JP2001287926A - Method for drawing and leading wire and apparatus for drawing wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the leading wire operation time when a preform for an optical fiber in a heating furnace is inserted to carry out wire drawing. SOLUTION: When the preform 1 for the optical fiber 6 is arranged with the axis in the vertical direction in the heating furnace 4 and the lower end of the preform 1 for the optical fiber 6 is heated with a heater 5 to melt and form the glass near the end into a dropwise glass part, the heating temperature of the heater 5 is increased from the heating temperature of the heater 5 when the wire is drawn at a steady wire speed to produce the optical fiber 6 by 100-200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for drawing an optical fiber from an optical fiber preform.

[0002]

2. Description of the Related Art To draw an optical fiber from an optical fiber preform, an optical fiber preform is placed in a heating furnace equipped with a heater so that the axis of the preform is vertical. The lower end of the base material is heated and melted by a heater, and a wire diameter of about 125
Pull out a μm optical fiber.

[0003] In this drawing operation, the procedure of the lead-out preparation operation up to the production of an optical fiber as a product will be described as follows. FIG. 3 is a view for explaining a part of the procedure. FIG. 3 (A) is a longitudinal sectional view showing a state at the start of heating, and FIG. 3 (B) is a state at the time when the drop glass part falls. FIG. In FIG. 3, 20 is an optical fiber base material, 21 is a heating furnace, 22 is a heater, 23 is a fibrous glass part, and 24 is a drop glass part.

[0004] First, as shown in FIG.
The heater 22 is energized to heat the heater 22 to a predetermined temperature, for example, 1950 ° C., and the optical fiber preform 20 is inserted into the heated heating furnace 21. Is heated by the heater 22. After a while, as shown in FIG. 3 (B), the lower end of the optical fiber preform 20 is melted and the molten glass has a tip portion of about 1 cm in diameter and about 2 cm to 3 cm in length. 24, the wire is dropped below the heating furnace 21 while being suspended from the optical fiber base material 20 by the fibrous glass portion 23 which is gradually reduced to a wire diameter of about 1 mm.

[0005] The drop-shaped glass portion 24 that has fallen below the heating furnace 21 is received in a suitable container, and the fibrous glass portion 23 is received.
Is cut with scissors, nippers or the like, and the fibrous glass portion 23 further descending from the optical fiber preform is dragged downward with a hand wearing leather gloves or the like. Then, the descending fibrous glass portion 23 gradually becomes thin, so that the wire diameter becomes 1.
When cut to about 50 μm, the tip of the fibrous glass portion 23 which is connected to the optical fiber preform and descends, is coated with a coating resin coating device (not shown), a coating curing device, Through the collection device, etc.
The take-up device is started at a relatively low linear speed of, for example, about 40 m / min. Here, the fibrous glass portion 23 which is thin enough to be passed through the coating resin coating device is used.
Is called an optical fiber.

When the fiber diameter of the optical fiber has stabilized at, for example, 125 μm, the supply of ultraviolet curable resin to the coating resin coating device is started, the resin is applied around the optical fiber, and ultraviolet light is applied by the coating curing device. Irradiate to cure the resin. In addition, the optical fiber with the coating layer exiting the take-up device is wound around a take-up reel, and the take-up device is started. Then, the tension of the optical fiber is examined by sandwiching the optical fiber between the heating furnace and the coating resin coating device with a three-point tensiometer.
Normally, the tension of the optical fiber gradually rises with the passage of time and then becomes a stable state of approximately constant, for example, 400 mN. Wait until such a state is reached and confirm that the stable state has been reached.

Thereafter, the linear velocity of the take-off device is increased to a predetermined linear velocity of, for example, 150 m / min, and the outer diameter of the coating layer and the optical fiber diameter of the optical fiber are stabilized when the linear velocity is stabilized. Confirm that the values are within the specified range.
If there is no problem, a good optical fiber with a coating layer that can be adopted as a product can be manufactured. Therefore, the take-up reel is switched to the product and the process shifts from the optical fiber feeding process to the regular manufacturing process.

[0008]

During the above-described optical fiber tapping operation, the lower end of the optical fiber preform is heated and melted, and the lower end of the optical fiber preform is formed into a drop-shaped glass portion, which is placed under the heating furnace. Although there is an operation of dropping to the outside, a considerably long heating time is required from the insertion of the optical fiber base material into the heating furnace to the dropping of the drop glass. Depending on the type of optical fiber, the type and amount of the dopant added to the silica glass, which is the material of the optical fiber, differ, and the optimum heating temperature when drawing the heater of the heating furnace varies accordingly. Although there is a difference in time, an example of the dispersion compensating optical fiber requires a heating time of about 70 minutes.

Also, in the case of the same optical fiber, it takes about 35 minutes from the dropping of the drop-shaped glass part to the stabilization of the diameter and the tension of the optical fiber. Therefore, it takes about 105 minutes from the insertion of the optical fiber preform into the heating furnace to the stabilization of the optical fiber diameter and tension. In addition, this tapping preparation work is required every time the optical fiber preform is replaced, and the time required for drawing one optical fiber preform is about 5 to 6 hours.
About 20% of the entire drawing time is used for the preparation work.

The present invention provides a wire drawing method and a wire drawing apparatus capable of shortening the time required for such a wire drawing preparation work and performing a wire drawing work of an optical fiber preform efficiently.

[0011]

According to the present invention, there is provided a wire drawing method for heating a lower end portion of an optical fiber preform disposed in a heating furnace provided with a heater so that an axis of the preform is vertical. The heating temperature of the heater when the glass near the end is melted to form a drop-shaped glass portion is higher than the heating temperature of the heater when the optical fiber is manufactured by drawing at a constant linear velocity. . As a result, the operation time required for inserting the optical fiber base material into the heating furnace and for stabilizing the wire diameter and tension of the optical fiber is reduced. The steady linear velocity refers to the running speed of the optical fiber when the optical fiber as a product is continuously manufactured.

[0012] Further, the method for drawing out a wire comprises a heating furnace provided with a heater for heating the lower end of the optical fiber preform disposed therein, and a drop glass portion disposed below the heating furnace. The present invention can be implemented by using a drawing apparatus including means for detecting passage and heater temperature control means for controlling the temperature of the heater based on a signal from the passage detection means.

[0013]

FIG. 1 is a conceptual diagram showing a main part of an example of a drawing apparatus for carrying out a drawing and drawing method according to the present invention, wherein 1 is an optical fiber base material, 2 is a dummy rod, and 3 is Lifting device, 4 a heating furnace, 5 a heater, 6 an optical fiber, 7
Is a temperature sensor, 8 is a wire diameter measuring device, 9 and 11 are coating resin coating devices, 10 and 12 are coating curing devices, 13 is an optical fiber with a coating layer, 14 is a take-off device, 15 is a dancer roll, and 16 is a winding. A picking device, 17 is a wire diameter control means, and 18 is a heater temperature control means.

The wire drawing method of the present invention is specifically performed as follows. The optical fiber preform 1 is inserted into the heating furnace 4 heated by energizing the heater 5. The dummy rod 2 joined to the upper end of the optical fiber preform 1 is supported by the elevating device 3, and the operation of the elevating device 3 places the optical fiber preform 1 into the heating furnace 4 from above the heating furnace 4. insert. Then, the lower end of the optical fiber preform 1 is heated by the heater 5. When the drawing of the optical fiber preform has been completed and the next drawing operation is to be performed, the heater 5 has already been heated to a heating temperature for drawing at a steady linear speed, for example, 1.
Since it is heated to 950 ° C., the optical fiber preform 1 is inserted into the heating furnace 4 in the heated state. Thereafter, in the present invention, the heating temperature of the heater 5 is immediately increased by 100 ° C. to 200 ° C. higher than that temperature, for example, 2050 ° C.
Raise the temperature to 2150 ° C.

If the lower end of the optical fiber preform 1 is continuously heated in this state, the optical fiber preform 1
The lower end portion of the glass melts and the tip portion of the molten glass becomes a drop-shaped glass portion and falls to the outside below the heating furnace 4. The time at which the drop of the glass drop occurs can be predicted by observing the lower end of the optical fiber preform 1 by eye, so that the drop of the glass drop is received in an appropriate container and connected to it. The fibrous glass part is cut with scissors, nippers or the like. At this time, an operation is performed to return the heating temperature of the heater 5 of the heating furnace 4 to the original temperature, that is, 1950 ° C., which is suitable for drawing at a constant linear speed.

A means for detecting the passage of the drop glass portion when the drop glass portion falls below the heating furnace 4 is provided below the heating furnace 4, and the heater 5 is detected based on a signal from the passage detection means. If the heating temperature is controlled, operation errors such as an incorrect set temperature are less likely to occur than in the case where the temperature of the heater 4 is manually changed, and the temperature switching operation is easy and other operations such as a fiber glass portion The temperature of the heater can be switched in parallel with the cutting and dragging operation of the heater.
In addition, as a means for detecting the passage of the droplet glass portion, a temperature sensor 7 or a wire diameter measuring device 8 can be used. In this case, the temperature of the heater 5 is automatically switched by the heater temperature control means 18 based on a signal from the temperature sensor 7 or the wire diameter measuring device 8.

Then, the fibrous glass portion descending further from the optical fiber preform 1 is pulled downward by a hand wearing leather gloves and the like, and the fibrous glass portion gradually becomes thinner to have a wire diameter of about 150 μm. Cut when it becomes. Then, the tip of a fibrous glass portion (which can also be called an optical fiber at this stage) 6 connected to the optical fiber base material 1 is connected to a coating resin coating device 9 disposed below the heating furnace 4,
11, through the coating hardening device 10, 12, the take-up device 14, etc., the take-up device 14
Start at a linear speed of about / min.

The optical fiber has a wire diameter of, for example, 125
μm, the coating resin coating device 9, 1
1. The supply of the ultraviolet curable resin to the optical fiber 6 is started.
Is applied to the periphery of the substrate, and ultraviolet rays are irradiated by the coating and curing devices 10 and 12 to cure the resin. In addition, the optical fiber 13 with the coating layer that has exited the take-up device 14 is wound around the take-up reel through the dancer roller 15 to activate the take-up device 16. Then, the tension of the optical fiber 6 is checked between the heating furnace 4 and the coating resin coating device 9 by sandwiching the optical fiber 6 with a three-point tensiometer.
Wait until a stable state such as 00 mN is reached, and confirm that the state has been achieved. The three-point tensiometer is only used to check the tension of the optical fiber at the time of tapping the optical fiber, but the three-point tensiometer is not used when the optical fiber is manufactured at a constant linear velocity.

According to the tapping method of the present invention, the melting of the lower end portion of the optical fiber base material is accelerated by the temperature rise of the heater, and the drop of the droplet glass portion is accelerated. In addition, since it takes time to return the heater temperature thereafter, the time required for the optical fiber diameter and tension to stabilize is longer than when the heater temperature is not increased, but the heater temperature is kept constant. In this case, the total taping time from insertion of the optical fiber preform into the heating furnace to stabilization of the optical fiber diameter and tension is reduced. An example of a specific working time is as follows.

The time from the insertion of the optical fiber preform into the heating furnace to the dropping of the drop glass portion took about 70 minutes when the temperature of the heater was not increased.
By raising the temperature to 00 ° C., the time is reduced to about 30 minutes. Further, the time from the dropping of the droplet glass portion to the stabilization of the wire diameter and the tension of the optical fiber is about 35 when the temperature of the heater is not increased.
It took about 5 minutes to increase the temperature of the heater.
Extends to 0 minutes. As a result, the total time from the insertion of the optical fiber preform into the heating furnace to the stabilization of the fiber diameter and tension of the optical fiber took about 105 minutes when the temperature of the heater was not increased. Depending on the temperature, this can be reduced to about 80 minutes, which can reduce the tapping time by about 20%.

FIG. 2 shows the case where the heating temperature of the heater at a constant linear speed is 1950 ° C. and the temperature of the heater is changed variously until the drop glass portion is formed at the lower end of the optical fiber preform. The time from the insertion of the optical fiber base material to the dropping of the drop glass part (a), the time from the drop of the drop glass part to the stabilization of the wire diameter and tension of the optical fiber (b)
5 is a graph showing the total time (a + b) of the two. According to this, the heater temperature is set to 2050 ° C. to 2150 ° C.
The total time is shortest when the temperature is raised to the range of ° C. That is, if the temperature of the heater at the time of forming the drop-shaped glass portion is raised from 1950 ° C. at the steady linear velocity to a temperature higher by 100 ° C. to 200 ° C., the tapping operation time can be minimized.

Even if the kind and the addition amount of the dopant contained in the glass of the optical fiber base material are different because the type of the optical fiber is different, if the main component of the optical fiber base material is quartz glass, The optimum value of the heater temperature at the time of steady linear velocity is in the range of 1800 ° C. to 2200 ° C., and does not change much. Therefore, even if the type of the optical fiber is changed, the heater temperature may be raised in the range of 100 ° C to 200 ° C.

In the above description, an example has been described in which the temperature of the heater is increased from the heater temperature at the time of steady linear velocity after the optical fiber preform is inserted into the heating furnace. When preparing the material to be taken out, the optical fiber preform may be inserted into the heating furnace after the heater temperature has reached the temperature at the time of temperature rise, or the heating furnace may not be heated at a stage where the heater temperature does not rise sufficiently. An optical fiber preform may be inserted into the inside.

After completing the above-mentioned tapping operation and confirming that the tension and the like are within a predetermined range, the linear speed of the take-up device is set to a steady linear speed from a low speed, for example, 150 m / sec. To a predetermined linear speed, and after confirming that the outer diameter of the coating layer, the wire diameter of the optical fiber, etc. are within the predetermined ranges, switch the take-up reel to the product, and attach the coating layer for the product. Move to optical fiber manufacturing. In addition,
While monitoring the wire diameter of the optical fiber 6 with the wire diameter measuring device 8, the wire speed of the take-off device 14 is controlled by the wire diameter control means 17 so that the wire diameter is within a predetermined range.

[0025]

According to the wire drawing method of the present invention, when starting the wire drawing operation, the lower end of the optical fiber preform is heated by a heater to melt the glass near the end and to form a drop-shaped glass portion. The heating temperature of the heater at the time of heating is made higher than the heating temperature of the heater at the time of producing an optical fiber by drawing at a constant linear velocity. It is possible to shorten the time required for tapping until the fiber diameter and the tension of the fiber are stabilized.

[0026] Further, the wire drawing device is provided with a heating furnace provided with a heater for heating the lower end of the optical fiber preform disposed therein and a passage of a drop-shaped glass portion disposed below the heating furnace. And a heater temperature control means for controlling the temperature of the heater based on a signal from the passage detection means, so that the heater temperature is automatically switched in accordance with the drop of the droplet glass portion. Therefore, there is no mistake in the temperature setting due to the temperature switching operation, and there is no influence on other outlet preparation operations.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a main part of an example of a drawing apparatus for performing a drawing opening method according to the present invention.

FIG. 2 shows the time (a) from the insertion of the optical fiber base material to the dropping of the dropping glass part when the temperature of the heater until the dropping glass part drops is changed. Time until the fiber diameter and tension of the optical fiber are stabilized (b)
5 is a graph showing the total time (a + b) of the two.

FIG. 3 is a diagram for explaining a procedure of an extraction operation;
(A) is a longitudinal sectional view showing a state at the start of heating, and (B) is a longitudinal sectional view showing a state when a drop-shaped glass portion falls.

[Description of Signs] 1: Base material for optical fiber 2: Dummy rod 3: Lifting device 4: Heating furnace 5: Heater 6: Optical fiber 7: Temperature sensor 8: Wire diameter measuring device 9, 11: Coating resin coating device 10 , 12: coating curing device 13: optical fiber with coating layer 14: take-up device 15: dancer roll 16: take-up device 17: wire diameter control means 18: heater temperature control means 20: base material for optical fiber 21: heating furnace 22: heater 23: fibrous glass part 24: drop glass part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuyuki Tsuneishi, Inventor, 1 Tayacho, Sakae-ku, Yokohama, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor, Shigeru Koyanagi 1-Tagamachi, Sakae-ku, Yokohama, Kanagawa Prefecture Sumitomo Electric Ki Kogyo Co., Ltd. Yokohama Works F-term (reference) 4G021 HA05

Claims (4)

[Claims] 1. A lower end of an optical fiber preform placed in a heating furnace equipped with a heater with its axis set in a vertical direction is heated by the heater to melt glass near the end and form a droplet. A drawing method, wherein a heating temperature of a heater for forming a glass portion is drawn downward at a constant linear velocity to be higher than a heating temperature of a heater for manufacturing an optical fiber. 2. The heating temperature of the heater when the glass near the end of the optical fiber base material is formed as a drop-shaped glass portion is determined from the heating temperature of the heater when the optical fiber is drawn at the steady linear velocity. The drawing method according to claim 1, wherein the temperature is also raised by 100C to 200C. 3. A heating furnace provided with a heater for heating a lower end portion of an optical fiber preform disposed therein, and means for detecting passage of a drop glass portion disposed below the heating furnace. A heater temperature control means for controlling the temperature of the heater based on a signal from the passage detection means. 4. The drop glass part passage detecting means is a temperature sensor or a wire diameter measuring device.
The wire drawing device according to claim 1.