of the manufacturing apparatus 1 is the direction X, the width direction is the direction Y, and the depth direction is the direction Z. In the present embodiment, the directions X, Y, and Z are orthogonal to each other. The cooling device 3 has seven non-contact guides 20 (non-contact rollers). The non-contact guides 20A, 20B, 20C, 20D, 20E, 20F, and 20G are provided in this order in the traveling path of the optical fiber bare wire Fb. Hereinafter, when it is not necessary to distinguish each non-contact guide 20, the description will be made by simply referring to them as non-contact guides 20. The number of non-contact guides 20 provided in the cooling device 3 may be a plurality and is not limited to seven. For example, the cooling device 3 may have at least three non-contact guides 20, or may have five or more and 15 or less non-contact guides 20.

[0023] Each non-contact guide 20 is a component that changes the direction of movement of the bare optical fiber Fb. The non-contact guide 20 is a disc-shaped component through which the bare optical fiber Fb passes (see Figure 2) along a gap 80 provided on its outer circumference. Each non-contact guide 20 may be movable along direction Y across the internal space S, or it may remain in a predetermined position without moving. If the non-contact guide 20 is movable, the length of the bare optical fiber Fb passing through the internal space S of the cooling device 3 can be adjusted. In this embodiment, three non-contact guides 20 (non-contact guides 20B, 20D, 20F) move along direction Y toward the right side of the paper in Figure 1.

[0024] Furthermore, each non-contact guide 20 also functions as a cooling component for the bare optical fiber Fb. Specifically, the gas (dry air) supplied from the gas supply device 10 into the non-contact guide 20 is blown radially outward from the gap 80 in the non-contact guide 20. The blown-out dry air is blown from the inside onto the bare optical fiber Fb that passes through the gap 80. The bare optical fiber Fb is cooled in a suspended state by the direct blowing of dry air onto it. The bare optical fiber Fb cooled by this cooling device 3 is then sent to the coating section 4. Details of the gas supply device 10 and the non-contact guide 20 will be described later. Note that the dry air is not limited to air, but can be any gas. For example, the dry air may be nitrogen.

[0025] The coating unit 4 applies a coating resin to the outer circumference of the bare optical fiber Fb. The coating resin is, for example, an ultraviolet-curing resin. The coating unit 4 may apply two different types of coating resins to the outer circumference of the bare optical fiber Fb. For example, the coating unit 4 may apply a primary resin to the bare optical fiber Fb, and then apply a secondary resin to the outside of the primary resin. The coating unit 4 may apply the primary resin and the secondary resin to the bare optical fiber Fb almost simultaneously. The bare optical fiber Fb coated with the coating resin is sent to the curing unit 5.

[0026] The curing unit 5 cures the coating resin applied to the bare optical fiber Fb by irradiating it with ultraviolet light. The curing unit 5 has a light-emitting element such as an ultraviolet lamp that emits ultraviolet light. When the coating resin applied to the bare optical fiber Fb hardens, the optical fiber strand Fc is completed. The completed optical fiber strand Fc is then fed to the roller 6 directly below.

[0027] The lower roller 6 changes the direction of movement of the optical fiber strand Fc from along direction X to a predetermined direction. The optical fiber strand Fc whose direction of movement has been changed by the lower roller 6 is sent to the traction roller 7. The traction roller 7 pulls and moves the optical fiber strand Fc. The speed at which the optical fiber strand Fc moves may be adjustable by changing the rotation speed of the traction roller 7. The optical fiber strand Fc is sent from the traction roller 7 to the winding unit 8 and is wound up by the winding unit 8. This completes the manufacturing process of the optical fiber strand Fc.

[0028] Next, the gas supply device 10 and control device 11, which supply cooling gas (dry air) to the cooling device 3 (non-contact guide 20), will be described with reference to Figure 1. The gas supply device 10 supplies dry air to the cooling device 3, which is controlled so that the dew point is 0°C or lower based on the control device 11. More specifically, the gas supply device 10 supplies dry air to each non-contact guide 20 via the filter 12 and the on / off valve 13. Note that a different cooling gas may be supplied into the housing 3a of the cooling device 3 from another gas supply device.

[0029] The filter 12 used for supplying dry air is, for example, a gas filter for removing impurities from the dry air. For example, a gas filter with a filtration accuracy (also called "filtration degree") of 0.03 μm or less can be used. Alternatively, a gas filter with a filtration accuracy of 0.01 μm or less may be used as filter 12. Since dry air contains many foreign objects on the order of 0.01 μm, setting the filtration accuracy of filter 12 to 0.03 μm or less can reduce the frequency of breakage of the bare optical fiber Fb due to collisions with impurities, etc., by about half. By setting the filtration accuracy of the filter 12 used to 0.01 μm or less, the frequency of breakage can be further reduced. Here, "filtration accuracy" means that the collection efficiency of particles of the corresponding size (for example, if the filtration accuracy is 0.01 μm, particles of 0.01 μm or larger) is 99.99% or higher. Furthermore, the on / off valve 13 for adjusting the flow rate of dry air is, for example, a valve (control valve) that does not have a metal sliding part, and the generation of dust (metal powder) associated with sliding is suppressed. As such an on / off valve 13, for example, an air-operated valve can be used. A solenoid valve may be used to control the opening and closing of the air-operated valve. If the dust collection capacity of the filter 12 located downstream is sufficient, the on / off valve 13 may be a solenoid valve.

[0030] The gas supply device 10 includes a gas supply source 10a, a dryer 10b, and a dew point meter 10c. Gas is supplied from the gas supply source 10a at a predetermined pressure. This gas is, for example, air, but may also be nitrogen. The dryer 10b generates dry air by drying the gas supplied from the gas supply source 10a. Drying by the dryer 10b reduces the amount of water vapor contained in the dry air supplied from the gas supply source 10a, thereby lowering the dew point of the dry air. More specifically, the dry air is dried by the dryer 10b so that its dew point is 0°C or lower. The reduction of water vapor may be achieved, for example, by evaporation or adsorption of water vapor. The term "dew point" refers to the temperature at which condensation from water vapor to water begins when a gas containing water vapor is cooled. When the dew point is 0°C or lower, cooling the gas containing water vapor to the dew point will cause condensation from water vapor to water and solidification from water to ice to begin. The dry air used here may be dried by the dryer 10b so that its dew point is -10°C or lower, or it may be dried by the dryer 10b so that its dew point is -20°C or lower.

[0031] The dew point meter 10c of the gas supply device 10 measures the dew point of the dry air dried by the dryer 10b. The dry air is dried by the dryer 10b until the dew point measured by the dew point meter 10c falls below a preset dew point of 0°C. In other words, the gas supply device 10, under the control of the control device 11, manages the dew point of the dry air supplied to the non-contact guide 20, etc., of the cooling device 3 so that it is below 0°C. The dew-point controlled dry air is supplied to the cooling device 3 (non-contact guide 20, etc.) via the filter 12 as described above, and the internal space S in the cooling device 3 is filled with the dew-point controlled dry air.

[0032] As described above, the control device 11 is a device that controls the gas supply device 10. The control device 11 is, for example, a computer and is configured to include a CPU, a storage medium such as memory, and an input / output interface. The control device 11 controls the flow rate of the gas supplied from the gas supply source 10a and the drying of the gas by the dryer 10b so that the dry air supplied from the gas supply device 10 has a predetermined dew point of 0°C or lower as measured by the dew point meter 10c.

[0033] Next, with reference to Figures 2 and 3, the structure of a non-contact guide 20, which is an example of a non-contact roller, will be described. Figure 2 is a perspective view showing the non-contact guide 20. Figure 3 is an enlarged view of the vicinity of the gap 80 in Figure 2.

[0034] The non-contact guide 20 is a component that changes the direction of movement of the bare optical fiber Fb in a non-contact manner. The non-contact guide 20 has a circular shape in plan view. As shown in Figure 2, the non-contact guide 20 has a gap 80 between the first flange 30 and the second flange 70. The gap 80 is provided in an annular shape along the outer circumference of the non-contact guide 20. The bare optical fiber Fb is passed through the gap 80. Dry air introduced into the interior of the non-contact guide 20 is blown out radially from the gap 80. The blown-out dry air is blown onto the bare optical fiber Fb that is passed through the gap 80. The bare optical fiber Fb floats due to the blowing of dry air and does not come into contact with the first flange 30 and the second flange 70. In addition, as described above, the bare optical fiber Fb is cooled by the blowing of this dry air. In the non-contact guide 20, the second flange 70 is configured to be movable relative to the first flange 30, allowing the width of the gap 80 between them to be adjusted.

[0035] Next, with reference to Figures 3 and 4, the configuration of the non-contact guide 20 when a bare optical fiber Fb is passed through the gap 80 will be described. Figure 4 is a cross-sectional view of the non-contact guide 20 when cut along the IV-IV line shown in Figure 2. The first flange 30 and the second flange 70 are attached to the internal member 40 such that a gap 80 is provided between the outer edge of the first flange 30 and the outer edge of the second flange 70, as shown in Figure 3. In this embodiment, a gap 80 is provided between the outer circumferential surface 32a of the peripheral wall portion 32 of the first flange 30 and the outer circumferential surface 72a of the peripheral wall portion 72 of the second flange 70.

[0036] As shown in Figure 4, the gap 80 is provided along the circumferential direction of the non-contact guide 20, surrounding the central axis C. A bare optical fiber Fb is passed through the gap 80. Specifically, the bare optical fiber Fb enters the gap 80 from the entry point 81, moves along the gap 80, and then exits to the outside from the exit point 82. In the example shown in Figure 4, the bare optical fiber Fb moves over an area of ​​approximately half the size of the gap 80. That is, the direction of movement of the bare optical fiber Fb is changed by approximately 180° by the non-contact guide 20. The positions of the entry point 81 and exit point 82 described above are determined by the amount of change in the direction of movement of the bare optical fiber Fb. In this embodiment, as described above, the direction of movement of the bare optical fiber Fb is changed by approximately 180°. Therefore, the exit point 82 is set at a position offset from the entry point 81 by approximately half the length of the circumferential direction of the gap 80. For example, if the direction of movement of the bare optical fiber Fb is changed by approximately 90°, the exit portion 82 may be set at a position shifted from the entry portion 81 by approximately one-quarter of the circumferential length of the gap 80 (at the top of the gap 80 in Figure 4).

[0037] As shown in Figures 3 and 4, the gap 80 is spatially connected to the buffer groove 51 and the nozzle 47. As a result, the dry air ejected from the nozzle 47 passes through the buffer groove 51 and is blown out of the gap 80 to the outside of the non-contact guide 20. The dry air ejected from the gap 80 is blown onto the bare optical fiber Fb that passes through the gap 80. The air pressure of the dry air maintains a state in which the bare optical fiber Fb is suspended above the outer circumferential surface 32a of the first flange 30 and the outer circumferential surface 72a of the second flange 70. In other words, the bare optical fiber Fb is suspended in the gap 80.

[0038] The pressure of the dry air blown out from the gap 80 (blow-out pressure) changes depending on factors such as the pressure of the dry air supplied to the gas flow path (not shown) in the non-contact guide 20 (inlet pressure), the width W of the gap 80, and is also affected by factors such as the winding diameter D1 of the non-contact guide 20. Here, the winding diameter D1 refers to the diameter of the circle formed by the bare optical fiber Fb (circle B shown as a solid and dashed line in Figure 4) when the bare optical fiber Fb is passed around the entire circumference of the gap 80. The blow-out pressure is optimized by adjusting each of the above factors according to the tension of the bare optical fiber Fb or the diameter of the bare optical fiber Fb.

[0039] Generally, when increasing the linear velocity (movement speed) of the bare optical fiber Fb, the tension on the bare optical fiber Fb is small, and if the pressure of the blown dry air is high, the bare optical fiber Fb resonates and comes into contact with the non-contact guide 20. Therefore, the blown pressure is reduced when increasing the linear velocity of the bare optical fiber Fb. On the other hand, when the linear velocity is stable, the tension of the bare optical fiber Fb is maintained at a high level, so the blown pressure is increased. Methods for increasing the blown pressure include, for example, increasing the inlet pressure or reducing the width W of the gap 80.

[0040] For example, when suspending a bare optical fiber Fb with a diameter of 125 μm, the inlet pressure may be set to 50 kPa or more and 200 kPa or less, and the width W of the gap 80 may be set to approximately 0.2 mm. In this case, the flow rate of air blown out from the gap 80 of one non-contact guide 20 may be 30 L / min or more and 150 L / min or less.

[0041] When adjusting the discharge pressure to an appropriate level, first, with a constant flow rate of dry air flowing, the width W of the gap 80 is reduced until the inlet pressure reaches a predetermined value (e.g., 200 kPa). At this time, the width W of the gap 80 may be reduced by, for example, bringing the second flange 70 closer to the first flange 30. After that, the width W of the gap 80 is gradually increased until the discharge pressure reaches an optimal level (a level that allows the bare optical fiber Fb to float properly). At this time, the width W of the gap 80 may be increased by, for example, moving the second flange 70 away from the first flange 30. This discharge pressure adjustment work may be performed for each non-contact guide 20 shown in Figure 1. Furthermore, the adjustment work may be performed at any timing during the manufacturing process of the optical fiber strand Fc.

[0042] The non-contact guide 20 has a sealing member 68, as shown in Figure 4. For convenience of explanation, the sealing member 68 is not shown in figures other than Figure 4. The sealing member 68 seals at least one of the multiple nozzles 47, preventing dry air from passing through the nozzle 47. The sealing member 68 may be made of an elastic material such as resin. The sealing member 68 has an elongated shape and is fitted into a portion of the buffer groove 51 so as to block the nozzle 47. In this embodiment, the sealing member 68 is fitted into approximately half of the buffer groove 51. Dry air does not flow into the portion of the air passage 46 where the nozzle 47 is sealed by the sealing member 68, but it flows into the other air passages 46 where the nozzle 47 is not sealed.

[0043] In the direction from the central axis C toward the outer circumference of the non-contact guide 20 (radial direction of the non-contact guide 20), most of the sealing member 68 is provided so as not to overlap with the bare optical fiber Fb passed through the gap 80. In the example shown in Figure 4, the portion of the sealing member 68 excluding both ends is provided so as not to overlap with the circumferential position of the bare optical fiber Fb passed through the gap 80. In addition, a pair of air vents 84 are provided between both ends of the sealing member 68 and the bare optical fiber Fb, allowing dry air from inside the buffer groove 51 to flow out. By allowing the dry air accumulated in the buffer groove 51 to flow out smoothly from the air vents 84, excessively high-pressure dry air is not blown out from the gap 80, making it possible to suspend the bare optical fiber Fb in a stable state. The shape of the sealing member 68 is not limited to that described above. In this embodiment, multiple nozzles 47 are sealed by a single continuous sealing member 68, but for example, multiple nozzles 47 may be sealed by multiple separate sealing members 68.

[0044] Here, with reference to Figure 1, a method for manufacturing optical fibers using the optical fiber manufacturing apparatus 1 described above will be explained. First, the optical fiber base material Fa is melted using the drawing furnace 2, and the molten optical fiber strands Fc are wound up by the winding unit 8 to start drawing. At this time, the bare optical fiber strands Fb to be drawn are arranged so that their direction of travel is changed by each non-contact guide 20.

[0045] Next, the direction of travel of the bare optical fiber Fb drawn from the optical fiber matrix Fa is changed by each non-contact guide 20, while the bare optical fiber Fb is cooled by dry air blown from inside each non-contact guide 20 toward the bare optical fiber Fb. As described above, this dry air has a dew point of 0°C or lower controlled by the gas supply device 10 and the control device 11. This dew-point controlled dry air is supplied from the gas supply device 10 to each non-contact guide 20 via the on / off valve 13 and the filter 12.

[0046] Next, the sufficiently cooled bare optical fiber Fb exits the cooling device 3 and is coated with a predetermined resin in the coating section 4. After that, the coating resin is cured in the curing section 5, and the optical fiber strand Fc is wound up by the winding section 8.

[0047] As described above, according to the optical fiber manufacturing method and apparatus of this embodiment, dry air is ejected from inside the non-contact guide 20 toward the bare optical fiber Fb, which changes the direction of travel of the bare optical fiber Fb without contact. In this case, since the dry air is blown directly onto the bare optical fiber Fb in an area close to the bare optical fiber Fb, the bare optical fiber Fb can be efficiently cooled. Furthermore, the non-contact guide 20, which changes the direction of the bare optical fiber without touching it by ejecting dry air, has a portion (for example, a gap 80) that receives and guides the bare optical fiber Fb. When the direction of travel of the bare optical fiber Fb is changed, the ejected dry air is rapidly released from the narrow gap 80 to a wide area along the entire portion of the non-contact guide 20. At this time, a localized temperature drop occurs due to the effect of adiabatic expansion, causing condensation of the dry air, and there is a risk that this condensation may come into contact with the bare optical fiber Fb and cause a break. However, in the manufacturing method according to the above embodiment, the dew point of the dry air is controlled to be 0°C or lower, so the occurrence of such condensation is prevented. Therefore, this manufacturing method makes it possible to efficiently cool the bare optical fiber using the non-contact guide 20, etc., without causing the bare optical fiber to break due to condensation.

[0048] Furthermore, in the above embodiment, when cooling the bare optical fiber Fb, dry air is supplied to the non-contact guide 20 via a filter 12 with a filtration accuracy of 0.03 μm or less. In this case, since impurities are removed from the dry air blown directly onto the bare optical fiber Fb from the non-contact guide 20, it is possible to prevent the bare optical fiber Fb from breaking due to collisions with impurities contained in the dry air. This makes it possible to efficiently cool the bare optical fiber without causing it to break.

[0049] Furthermore, in the above embodiment, the amount of dry air supplied to the non-contact guide 20 is adjusted by an on-off valve 13 that does not have a metal sliding part. In this case, dust generation (metal powder, etc.) from the on-off valve that adjusts the amount of dry air supplied to the non-contact guide 20 can be reduced, thereby preventing the breakage of the bare optical fiber due to dust generation. [Explanation of Symbols]

[0050] 1...Manufacturing equipment 2…Line drawing furnace (melting device) 3...Cooling device 4…Coating section (coating device) 5…Hardened part 6... Directly below roller 7... Towing roller 8... Winding section 10...Gas supply device 10a... Gas supply source 10b…Dryer 10c…Dew point meter 11…Control device 12…Filter 13…Opening / closing valve 20, 20A, 20B, 20C, 20D, 20E, 20F, 20G... Air guide (non-contact guide) 30…First flange 32, 72...peripheral wall part 32a, 72a...outer surface 40…Internal components 46…Airflow channel 47... spout 51... Buffer groove 68...Sealing member 70…Second flange 80... Gap 81...Entry point 82…Outgoing line part 84...Air Escape Club Fa... Optical fiber base material Fb... bare optical fiber Fc... Optical fiber strand S…interior space

Claims

1. The process involves melting the optical fiber preform and drawing bare optical fiber wires, A step of cooling the bare optical fiber while changing the direction of travel of the bare optical fiber using at least one non-contact guide, The process of forming optical fiber strands by coating the aforementioned bare optical fiber with resin, Equipped with, In the cooling step, gas is ejected from the inside of the non-contact guide toward the bare optical fiber, and the gas is dry air with a dew point controlled to be 0°C or lower, so that no condensation forms on the bare optical fiber as it passes through the non-contact guide. A method for manufacturing optical fibers.

2. In the cooling step, the dry air is supplied to the non-contact guide via a gas filter with a filtration accuracy of 0.03 μm or less. A method for manufacturing an optical fiber according to claim 1.

3. In the cooling process, the amount of dry air supplied to the non-contact guide is adjusted by an on / off valve that does not have a metal sliding part. A method for manufacturing an optical fiber according to claim 1 or claim 2.

4. A melting apparatus for melting the optical fiber preform in order to draw bare optical fiber wires from the optical fiber preform, A cooling device for cooling the aforementioned bare optical fiber, A supply device that supplies gas to the cooling device, A coating apparatus for forming optical fiber strands by coating the aforementioned bare optical fiber with resin, Equipped with, The cooling device has at least three non-contact guides configured to eject the gas from the inside outwards in order to change the direction of travel of the bare optical fiber without contact, An optical fiber manufacturing apparatus wherein the gas supplied from the supply device to the non-contact guide is dry air with a dew point controlled to be 0°C or lower, and does not condense on the bare optical fiber when the bare optical fiber passes through the non-contact guide.

5. The device further comprises a filter positioned between the non-contact guide and the supply device, The aforementioned filter is a gas filter with a filtration accuracy of 0.03 μm or less. The optical fiber manufacturing apparatus according to claim 4.

6. The device further comprises an on / off valve positioned between the non-contact guide and the supply device, which adjusts the amount of dry air supplied to the non-contact guide. The aforementioned on-off valve is an on-off valve that does not have a metal sliding part. An apparatus for manufacturing optical fibers according to claim 4 or claim 5.

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