JPH08208262A - Drawing of optical fiber and apparatus therefor - Google Patents

Abstract

PURPOSE: To provide both a method for drawing an optical fiber by which the optical fiber of a low noncircularity ratio can be drawn and an apparatus for drawing the optical fiber capable of realizing the method for drawing the optical fiber. CONSTITUTION: This apparatus for drawing an optical fiber is equipped with a means 13 for thermally melting the lower end of a preform 11 for the optical fiber and drawing the optical fiber 19 from the lower end of the preform 11 for the optical fiber, a means 32 for calculating the noncircularity ratio of the drawn optical fiber 19 and a means for regulating the temperature distribution around the preform 11 for the optical fiber so as to reduce the calculated noncircularity ratio of the optical fiber 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber drawing method capable of drawing an optical fiber having a small non-circularity and an optical fiber drawing apparatus capable of realizing the optical fiber drawing method.

[0002]

2. Description of the Related Art An optical fiber is obtained by heating and melting an optical fiber preform in a drawing furnace of an optical fiber drawing apparatus and drawing the lower end of the optical fiber preform. More specifically, as disclosed in, for example, Japanese Patent Laid-Open No. 63-8233, an optical fiber pulled out from the lower end of an optical fiber preform is immediately cured by a resin applicator on its outer peripheral surface with an ultraviolet curable resin. A resin protective film such as the above is applied, and the resin protective film is passed through a resin curing device to cure the resin protective film, after which it is taken up by a winder as an optical fiber element wire. Then, the outer diameter of the optical fiber is measured by an outer diameter measuring device provided between the drawing furnace and the resin applicator, and the light extracted from the optical fiber preform is kept so that the outer diameter becomes constant. The fiber drawing speed is adjusted.

By the way, if the optical fiber is out of the perfect circle, the diameter of the hole for mounting the optical fiber formed in the ferrule for positioning the optical connector must be increased, and the axis of this hole and the optical fiber. There is a possibility that the misalignment with the axis line of (1) becomes large, and eventually the connection loss becomes large. Similarly, when a pair of optical fibers are butted against each other by utilizing the V groove formed in the positioning block and these are connected to each other, the radius of the optical fiber in the portion in contact with the V groove varies, so Deviating from a perfect circle causes misalignment and connection loss during connection.

The non-circularity is known as a parameter indicating how far the cross-sectional shape of an optical fiber deviates from a perfect circle. This is the measurement of the outer diameter of an optical fiber at multiple points along the circumference, and the longest outer diameter obtained by this measurement is the long diameter, the shortest outer diameter is the short diameter, and the average of all measured values is averaged. The diameter is defined by (major axis-minor axis) / average diameter.

Conventionally, in order to make the non-circularity as close to 0 as possible, the lower end of the optical fiber preform is matched with the center of the drawing furnace so that the optical fiber preform is uniformly heated along its circumferential direction. I have to. In addition, JP-A-1-9604
As disclosed in Japanese Patent Publication No. 2 (1994), it has been proposed to eliminate temperature unevenness and reduce non-circularity by rotating the core tube.

[0006]

In recent years, along with the cost reduction of optical fibers, the diameter of optical fiber preforms has become larger and the drawing speed thereof has become faster. In addition, the drawing furnace itself, for example, due to the presence of electrodes and cooling water flow furnace,
Some non-uniformity along the circumferential direction cannot be avoided. Such non-uniformity of temperature distribution along the circumferential direction is
Since the diameter of the optical fiber preform is larger than that of the small diameter, the temperature unevenness is caused inside the optical fiber preform.
Moreover, when the optical fiber is drawn at a higher speed than in the conventional case, the passage time of the neck-down portion where the optical fiber preform is melt-reduced and the temperature unevenness is alleviated becomes short, resulting in the above-mentioned temperature unevenness. Since it is more difficult to eliminate it, the non-circularity tends to increase.

Further, in the method of rotating the core tube disclosed in Japanese Patent Laid-Open No. 1-96042, the temperature unevenness of the optical fiber preform along the circumferential direction is alleviated, so that the non-circular shape of the optical fiber is eliminated. Although the rate can be reduced, conversely, by rotating the core tube, the flow of gas in the furnace is disturbed and the fluctuation of the outer diameter becomes large, and the connection using the optical connector and the connection end This results in an increase in connection loss in the case of melting and connecting each other.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical fiber drawing method capable of drawing an optical fiber having a small non-circularity and an optical fiber drawing apparatus capable of realizing the optical fiber drawing method.

[0009]

The first embodiment of the present invention comprises the steps of heating and melting the lower end of the optical fiber preform and drawing the optical fiber from the lower end of the optical fiber preform. A step of calculating a non-circularity of the optical fiber, and a step of adjusting a temperature distribution around the optical fiber preform so that the calculated non-circularity of the optical fiber becomes small. It is a characteristic optical fiber drawing method.

Here, the step of calculating the non-circularity of the optical fiber includes the step of calculating an average value of the outer diameter dimension along the circumferential direction of the optical fiber, and the step of calculating the non-circularity along the circumferential direction of the optical fiber. And a step of obtaining the maximum value and the minimum value of the outer diameter, respectively, preferably, is calculated based on the average value and the maximum value and the minimum value of the outer diameter of the optical fiber, It is effective that the average value of the outer diameter dimension of the optical fiber is the average value of at least two measurement points along the circumferential direction of the optical fiber. Further, it may further comprise a step of adjusting the drawing speed of the optical fiber so that the average value of the outer diameter dimension of the optical fiber is constant, the maximum value and the minimum value of the outer diameter dimension of the optical fiber, It may be measured over at least 180 degrees in the circumferential direction of the optical fiber. Furthermore, the step of adjusting the temperature distribution around the optical fiber preform can be performed by moving a heat insulating material surrounding a heater that heats and melts the lower end of the optical fiber preform. Further, further comprising the step of obtaining each phase of the maximum value and the minimum value of the outer diameter dimension along the circumferential direction of the optical fiber, the step of adjusting the temperature distribution around the base material for the optical fiber, The temperature distribution around the optical fiber preform may be adjusted based on the phases of the maximum value and the minimum value of the outer diameter along the circumferential direction of the fiber.

On the other hand, according to a second aspect of the present invention, means for heating and melting the lower end of the optical fiber preform to draw the optical fiber from the lower end of the optical fiber preform, and the drawn optical fiber. And a means for adjusting a temperature distribution around the optical fiber preform so that the calculated non-circularity of the optical fiber becomes small. It is in a fiber drawing device.

Here, the means for calculating the non-circularity of the optical fiber includes means for calculating the average value of the outer diameter dimension along the circumferential direction of the optical fiber, and the direction along the circumferential direction of the optical fiber. And a means for obtaining the maximum value and the minimum value of the outer diameter dimension, and may be calculated based on the average value and the maximum value and the minimum value of the outer diameter dimension of the optical fiber, The means for calculating the average value of the outer diameter dimension of the optical fiber has at least two outer diameter measuring devices along the circumferential direction of the optical fiber, and the average value of the outputs from these outer diameter measuring machines. You can Further, it may further comprise means for adjusting the drawing speed of the optical fiber so that the average value of the outer diameter dimension of the optical fiber is constant, and the maximum value and the minimum value of the outer diameter dimension of the optical fiber, respectively. The means for determining may include a rotary table which rotates about the optical fiber in the circumferential direction thereof at least 180 degrees, and one outer diameter measuring device provided on the rotary table. It is valid. Further, the means for adjusting the temperature distribution around the optical fiber preform includes a part of a heat insulating material surrounding a heater for heating and melting the lower end of the optical fiber preform in a radial direction of the optical fiber preform. It is preferable that the heat insulating material that moves in the radial direction of the optical fiber preform is arranged at a position facing the heating and melting portion of the optical fiber preform. . Further, further comprising means for detecting each phase of the maximum value and the minimum value of the outer diameter dimension along the circumferential direction of the optical fiber, means for adjusting the temperature distribution around the optical fiber preform, The temperature distribution around the optical fiber preform may be adjusted based on each phase of the maximum value and the minimum value of the outer diameter dimension along the circumferential direction of the optical fiber.

[0013]

According to the present invention, the lower end of the optical fiber preform is heated and melted, the optical fiber is drawn from the lower end of the optical fiber preform, and the non-circularity of the drawn optical fiber is calculated. The temperature distribution around the optical fiber preform is adjusted so that the non-circularity of the formed optical fiber becomes small.

Here, while the average value of the outer diameter dimension along the circumferential direction of the optical fiber is calculated, the maximum value and the minimum value of the outer diameter dimension along the circumferential direction of the optical fiber are respectively obtained, and these light values are calculated. The non-circularity of the optical fiber is calculated based on the average value and the maximum value and the minimum value of the outer diameter dimension of the fiber.
Further, the average value of the outputs from at least two outer diameter measuring devices along the circumferential direction of the optical fiber is adopted as the average value of the outer diameter dimension of the optical fiber, and at least 180 times in the circumferential direction around the optical fiber. The maximum value and the minimum value of the outer diameter dimension of the optical fiber are obtained by a single outer diameter measuring device provided on a rotary table that turns at various degrees. Furthermore, the temperature distribution around the optical fiber preform is adjusted by moving a part of the heat insulating material surrounding the heater that heats and melts the lower end of the optical fiber preform in the radial direction of the optical fiber preform. . The heat insulating material that moves in the radial direction of the optical fiber preform is arranged at a position facing the heating and melting part of the optical fiber preform, and the ambient temperature near the heating and melting part of the optical fiber preform is adjusted. .

On the other hand, the drawing speed of the optical fiber is simultaneously adjusted so that the average value of the outer diameter of the optical fiber becomes constant. It also detects the maximum and minimum phases of the outer diameter along the circumference of the optical fiber, and detects the maximum and minimum phases of the outer circumference along the circumference of this optical fiber. Based on this, the temperature distribution around the optical fiber preform is adjusted.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical fiber drawing apparatus according to the present invention will be described in detail with reference to FIGS.

As shown in FIG. 1 showing the schematic structure of the present embodiment, the light is provided below the vertically movable chuck device 12 which holds the optical fiber preform 11 vertically downward through a support rod (not shown). A drawing furnace 13 for heating and melting the lower end of the fiber preform 11 is provided.

As shown in FIG. 2 showing the enlarged sectional structure of the drawing furnace 13 and FIG. 3 showing the sectional structure taken along the line III-III thereof, the drawing furnace 13 is provided so as to penetrate the furnace body 15 lined with the fixed heat insulating material 14. The lower end of the optical fiber preform 11 is fed into the core tube 16. In addition, the upper end of the furnace body 15 is communicated with the inner side of the furnace core tube 16 through a supply port 17 opening to the inner peripheral surface of the furnace body 15 in order to prevent the material constituting the furnace core tube 16 and the like from being oxidized. An inert gas supply duct 18 such as helium or nitrogen is formed, and the inert gas supply duct 18 is supplied with an inert gas from an inert gas supply source (not shown). Further, between the central portion of the furnace body 15 and the furnace tube 16, a heater 2 having a cylindrical shape for heating and melting the lower end portion of the optical fiber preform 11 to draw the optical fiber 19 is formed.
No. 0 is provided, and a pair of connecting terminals 21 that are linearly opposed to each other at 180 degrees are provided on the heater 20 so as to project outward in the radial direction. The connecting terminals 21 penetrate the furnace body 15 and are not shown. A pair of electrodes 22 connected to the power source are connected. Further, the fixed heat insulating material 14 is arranged so as to surround the upper and lower sides and the outer peripheral side of the heater 20 so that the heat generated by the heater 20 does not escape to the outside as much as possible.

A movable heat insulator which is slidably surrounded by the fixed heat insulating material 14 in the direction orthogonal to the facing direction of the electrode 22 (left and right direction in FIG. 3) and which is located at a portion facing the heater 20. The material 23 can be reciprocated in a direction opposite to the heater 20 by a heat insulating material drive motor 25 capable of forward and reverse rotations via a heat insulating material drive mechanism 24 using a rack and pinion attached to the furnace body 15. There is. And
By driving the heat insulating material driving motor 25 so that the movable heat insulating material 23 moves away from the heater 20, the heat insulating property to the heater 20 is lowered, and the heat insulating material for the optical fiber facing the movable heat insulating material 23 with the heater 20 and the furnace core tube 13 interposed therebetween. The temperature near the neck-down portion 26 of the base material 11 decreases. vice versa,
By driving the heat insulating material drive motor 25 so that the movable heat insulating material 23 approaches the heater 20, heat retention is ensured for the heater 20, and the neck down portion 26 of the optical fiber preform 11 facing the movable heat insulating material 23 is secured. The temperature in the vicinity is rising.

By the way, the non-circularity ε can be changed by changing the temperature distribution in the circumferential direction of the neck-down portion 26 of the optical fiber preform 11. For example, at a location where the temperature distribution along the circumferential direction is relatively high, the portion of the optical fiber preform 11 in the circumferential direction corresponding thereto also becomes hot, and the viscosity at the neck-down portion 26 becomes circumferential. Since it is lower than the other portions along the line, the diameter reduction ratio becomes large and tends to be small, that is, the minor axis of the ellipse.

Therefore, when a certain direction along the circumferential direction of the optical fiber 19 is the major axis of the ellipse, the non-circularity ε can be lowered by raising the temperature of the neck-down portion 26 corresponding to this. You can That is, by pulling back the movable heat insulating material 23 to the outside in the radial direction, the heat radiation in the vicinity of the movable heat insulating material 23 increases and the temperature of this portion relatively decreases, and the optical fiber preform 11 facing this portion. If the neck-down portion 26 of is on the minor axis side of the ellipse, the non-circularity ε can be improved. On the contrary, the base material for optical fiber 1
When the neck down portion 26 of No. 1 is on the major axis side of the ellipse, the non-circularity ε can be improved by pushing the movable heat insulating material 23 inward in the radial direction.

In this embodiment, only one movable heat insulating material 23 is provided, but the opposite side, ie, 1
A pair of movable heat insulating materials 23 are arranged symmetrically with a distance of 80 degrees,
These may be moved in the radial direction at the same time. Further, the operation of the heat insulating material drive motor 25 described above is controlled based on a command from a shape control device 33 described later.

On the other hand, below the drawing furnace 13 from which the optical fiber 19 is drawn out, a pair of outer diameter measuring devices 27 for measuring the outer diameter dimension of the optical fiber 19 from two different directions.
Are provided, and the detection signals from these outer diameter measuring devices 27 are
It is adapted to be output to an outer diameter control device 40 described later. Further, a second outer diameter measuring device 28 is arranged between the outer diameter measuring device 27 and the drawing furnace 13. The second outer diameter measuring device 28 is mounted on an annular rotary table 29 having the optical fiber 19 as the center of rotation, and the rotary table 29 has a table drive mechanism 31 using gears or the like and a table drive motor 31. By this, the range of 180 degrees rotates forward and backward at a predetermined speed. Further, the table drive motor 31 is provided with an encoder 32 for detecting the rotation phase of the rotary table 29 corresponding to the detection signal from the second outer diameter measuring device 28.

The detection signal from the second outer diameter measuring device 28 and the phase signal from the encoder 32 corresponding to this detection signal are output to the shape control device 33, respectively. The shape control device 33 reads each the maximum value D _L and the minimum value D _S of the outer diameter during its rotation for each switching the rotational direction of the rotary table 29, the maximum value D _L, and their outer diameter Minimum value D _S and outer diameter control device 4 described later
The non-circularity ε of the optical fiber 19 is calculated based on the average value D _M of the outer diameter dimensions calculated at 0 according to the following equation.

[0025]

[Equation 1] ε = (D _L −D _S ) / D _M Then, based on this non-circularity ε and the phase of the ellipse of the optical fiber 19, the heat insulating material drive motor is set so that the drive condition is set in advance. It is designed to control the operation of 25.

As described above, in the present embodiment, the average value D _M of the outer diameter dimension of the optical fiber 19 is obtained by the two outer diameter measuring devices 27 other than the second outer diameter measuring device 28, and this is used. Since the drawing speed of the optical fiber 19 is controlled on the basis of the optical fiber 19, as compared with the case where only the second outer diameter measuring device 28 is used without providing the pair of outer diameter measuring devices 27, When controlling the outer diameter dimension, the disturbance factor due to the rotation of the second outer diameter measuring device 28 can be eliminated, so that the outer diameter dimension is not affected by the non-circularity ε and more accurate. It is possible to control the outer diameter dimension, and the accuracy of measuring the non-circularity ε is improved.

In this embodiment, the rotary table 18 is set to 1
Although the forward / reverse rotation is performed in the range of 80 degrees, it is also possible to continuously rotate in one direction. In this case, the shape control device 33 causes the outer diameter of the optical fiber 19 to be changed every time the rotary table 18 rotates 180 degrees. The maximum value D _L and the minimum value D _{S of the} dimensions may be read out and the rotation phase of the rotary table 29 corresponding to the maximum value D _L and the minimum value D _S may be grasped. The specific structures of these outer diameter measuring devices 27, 28 are well known in the art, for example, Japanese Patent Laid-Open No.
It is possible to directly adopt the one disclosed in Japanese Patent Laid-Open No. 3-8233.

Immediately below the rotary table 18, there is provided a resin coating device 34 for forming a resin protective layer of an ultraviolet curable resin or the like on the outer peripheral surface of the drawn optical fiber 19, and this resin coating device is provided. A resin curing device 35 incorporating an ultraviolet lamp or the like for curing the resin protective layer applied to the outer peripheral surface of the optical fiber 19 is installed below the optical fiber 34.

Below the resin curing device 35, a guide roller 38 for guiding the optical fiber 19 on which the resin protective layer is formed to the winding bobbin 37 of the winding device 36 is rotatably provided. A capstan 39 for drawing in the optical fiber 19 having a resin protective layer formed between it and the take-up bobbin 37 from the guide roller 38 side and sending it to the take-up bobbin 37 side is driven and rotated by a capstan drive motor (not shown). It has become.

This capstan drive motor averages the detection signals from the above-mentioned pair of outer diameter measuring instruments 27, 28, and the rotational speed of the capstan 39, that is, the optical fiber, so that the detection signals are equal to a preset reference value. The operation is controlled by an outer diameter control device 40 which controls the drawing speed of 19. Further, the average value D _M of the outer diameter dimension of the optical fiber 19 calculated by the outer diameter control device 40 is output to the shape control device 33.

Using the optical fiber drawing apparatus as shown in FIG. 1 described above, the non-circularity ε of the drawn optical fiber 19 is calculated while moving the movable heat insulating material 23 from the innermost to the outermost in the radial direction. The optical fiber 19 was compared with the result calculated by the contact method off-line. In this case, the capstan 39 is adjusted so that the average value D _M of the outer diameters of the optical fiber 19 measured by the two outer diameter measuring devices 27 becomes 125 μm.
The rotation speed of the rotary table 18 is controlled by the table driving motor 31 together with the second outer diameter measuring device 28 so that the amplitude is 1
Move the rocking motion of 80 degrees to make one reciprocation in 30 seconds,
10 the maximum value D _L the average value of the maximum diameter in the case of back and forth, and the minimum value D _S the average value of the minimum diameter.

The second outer diameter measuring device 27 is not rotated to measure the maximum diameter and the minimum diameter at the same time, and the variation in the outer diameter dimension causes an error in the calculation of the non-circularity ε. Since it may occur, it is effective to control the rotation speed of the capstan 39 by using the average value D _M of the outer diameter dimension and stabilize this average value D _M in order to improve the accuracy of the non-circularity ε. is there.

According to this, the non-circularity ε of the optical fiber 19
Is 0 to 2.5% in the method of the present invention, and the average value of the difference in non-circularity ε is 0.1% as compared with the method by the offline method.
Below, the standard deviation was 0.11%, and it was confirmed that the online method for measuring the non-circularity ε according to the present invention has sufficient reliability.

Next, the movable heat insulating material 23 is placed closest to the heater 20 (in this case, the movable heat insulating material 23 and the fixed heat insulating material 14 are set so that the inner and outer circumferences thereof match).
Then, in this state, the movable heat insulating material 23 is pulled out by 7 cm in the radial direction, that is, in a state of being retracted away from the heater 20, the optical fiber 19 is drawn, and the non-circularity ε is measured over its entire length. As a result, the length of the optical fiber preform 11 which is suspended by a support rod (not shown) and is not drawn (hereinafter, referred to as extra length) and the non-circularity ε of the optical fiber 19 being drawn. As shown in FIG. 4 showing the relationship, in the state where the movable heat insulating material 23 shown by the solid line is closest to the heater 20 side in the figure, the non-circularity ε as the extra length of the optical fiber preform 11 decreases. On the other hand, in the state where the movable heat insulating material 23 indicated by the broken line in the drawing is retracted radially outward by 7 cm, the non-circularity ε decreases as the extra length of the optical fiber preform 11 decreases. It was found to have a tendency to

Since the phase of the maximum value D _L of the outer diameter dimension of the optical fiber 19 is shifted by 90 degrees in the two states of the movable heat insulating material 23 described above, the two positions of the movable heat insulating material 23 described above are different. It is predicted that there is a portion where the non-circularity ε of the optical fiber 19 becomes the minimum during the period.

Therefore, by grasping the characteristics of the drawing furnace 13 in advance, the movable heat insulating material 23 is moved according to the descending amount of the optical fiber preform 11 with respect to the drawing furnace 13, and the non-circularity of the optical fiber 19 is increased. It is also possible to keep ε small, in which case the encoder 32 need not be used. However, the characteristics shown in FIG. 4 are peculiar to the drawing furnace 13 in the present embodiment, and have different characteristics in the case of a drawing furnace having another structure.

Therefore, the movable heat insulating material 23 is most used for the heater 20.
When the non-circularity ε exceeds 0.15% continuously for 10 minutes or more when the optical fiber 19 is pulled out from this state by pulling it out to the outside by 2 cm in the radial direction from the state in which it is close to the side, the movable heat insulating material 23 is removed. Furthermore, it was controlled so that it was moved radially outward by 5 mm. In this case, the moving average of the data over the 5 minutes as the mean D _M of the outer diameter of the optical fiber 19 employed, if the non-circularity of the optical fiber 19 epsilon is had increased by the movement of the movable heat insulating member 23 In contrast, on the contrary, the movable heat insulating material 23 is moved inward by 1 cm in the radial direction. As a result, the non-circularity is 0.3% over the entire length of the optical fiber 19.
We were able to hold: The non-circularity of the optical fiber 19 obtained by applying this method to five optical fiber preforms 11 and drawing them is 0.3% or less in all cases, and the average non-circularity of these is Is 0.16%
Became.

Further, when the maximum value D _L of the outer diameter dimension of the optical fiber 19 is close to the direction of the movable heat insulating material 23 by using the information on the phase by the encoder, the movable heat insulating material is pushed out by 5 mm in the radial direction. When the maximum outer diameter D _{L of} the optical fiber 19 is close to the direction perpendicular to the movable heat insulating material 23, the movable heat insulating material is pulled back by 5 mm in the radial direction. In this case as well, the optical fiber 19 has a length of 0.
A non-circularity ε of 5% or less could be achieved.

For comparison, it is considered from FIG. 4 that the non-circularity ε is the best at the position where the movable heat insulating material 23 is pulled out to the outside by 4.5 cm in the radial direction. Under this condition, the optical fiber preform 11 is drawn to draw the optical fiber 19. As a result, the average non-circularity is 0.2
Although it was as low as 2%, the maximum non-circularity ε was as large as 0.6%, and when drawing five optical fiber preforms 11,
This maximum non-circularity ε varied from 0.5% to 0.75%.

[0040]

According to the present invention, the non-circularity of the optical fiber drawn from the drawing furnace is measured online, and the temperature distribution around the optical fiber preform is adjusted so as to reduce the non-circularity. Since this is done, it is possible to draw an optical fiber having a good dimensional shape and high circularity.

[Brief description of drawings]

FIG. 1 is a mechanism conceptual diagram showing a schematic structure of an embodiment of an optical fiber drawing device according to the present invention.

FIG. 2 is a sectional view showing a structure of a portion of an optical fiber drawing furnace in the embodiment shown in FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is a graph showing the relationship between the extra length of the optical fiber preform and the non-circularity depending on the position of the heat insulating material.

[Explanation of symbols]

 11 Optical Fiber Base Material 12 Chuck Device 13 Drawing Furnace 14 Fixed Insulation Material 15 Furnace Body 16 Core Tube 17 Supply Port 18 Inert Gas Supply Duct 19 Optical Fiber 20 Heater 21 Connection Terminal 22 Electrode 23 Movable Insulation Material 24 Insulation Material Drive Mechanism 25 Heat Insulation Material Driving Motor 26 Neck Down Part 27 Outer Diameter Measuring Instrument 28 Second Outer Diameter Measuring Instrument 29 Rotating Table 30 Table Driving Mechanism 31 Table Driving Motor 32 Encoder 33 Shape Control Device 34 Resin Coating Device 35 Resin Curing Device 36 Winding Device 37 Winding bobbin 38 Guide roller 39 Capstan 40 Outer diameter control device

Claims (15)

[Claims] 1. A step of heating and melting a lower end portion of an optical fiber preform to draw an optical fiber from the lower end of the optical fiber preform, and a step of calculating a non-circularity of the drawn optical fiber. Adjusting the temperature distribution around the base material for the optical fiber so that the calculated non-circularity of the optical fiber becomes small. 2. The step of calculating the non-circularity of the optical fiber includes the step of calculating an average value of the outer diameter dimension along the circumferential direction of the optical fiber, and the step of calculating the non-circularity along the circumferential direction of the optical fiber. And a step of obtaining the maximum value and the minimum value of the outer diameter dimension, respectively, and is calculated based on the average value and the maximum value and the minimum value of the outer diameter dimension of the optical fiber. The optical fiber drawing method described in Item 1. 3. The average value of the outer diameter dimension of the optical fiber is
The optical fiber drawing method according to claim 2, which is an average value of at least two measurement points along a circumferential direction of the optical fiber. 4. The method according to claim 2, further comprising a step of adjusting a drawing speed of the optical fiber so that an average value of outer diameters of the optical fiber becomes constant. Optical fiber drawing method. 5. The maximum value and the minimum value of the outer diameter dimension of the optical fiber are at least 1 in the circumferential direction of the optical fiber.
The optical fiber drawing method according to claim 2, 3 or 4, wherein the optical fiber drawing is performed over 80 degrees. 6. The step of adjusting the temperature distribution around the optical fiber preform is performed by moving a heat insulating material surrounding a heater for heating and melting the lower end of the optical fiber preform. Claim 1 or claim 2
Alternatively, the optical fiber drawing method according to claim 3, claim 4, or claim 5. 7. The method further comprises the step of obtaining each phase of the maximum value and the minimum value of the outer diameter dimension along the circumferential direction of the optical fiber, and the step of adjusting the temperature distribution around the optical fiber preform. The temperature distribution around the optical fiber preform is adjusted based on each phase of the maximum value and the minimum value of the outer diameter dimension along the circumferential direction of the optical fiber. The optical fiber drawing method according to claim 2 or claim 3 or claim 4 or claim 5 or claim 6. 8. A means for drawing the optical fiber from the lower end of the optical fiber preform by heating and melting the lower end of the optical fiber preform, and a means for calculating the non-circularity of the drawn optical fiber. An optical fiber drawing apparatus comprising: means for adjusting a temperature distribution around the optical fiber preform so that the calculated non-circularity of the optical fiber becomes small. 9. The means for calculating the non-circularity of the optical fiber includes means for calculating an average value of outer diameters along the circumferential direction of the optical fiber, and means for calculating the non-circularity along the circumferential direction of the optical fiber. A means for obtaining the maximum value and the minimum value of the outer diameter dimension, respectively, and is calculated based on the average value and the maximum value and the minimum value of the outer diameter dimension of the optical fiber. Item 8. The optical fiber drawing device described in item 8. 10. The means for calculating the average value of the outer diameter dimension of the optical fiber has at least two outer diameter measuring devices along the circumferential direction of the optical fiber, and outputs from these outer diameter measuring machines. The optical fiber drawing apparatus according to claim 9, wherein the optical fiber drawing apparatus is an average value of 11. The method according to claim 9, further comprising means for adjusting a drawing speed of the optical fiber so that an average value of outer diameters of the optical fiber becomes constant. Optical fiber drawing device. 12. A means for obtaining the maximum value and the minimum value of the outer diameter of the optical fiber, the rotary table rotating about the optical fiber in the circumferential direction thereof at least 180 degrees, and the rotary table. The optical fiber drawing device according to claim 9, 10 or 11, further comprising one outer diameter measuring device provided on the table. 13. The means for adjusting the temperature distribution around the optical fiber preform includes a part of a heat insulating material surrounding a heater for heating and melting the lower end of the optical fiber preform, and the optical fiber preform. The optical fiber drawing device according to claim 8 or claim 9, claim 10 or claim 11 or claim 12, wherein the optical fiber drawing device is moved in the radial direction. 14. The heat insulating material, which moves in the radial direction of the optical fiber preform, is arranged at a position facing the heating and melting portion of the optical fiber preform. Optical fiber drawing device. 15. A means for detecting each phase of a maximum value and a minimum value of an outer diameter dimension along a circumferential direction of the optical fiber, further comprising means for adjusting a temperature distribution around the optical fiber preform. Adjusts the temperature distribution around the optical fiber preform based on each phase of the maximum value and the minimum value of the outer diameter dimension along the circumferential direction of the optical fiber. The optical fiber drawing device according to claim 9 or claim 10 or claim 11 or claim 12 or claim 13 or claim 14.