Optical fiber manufacturing apparatus and manufacturing method

Abstract

To suppress the mixture of the air from a lower extension pipe in an optical fiber drawing furnace to suppress the reduction of the intensity of an obtained optical fiber.SOLUTION: An apparatus for manufacturing an optical fiber includes a drawing furnace for heating, melting and drawing an optical fiber preform to form a glass fiber. The drawing furnace includes: a heating furnace for heating and melting the optical fiber preform; a lower extension pipe provided in the lower end of the heating furnace and having a glass fiber passing through the inside; and a gas purge pipe provided in the lower end of the lower extension pipe and axially symmetrically injecting gas from the periphery to the glass fiber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an optical fiber drawing furnace in which a lower extension pipe (lower chimney) is provided below a core tube into which an optical fiber glass preform is inserted. Patent Document 1 also describes that the inert gas introduced into the core tube flows into the lower extension pipe, and that it is desired to suppress the use of the inert gas in order to reduce manufacturing costs. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2013-203622 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] In the optical fiber drawing furnace described in Patent Document 1, air may enter the lower extension pipe from the fiber outlet at the lower end of the lower extension pipe. In particular, when the pressure inside the lower extension pipe becomes negative relative to the outside due to a reduction in the amount of inert gas introduced into the core tube, air easily enters the lower extension pipe from the fiber outlet. If particles and moisture contained in the air that has entered the lower extension pipe adhere to the glass fiber, this causes a reduction in the strength of the resulting optical fiber.

[0005] An object of the present disclosure is to suppress the intrusion of air from the lower extension pipe in an optical fiber drawing furnace, and thereby suppress a reduction in the strength of the obtained optical fiber. [Means for Solving the Problem]

[0006] An optical fiber manufacturing apparatus according to an aspect of the present disclosure includes: An optical fiber manufacturing apparatus equipped with a drawing furnace that heats and melts an optical fiber base material to draw it into a wire and form a glass fiber, The aforementioned wire drawing furnace is A heating furnace for heating and melting the preform material for optical fibers, A lower extension tube is provided at the lower end of the heating furnace, through which the glass fiber passes; The system includes a gas purge pipe provided at the lower end of the lower extension pipe, which injects gas axially symmetrically onto the glass fiber from the surrounding area.

[0007] A method for manufacturing an optical fiber according to one aspect of this disclosure is: A method for manufacturing optical fibers, in which a base material for optical fibers is heated and melted in a drawing furnace and drawn to form a glass fiber, The aforementioned wire drawing furnace is A heating furnace for heating and melting the preform material for optical fibers, A lower extension tube is provided at the lower end of the heating furnace, through which the glass fiber passes; The lower extension pipe is provided with a gas purge pipe, Gas is injected from the gas purging pipe onto the glass fiber in an axisymmetric manner from all sides to draw a line. [Effects of the Invention]

[0008] According to the configuration of the above disclosure, it is possible to suppress the ingress of air from the lower extension tube in the optical fiber drawing furnace and suppress the decrease in the strength of the resulting optical fiber. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a manufacturing apparatus for optical fibers according to one embodiment of the present disclosure. [Figure 2] Figure 1 is a schematic diagram showing the structure of a gas purge pipe. [Figure 3] Figure 2 is a schematic diagram showing a first modified example of the inner wall of a gas purge pipe. [Figure 4] Figure 2 is a schematic diagram showing a second modified example of the inner wall of a gas purge pipe. [Figure 5] It is a schematic diagram showing a third modification of the inner wall of the gas purge pipe shown in Fig. 2. [Figure 6] It is a schematic diagram showing another example of the gas purge pipe shown in Fig. 2. [Figure 7] It is a schematic diagram showing a first modification of the gas purge pipe shown in Fig. 6. [Figure 8] It is a schematic diagram showing a second modification of the gas purge pipe shown in Fig. 6. MODE FOR CARRYING OUT THE INVENTION

[0010] Description of Embodiments of the Present Disclosure First, embodiments of the present disclosure will be listed and described. An optical fiber manufacturing apparatus according to one aspect of the present disclosure, is an optical fiber manufacturing apparatus provided with a drawing furnace that heats and melts an optical fiber preform and draws the same to form a glass fiber, wherein: the drawing furnace comprises: a heating furnace that heats and melts the optical fiber preform; a lower extension pipe provided at a lower end of the heating furnace and allowing the glass fiber to pass through an interior thereof; and a gas purge pipe provided at a lower end of the lower extension pipe and configured to inject gas toward the glass fiber axisymmetrically from surroundings thereof. According to this configuration, mixing of air from the lower extension pipe in the optical fiber drawing furnace can be suppressed, and a decrease in strength of the obtained optical fiber can be suppressed.

[0011] In the optical fiber manufacturing apparatus, the heating furnace is provided with a gas inlet that introduces a gas containing helium gas into the heating furnace, the lower extension pipe is provided with a gas suction port that sucks the internal gas containing helium gas and discharges the gas to the outside of the lower extension pipe, it is preferable that the optical fiber manufacturing apparatus further comprises a helium regeneration device that regenerates and reuses the gas containing helium gas discharged from the gas suction port. When helium gas is sucked from the lower extension pipe, the pressure inside the lower extension pipe decreases, which makes it easy for air to mix into the lower extension pipe. However, according to the above configuration, since a gas purge pipe is provided at the lower end of the lower extension pipe and gas is injected into the gas purge pipe, it is possible to suppress the mixing of air into the lower extension pipe while allowing expensive helium gas to be reused.

[0012] A method for manufacturing an optical fiber according to an aspect of the present disclosure is A method for manufacturing an optical fiber, comprising heating and melting an optical fiber preform in a drawing furnace to draw the preform and form a glass fiber, wherein The drawing furnace comprises: a heating furnace that heats and melts the optical fiber preform; a lower extension pipe provided at the lower end of the heating furnace, through which the glass fiber passes inside; and a gas purge pipe provided at the lower end of the lower extension pipe, wherein drawing is performed by injecting gas axially symmetrically from the surroundings toward the glass fiber from the gas purge pipe. According to this configuration, it is possible to suppress the mixing of air from the lower extension pipe in the optical fiber drawing furnace, and suppress a decrease in the strength of the obtained optical fiber.

[0013] In the method for manufacturing the optical fiber, it is preferable that the temperature of the glass fiber exiting from the gas purge pipe is 1200°C or higher and 1700°C or lower. By setting the exit temperature of the glass fiber exiting from the gas purge pipe to 1700°C or lower, it is possible to suppress the promotion of reaction between the glass fiber and moisture in the air during exiting, and the generation of defects on the surface of the glass fiber caused by collision with dust in the air. In addition, by setting the exit temperature of the glass fiber to 1200°C or higher, it is possible to suppress a situation where the glass fiber is rapidly cooled before exiting from the gas purge pipe, causing fluctuations in outer diameter. As a result, a decrease in the strength of the optical fiber can be further suppressed.

[0014] In the method for manufacturing the optical fiber, It is preferable to maintain a positive pressure inside the gas purge tube while drawing the line. This configuration makes it possible to further suppress the ingress of air and impurities into the gas purge tube by creating a positive pressure inside the gas purge tube relative to the atmospheric pressure outside the gas purge tube and the internal pressure inside the lower extension tube.

[0015] The method for manufacturing the optical fiber is as follows: It is preferable that the flow rate of the gas ejected from the gas purging pipe is 30 liters / minute or more and 150 liters / minute or less. By increasing the gas flow rate from the gas purge pipe to 30 liters / minute or more, it becomes easier to suppress the mixing of air into the gas purge pipe. Furthermore, by keeping the gas flow rate from the gas purge pipe below 150 liters / minute, it is possible to suppress the deterioration of glass fiber quality caused by the injected gas hitting the glass fiber with strong force (high flow velocity).

[0016] [Details of the embodiments of this disclosure] Hereinafter, examples of embodiments of the optical fiber manufacturing apparatus and manufacturing method relating to this disclosure will be described with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals or names even in different drawings, and redundant explanations will be omitted as appropriate. Furthermore, the dimensions of each component shown in each drawing are for illustrative purposes only and may differ from the actual dimensions of each component.

[0017] (Equipment for manufacturing optical fibers) Figure 1 is a schematic diagram of a manufacturing apparatus 1 for optical fibers according to one embodiment of the present disclosure. The manufacturing apparatus 1 includes a wire drawing furnace 100. The wire drawing furnace 100 is a device that heats and melts a base material 2 for optical fibers and draws it to form a glass fiber 3. Although not shown, the manufacturing apparatus 1 may further include a cooling device for cooling the glass fiber 3, a coating device for applying a coating resin to the outer circumference of the glass fiber 3, a winding device for winding the glass fiber 3 coated with the coating resin, and so on.

[0018] The fiber drawing furnace 100 comprises a heating furnace 10, a lower extension tube 20, and a gas purge tube 30. The heating furnace 10 heats and melts the optical fiber base material 2. The heating furnace 10 comprises a housing 11, a furnace core tube 12, and a heater 13. The housing 11 is configured to surround the furnace core tube 12 and the heater 13. The heater 13 is positioned to surround the furnace core tube 12. An insulating material (not shown) is placed between the heater 13 and the housing 11. The optical fiber base material 2 is suspended inside the furnace core tube 12 by a base material suspension mechanism (not shown). The lower part of the suspended optical fiber base material 2 is melted by the heat from the heater 13, and the fiber is drawn so that glass fibers 3 with a predetermined outer diameter are continuously obtained.

[0019] The reactor core tube 12 is equipped with a gas inlet 16. One end of a gas pipe 14 is connected to the gas inlet 16. An inert gas supply unit 15, which supplies inert gases such as argon, helium, and nitrogen, is connected to the other end of the gas pipe 14. The inert gas supplied from the inert gas supply unit 15 is supplied into the reactor core tube 12 through the gas inlet 16 via the gas pipe 14. The inert gas supplied into the reactor core tube 12 flows into the lower extension pipe 20.

[0020] The lower extension tube 20 is provided at the lower end of the heating furnace 10. The lower extension tube 20 is provided so that its inlet connects to the outlet of the furnace core tube 12, and it is preferable that it is provided so as to be in close contact with the lower part of the heating furnace 10. The lower extension tube 20 may be formed integrally with the heating furnace 10, or it may be provided so as to be detachable from the heating furnace 10. The glass fibers 3 drawn in the furnace core tube 12 pass continuously through the lower extension tube 20. By providing the lower extension tube 20, it is possible to suppress the rapid cooling of the heated and softened glass fibers 3 while still allowing them to cool and harden to some extent, thereby suppressing fluctuations in the outer diameter of the glass fibers 3.

[0021] The lower extension tube 20 is equipped with a gas suction port 23. The gas suction port 23 is provided to draw in a mixed gas containing inert gas supplied into the core tube 12 and flowing into the lower extension tube 20, and other gases including impurities generated during the drawing process, and discharge it to the outside of the lower extension tube 20. In the example in Figure 1, two gas suction ports 23 are provided. One end of the gas piping 21a is connected to one gas suction port 23. One end of the gas piping 21b is connected to the other gas suction port 23. Although part of the gas piping 21b is not shown, a gas regeneration device 22 is connected to the other ends of gas piping 21a and 21b. The gas regeneration device 22 separates and purifies the inert gas (e.g., helium gas) from the mixed gas drawn in from the gas suction port 23 and regenerates the inert gas into a reusable state. The gas regeneration device 22 and the inert gas supply device 15 may be connected by piping (not shown) to supply the inert gas regenerated by the gas regeneration device 22 to the inert gas supply device 15.

[0022] The gas purge pipe 30 is provided at the lower end of the lower extension pipe 20. The gas purge pipe 30 is provided so that the outlet of the lower extension pipe 20 and the inlet of the gas purge pipe 30 are connected, and it is preferable that it is provided so as to be in close contact with the lower part of the lower extension pipe 20. The gas purge pipe 30 may be formed integrally with the lower extension pipe 20, or it may be provided so as to be detachable from the lower extension pipe 20. If it is to be detachable from the lower extension pipe 20, the gas purge pipe 30 may, for example, adopt a split structure. The material of the gas purge pipe 30 is not particularly limited, but it is a metal such as SUS (Steel Use Stainless).

[0023] Glass fibers 3, which emerge from the lower extension pipe 20, continuously pass through the gas purge pipe 30. The glass fibers 3 also emerge from the fiber outlet 34 at the lower end of the gas purge pipe 30. In the example in Figure 1, the gas purge pipe 30 includes pipe connection ports 31a and 31b, an outer wall 32, and an inner wall 33. One end of the pipe connection ports 31a and 31b is connected to one end of the gas pipes 35a and 35b, respectively. Although a portion of the gas pipe 35b is not shown, a first gas supply unit 36 ​​is connected to the other end of the gas pipes 35a and 35b. The first gas supply unit 36 ​​supplies a first gas. The first gas is preferably an inert gas as described above, and from the viewpoint of cost reduction, nitrogen gas is more preferable. Alternatively, the first gas may be dry air with a dew point temperature of 10°C or lower. By using such dry air, the reduction in strength due to moisture adhering to the glass fibers 3 can be suppressed. The first gas supplied from the first gas supply unit 36 ​​is supplied into the gas purge pipe 30 through gas pipes 35a and 35b and gas inlets 32a and 32b provided in the outer wall 32.

[0024] The gas purge pipe 30 will be described in detail below using Figure 2. Figure 2 is a schematic diagram showing the structure of the gas purge pipe 30 shown in Figure 1. Reference numeral 30A in Figure 2 indicates a side view of the gas purge pipe 30, and reference numeral 30B indicates a top view of the gas purge pipe 30. As shown in these figures, the pipe connection ports 31a and 31b are connected to the gas inlet ports 32a and 32b provided in the outer wall 32, respectively. An inner wall 33 is provided inside the outer wall 32. The outer wall 32 and the inner wall 33 form a double-wall structure. Specifically, the outer wall 32 and the inner wall 33 form pipes that extend along the direction of travel of the glass fiber 3. There is a cavity between the outer wall 32 and the inner wall 33.

[0025] The lower part of Figure 2 shows an unfolded view of the inner wall 33. As shown in this unfolded view, the inner wall 33 is provided with a plurality of gas injection ports 33a. The plurality of gas injection ports 33a are provided, for example, at positions that are point-symmetric with respect to the position through which the glass fiber 3 passes in the radial direction. It is preferable that the plurality of gas injection ports 33a are the same size and shape, but it is sufficient if they are the same size and shape between two gas injection ports 33a that have point symmetry. In the example in Figure 2, all of the plurality of gas injection ports 33a are circular holes and are the same size.

[0026] In the unfolded view of the inner wall 33 shown in Figure 2, the positions corresponding to the gas inlets 32a and 32b of the outer wall 32 are indicated by dashed lines. The first gas introduced into the interior of the outer wall 32 from the gas inlets 32a and 32b is diffused into the cavity between the outer wall 32 and the inner wall 33 by colliding with the inner wall 33, and is then injected into the interior of the inner wall 33 from a plurality of point-symmetric gas injection ports 33a. As a result, within the inner wall 33, the first gas is injected axially symmetrically with respect to the glass fiber 3, with the glass fiber 3 as the axis of symmetry.

[0027] Furthermore, as shown in the example in Figure 2, by configuring the system to inject the first gas introduced from gas inlets 32a and 32b from multiple gas inlet ports 33a, rather than directly onto the glass fiber 3, it is possible to suppress an increase in the flow velocity of the first gas injected from the gas inlet ports 33a, even when the flow rate of the first gas is increased. As a result, even when the flow rate of the first gas is increased, it is possible to suppress the deterioration of the quality of the glass fiber 3 caused by the first gas hitting the glass fiber 3 too strongly (at a high flow velocity).

[0028] In the example shown in Figure 2, the gas inlets 32a and 32b are positioned symmetrically with respect to the position through which the glass fiber 3 passes in the radial direction, and are of the same size and shape. However, the configuration is not limited to these. As long as the first gas can be injected into the inner wall 33 from around the glass fiber 3 in an axially symmetric manner, the position, shape, and size of the gas inlets 32a and 32b can be changed as appropriate.

[0029] Similarly, if the first gas can be injected into the inner wall 33 from the periphery with respect to the glass fiber 3 in an axisymmetric manner, the position, shape, and size of the multiple gas injection ports 33a can be changed as appropriate. Figures 3 to 5 are schematic diagrams showing modified examples of the inner wall 33 of the gas purge pipe 30 shown in Figure 2. Figure 3 shows an unfolded view of the inner wall 133, which is the first modified example of the inner wall 33. In the inner wall 133, the multiple point-symmetric gas injection ports 133a are rectangular holes with their longer sides in the circumferential direction. Figure 4 shows an unfolded view of the inner wall 233, which is the second modified example of the inner wall 33. In the inner wall 233, the multiple point-symmetric gas injection ports 233a are rectangular holes with their longer sides in the axial direction of the glass fiber 3. Figure 5 shows an unfolded view of the inner wall 333, which is the third modified example of the inner wall 33. In the inner wall 333, the multiple point-symmetric gas injection ports 333a are square holes.

[0030] Next, another example of the gas purge pipe 30 shown in Figure 2 will be described using Figure 6. In Figure 6, reference numeral 430A indicates a side view of the gas purge pipe 430, and reference numeral 430B indicates a top view of the gas purge pipe 430. The lower part of Figure 6 shows an unfolded view of the outer wall 432 that constitutes the gas purge pipe 430.

[0031] In the gas purge pipe 430, the gas inlets 432a and 432b are located on the upper end side (lower extension pipe 20 side) of the gas purge pipe 430. That is, the gas inlets 432a and 432b are located above the center line M shown in the side view of Figure 6. By providing the gas inlets 432a and 432b on the upper end side of the gas purge pipe 430, the distance from the gas inlets 432a and 432b to the fiber outlet 34 can be increased, and the flow of the first gas near the fiber outlet 34 can be stabilized. As a result, the wire deflection of the glass fiber 3 exiting from the fiber outlet 34 can be suppressed.

[0032] Furthermore, the gas inlets 432a and 432b may be located below the center line M, that is, on the lower end side of the gas purge pipe 430 (on the fiber outlet 34 side). By providing the gas inlets 432a and 432b on the lower end side of the gas purge pipe 430 and introducing the first gas into the gas purge pipe 430 from the lower end side, the flow rate of the first gas near the fiber outlet 34 can be increased, and the inclusion of outside air into the gas purge pipe 430 can be suppressed. In addition, while increasing the flow rate of the first gas near the fiber outlet 34, the overall flow rate of the first gas supplied into the gas purge pipe 430 can not be increased or can be reduced, thus suppressing the amount of first gas used. The gas inlets 32a and 32b in the gas purge pipe 30 are located near the center line M, but they may be located on the lower extension pipe 20 side or on the fiber outlet 34 side, similar to the gas purge pipe 430.

[0033] In the gas purging pipe 430, the outer wall 432 forms a single pipe extending along the direction of travel of the glass fiber 3. In the outer wall 432, the gas inlets 432a and 432b are positioned at points symmetrical locations with respect to the position through which the glass fiber 3 passes in the radial direction, and have the same size and shape. The gas purging pipe 430 does not have an inner wall 33. However, because the gas inlets 432a and 432b are point symmetrical, the first gas introduced from the gas inlets 432a and 432b is injected axially symmetrical with respect to the glass fiber 3, with respect to the glass fiber 3 as the axis of symmetry.

[0034] Figures 7 and 8 are schematic diagrams showing modified versions of the gas purge pipe 430 shown in Figure 6. Figure 7 shows a gas purge pipe 530, which is a first modified version of the gas purge pipe 430. In Figure 7, reference numeral 530A indicates a side view of the gas purge pipe 530, and reference numeral 530B indicates a top view of the gas purge pipe 530. The lower part of Figure 7 shows an unfolded view of the outer wall 532 that constitutes the gas purge pipe 530.

[0035] As shown in the figures in Figure 7, baffles 537a and 537b are provided on the gas purge pipe 530 at positions opposite to the gas inlets 532a and 532b, respectively. The baffles 537a and 537b prevent the first gas introduced from the gas inlets 532a and 532b from directly hitting the glass fiber 3. That is, the first gas introduced into the gas purge pipe 530 collides with the baffles 537a and 537b and diffuses inside the gas purge pipe 530. By providing the baffles 537a and 537b, even when the flow rate of the first gas is increased, it is possible to suppress the deterioration of the quality of the glass fiber 3 caused by the first gas hitting the glass fiber 3 too strongly (at a high flow velocity).

[0036] Figure 8 shows a gas purge pipe 630, which is a second modified example of the gas purge pipe 430. In Figure 8, reference numeral 630A indicates a side view of the gas purge pipe 630, and reference numeral 630B indicates a top view of the gas purge pipe 630. The lower part of Figure 8 shows an unfolded view of the outer wall 632 that constitutes the gas purge pipe 630.

[0037] As shown in the top view of Figure 8, the gas purging pipe 630 is provided with pipe connection ports 31a and 31b that do not directly face the position through which the glass fiber 3 passes (the center of the outer wall 632 in the top view of Figure 8). With this configuration, even when the flow rate of the first gas is increased, the deterioration of the quality of the glass fiber 3 caused by the first gas introduced from the gas inlets 632a and 632b hitting the glass fiber 3 strongly (at a high flow velocity) can be suppressed.

[0038] (Manufacturing method for optical fibers) Next, we will describe a method for manufacturing optical fibers according to this embodiment, using the manufacturing apparatus 1 shown in Figure 1. Note that the configuration of the gas purging tube 30 may be one of the examples shown in Figures 3 to 8.

[0039] The method for manufacturing an optical fiber according to this embodiment includes a first step of heating and melting a base material 2 for optical fibers in a heating furnace 10, a second step of passing a glass fiber 3 exiting the heating furnace 10 through a lower extension tube 20, and a third step of passing a glass fiber 3 exiting the lower extension tube 20 through a gas purge tube 30.

[0040] In the first step, the optical fiber base material 2 is suspended inside the furnace tube 12, and the lower part of the optical fiber base material 2 is heated and melted by a heater 13. The molten optical fiber base material 2 is then continuously drawn into glass fibers 3 of a predetermined outer diameter due to the weight and tensile force of the molten glass. In the first step, an inert gas is introduced into the furnace tube 12 from the gas inlet 16. The inert gas can be one of the above-mentioned types. The following describes the case in which helium gas is used as the inert gas.

[0041] Inside the furnace tube 12, impurities such as silica particles formed from silica components volatilized from the optical fiber base material 2, and carbon particles detached from carbon components used in the heating furnace 10 are constantly generated. These impurities are carried to the lower extension tube 20 by the traction flow of an inert gas.

[0042] In the second step, the glass fiber 3 that emerges from the heating furnace 10 (furnace tube 12) passes through the lower extension tube 20. As the glass fiber 3 passes through the lower extension tube 20, the rapid cooling is mitigated and it cools and hardens to some extent, thus suppressing fluctuations in its outer diameter. In the second step, a mixed gas containing helium gas from the lower extension tube 20 and other gases, including impurities generated in the first and second steps, is drawn in through the gas intake port 23. The drawn mixed gas is separated and purified by a gas regeneration device and regenerated as reusable helium gas.

[0043] In the third step, a first gas is injected into the gas purging tube 30 in an axially symmetric manner with respect to the glass fiber 3, with the glass fiber 3 as the axis of symmetry. The first gas can be one of the above-mentioned types. The temperature of the glass fiber 3 exiting from the fiber outlet 34 of the gas purging tube 30 is preferably 1200°C or higher, and more preferably 1300°C or higher. Furthermore, the temperature of the glass fiber 3 exiting from the fiber outlet 34 is preferably 1700°C or lower, and more preferably 1600°C or lower. The temperature of the glass fiber 3 when exiting from the fiber outlet 34 can be controlled, for example, by changing the length of the gas purging tube 30 or by changing the temperature and flow rate of the first gas.

[0044] In the third step, it is preferable to maintain a positive pressure inside the gas purge tube 30. That is, it is preferable to maintain a state in which the pressure inside the gas purge tube 30 is higher than the pressure outside the fiber outlet 34 and inside the lower extension tube 20. Maintaining a positive pressure inside the gas purge tube 30 can be done, for example, by controlling the flow rate of the first gas and the amount of helium gas drawn in. The flow rate of the first gas is not particularly limited, but it is preferably 30 liters / min or more, and more preferably 50 liters / min or more. Also, the flow rate of the first gas is preferably 150 liters / min or less, and more preferably 100 liters / min or less.

[0045] Although the present invention 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 invention. Furthermore, the number, position, shape, etc. of the components described above are not limited to the embodiments described above and can be changed to a number, position, shape, etc. that is suitable for carrying out the present invention. In addition, the elements included in each of the examples described above can be combined with each other. [Explanation of Symbols]

[0046] 1: (Optical fiber) manufacturing equipment 2: Pre-fabricated material for optical fibers 3: Glass fiber 10:Heating furnace 11: Cabinet 12: Core tube 13: Heater 14, 21a, 21b, 35a, 35b: Gas piping 15: Inert gas supply unit 16: (Inert gas) gas inlet 20: Lower extension tube 22: Gas regeneration equipment 23: Gas intake port 30 (30A, 30B), 430 (430A, 430B), 530 (530A, 530B), 630 (630A, 630B): Gas purge pipes 31a, 31b: Pipe connection ports 32,432,532,632: Exterior wall 32a, 32b, 432a, 432b, 532a, 532b, 632a, 632b: Gas inlet 33,133,233,333:Inner wall 33a, 133a, 233a, 333a: Gas nozzles 34: Fiber outlet 36: First gas supply unit

Claims

1. An optical fiber manufacturing apparatus equipped with a drawing furnace that heats and melts an optical fiber base material to draw it into a wire and form a glass fiber, The aforementioned wire drawing furnace is A heating furnace for heating and melting the preform material for optical fibers, A lower extension tube is provided at the lower end of the heating furnace, through which the glass fiber passes; The lower extension pipe is provided with a gas purge pipe that sprays gas axially symmetrically onto the glass fiber from the surrounding area, The gas purging pipe is equipped with a gas inlet and is configured so that the gas introduced from the inlet does not directly come into contact with the glass fiber. Optical fiber manufacturing equipment.

2. The heating furnace is equipped with a gas inlet for introducing a gas containing helium gas into the heating furnace. The lower extension tube is equipped with a gas suction port that draws in the gas containing helium gas inside and discharges it to the outside of the lower extension tube. The optical fiber manufacturing apparatus further comprises a helium regeneration device for regenerating and reusing the gas containing helium gas discharged from the gas intake port. The apparatus for manufacturing optical fibers according to claim 1.

3. A method for manufacturing optical fibers, in which a base material for optical fibers is heated and melted in a drawing furnace and drawn to form a glass fiber, The aforementioned wire drawing furnace is A heating furnace for heating and melting the preform material for optical fibers, A lower extension tube is provided at the lower end of the heating furnace, through which the glass fiber passes; The lower extension pipe is provided with a gas purge pipe, From the gas purging pipe, gas is injected axially symmetrically from the surroundings onto the glass fiber. The line is drawn such that the gas introduced from the gas inlet of the gas purging pipe does not directly come into contact with the glass fiber. A method for manufacturing optical fibers.

4. The method for manufacturing an optical fiber according to claim 3, wherein the temperature of the glass fiber exiting the gas purging tube is 1200°C or higher and 1700°C or lower.

5. A method for manufacturing an optical fiber according to claim 3 or claim 4, wherein the inside of the gas purge tube is kept under positive pressure while drawing the fiber.

6. A method for manufacturing an optical fiber according to any one of claims 3 to 5, wherein the flow rate of the gas ejected from the gas purge pipe is 30 liters / minute or more and 150 liters / minute or less.

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