JP2023147926A - Apparatus and method for manufacturing optical fiber - Google Patents

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

The present disclosure relates to an optical fiber manufacturing apparatus and manufacturing method.

Patent Document 1 discloses an optical fiber drawing furnace in which a lower extension tube (lower chimney) is provided below a furnace tube into which an optical fiber glass preform is inserted. Patent Document 1 also states that the inert gas introduced into the reactor core tube flows into the lower extension tube, and that it is desired to suppress the use of inert gas in order to reduce manufacturing costs. It is stated that

JP2013-203622A

In the optical fiber drawing furnace described in Patent Document 1, air may enter the lower extension tube from the fiber outlet at the lower end of the lower extension tube. In particular, if the pressure inside the lower extension tube becomes more negative than that outside by reducing the amount of inert gas introduced into the reactor core tube, air tends to enter the lower extension tube from the fiber outlet. If particles or moisture contained in the atmosphere that has entered the lower extension tube adhere to the glass fiber, this will cause a decrease in the strength of the resulting optical fiber.

An object of the present disclosure is to suppress the intrusion of air from the lower extension tube in an optical fiber drawing furnace, and to suppress a decrease in the strength of the obtained optical fiber.

An optical fiber manufacturing apparatus according to one 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 and draws it to form a glass fiber, the apparatus comprising:
The drawing furnace is
A heating furnace that heats and melts an optical fiber base material;
a lower extension tube provided at the lower end of the heating furnace, through which the glass fiber passes;
A gas purge tube is provided at the lower end of the lower extension tube and injects gas axially symmetrically from the periphery to the glass fiber.

A method for manufacturing an optical fiber according to one aspect of the present disclosure includes:
A method for producing an optical fiber, the method comprising: heating and melting an optical fiber base material in a drawing furnace to form a glass fiber;
The drawing furnace is
A heating furnace that heats and melts an optical fiber base material;
a lower extension tube provided at the lower end of the heating furnace, through which the glass fiber passes;
a gas purge pipe provided at the lower end of the lower extension pipe,
Gas is injected from the gas purge tube axially symmetrically around the glass fiber to draw it.

According to the configuration disclosed above, it is possible to suppress the intrusion of air from the lower extension tube in the optical fiber drawing furnace, and to suppress a decrease in the strength of the obtained optical fiber.

1 is a schematic configuration diagram of an optical fiber manufacturing apparatus according to an embodiment of the present disclosure. 2 is a schematic diagram showing the structure of the gas purge pipe shown in FIG. 1. FIG. FIG. 3 is a schematic diagram showing a first modification of the inner wall of the gas purge pipe shown in FIG. 2. FIG. FIG. 3 is a schematic diagram showing a second modification of the inner wall of the gas purge pipe shown in FIG. 2. FIG. FIG. 3 is a schematic diagram showing a third modification of the inner wall of the gas purge pipe shown in FIG. 2. FIG. 3 is a schematic diagram showing another example of the gas purge pipe shown in FIG. 2. FIG. 7 is a schematic diagram showing a first modification of the gas purge pipe shown in FIG. 6. FIG. 7 is a schematic diagram showing a second modification of the gas purge pipe shown in FIG. 6. FIG.

[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 includes:
An optical fiber manufacturing apparatus equipped with a drawing furnace that heats and melts an optical fiber base material and draws it to form a glass fiber, the apparatus comprising:
The drawing furnace is
A heating furnace that heats and melts an optical fiber base material;
a lower extension tube provided at the lower end of the heating furnace, through which the glass fiber passes;
A gas purge tube is provided at the lower end of the lower extension tube and injects gas axially symmetrically from the periphery to the glass fiber.
According to this configuration, it is possible to suppress the intrusion of air from the lower extension tube in the optical fiber drawing furnace, and to suppress a decrease in the strength of the obtained optical fiber.

In the optical fiber manufacturing apparatus,
The heating furnace includes a gas inlet for introducing a gas containing helium gas into the heating furnace,
The lower extension tube includes a gas suction port that sucks gas containing helium gas inside and discharges it to the outside of the lower extension tube,
Preferably, the optical fiber manufacturing apparatus further includes a helium regeneration device that regenerates and reuses gas containing helium gas discharged from the gas suction port.
When helium gas is sucked from the lower extension tube, the pressure inside the lower extension tube decreases, making it easier for air to enter the lower extension tube. However, according to the above configuration, a gas purge pipe is provided at the lower end of the lower extension pipe and gas is injected into the gas purge pipe, so while it is possible to reuse expensive helium gas, atmospheric air is not allowed to enter the lower extension pipe. This makes it possible to suppress contamination.

A method for manufacturing an optical fiber according to one aspect of the present disclosure includes:
A method for producing an optical fiber, the method comprising: heating and melting an optical fiber base material in a drawing furnace to form a glass fiber;
The drawing furnace is
A heating furnace that heats and melts an optical fiber base material;
a lower extension tube provided at the lower end of the heating furnace, through which the glass fiber passes;
a gas purge pipe provided at the lower end of the lower extension pipe,
Gas is injected from the gas purge tube axially symmetrically around the glass fiber to draw it.
According to this configuration, it is possible to suppress the intrusion of air from the lower extension tube in the optical fiber drawing furnace, and to suppress a decrease in the strength of the obtained optical fiber.

The method for manufacturing the optical fiber includes:
It is preferable that the temperature of the glass fiber coming out from the gas purge tube is 1200°C or more and 1700°C or less.
By keeping the temperature of the glass fiber coming out from the gas purge tube below 1700°C, the reaction between the glass fiber and moisture in the atmosphere is promoted, and the surface of the glass fiber due to collision with dust in the atmosphere is prevented. The generation of defects can be suppressed. Further, by setting the output temperature of the glass fiber to 1200° C. or higher, it is possible to suppress a situation in which the glass fiber is rapidly cooled before being output from the gas purge pipe and the outer diameter fluctuates. As a result, a decrease in the strength of the optical fiber can be further suppressed.

The method for manufacturing the optical fiber includes:
It is preferable to draw the wire while maintaining the inside of the gas purge tube at a positive pressure.
According to this configuration, by making the pressure inside the gas purge pipe positive with respect to the atmospheric pressure outside the gas purge pipe and the internal pressure inside the lower extension pipe, it is possible to further suppress air and impurities from entering the gas purge pipe. Can be done.

The method for manufacturing the optical fiber includes:
It is preferable that the flow rate of the gas ejected from the gas purge pipe is 30 liters/minute or more and 150 liters/minute or less.
By setting the flow rate of the gas ejected from the gas purge pipe to 30 liters/minute or more, it becomes easier to suppress air from entering the gas purge pipe. Further, by setting the flow rate of the gas ejected from the gas purge tube to 150 liters/min or less, it is possible to suppress the quality deterioration of the glass fiber due to the ejected gas hitting the glass fiber strongly (at a high flow rate).

[Details of embodiments of the present disclosure]
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an optical fiber manufacturing apparatus and manufacturing method according to the present disclosure will be described with reference to the drawings. In the following description, the same or equivalent elements will be given the same reference numerals or names even in different drawings, and overlapping description will be omitted as appropriate. Further, the dimensions of each member shown in each drawing are for convenience of explanation, and may differ from the actual dimensions of each member.

(Optical fiber manufacturing equipment)
FIG. 1 is a schematic configuration diagram of an optical fiber manufacturing apparatus 1 according to an embodiment of the present disclosure. The manufacturing apparatus 1 includes a drawing furnace 100. The drawing furnace 100 is a device that heats and melts the optical fiber preform 2 and draws it to form the glass fiber 3. Although not shown, the manufacturing apparatus 1 further includes a cooling device that cools the glass fiber 3, a coating device that applies coating resin to the outer periphery of the glass fiber 3, and a winding device that winds up the glass fiber 3 coated with the coating resin. etc. may also be provided.

The drawing furnace 100 includes 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 includes 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 arranged to surround the furnace core tube 12. A heat insulating material (not shown) is arranged between the heater 13 and the housing 11. An optical fiber preform 2 is suspended within the furnace tube 12 by a preform suspension mechanism (not shown). The lower part of the suspended optical fiber preform 2 is melted by heat from the heater 13, and the glass fiber 3 having a predetermined outer diameter is continuously drawn.

The furnace core tube 12 includes a gas inlet 16 . One end of the gas pipe 14 is connected to the gas inlet 16 . The other end of the gas pipe 14 is connected to an inert gas supply device 15 that supplies an inert gas such as argon gas, helium gas, nitrogen gas, or the like. The inert gas supplied from the inert gas supply device 15 passes through the gas pipe 14 and is supplied into the reactor core tube 12 from the gas inlet 16. The inert gas supplied into the furnace core tube 12 flows into the lower extension tube 20.

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 the inlet of the lower extension tube 20 and the outlet of the furnace core tube 12 are connected, and is preferably provided, for example, 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 may be provided in a detachable manner with respect to the heating furnace 10. The glass fiber 3 drawn in the furnace core tube 12 continuously passes through the lower extension tube 20 . By providing the lower extension tube 20, while suppressing rapid cooling of the heated and softened glass fiber 3, it is possible to cool and harden it to some extent, thereby suppressing fluctuations in the outer diameter of the glass fiber 3.

The lower extension tube 20 includes a gas suction port 23 . The gas suction port 23 sucks a mixed gas containing an inert gas supplied into the core tube 12 and flowing into the lower extension tube 20 and other gas containing impurities generated during the drawing process. , are provided for discharging to the outside of the lower extension pipe 20. In the example of FIG. 1, two gas suction ports 23 are provided. One end of the gas pipe 21a is connected to one gas suction port 23. One end of the gas pipe 21b is connected to the other gas suction port 23. Although a part of the gas pipe 21b is omitted from illustration, a gas regeneration device 22 is connected to the other ends of the gas pipes 21a and 21b. The gas regeneration device 22 separates and purifies an inert gas (for example, helium gas) from the mixed gas sucked through 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 via piping (not shown), and the inert gas regenerated by the gas regeneration device 22 may be supplied to the inert gas supply device 15. .

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 is preferably provided, for example, in close contact with the lower extension pipe 20. The gas purge pipe 30 may be formed integrally with the lower extension pipe 20 or may be provided in a detachable manner with respect to the lower extension pipe 20. When the gas purge pipe 30 is made detachable from the lower extension pipe 20, the gas purge pipe 30 may have a half-split structure, for example. The material of the gas purge pipe 30 is not particularly limited, and is, for example, a metal such as SUS (Steel Use Stainless).

The glass fiber 3 coming out from the lower extension tube 20 continuously passes through the gas purge tube 30 . Further, the glass fiber 3 exits from the fiber outlet 34 at the lower end of the gas purge pipe 30. In the example of FIG. 1, the gas purge pipe 30 includes pipe connection ports 31a and 31b, an outer wall 32, and an inner wall 33. One ends of gas pipes 35a and 35b are connected to one ends of pipe connection ports 31a and 31b, respectively. Although a part of the gas pipe 35b is not shown, a first gas supply device 36 is connected to the other ends of the gas pipes 35a and 35b. The first gas supply device 36 supplies the first gas. It is preferable that the first gas is, for example, the above-mentioned inert gas, and from the viewpoint of cost reduction, it is more preferable to use nitrogen gas. Further, the first gas may be dry air having a dew point temperature of 10° C. or lower. By using such dry air, a decrease in strength due to moisture adhering to the glass fiber 3 can be suppressed. The first gas supplied from the first gas supply device 36 passes through gas pipes 35a and 35b and is supplied into the gas purge pipe 30 from gas inlets 32a and 32b provided in the outer wall 32.

Hereinafter, the gas purge pipe 30 will be explained in detail using FIG. 2. FIG. 2 is a schematic diagram showing the structure of the gas purge pipe 30 shown in FIG. 1. Reference numeral 30A in FIG. 2 shows a side view of the gas purge pipe 30, and reference numeral 30B shows a top view of the gas purge pipe 30. As shown in these figures, the piping connection ports 31a and 31b are connected to gas introduction 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 tube structure. Specifically, the outer wall 32 and the inner wall 33 each form a tube extending along the traveling direction of the glass fiber 3. Furthermore, there is a cavity between the outer wall 32 and the inner wall 33.

In the lower part of FIG. 2, a developed view of the inner wall 33 is shown. As shown in this developed 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 symmetrical with respect to the position where the glass fiber 3 passes in the radial direction. It is preferable that the plurality of gas injection ports 33a have the same size and shape, but it is sufficient if the two gas injection ports 33a having point symmetry have the same size and shape. In the example of FIG. 2, the plurality of gas injection ports 33a are all circular holes and have the same size.

In the developed view of the inner wall 33 shown in FIG. 2, the positions of the outer wall 32 corresponding to the gas introduction ports 32a and 32b are indicated by broken lines. The first gas introduced into the outer wall 32 from the gas introduction ports 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, etc., and a plurality of gas injection ports having point symmetry are formed. It is injected into the inside of the inner wall 33 from 33a. As a result, within the inner wall 33, the first gas is injected from the periphery to be axially symmetrical with respect to the glass fiber 3 with the glass fiber 3 as the symmetrical axis.

Furthermore, as in the example of FIG. 2, the first gas introduced from the gas introduction ports 32a and 32b is not directly applied to the glass fiber 3, but is configured to be injected from a plurality of gas injection ports 33a. Even if the flow rate of the first gas is increased, the flow velocity of the first gas injected from the gas injection port 33a can be suppressed from increasing. As a result, even when the flow rate of the first gas is increased, it is possible to suppress quality deterioration of the glass fiber 3 due to the first gas hitting the glass fiber 3 strongly (at a high flow rate).

In the example of FIG. 2, the gas introduction ports 32a and 32b are also provided at positions that are symmetrical with respect to the position where the glass fiber 3 passes in the radial direction, and have the same size and shape. However, the configuration is not limited to these. As long as the first gas can be injected within the inner wall 33 so as to be axially symmetrical around the glass fiber 3, the positions, shapes, and sizes of the gas introduction ports 32a and 32b can be changed as appropriate.

Similarly, if the first gas can be injected within the inner wall 33 so as to be axially symmetrical from the circumference to the glass fiber 3, the positions, shapes, and sizes of the plurality of gas injection ports 33a can be changed as appropriate. Can be done. 3 to 5 are schematic diagrams showing modifications of the inner wall 33 of the gas purge pipe 30 shown in FIG. 2. FIG. 3 shows a developed view of the inner wall 133, which is a first modified example of the inner wall 33. As shown in FIG. In the inner wall 133, the plurality of gas injection ports 133a having point symmetry are rectangular holes having long sides in the circumferential direction. FIG. 4 shows a developed view of an inner wall 233, which is a second modified example of the inner wall 33. In the inner wall 233, the plurality of gas injection ports 233a having point symmetry are rectangular holes having long sides in the axial direction of the glass fiber 3. FIG. 5 shows a developed view of an inner wall 333 that is a third modified example of the inner wall 33. As shown in FIG. In the inner wall 333, the plurality of gas injection ports 333a having point symmetry are square holes.

Next, another example of the gas purge pipe 30 shown in FIG. 2 will be described using FIG. 6. Reference numeral 430A in FIG. 6 indicates a side view of the gas purge pipe 430, and reference numeral 430B indicates a top view of the gas purge pipe 430. A developed view of the outer wall 432 constituting the gas purge pipe 430 is shown at the bottom of FIG. 6 .

In the gas purge pipe 430, the gas introduction ports 432a and 432b are provided on the upper end side (lower extension pipe 20 side) of the gas purge pipe 430. That is, the gas introduction ports 432a and 432b are provided above the center line M shown in the side view of FIG. By providing the gas inlet ports 432a and 432b on the upper end side of the gas purge pipe 430, the distance from the gas inlet ports 432a and 432b to the fiber outlet port 34 can be increased, and the first gas near the fiber outlet port 34 can be The flow can be stabilized. As a result, wire wobbling of the glass fiber 3 coming out from the fiber outlet 34 can be suppressed.

Moreover, the positions of the gas inlet ports 432a and 432b may be provided below the center line M, that is, on the lower end side of the gas purge tube 430 (on the fiber outlet 34 side). By providing gas inlet ports 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 of the gas purge pipe 430, the first gas in the vicinity of the fiber outlet 34 is reduced. The flow rate can be increased, and atmospheric air outside the fiber outlet 34 can be prevented from being drawn into the gas purge pipe 430. Furthermore, while increasing the flow rate of the first gas in the vicinity of the fiber outlet 34, the overall flow rate of the first gas supplied into the gas purge pipe 430 can be reduced or not increased, so the usage amount of the first gas can be reduced. Can be suppressed. Note that the positions of the gas inlets 32a and 32b in the gas purge pipe 30 correspond to the vicinity of the center line M, but like the gas purge pipe 430, they may be provided on the lower extension pipe 20 side, or on the fiber outlet 34 side. may be provided.

In the gas purge tube 430, the outer wall 432 forms one tube extending along the traveling direction of the glass fiber 3. In the outer wall 432, the gas introduction ports 432a and 432b are provided at positions symmetrical about the position where the glass fiber 3 passes in the radial direction, and have the same size and shape. Gas purge pipe 430 does not have inner wall 33. However, since the gas introduction ports 432a and 432b have point symmetry, the first gas introduced from the gas introduction ports 432a and 432b becomes axially symmetrical from the surroundings to the glass fiber 3 with the glass fiber 3 as the symmetrical axis. It will be sprayed like this.

7 and 8 are schematic diagrams showing modifications of the gas purge pipe 430 shown in FIG. 6. FIG. 7 shows a gas purge pipe 530 that is a first modification of the gas purge pipe 430. Reference numeral 530A in FIG. 7 indicates a side view of the gas purge pipe 530, and reference numeral 530B indicates a top view of the gas purge pipe 530. A developed view of the outer wall 532 constituting the gas purge pipe 530 is shown at the bottom of FIG. 7 .

As shown in each figure in FIG. 7, the gas purge pipe 530 is provided with baffle plates 537a and 537b at positions facing the gas introduction ports 532a and 532b, respectively. The baffle plates 537a and 537b prevent the first gas introduced from the gas introduction ports 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 baffle plates 537a and 537b and is diffused into the gas purge pipe 530. By providing the baffle plates 537a and 537b, even when the flow rate of the first gas is increased, it is possible to suppress quality deterioration of the glass fiber 3 due to the first gas strongly hitting the glass fiber 3 (at a high flow rate).

FIG. 8 shows a gas purge pipe 630 that is a second modification of the gas purge pipe 430. Reference numeral 630A in FIG. 8 indicates a side view of the gas purge pipe 630, and reference numeral 630B indicates a top view of the gas purge pipe 630. A developed view of the outer wall 632 constituting the gas purge pipe 630 is shown at the bottom of FIG. 8 .

As shown in the top view of FIG. 8, in the gas purge pipe 630, the pipe connection ports 31a and 31b are provided so as not to directly face the position through which the glass fiber 3 passes (the center of the outer wall 632 in the top view of FIG. 8). ing. With this configuration, even when the flow rate of the first gas is increased, the first gas introduced from the gas inlet ports 632a and 632b strongly hits the glass fiber 3 (at a high flow rate), thereby preventing damage to the glass fiber 3. Quality deterioration can be suppressed.

(Optical fiber manufacturing method)
Subsequently, as a method for manufacturing an optical fiber according to this embodiment, a method for manufacturing an optical fiber using the manufacturing apparatus 1 shown in FIG. 1 will be described. Note that the configuration of the gas purge pipe 30 may adopt the configurations of the examples shown in FIGS. 3 to 8.

The method for manufacturing an optical fiber according to the present embodiment includes a first step of heating and melting an optical fiber preform 2 in a heating furnace 10, and a step of passing a glass fiber 3 exiting from the heating furnace 10 through a lower extension tube 20. The method includes two steps, and a third step in which the glass fiber 3 coming out of the lower extension tube 20 is made to pass through the gas purge tube 30.

In the first step, the optical fiber preform 2 is suspended in the furnace core tube 12, and the lower part of the optical fiber preform 2 is heated and melted by the heater 13. The molten optical fiber preform 2 is continuously drawn into a glass fiber 3 having a predetermined outer diameter by the weight and tensile force of the molten glass. Furthermore, in the first step, an inert gas is introduced into the reactor core tube 12 from the gas introduction port 16 . As the inert gas, those mentioned above can be used. In the following, a case will be described in which helium gas is used as the inert gas.

In the furnace core tube 12, for example, silica particles formed from silica components volatilized from the optical fiber base material 2, carbon particles peeled off from carbon parts used in the heating furnace 10, etc. are constantly generated. These impurities are carried into the lower extension tube 20 by the towed flow of inert gas.

In the second step, the glass fiber 3 exiting from the heating furnace 10 (furnace core tube 12) passes through the lower extension tube 20. By passing through the lower extension tube 20, the glass fiber 3 is not rapidly cooled, and is cooled and hardened to some extent, so that fluctuations in outer diameter are suppressed. Further, in the second step, a mixed gas containing helium gas in the lower extension tube 20 and other gas containing impurities generated in the first step and the second step is sucked from the gas suction port 23. The sucked mixed gas is separated and purified by a gas regeneration device, thereby being regenerated as reusable helium gas.

In the third step, the first gas is injected into the gas purge tube 30 so as to be axially symmetrical with respect to the glass fiber 3 from the periphery with the glass fiber 3 as the symmetrical axis. As the first gas, those mentioned above can be used. The temperature of the glass fiber 3 exiting from the fiber outlet 34 of the gas purge tube 30 is preferably 1200°C or higher, more preferably 1300°C or higher. Further, the temperature of the glass fiber 3 exiting from the fiber outlet 34 is preferably 1700°C or lower, more preferably 1600°C or lower. The temperature of the glass fiber 3 when it exits from the fiber outlet 34 can be controlled by, for example, changing the length of the gas purge tube 30 or changing the temperature, flow rate, etc. of the first gas.

In the third step, it is preferable to maintain a positive pressure inside the gas purge pipe 30. That is, it is preferable to maintain a higher pressure inside the gas purge tube 30 than outside the fiber outlet 34 and inside the lower extension tube 20. Maintaining the positive pressure inside the gas purge pipe 30 is possible, for example, by controlling the flow rate of the first gas, the suction amount of helium gas, and the like. Although the flow rate of the first gas is not particularly limited, it is preferably 30 liters/minute or more, and more preferably 50 liters/minute or more, for example. Further, the flow rate of the first gas is preferably, for example, 150 liters/minute or less, and more preferably 100 liters/minute or less.

Although the 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. Further, the number, position, shape, etc. of the constituent members explained above are not limited to the above embodiment, and can be changed to a suitable number, position, shape, etc. for implementing the present invention. Moreover, the elements included in each of the examples described above can be combined with each other.

1: Manufacturing equipment (of optical fiber) 2: Optical fiber base material 3: Glass fiber 10: Heating furnace 11: Housing 12: Furnace tube 13: Heater 14, 21a, 21b, 35a, 35b: Gas piping 15: Non-heating Active gas supply device 16: Gas inlet (for inert gas) 20: Lower extension pipe 22: Gas regenerator 23: Gas suction port 30 (30A, 30B), 430 (430A, 430B), 530 (530A, 530B) , 630 (630A, 630B): Gas purge pipe 31a, 31b: Piping connection port 32, 432, 532, 632: Outer wall 32a, 32b, 432a, 432b, 532a, 532b, 632a, 632b: Gas inlet port 33, 133, 233 , 333: Inner wall 33a, 133a, 233a, 333a: Gas injection port 34: Fiber outlet 36: First gas supply device

Claims (6)

An optical fiber manufacturing apparatus equipped with a drawing furnace that heats and melts an optical fiber base material and draws it to form a glass fiber, the apparatus comprising:
The drawing furnace is
A heating furnace that heats and melts an optical fiber base material;
a lower extension tube provided at the lower end of the heating furnace, through which the glass fiber passes;
a gas purge tube provided at the lower end of the lower extension tube and injecting gas axially symmetrically from the periphery to the glass fiber;
Optical fiber manufacturing equipment. The heating furnace includes a gas inlet for introducing a gas containing helium gas into the heating furnace,
The lower extension tube includes a gas suction port that sucks gas containing helium gas inside and discharges it to the outside of the lower extension tube,
The optical fiber manufacturing apparatus further includes a helium regeneration device that regenerates and reuses gas containing helium gas discharged from the gas suction port.
The optical fiber manufacturing apparatus according to claim 1. A method for producing an optical fiber, the method comprising: heating and melting an optical fiber base material in a drawing furnace to form a glass fiber;
The drawing furnace is
A heating furnace that heats and melts an optical fiber base material;
a lower extension tube provided at the lower end of the heating furnace, through which the glass fiber passes;
a gas purge pipe provided at the lower end of the lower extension pipe,
Injecting gas from the gas purge tube axially symmetrically around the glass fiber to draw it;
Method of manufacturing optical fiber. The method for manufacturing an optical fiber according to claim 3, wherein the temperature of the glass fiber coming out from the gas purge tube is 1200°C or more and 1700°C or less. 5. The method for manufacturing an optical fiber according to claim 3, wherein the drawing is performed while maintaining the inside of the gas purge tube at a positive pressure. The 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 tube is 30 liters/minute or more and 150 liters/minute or less.

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