JP7632309B2 - Optical fiber manufacturing method and optical fiber manufacturing apparatus - Google Patents

Description

The present disclosure relates to a method and an apparatus for manufacturing an optical fiber.
This application claims priority based on Japanese Patent Application No. 2019-232834 filed on December 24, 2019, and incorporates all of the contents of the above application by reference.

Patent documents 1 and 2 disclose a technique of providing a slow-cooling heating furnace between a wire drawing furnace and a cooling device.

When starting to draw an optical fiber, a tip-drawing process is first performed. Patent Document 3 discloses that in this tip-drawing process, the tip of the optical fiber preform is heated and melted, and the molten glass lump (also called a drop seed) is dropped.

Japanese Patent Application Publication No. 2010-168247 Japanese Patent Application Publication No. 2000-335934 Japanese Patent Application Publication No. 2008-120643

A method for producing an optical fiber according to one aspect of the present disclosure includes the steps of:
A method for manufacturing an optical fiber by an optical fiber manufacturing apparatus including a drawing furnace for heating an optical fiber preform, a lower chamber and a protective tube provided below the drawing furnace for protecting a glass fiber drawn from the optical fiber preform from outside air, and a slow-cooling furnace located below the protective tube for controlling the drawn glass fiber to a predetermined temperature, comprising:
a step of drawing a lump of a molten portion dropping from the tip of the optical fiber preform before the start of drawing, and a step of drawing a glass fiber having a predetermined diameter after the end of the step of drawing,
The lead-out step comprises:
moving only the protective tube in a direction intersecting a drawing direction of the glass fiber without retracting the annealing furnace ;
a step of disposing a receiver for receiving the descending mass of the molten portion in a space generated between the drawing furnace and the slow cooling heating furnace by the movement of the protective tube;
receiving the falling mass of molten portion after the step of placing the receiver;
a step of removing the receiver from below the wire drawing furnace after the step of receiving the descending molten portion ;
a step of returning the protective tube to below the wire drawing furnace after the step of retracting the receiving tool ;
Includes.
An optical fiber manufacturing apparatus according to one aspect of the present disclosure includes:
An optical fiber manufacturing apparatus comprising: a drawing furnace for heating an optical fiber preform; a lower chamber and a protective tube provided below the drawing furnace for protecting a glass fiber drawn from the optical fiber preform from outside air; and a slow-cooling furnace located below the protective tube for controlling the glass fiber drawn in the drawing furnace to a predetermined temperature,
the protective tube is movable in a direction intersecting a drawing direction of the glass fiber,
A receiver for receiving the mass of the molten portion dropping from the tip of the optical fiber preform is placed on the annealing furnace with the protective tube moved from above the annealing furnace .

FIG. 1 is a schematic diagram of an apparatus for manufacturing optical fiber according to one aspect of the present disclosure. FIG. 2 is a diagram illustrating the protective tube according to the first embodiment. FIG. 3A is a diagram illustrating the lead-out step according to the first embodiment. FIG. 3B is a diagram illustrating the lead-out step according to the first embodiment. FIG. 3C is a diagram illustrating the lead-out step according to the first embodiment. FIG. 4 is a diagram illustrating a protective tube according to the second embodiment. FIG. 5A is a diagram illustrating the lead-out step according to the second embodiment. FIG. 5B is a diagram illustrating the lead-out step according to the second embodiment. FIG. 5C is a diagram illustrating the lead-out step according to the second embodiment.

[Problem to be solved by this disclosure]
The dropping seeds must be allowed to fall under their own weight without coming into contact with any equipment. On the other hand, since the dropping seeds usually have a diameter of φ15 mm or more, they cannot pass through the resin coating device (die), and so they must be received at least before the coating device and narrowed down to a size that allows them to pass through the coating device.
One method for dropping the seed to a position above the coating device is to make the diameter of the core tube of the annealing furnace larger than that of the seed, pass the seed through the core tube, and receive the seed above the coating device. However, in this case, it is necessary to widen the openings at both ends of the core tube, which makes it easier for radiant heat to dissipate outside the furnace, and also increases the distance between the core tube and the fiber, which reduces the efficiency of heat transfer and increases the power consumption of the annealing furnace.

Another method is to retract the annealing furnace from the line where the seeds fall. In this case, it is not necessary to increase the diameter of the annealing furnace core tube. However, in order to retract the annealing furnace, which is larger than the protective tube provided as an accessory to the drawing furnace, a large retraction mechanism is required, and space is required to accommodate this large retraction mechanism. In addition, providing this mechanism increases equipment costs, which increases the manufacturing costs of optical fiber.
As an alternative method, a work space for the spouting operation may be provided between the lower chamber and protective tube provided below the drawing furnace and the annealing furnace, and the dropped seeds may be received above the annealing furnace; however, taking into consideration the height limit of the drawing tower, it is difficult to provide such a work space.

The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide an optical fiber manufacturing method and optical fiber manufacturing apparatus that can perform the lead-out work while suppressing increases in costs.

[Effects of the present disclosure]
According to the present disclosure, it is possible to carry out lead-out work while suppressing increases in costs.

[Description of the embodiments of the present disclosure]
First, the contents of the embodiments of the present disclosure will be listed and described.
The method for manufacturing an optical fiber according to the present disclosure is (1) a method for manufacturing an optical fiber by an optical fiber manufacturing apparatus including a drawing furnace for heating an optical fiber preform, a lower chamber and a protective tube provided below the drawing furnace for protecting a glass fiber drawn from the optical fiber preform from outside air, and a slow-cooling furnace located below the protective tube for controlling the drawn glass fiber to a predetermined temperature, the method including a tip-drawing step of drawing a lump of a molten portion dropping from a tip of the optical fiber preform before starting drawing, and a step of drawing a glass fiber having a predetermined diameter after the tip-drawing step is completed. The outlet process includes the steps of: moving only the protective tube in a direction intersecting the drawing direction of the glass fiber , without retracting the annealing furnace ; arranging a receiving tool to receive the descending mass of molten portion in a space generated between the annealing furnace and the annealing furnace by the movement of the protective tube ; receiving the descending mass of molten portion after the receiving tool placing step; retracting the receiving tool from below the annealing furnace after the receiving process of the descending mass of molten portion ; and returning the protective tube to below the annealing furnace after the receiving tool retracting step.
According to the above-mentioned method for manufacturing an optical fiber, the lump of the molten portion that falls from the tip of the optical fiber preform can be received by a receiver installed above the annealing furnace without passing it through the annealing furnace. Therefore, it is not necessary to make the core tube of the annealing furnace larger than the size of the lump of the molten portion. This makes it possible to avoid an increase in the power consumption of the annealing furnace and an increase in the manufacturing cost of the optical fiber. In addition, since a protective tube smaller than the annealing furnace is moved to ensure space for the tapping operation, it is not necessary to retract the annealing furnace from the line where the lump of the molten portion falls. Therefore, a large retraction mechanism is not required.

(2) In one aspect of the method for producing an optical fiber according to the present disclosure, the protective tube has a structure in which two halves are butted together to form a cylindrical shape.
By making the protective tube into a half-split structure, the mass of molten portion that drops from the tip of the optical fiber preform can easily pass through the protective tube, and the optical fiber after being exposed can easily be passed through the protective tube.

(3) In one aspect of the optical fiber manufacturing method disclosed herein, the optical fiber manufacturing apparatus further has a moving mechanism that moves the protective tube from below the drawing furnace, and uses the moving mechanism to perform a step of moving the protective tube and a step of returning the protective tube.
The moving mechanism for moving the protective tube can be made smaller than the retracting mechanism for retracting the annealing furnace, and can therefore be easily installed in a limited space.

(4) An optical fiber manufacturing apparatus according to the present disclosure is an optical fiber manufacturing apparatus including a drawing furnace for heating an optical fiber preform, a lower chamber and a protective tube disposed below the drawing furnace for protecting a glass fiber drawn from the optical fiber preform from outside air, and an annealing furnace located below the protective tube for controlling the glass fiber drawn in the drawing furnace to a predetermined temperature, wherein the protective tube is movable in a direction intersecting the drawing direction of the glass fiber, and a receiving device for receiving a lump of molten portion descending from the tip of the optical fiber preform is placed on the annealing furnace with the protective tube moved from above the annealing furnace .
According to the manufacturing device as described above, the lump of the molten part that has dropped from the tip of the optical fiber preform can be received by a receiver placed in the space above the annealing furnace, which is created by the movement of the protective tube. Therefore, it is possible to avoid an increase in the power consumption of the annealing furnace. In addition, a large-scale retraction mechanism is not required.

[Details of the embodiment 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 accompanying drawings. Fig. 1 is a schematic diagram of an optical fiber manufacturing apparatus according to one embodiment of the present disclosure.
As shown in FIG. 1, an optical fiber manufacturing apparatus 10 includes a drawing furnace 11 for heating and softening an optical fiber preform G at its most upstream position.

The drawing furnace 11 has a cylindrical furnace tube 12 into whose inside an optical fiber preform G is supplied, a heating element 13 surrounding the furnace tube 12, and a gas supply unit 14 for supplying, for example, argon gas into the furnace tube 12. The atmosphere inside the furnace is set to an atmosphere of Ar, He, _N2 , or a mixed gas thereof by the gas supply unit 14. The drawing furnace 11 may be a resistance furnace or an induction furnace.
An upper portion of the optical fiber preform G is held by a preform feeding unit F, and the optical fiber preform G is fed into the furnace tube 12 by the preform feeding unit F. When a lower end portion of the optical fiber preform G is heated by a heating element 13 and drawn downward, a glass fiber G1, which is a component of the optical fiber G2, is formed.

A lower chamber 11a is installed at the lower end of the drawing furnace 11. The lower chamber 11a can protect the glass fiber G1 drawn from the optical fiber preform G from the outside air. The optical fiber manufacturing apparatus 10 also includes a slow-cooling furnace 15 downstream of the lower chamber 11a. The glass fiber G1 drawn from the optical fiber preform G is controlled to a predetermined temperature in the slow-cooling furnace 15 (also called slow-cooling process). Note that a forced cooling device to which a cooling gas such as helium gas is supplied may be provided downstream of the slow-cooling furnace 15 to force-cool the glass fiber G1.

The optical fiber manufacturing apparatus 10 includes an outer diameter measuring unit 16 downstream of the annealing furnace 15. The outer diameter measuring unit 16 is configured to measure the outer diameter of the glass fiber G1 using, for example, laser light, and the glass fiber G1 cooled to a predetermined temperature in the annealing furnace 15 is sent downward after its outer diameter is measured by the outer diameter measuring unit 16. Note that the outer diameter measuring unit 16 may measure the outer diameter of the glass fiber G1 using a measurement method other than laser light as long as it can measure the outer diameter of the glass fiber G1 in a non-contact manner.

The optical fiber manufacturing apparatus 10 is equipped with a UV resin applicator 17a and a UV curing furnace 17b downstream of the outer diameter measurement unit 16. The glass fiber G1, whose outer diameter has been measured, is coated with, for example, a UV-curable resin, urethane acrylate resin, by the UV resin applicator 17a, and the urethane acrylate resin is cured by irradiation with ultraviolet light in the UV curing furnace 17b. As a result, the glass fiber G1 becomes an optical fiber G2 with a resin layer formed around it.

The optical fiber production apparatus 10 includes a direct below roller 18 and a guide roller 19 downstream of the UV curing furnace 17b. The direct below roller 18 is disposed directly below the drawing furnace 11, and changes the running direction of the optical fiber G2 from the vertical direction to, for example, the horizontal direction.
The optical fiber G2, whose running direction has been changed by the immediately below roller 18, is then changed by the guide roller 19 from the horizontal direction to, for example, an obliquely upward direction.

The optical fiber manufacturing apparatus 10 further includes a take-up device 20, a guide roller 21, a dancer roller 22, and a winding device 23 downstream of the guide roller 19. The optical fiber G2 is taken up at a predetermined speed by the capstan of the take-up device 20, and wound onto a bobbin B of the winding device 23 via the dancer roller 22. The process of taking up the optical fiber G2 by the take-up device 20 and winding it onto the winding device 23 in this manner is referred to as the drawing process.

On the other hand, before the start of drawing the optical fiber, a drawing process is performed. In this drawing process, the tip of the optical fiber preform G is heated and melted. The molten glass lump (dropping seed L (see FIG. 3A) described later) falls from the tip of the optical fiber preform G under its own weight. When the dropping seed L is removed, glass (also called rod-shaped glass) with a diameter larger than the optical fiber diameter is drawn from the tip of the optical fiber preform G. When this rod-shaped glass is further pulled and cut, the rod-shaped glass becomes fibrous. Next, the diameter of this rod-shaped glass is thinned to about 150 μm, for example, and then the rod-shaped glass is passed through the UV resin coating device 17a, where it is drawn through the subsequent pass line. After that, the speed (linear speed) of drawing from the optical fiber preform G is adjusted so that the diameter of the glass fiber G1 drawn through the pass line is, for example, 125 μm.

Here, as described above, the lower chamber 11a is installed at the lower end of the drawing furnace 11, and the glass fiber G1 drawn from the optical fiber preform G can be protected from the outside air. In this disclosure, for example, half-split protective tubes 30A and 30B that are butted together to form a cylindrical shape are arranged between the lower chamber 11a and the slow-cooling heating furnace 15. The half-split protective tubes 30A and 30B correspond to the protective tubes of this disclosure. The protective tubes also protect the glass fiber G1 drawn from the optical fiber preform G from the outside air.

Specifically, the half-split protective tubes 30A and 30B are butted together to form a cylinder during the drawing process, and the upper ends of the half-split protective tubes 30A and 30B are connected to the lower chamber 11a, and together with the lower chamber 11a, they protect the glass fiber G1 drawn from the optical fiber preform G from the outside air. However, the half-split protective tubes 30A and 30B are configured to be detachable from the lower chamber 11a and have a half-split structure so that they can be moved in a direction intersecting the drawing direction from the line directly below the drawing furnace 11 that connects the drawing furnace 11 and the annealing furnace 15 during the drawing process.

Figure 2 is a diagram showing a protective tube according to embodiment 1. The half protective tubes 30A and 30B shown in Figure 2 are, for example, a cylinder divided into two along an axis in the vertical direction perpendicular to the radial direction. When the half protective tubes 30A and 30B are butted together, they form a cylindrical shape with an inner diameter of about φ15 mm to φ100 mm, and the vertical length of the half protective tubes 30A and 30B is, for example, 1 m or more. Note that the half protective tubes 30A and 30B are not limited to the above length and diameter, and may be divided into four parts rather than two. In addition, a gasket may be placed at the joint of the halves to increase airtightness.

3A to 3C are diagrams illustrating the lead-out step according to the first embodiment.
In the lead-out step, the upper ends of the half protective tubes 30A and 30B are separated from the lower end of the lower chamber 11a, and the half protective tubes 30A and 30B are each moved in a direction intersecting the drawing direction of the glass fiber G1 (for example, a horizontal direction perpendicular to a line connecting the drawing furnace 11 and the annealing furnace 15) as shown by the leftward and rightward arrows in Fig. 3A, respectively. It is also possible to move only either the half protective tube 30A or the half protective tube 30B. Also, a protective tube moving mechanism 40 (see Fig. 1) may be provided to move the half protective tube 30A and the half protective tube 30B to fixed positions.

Next, as shown in Fig. 3B, a cylindrical cup 31 is placed in the space created between the drawing furnace 11 and the annealing furnace 15 by the movement of the half protective tubes 30A and 30B. The cup 31 corresponds to the receiving tool of the present disclosure. Specifically, by placing the cup 31 on, for example, the furnace core tube of the annealing furnace 15, the seeds L dropping from the tip portion of the optical fiber preform G are received by the cup 31 as shown in Fig. 3C.
As mentioned above, the diameter of the dropped seeds L is usually φ15 mm or more, and is generally about φ40 mm.

Next, the dropped seeds L are removed, and the cup 31 is removed from above the slow-cooling heating furnace 15, i.e., from below the drawing furnace 11.
Thereafter, the rod-shaped glass from which the seeds L have been removed is thinned to a certain diameter and passed through the pass line following the annealing furnace 15. The halved protective tubes 30A and 30B are returned to the bottom of the lower chamber 11a and butted together, and the glass fiber is removed, completing the lead-out process. At this time, it is preferable to reconnect the upper ends of the halved protective tubes 30A and 30B to the lower end of the lower chamber 11a to improve airtightness.

In this way, the seed L descending from the tip of the optical fiber preform G is received by the cup 31 installed above the annealing furnace 15 without passing through the annealing furnace 15. Therefore, in the optical fiber manufacturing apparatus 10, it is not necessary to make the core tube of the annealing furnace 15 larger than the size of the seed L. This makes it possible to avoid an increase in the power consumption of the annealing furnace 15 and an increase in the manufacturing cost of the optical fiber G2. The inner diameter of the core tube of the annealing furnace 15 is φ10 mm to φ40 mm, and more preferably φ10 mm to φ30 mm.
In addition, in the optical fiber manufacturing apparatus 10, the half-split protective tubes 30A, 30B, which are smaller than the annealing furnace, are moved to secure space for the tapping operation, so there is no need to retract the annealing furnace 15 from the line onto which the seeds L fall. Therefore, a large retraction mechanism for retracting the annealing furnace 15 is not required.

In the above embodiment 1, the semi-cylindrical half-split protective tubes 30A and 30B are described as an example, but the present disclosure is not limited to this example. For example, as shown in FIG. 4, the cylindrical protective tube 30 may be configured as a cylindrical integral structure. The cylindrical protective tube 30 also corresponds to the protective tube of the present disclosure.

5A to 5C are diagrams illustrating the lead-out process according to the second embodiment.
The cylindrical protective tube 30 is held by a moving mechanism 40 (see FIG. 1). In the leading out step, as shown by the downward arrow in FIG. 5A, the upper end of the cylindrical protective tube 30 is separated from the lower end of the lower chamber 11a, and then, as shown by the rightward arrow, for example, the cylindrical protective tube 30 is moved in a direction intersecting the drawing direction of the glass fiber G1.

Next, as shown in Fig. 5B, the cup 31 is placed in the space created between the drawing furnace 11 and the annealing furnace 15 by the movement of the cylindrical protective tube 30. Specifically, by placing the cup 31 on, for example, the furnace core tube of the annealing furnace 15, the seeds L dropping from the tip portion of the optical fiber preform G are received by the cup 31 as shown in Fig. 5C.
Then, similarly to the first embodiment, the dropped seeds L are removed, and the cup 31 is removed from above the slow-cooling furnace 15 .
Thereafter, the rod-shaped glass from which the seeds L have been removed is thinned to a certain diameter, and then the moved cylindrical protective tube 30 is returned to its original position, and the glass fiber is passed through the cylindrical protective tube 30, the annealing furnace 15, and the subsequent pass lines. The glass fiber is then removed, completing the lead-out process. When the cylindrical protective tube 30 is returned to its original position, it is preferable to reconnect the upper end of the cylindrical protective tube 30 to the lower end of the lower chamber 11a to improve airtightness.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by the scope of the claims, not by the meaning described above, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

10...optical fiber manufacturing equipment, 11...drawing furnace, 11a...lower chamber, 12...furnace tube, 13...heating element, 14...gas supply section, 15...heating furnace for slow cooling, 16...outer diameter measurement unit, 17a...UV resin application device, 17b...UV curing furnace, 18...directly below roller, 19...guide roller, 20...take-up device, 21...guide roller, 22...dancer roller, 23...winding device, 30...cylindrical protective tube, 30A, 30B...half-split protective tube, 31...cup, F...base material feed unit, G...optical fiber base material, L...drop seed, G1...glass fiber, G2...optical fiber, B...bobbin.

Claims (4)

A method for manufacturing an optical fiber by an optical fiber manufacturing apparatus including a drawing furnace for heating an optical fiber preform, a lower chamber and a protective tube provided below the drawing furnace for protecting a glass fiber drawn from the optical fiber preform from outside air, and a slow-cooling furnace located below the protective tube for controlling the drawn glass fiber to a predetermined temperature, comprising:
a step of drawing a lump of a molten portion dropping from the tip of the optical fiber preform before the start of drawing, and a step of drawing a glass fiber having a predetermined diameter after the end of the step of drawing,
The lead-out step comprises:
moving only the protective tube in a direction intersecting a drawing direction of the glass fiber without retracting the annealing furnace ;
a step of disposing a receiver for receiving the descending mass of the molten portion in a space generated between the drawing furnace and the slow cooling heating furnace by the movement of the protective tube;
receiving the falling mass of molten portion after the step of placing the receiver;
a step of removing the receiver from below the wire drawing furnace after the step of receiving the descending molten mass ;
a step of returning the protective tube to below the wire drawing furnace after the step of retracting the receiving tool ;
A method for manufacturing an optical fiber, comprising: The method for manufacturing optical fiber according to claim 1, wherein the protective tube has a split structure in which two halves are butted together to form a cylindrical shape. the optical fiber manufacturing apparatus further includes a moving mechanism for moving the protective tube from below the drawing furnace,
3. The method for manufacturing an optical fiber according to claim 1, further comprising the steps of: moving the protective tube and returning the protective tube to its original position, the step being performed by using the moving mechanism. An optical fiber manufacturing apparatus comprising: a drawing furnace for heating an optical fiber preform; a lower chamber and a protective tube provided below the drawing furnace for protecting a glass fiber drawn from the optical fiber preform from outside air; and a slow-cooling furnace located below the protective tube for controlling the glass fiber drawn in the drawing furnace to a predetermined temperature,
the protective tube is movable in a direction intersecting a drawing direction of the glass fiber,
an optical fiber manufacturing apparatus, wherein a receiving device for receiving a mass of molten portion descending from the tip of the optical fiber preform is placed on the annealing furnace with the protective tube moved from above the annealing furnace .

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