JP2004168572A - Apparatus and method for drawing optical fiber preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drawing apparatus for an optical fiber preform, which can be prevented from becoming a large size. <P>SOLUTION: The drawing apparatus 1 is equipped with a first chuck 4 and a second chuck 5 which are constituted so as to able to hold one end and the other end of the optical fiber preform 2 to be drawn, respectively, and to move along the drawing direction, a heater 32 for heating the main body 21 of the optical fiber preform 2 to a temperature at which the main body 21 can be drawn, and rollers 60, 61 which are provided between the heater 32 and the second chuck 5 and can draw and take off the optical fiber preform 2. The first part of the main body 21 is drawn by moving the first chuck 4 at a first speed along the drawing direction, and at the same time, moving the second chuck 5 at a second speed higher than the first speed along the drawing direction, and the second part of the main body 21 is drawn by the rollers 60, 61. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical fiber preform stretching apparatus and an optical fiber preform stretching method.
[0002]
[Prior art]
In the production of optical fibers, a glass material in the gaseous phase is hydrolyzed in a flame to produce glass particles, which are deposited to form a long optical fiber preform (porous glass particle deposit). After that, the optical fiber preform is dehydrated and transparentized in a heating furnace, then stretched in the longitudinal direction to reduce the diameter to a predetermined diameter, and drawn to form a small-diameter optical fiber.
[0003]
The drawing apparatus for drawing the optical fiber preform in the drawing step of the production of the optical fiber includes a heating furnace which is opened in a vertical direction and through which the optical fiber preform can be inserted, and an upper chuck is provided above the heating furnace. The lower chuck is disposed below the lower chuck so that the optical fiber preform can be gripped, and the upper chuck and the lower chuck can be vertically moved, and the optical fiber preform is disposed vertically. There is an attempt to make it possible to stretch a large-diameter optical fiber preform or to increase the diameter-reducing ratio by stretching the optical fiber preform (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
JP-A-6-40738
[Problems to be solved by the invention]
The conventional drawing apparatus needs to move the lower chuck by at least the same distance as the length of the optical fiber to be obtained. Therefore, in order to obtain a long optical fiber, it is necessary to secure the working area of the lower chuck and the upper chuck, and it is necessary to increase the size of the stretching apparatus corresponding to the working area.
[0006]
In view of the above, an object of the present invention is to provide an optical fiber preform stretching apparatus and an optical fiber preform stretching method capable of minimizing the size of the apparatus.
[0007]
[Means for Solving the Problems]
An optical fiber preform stretching apparatus of the present invention is configured so as to be able to grip one end and the other end of an optical fiber preform to be stretched, respectively, and to be movable along a stretching direction of the optical fiber preform. Supporting means and second supporting means, disposed between the first supporting means and the second supporting means, heating means for heating a predetermined portion of the optical fiber preform to a temperature capable of stretching, heating means and A third supporting means disposed between the supporting means and the optical fiber preform, the first supporting means being arranged at a first speed along the stretching direction. While moving, the second support means moves at a second speed higher than the first speed along the stretching direction to extend the first portion of the predetermined portion, and the third support means extends the second portion of the predetermined portion. .
[0008]
According to the optical fiber preform stretching apparatus of the present invention, the first support means and the second support means move in the stretching direction with a relative speed difference, so that the predetermined portion of the optical fiber preform is Since the first portion is stretched and the remaining second portion of the predetermined portion is stretched by the third support means, the moving distance of the second support means is smaller than when the entire predetermined portion of the optical fiber preform is stretched. Be shorter.
[0009]
In the optical fiber preform stretching apparatus of the present invention, at least one of the first support means and the second support means is moved so that the optical fiber preform is arranged at a predetermined position with respect to the third support means. It is also preferred. Thereby, bending of the stretched body stretched by the third support means is suppressed.
[0010]
The optical fiber preform stretching apparatus of the present invention further includes measuring means for measuring an outer shape at a position corresponding to the third supporting means of the optical fiber preform, and based on the measurement result, the direction along the outer shape and the stretching. It is also preferable to move at least one of the first support means or the second support means so as to be along the direction. Since the direction along the outer shape of the position corresponding to the third support means, that is, the direction along the outer edge at that position is along the extending direction of the optical fiber preform, for example, the optical fiber preform with respect to the third support means Can be reduced when it is located at a predetermined position but obliquely.
[0011]
In the optical fiber preform stretching apparatus of the present invention, when the optical fiber preform is stretched by the third support means, it is preferable that the optical fiber preform further includes a cutting means for cutting out a stretched body obtained by stretching the optical fiber preform. Since the stretched body is cut, a stretched body of a predetermined length can be obtained. Further, the stretched body does not become too long, and the place for taking the stretched body is small.
[0012]
The stretching method of the optical fiber preform of the present invention, while gripping one end of the optical fiber preform to be stretched by the first support means, and gripping the other end of the optical fiber preform by the second support means, A heating step of heating a predetermined portion of the optical fiber preform to a temperature at which a predetermined portion of the optical fiber preform can be drawn by a heating means disposed between the first supporting means and the second supporting means; and A first stretching step of moving the second supporting means at a second speed higher than the first speed along the stretching direction to stretch the first portion of the predetermined portion, while moving at the first speed, A second extending step of extending the second portion of the predetermined portion by the third supporting means disposed between the supporting portion and the third supporting portion.
[0013]
According to the method for drawing an optical fiber preform of the present invention, the first support means and the second support means move in the drawing direction with a relative speed difference, so that a predetermined portion of the optical fiber preform is Since the first portion is stretched and the remaining second portion of the predetermined portion is stretched by the third support means, the moving distance of the second support means is smaller than when the entire predetermined portion of the optical fiber preform is stretched. Be shorter.
[0014]
Further, in the method for drawing an optical fiber preform of the present invention, prior to the second drawing step, the first supporting means or the second supporting means is arranged so that the optical fiber preform is arranged at a predetermined position with respect to the third supporting means. Preferably, the method further includes an adjusting step of moving at least one of the support means. Since the third support means is arranged at a predetermined position when the optical fiber preform is drawn, the bending of the predetermined portion of the optical fiber preform to which the third support means is drawn is suppressed.
[0015]
In the stretching method of the optical fiber preform of the present invention, in the adjusting step, the outer shape is measured by measuring means for measuring the outer shape at a position corresponding to the third supporting means of the optical fiber preform, and the outer shape is measured based on the measurement result. It is also preferable to move at least one of the one support means and the second support means. Since the direction along the outer shape of the position corresponding to the third support means, that is, the direction along the outer edge at that position is along the extending direction of the optical fiber preform, for example, the optical fiber preform with respect to the third support means Can be reduced when it is located at a predetermined position but obliquely.
[0016]
The method for stretching an optical fiber preform of the present invention preferably further includes a cutting step of cutting the stretched body stretched by the third support means in the second stretching step by a cutting means. Since the stretched body is cut, a stretched body of a predetermined length can be obtained. Further, the stretched body does not become too long, and the place for taking the stretched body is small.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
The findings of the present invention can be readily understood by considering the following detailed description with reference to the accompanying drawings shown by way of example only. Subsequently, embodiments of the present invention will be described with reference to the accompanying drawings. When possible, the same parts are denoted by the same reference numerals, and redundant description will be omitted.
[0018]
An optical fiber preform stretching apparatus 1 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a sectional view of an optical fiber preform stretching device 1. In FIG. 1, a drawing furnace 1 is provided with a heating furnace 3 for heating an optical fiber preform 2. The heating furnace 3 has an insertion space 31 opened along the extending direction of the optical fiber preform 2 (longitudinal direction of the optical fiber preform 2), and the optical fiber preform 2 inserted into the insertion space 31. A heater (heating means) 32 for heating is provided. The insertion space 31 is a space for heating and drawing the optical fiber preform 2 and has a cross-sectional opening larger than at least the outer diameter of the optical fiber preform 2 so that the optical fiber preform 2 to be drawn can be inserted. ing. A discharge port 33 is formed at one end of the insertion space 31 so that the stretched optical fiber preform 2 can be discharged through the discharge port 33. An opening 34 is provided at the other end of the insertion space 31 for extending the end of the optical fiber preform 2 to the outside. The opening 34 is provided as small as possible to keep the heat in the insertion space 31. On the other hand, the heater 32 is a heating means for applying heat to the insertion space 31 to make the inside thereof a high temperature state. For example, an annular heater is used to surround the inner periphery of the insertion space 31, and the heating furnace 3 is used. Built in. As the heater 32, a known heater such as an electric heater that generates heat when energized is employed.
[0019]
In addition, the heating furnace 3 is preferably arranged such that the insertion space 31 is oriented in the vertical direction, and when the optical fiber preform 2 is stretched so that the optical fiber preform 2 is stretched, They will be arranged vertically. Therefore, even when the own weight direction of the optical fiber preform 2 matches the stretching direction and the stretched optical fiber preform 2 is elongated or the large optical fiber preform 2 is stretched, 2 can be reliably supported without bending, and can be heated and stretched. Here, the optical fiber preform 2 to be drawn has a structure in which support rods 22 are respectively extended from both ends of a preform main body 21 on which glass fine particles are deposited and sintered, and the main body 21 is heated. It will be stretched.
[0020]
As shown in FIG. 1, a first chuck (first support means) 4 is installed in the extension direction of the insertion space 31 on the opening 34 side, and supports the optical fiber preform 2 inserted into the insertion space 31. One of the rods 22 is gripped. That is, the first chuck 4 is a member for fixedly supporting the support rod 22 of the optical fiber preform, and is disposed on the extension of the insertion space 31 so as to be separated from the heating furnace 3. A known mechanism such as a manual chuck or a hydraulic chuck is used as the first chuck 4. The first chuck 4 is installed movably along the extending direction of the optical fiber preform 2, that is, the direction in which the insertion space 31 is formed, so that the supported optical fiber preform 2 can be transferred.
[0021]
Also, as shown in FIG. 1, a second chuck (second support means) 5 is provided in the direction in which the insertion space 31 extends on the discharge port 33 side. The second chuck 5 is a member for gripping the support rod 22 of the optical fiber preform 2 inserted into the insertion space 31 and is disposed at a predetermined distance from the heating furnace 3. As with the first chuck 4, a known chuck is used. The second chuck 5 is also installed so as to be movable in the direction in which the optical fiber preform 2 is stretched, and the second chuck 5 and the above-mentioned first chuck 4 are respectively moved in the same direction, that is, the first chuck 4 installation side. By moving the optical fiber preform 2 supported by them to the second chuck 5 side by moving the optical fiber preform 2 to the second chuck 5 installation side.
[0022]
In the second chuck 5, it is desirable to dispose a material having heat resistance and flexibility in a portion that comes into contact with the support rod 22. That is, in the second chuck 5, it is preferable that a member that comes into contact with the support bar 22 when the support bar 22 is supported is configured to be detachable, and the contact surface of the contact member is formed of heat-resistant resin. Alternatively, it is desirable to use plating. With this configuration, the support rod 22 of the optical fiber preform 2 supported by the second chuck 5 can be prevented from being damaged, so that the support rod 22 can be prevented from being damaged, and the recycling thereof can be prevented. Can be achieved. Such materials include, for example, phenolic resins, acrylic resins, polyimide resins, epoxy resins, bismaleimide resins, polyester resins, polyetherimide resins, polyetheretherketone resins, polyarylate resins Resins, polysulfone resins, polyethersulfone resins, polyphenylene sulfide resins, and the like are employed.
[0023]
The second chuck 5 is configured to move faster than the moving speed of the first chuck 4, and by moving the second chuck 5 faster than the first chuck 4, as shown in FIG. The main body 21 of the optical fiber preform 2 heated in the vicinity can be stretched by applying a tensile force. The first chuck 4 and the second chuck 5 are not limited to a structure like a chuck as long as they can support the end of the optical fiber preform 2, and other known support mechanisms may be adopted.
[0024]
As shown in FIG. 1, a pair of rollers (third support means) 60 and rollers (third support means) 61 are provided between the heating furnace 3 and the second chuck 5. The roller 60 and the roller 61 are members for holding and drawing the stretched body 23 of the optical fiber preform 2 carried out from the outlet 33 of the heating furnace 3. The rollers 60 and 61 are configured to be rotated by a motor (not shown), and are configured such that the rotation direction and the rotation speed can be independently set. Further, the rollers 60 and 61 are configured to be independently approachable or separable toward the elongated body 23. The drive mechanism of the rollers 60 and the rollers 61 is realized by combining mechanical elements such as a motor, a shaft, and a gear. It is sufficient that the rollers 60 and the rollers 61 can approach or separate from the stretched body 23 independently. .
[0025]
At positions corresponding to the rollers 60 and 61 of the stretching device 1, a CCD camera 50 and a CCD camera 51 are provided (not shown in FIG. 1). The arrangement of the CCD camera 50 and the CCD camera 51 will be described with reference to FIGS. FIG. 2 is a top view of a portion where the CCD camera 50 and the CCD camera 51 are arranged. According to FIG. 2, the CCD camera 50 and the CCD camera 51 are provided such that their optical axes are substantially orthogonal. Accordingly, the CCD camera 50 and the CCD camera 51 can measure the position and the outer shape of the main body 21 of the optical fiber preform 2 (the same applies to the stretched body 23) in the vicinity of the rollers 60 and 61.
[0026]
A reference position 21 a of the main body 21 of the optical fiber preform 2 with respect to the rollers 60 and 61 is set in a control unit (not shown) of the stretching device 1. The actual position information of the main body 21 of the optical fiber preform 2 measured by the CCD camera 50 and the CCD camera 51 is output to the control unit. The control unit compares the actual position of the main body 21 of the optical fiber preform 2 with the reference position 21a, and calculates a shift amount a in the x-axis direction and a shift amount b in the y-axis direction. The control unit controls the first chuck 4 and the second chuck 5 based on the calculated value so that the main body 21 of the optical fiber preform 2 is located at the reference position 21a. When adjusting the position of the main body 21 of the optical fiber preform 2, it is preferable to move both the first chuck 4 and the second chuck 5. If one of them can be moved to the reference position 21a, only one of them may be moved. Although a CCD camera is used in the present embodiment, a laser emitting section and a laser receiving section may be provided with the optical fiber preform 2 interposed therebetween. By emitting a laser beam from the laser emitting section toward the optical fiber preform 2 and the laser receiving section and scanning, the position of the optical fiber preform 2 can be recognized.
[0027]
FIG. 3 is a side view of a portion where the CCD cameras 50 and 51 are arranged. The main body 21 of the optical fiber preform 2 (the same applies to the stretched body 23) may be arranged obliquely at an angle α with respect to the reference position 21a as shown in FIG. If the stretched body 23 of the optical fiber preform 2 is sandwiched between the rollers 60 and 61 in such a state of being obliquely arranged, the extended optical fiber may be bent. Accordingly, the control unit (not shown) of the drawing device 1 includes an outer edge portion (a two-dot chain line portion in the figure) of a preset reference position 21a and an outer edge portion of the actual main body 21 of the optical fiber preform 2 (a solid line in the diagram). The first chuck 4 and the second chuck 5 are moved so that the first and second parts are aligned with each other.
[0028]
The control unit (not shown) of the stretching device 1 measures the change in the outer shape of the main body 21 of the optical fiber preform 2 (the same applies to the stretched body 23) with the CCD camera 50 and the CCD camera 51, and based on the measurement result. It is also preferable to move the first chuck 4 and the second chuck 5.
[0029]
Subsequently, a method of using the stretching device 1 will be described. In FIG. 1, the optical fiber preform 2 is set in the heating furnace 3 so that the optical fiber preform 2 to be drawn is sequentially heated in the heating furnace 3. That is, the support bar 22 above the optical fiber preform 2 is gripped by the first chuck 4, the first chuck 4 is lowered, and the optical fiber preform 2 is inserted into the heating furnace 3 from above the heating furnace 3. . At this time, the upper lid 35 of the heating furnace 3 is separated from the main body of the heating furnace 3 and is passed through the upper support rod 22 in advance before the work of inserting the optical fiber preform 2 is performed. Before the optical fiber preform 2 is inserted, the outlet 33 of the heating furnace 3 is covered with a lid in order to prevent air from entering the inside of the heating furnace 3, and the optical fiber preform 2 is inserted into the heating furnace 3. After being inserted and the upper part of the heating furnace 3 is closed by the upper lid 35, the lid attached to the discharge port 33 is removed. Then, when the support bar 22 below the optical fiber preform 2 comes out of the outlet 33, the support bar 22 is gripped by the second chuck 5. Then, the optical fiber preform 2 is moved along the direction in which the insertion space 31 is formed by the movement of the first chuck 4 and the second chuck 5.
[0030]
In this state, as shown in FIG. 1, after the heater 32 is sufficiently heated, the first chuck 4 and the second chuck 5 are moved so that the main body 21 of the optical fiber preform 2 passes near the heater 32. Let it. The moving speed of the second chuck 5 with respect to the first chuck 4 is increased so that the main body 21 of the optical fiber preform 2 passes near the heater 32 and the portion of the main body 21 near the heater 32 is extended. At this time, the relative movement speed of the second chuck 5 with respect to the first chuck 4 may be increased by making the speed of the first chuck 4 slower than the movement speed of the second chuck 5.
[0031]
As shown in FIG. 4, at the stage where the second chuck 5 is lowered until the main body 21 of the optical fiber preform 2 reaches a predetermined length, the rollers 60 and 61 are moved toward the main body 21 of the optical fiber preform 2. (The part taken up so far corresponds to the first part.) At this time, as described above, the outer shape is measured by the CCD camera 50 and the CCD camera 51, and the first position of the main body 21 of the optical fiber preform 2 is set to a predetermined position based on the measurement result. The positions of the chuck 4 and the second chuck 5 are controlled. When controlling the positions of the first chuck 4 and the second chuck 5, even if the position and the angle of the main body 21 (stretched body 23) of the optical fiber preform 2 are controlled to be predetermined positions and angles. Good.
[0032]
Before the roller 60 and the roller 61 pinch and pull the stretched body 23 of the optical fiber preform 2, the support rod 22 on the second chuck 5 side is cut off by a grinder (cutting means) 80. In this case, the second chuck 5, the rollers 60 and 61, and the grinder 80 move downward in the drawing at the same speed. Thereafter, the main body 21 of the optical fiber preform 2 is stretched by the rollers 60 and 61 and is drawn as a stretched body 23 (the portion drawn by the rollers 60 and 61 corresponds to the second portion). In this case, the stretching speed (feeding speed of the stretched body) by the rollers 60 and 61 and the moving speed of the second chuck 5 are matched.
[0033]
The pulled-out stretched body 23 of the optical fiber preform 2 may be cut by a grinder 80 at predetermined lengths. More specifically, the stretched body 23 of the optical fiber preform 2 is scratched by a grinder 80 for more than half a circumference, and cut off by applying an impact with a hammer or the like. In this manner, if the sheet is cut at predetermined lengths, the stretching device 1 can be further reduced in size. That is, when the large optical fiber preform 2 is stretched, the stretched optical fiber becomes longer. In this case, if the optical fiber preform 2 is continuously stretched, the size of the apparatus increases. When the device is actually used, it may be cut into a predetermined length for the sake of handling, so if the device is cut every predetermined length, the size of the device can be reduced. When the main body 21 of the optical fiber preform 2 is completely taken out, as shown in FIG. 5, the heat of the heater 32 causes the support rod 22 supported by the first chuck 4 to melt, and at the same time, the second chuck 5 and a pair of rollers 60. And the roller 61 is moved down at a high speed to cut it off.
[0034]
In the present embodiment, the rollers 60 and 61 are used as the third support means, but a chuck mechanism similar to the first chuck 4 and the second chuck 5 may be employed. In this case, the third support means of the chuck mechanism stretches and pulls the main body 21 of the optical fiber preform 2 while moving downward in the figure.
[0035]
In the present embodiment, the stretching device 1 is installed so that the stretching direction extends along the vertical direction, but may be installed so as to extend along the horizontal direction. In this case, since the optical fiber preform 2 needs to be rotated, each supporting means such as the first chuck 4, the rollers 60 and 61, and the second chuck 5 is rotated.
[0036]
In this embodiment, the first part of the main body 21 of the optical fiber preform 2 is drawn by moving the first chuck 4 and the second chuck 5 in the drawing direction with a relative speed difference. Since the remaining second portion of the main body 21 is stretched and pulled by the rollers 60 and 61, the moving distance of the second chuck 5 is shorter than when the entire main body 2 of the optical fiber preform 2 is stretched.
[0037]
When the rollers 60 and 61 support the optical fiber preform 2, the rollers 60 and 61 are aligned with the stretched body 23, so that the main body 21 (of the optical fiber preform 2 where the rollers 60 and 61 are stretched) The bending of the stretched body 23) is suppressed.
[0038]
The direction along the outer shape at the position corresponding to the rollers 60 and 61 of the main body 21 of the optical fiber preform 2 to be stretched, that is, the direction along the outer edge at that position, follows the stretching direction of the optical fiber preform 2. For example, it is possible to reduce the occurrence of a case where the main body 21 of the optical fiber preform 2 is at a predetermined position but is oblique to the rollers 60 and 61.
[0039]
【The invention's effect】
According to the present invention, the first support means and the second support means move in the stretching direction with a relative speed difference, thereby stretching the first part of the predetermined part of the optical fiber preform, and Since the third supporting means stretches and pulls the remaining second portion of the portion, the moving distance of the second supporting means is shorter than when the entire predetermined portion of the optical fiber preform is stretched. Therefore, it was possible to provide an optical fiber preform stretching apparatus and an optical fiber preform stretching method which can minimize the size of the apparatus as much as possible.
[Brief description of the drawings]
FIG. 1 is a diagram showing a stretching device according to an embodiment of the present invention.
FIG. 2 is a diagram showing a part of the stretching device of FIG.
FIG. 3 is a view showing a part of the stretching apparatus of FIG. 1;
FIG. 4 is a view for explaining a method of using the stretching apparatus of FIG. 1;
FIG. 5 is a view for explaining a method of using the stretching apparatus of FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Stretching apparatus, 2 ... Optical fiber preform, 21 ... Main body, 22 ... Support rod, 23 ... Stretched body, 3 ..., 31 ... Insertion space, 32 ... Heater, 33 ... Discharge port, 34 ... Opening, 35 ... Top lid 4, a first chuck, 5: a second chuck, 61: a roller, 62: a roller.

Claims (8)

First support means and second support means configured to grip one end and the other end of the optical fiber preform to be stretched, respectively, and to be movable along the stretching direction of the optical fiber preform,
Heating means disposed between the first support means and the second support means, and heating a predetermined portion of the optical fiber preform to a temperature at which it can be stretched,
A third support unit disposed between the heating unit and the second support unit, and configured to be able to stretch the optical fiber preform,
The first support means moves at a first speed along the stretching direction, and the second support means moves at a second speed higher than the first speed along the stretching direction to move the predetermined portion. An optical fiber preform stretching device for stretching a first portion, and wherein the third support means stretches a second portion of the predetermined portion. The optical fiber preform according to claim 1, wherein at least one of the first support means or the second support means is moved such that the optical fiber preform is disposed at a predetermined position with respect to the third support means. Equipment for stretching materials. Measuring means for measuring the outer shape of the optical fiber preform at a position corresponding to the third supporting means, further comprising:
3. The optical fiber preform according to claim 2, wherein at least one of the first support unit and the second support unit is moved so that a direction along the external shape and the extension direction are along the measurement result. 4. apparatus. 4. The optical fiber according to claim 1, further comprising a cutting unit that cuts out a stretched body obtained by stretching the optical fiber preform when the optical fiber preform is stretched by the third support unit. 5. Base material stretching device. A gripping step of gripping one end of the optical fiber preform to be drawn by the first support means, and gripping the other end of the optical fiber preform by the second support means,
By heating means disposed between the first support means and the second support means, a heating step of heating a predetermined portion of the optical fiber preform to a temperature at which it can be stretched,
The first supporting means is moved at a first speed along the stretching direction, and the second supporting means is moved at a second speed higher than the first speed along the stretching direction to move the predetermined portion. A first stretching step of stretching the first portion;
A second stretching step of stretching the second portion of the predetermined portion by third supporting means provided between the heating means and the second supporting means. Prior to the second stretching step, at least one of the first support means or the second support means is moved so that the optical fiber preform is located at a predetermined position with respect to the third support means. The method of drawing an optical fiber preform according to claim 5, further comprising an adjusting step. In the adjusting step, the outer shape is measured by measuring means for measuring the outer shape of the optical fiber preform at a position corresponding to the third supporting means, and the first supporting means or the second supporting means is measured based on the measurement result. The method for drawing an optical fiber preform according to claim 6, wherein at least one of the means is moved. The method of stretching an optical fiber preform according to any one of claims 5 to 7, further comprising a cutting step of cutting the stretched body stretched by the third support means in the second stretching step by a cutting means.

Images