JPH08109036A - Method for drawing optical fiber and apparatus therefor - Google Patents

Abstract

PURPOSE: To provide a method for integrally joining the upper end of a preform for optical fibers during preceding drawing operation to the lower end of preform for new optical fiber which is successively drawn so as to provide high strength and enable continuous drawing operation of an optical fiber and provide a simple drawing apparatus capable of realizing the method. CONSTITUTION: This apparatus for drawing optical fiber is equipped with a drawing and heating part 13 for heating and melting the lower end part of a preform 11 for optical fiber and drawing an optical fiber 21 and a joining and heating part 18 for protruding the upper end joining face 14 of the preform 11 for optical fiber during heat-melting and the lower end joining face 16 of the new preform 15 for optical fiber to be heated and melted together and integrally joining these faces by a diffusion joining method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can realize a method for continuously producing an optical fiber by adding the optical fiber preforms when the optical fiber is drawn from the optical fiber preform and this method. Regarding the device.

[0002]

2. Description of the Related Art Usually, an optical fiber has a predetermined diameter, for example, by drawing an end portion of an optical fiber preform having a similar cross section to the optical fiber drawing furnace by heating it to 1800 ° C. or higher. It is manufactured to a diameter of 125 μm.

In the conventional method, since the length of the optical fiber preform is finite due to its handling restrictions and the size of the drawing furnace building, it is not possible to use one optical fiber preform. Therefore, only optical fibers with finite length can be obtained. Then, when the optical fiber drawing work for one optical fiber base material is completed, a new optical fiber base material to be heated and melted next to the drawing furnace is replaced, and the optical fiber drawing is started up accordingly. There is a problem in that work is required and the effective operating time of the equipment is impaired due to the time required for such setup change.

From the above, for example, Japanese Patent Laid-Open No. 52-
In Japanese Patent No. 78450, the joint surfaces of the pair of optical fiber preforms are finished to be smooth, and the lower end of a new optical fiber preform to be next heat-melted is provided at the upper end of the optical fiber preform being heated and melted. A method has been proposed in which an optical fiber is continuously drawn by optical bonding with an adhesive such as balsam. Further, in JP-A-61-197440,
An apparatus that abuts the upper end of the optical fiber preform during heating and melting with the lower end of the new optical fiber preform to be heated and melted by the burner and then joins them Proposed.

[0005]

[Patent Document 1] Japanese Patent Laid-Open No. 52-7
In the method disclosed in Japanese Patent No. 8450, since a pair of optical fiber preforms are bonded via an adhesive, it is difficult to secure sufficient bonding strength. In particular, when the joint is subjected to thermal stress in the drawing furnace, the adhesive deteriorates due to heat, these joint surfaces are separated, and the base material for optical fiber that is being heated and melted falls, causing There is a risk that some parts will be damaged. In addition, it is impossible to draw a wire at the adhesive portion interposed in the joint portion, and there is a problem that the optical fiber is broken at the adhesive portion.

Further, according to the method disclosed in Japanese Patent Laid-Open No. 61-197440, in which the joint ends of a pair of optical fiber preforms are heated and melted to each other by a burner, the longitudinal direction of the optical fiber preforms is considered. Since the wire is drawn vertically up and down, a large amount of heat must be applied to the joint end, and a part of the heat generated as a result flows upward in the wire drawing furnace. It is necessary to install very large-scale equipment at the upper end of the drawing furnace, which is a practical problem. In addition, since the burner heats the joint ends of the pair of optical fiber preforms, unexpected bubbles and bubbles whose shape is difficult to control easily remain on the joint surface, and these bubbles cause light to be emitted during drawing. This causes a problem that the fiber is broken.

In order to avoid such a problem, the splicing end portion of the optical fiber preform is rounded to a certain curvature to form a tapered taper shape, and fusion is started from the center of the splicing end portion while eliminating bubbles. However, the joining operation for this purpose is very complicated and it is extremely difficult to automate it.

[0008]

It is an object of the present invention to integrally join the upper end of the optical fiber preform during the preceding drawing operation and the lower end of a new optical fiber preform to be drawn next with high strength. ,
An object of the present invention is to provide a method that enables continuous drawing work of an optical fiber and a simple drawing apparatus that can realize this method.

[0009]

A first embodiment of the present invention is an optical fiber drawing method in which a lower end portion of an optical fiber preform is heated and melted to draw out an optical fiber. The upper end joint surface of the optical fiber preform during heating and melting and the new optical fiber preform so that the fiber preform and the new optical fiber preform to be heated and melted are aligned with each other. The lower end joint surface of the optical fiber is butt-joined and integrally joined by a diffusion joining method, and this joint portion is also continuously drawn so that the optical fiber can be continuously drawn to a plurality of optical fiber preforms. It is characterized by having done.

The diffusion bonding described in this specification means that the joint surfaces of the optical fiber preforms are in close contact with each other and plastic deformation is not caused as much as possible under the temperature conditions below the melting point of these optical fiber preforms. It is a method of applying pressure and joining each other by utilizing the diffusion phenomenon of atoms at these joining surfaces. Normally, the main component of the optical fiber preform, which is the optical fiber, is quartz glass, so there is no clearly defined melting point like metal, but it does not induce large plastic deformation of the optical fiber preform. Since it is necessary to set the temperature, it is preferable that the temperature is generally lower than the drawing temperature, specifically 1700 ° C. or lower, and particularly 1550 ° C. or lower and 1100 ° C. or higher to minimize deformation.

Here, the pressing force between the upper end joint surface of the optical fiber preform which is being heated and melted and the lower end joint surface of a new optical fiber preform to be subsequently heated and melted is continuously detected, and this pressing force is continuously detected. It is effective to abut these joint surfaces so that the pressure is always a predetermined value, for example, a pressing force of 50 g / cm ² or more.

Further, before the upper end joint surface of the optical fiber preform which is being heated and melted and the lower end joint surface of the new optical fiber preform to be subsequently heated and melted are butt-joined to each other and integrally joined, The upper joint surface of the optical fiber base material inside and the new lower end joint surface of the optical fiber base material are preheated at a certain distance, and the upper joint surface of the optical fiber base material being heated and melted After butt-joining the lower end joint surface of the optical fiber preform and integrally joining them by the diffusion joining method, after maintaining the joint portion at a temperature above the annealing point for 5 minutes or more, it is further cooled to below the annealing point. By doing so, the strain at the joint may be removed. Then, after joining the upper end joining surface of the optical fiber preform during heating and melting and the lower end joining surface of the new optical fiber preform to be heated and melting next to integrally join, the joining strength of this joining part It is also possible to perform a joint strength confirmation test for confirmation.
In this case, it is possible to confirm the joint strength of the joint by applying a tension more than the self-weight of the new optical fiber preform to be joined to the optical fiber preform being heated and melted to the joint. it can.

The position of the core portion at the upper end of the optical fiber preform during heating and melting and the position of the core portion at the lower end of the new optical fiber preform to be heated and melted next are detected by optical means. , Thereby aligning the core portion and then aligning the upper end joint surface of the optical fiber preform that is being heated and melted with the lower end joint surface of the new optical fiber preform to be heated and melted, and integrally. The upper end joint surface of the optical fiber preform that is being heated and melted and the lower end joint surface of the new optical fiber preform that is to be heated and melted may be butted and joined together. Prior to this, it is also effective to flame-polish these joint surfaces.

On the other hand, the pair of optical fiber preforms to be joined to each other may be joined to each other to reduce the diameter by removing the outer peripheral edges of the pair of optical fibers. It is preferable to set the center line average roughness Ra of the region of at least 10% of the diameter of these optical fiber preforms from the center of the joint surface of the fiber preform to 300 Å or less.

Here, a pair of optical fiber preforms to be joined to each other is integrally joined with a short optical fiber preform which has been preliminarily processed into a predetermined shape, thereby forming a joint end portion. You can

Further, the step of heating and melting the joint portion of the optical fiber preform by the diffusion joining method to draw out the optical fiber, the upper end joint surface of the optical fiber preform being heated and melted, and the new optical fiber preform It is desirable to simultaneously perform the step of abutting the lower end joint surface of the above and integrally joining them by a diffusion joining method.

According to a second aspect of the present invention, a drawing heating part for heating and melting the lower end of the optical fiber preform to draw out the optical fiber, and a drawing heating part provided above the drawing heating part are provided for the optical fiber. First base material holding and feeding means for holding the base material and sending it to the drawing heating section side, and an upper end of the optical fiber base material being heated and melted provided above the first base material holding and feeding means A joining heating section for abutting the joining surface and a lower end joining surface of a new optical fiber preform to be heated and melted together to integrally join by a diffusion joining method, and is provided above the joining heating section. It is characterized in that it further comprises a second preform holding and feeding means for holding the new optical fiber preform and sending it to the joining heating section side.

Here, the preform gripping and feeding means presses the outer peripheral surface of the preform for optical fiber against the outer peripheral surface of the preform for optical fiber at a predetermined pressure from at least two directions orthogonal to the feeding direction of the preform for optical fiber. At least three rotatable rollers may be provided, one roller of which is connected to a driving means to adjust the feed rate of the optical fiber preform.

Further, in order to improve the strength of the holding portion of the optical fiber preform by the first preform holding feed means and the second preform holding means and the joint portion of the optical fiber preform by the diffusion joining method, respectively. It is effective to provide a means for flame polishing between the first base material holding and feeding means and the drawing and heating section. Further, by making the means for flame polishing movable in the conveying direction of the optical fiber preform, the upper end joint surface of the optical fiber preform being heated and melted and a new optical fiber preform to be heated and melted next. It can also be used for flame-polishing the lower end joint surface of the.

The joint heating unit may be retractable.

[0021]

The holding portion of the optical fiber preform by the first preform holding feed means and the second preform holding feed means, and the joint portion of the optical fiber preform by the diffusion joining method are flame-polished by the flame polishing means. To be polished. Then, the lower end portion of the optical fiber preform grasped by the first preform grasping means is heated and melted in the drawing and heating section, and is drawn out as an optical fiber having a predetermined diameter.

On the other hand, the upper end of the optical fiber preform which is being heated and melted and the lower end of a new optical fiber preform which is to be heated and melted next and which is gripped by the second base metal gripping and feeding means are, for example, Butt at a pressing force of 50 g / cm ² or more, and at a temperature (for example, 1200 ° C to 1400 ° C) lower than these softening points (for example, about 1800 ° C) in the joint heating section.
When heated at, the solid-phase reaction in which the atoms, ions, or molecules that compose the optical fiber preform diffuse between the solids proceeds at these joint surfaces, resulting in a mirror-like state (for example, center line average roughness Ra of 300 Å or less) ), The joint surfaces of the optical fiber preforms are integrally joined to each other.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 showing a schematic structure of one embodiment of an optical fiber drawing apparatus capable of realizing an optical fiber drawing method according to the present invention and FIG. 2 showing a shape of a splicing end portion of an optical fiber preform, respectively. This will be described in detail with reference to FIG.

Above the wire drawing heating portion 13 provided with the annular heater 12 for heating and melting the lower end portion of the preceding optical fiber preform 11, the upper joining surface 14 of the preceding optical fiber preform 11 and A new optical fiber preform 15 to be drawn into the lower end joint surface 16 is preheated at a predetermined distance, while the pair of optical fiber preforms 11 and 1 are preheated.
A joining heating unit 18 is provided which is provided with an annular heater 17 for abutting and joining together 5 by a diffusion joining method. The heating temperature for the preceding optical fiber preform 11 by the drawing heating unit 13 is approximately 1800 ° C. or higher, and the optical fiber preform 1 by the joining heating unit 18 is used.
The heating temperature for the joint ends of 1, 15 is set to be in the range of 1100 ° C. or higher and 1700 ° C. or lower, preferably 1200 ° C. or higher and 1550 ° C. or lower. These conditions are defined as the bonding surfaces 14 and 16 of the optical fiber preforms 11 and 15.
On the other hand, by increasing the pressing force, which will be described later, it becomes possible to join at a lower temperature.

In particular, when joining is performed at 1500 ° C. or less, a special furnace that requires an inert atmosphere is not required, and it becomes possible to heat the optical fiber preform in the atmosphere,
It contributes to reducing the manufacturing cost of the furnace and extending the life of the furnace.

Immediately below the joining heating section 18, there is provided a lower preform holding and feeding means 19 for grasping the upper end of the optical fiber preform 11 being heated and melted and sending it to the drawing and heating section 13 side. There is. Similarly, above the joining heating section 18, an upper preform holding and feeding means 20 is provided which holds the upper end of a new optical fiber preform 15 to be heated and melted next and sends it to the joining heating section 18 side. Has been. These base material gripping and feeding means 19 and 20 are independent of each other
The feed rates of 1 and 15 can be adjusted, and a conventionally known structure can be adopted.

Here, when the joining ends of the optical fiber preforms 11 and 15 are heated by the joining heating section 18, these joining surfaces 14 and 16 are pressed with a pressing force of 50 g / cm ² or more, preferably 2
A pressing force of 00 g / cm ² or more is desirable. In this case, the better the surface roughness of the joint surfaces 14 and 16, that is, the closer to the mirror surface, the smaller the pressing force can be. Therefore, the feed rate of the optical fiber preform 15 by the upper preform holding and feeding means 20 is made higher than the feed rate of the optical fiber preform 11 by the lower preform holding and feeding means 19 at this time. The feeding speed of the material gripping and feeding means 20 is switched. This operation is performed by the diffusion bonding method for the optical fiber preform 1.
While joining the joining ends 1 and 15 in the joining heating section 18,
Continued.

Since the above-mentioned pressing force changes as the work of joining the optical fiber preforms 11 and 15 progresses, the pressing force is constantly monitored by a load cell or the like (not shown), and a predetermined value is determined based on this monitoring result. By controlling the feeding speed of the optical fiber preform 15 by the upper preform holding and feeding means 20 so that the pressing force becomes equal to or more than the pressing force, the joining quality can be secured.

In the case of this embodiment, the optical fiber preform 11,
The pressing force associated with the butting of 15 causes disturbance, and the diameter of the optical fiber 21 drawn out from the lower end of the preceding optical fiber preform 11 may vary. Further, since the joint portion of the optical fiber preforms 11 and 15 formed by the diffusion joining method may have poor characteristics, the joint portion of the optical fiber preforms 11 and 15 formed by the diffusion joining method is heated and melted to form an optical fiber. The process of pulling out the fiber 21 and the upper end joint surface of the optical fiber preform 15 being heated and melted and the lower end joint surface of a new optical fiber preform to be heated and melted are butted against each other and integrated by diffusion bonding method. So that the process of joining is done at the same time,
It is preferable to remove a portion in which the diameter of the optical fiber 21 has changed as a defective portion and remove it later.

However, if ideal joining can be realized, it is theoretically possible to obtain good products over the entire length of the optical fiber preforms 11 and 15 by adding control.

From such a point of view, it is generally desirable to perform the joining work of the optical fiber preforms 11 and 15 which are vertically aligned in a straight line as short as possible. Therefore, the upper end joint surface 14 of the preceding optical fiber preform 11 and the lower end joint surface 16 of the new optical fiber preform 15 to be heated and melted next.
Prior to joining and integrally joining with each other, the upper end joining surface 14 of the optical fiber preform 11 and the lower end joining surface 16 of the new optical fiber preform 15 which are being heated and melted are fixed as shown in FIG. Preheating is performed at a distance from each other, and when they reach a predetermined temperature sufficiently, a high-speed feed is given to the subsequent optical fiber preform 15 to join these joint surfaces 14, 16
It is effective to butt and move to the joining work.

When this joining work is completed, a joining strength confirmation test is conducted. Specifically, the base material is held so that the feed speed of the optical fiber preform 15 by the upper base material gripping feed means 20 is slower than the feed speed of the optical fiber preform 11 by the lower base material gripping feed means 19. Gripping feed means 2
Switch the 0 feed rate. As a result, a tensile force is applied to the joint to confirm the joint strength. This tensile force is a new optical fiber preform 15 to be heated and melted next.
It is sufficient if the pulling force is equal to or more than the own weight of.

It should be noted that the joined optical fiber preforms 11,
In order to remove the distortion of the joint portion of No. 15, the joint portion is heated for 5 minutes at the annealing point (about 1050 ° C. in this embodiment) or more at which the viscosity of the optical fiber preforms 11 and 15 corresponds to 10 ¹² Pa · s. It is preferable to maintain the above, but this can be achieved by utilizing the time required for the bonding portion to be fed to the drawing heating portion 13. After that, it is even better to cool once below the annealing point.

Further, immediately above the drawing heating section 13, the gripping portions of the optical fiber preforms 11 and 15 by the preform holding and feeding means 19 and 20 and the optical fiber preforms 11 and 15 by the diffusion bonding method are provided. A healing burner 22 is arranged in an annular shape, which fills minute cracks existing on the outer surfaces of these joints by flame-polishing the joints and corrects them smoothly. The heating area by the healing burner 22 is 0 from the surface of the optical fiber preforms 11 and 15 to the inside.
It is sufficient to reach a depth of about 1 mm, and it is possible to carry out with a low heat amount.

When the healing burner 22 is moved to the joint side of the optical fiber preforms 11 and 15 and is used as a cleaning burner before the start of the splicing, the optical fiber preforms 11 and 15 are removed. It is extremely effective for improving the quality of the joint surfaces 14 and 16. As described below,
Lapping and polishing are suitable for processing the joining surfaces 14 and 16 of the optical fiber preforms 11 and 15.
By performing flame polishing, mirror surface processing can be easily performed, and the above healing burner 22 is used as the optical fiber preform 1.
The healing burner 22 is used to move up and down along the conveying direction of 1, 15 to reliably remove foreign matter adhering to the bonding surface of the optical fiber preform by flame, and to bond the optical fiber preform. Can be improved. In this case, it is particularly effective to perform flame polishing immediately before joining.

The joint surfaces of the optical fiber preforms 11 and 15 are
The center line average roughness Ra is 300Å by polishing in advance.
It is shaped into the following mirror surface. In this case, the joint surfaces 14, 16
It is not necessary to make the entire surface a mirror surface having a centerline average roughness Ra of 300 Å or less, and an area of at least 10% of these diameters from the center of the optical fiber preforms 11 and 15 should have a centerline average roughness Ra of 300 Å or less. It should be shaped like a mirror. Further, it is not necessary to match the joint surfaces 14 and 16 with the outer diameter dimensions of the optical fiber preforms 11 and 15, and it suffices to secure an area that can withstand the drawing work of the optical fiber 21.

For example, as shown in FIGS. 2 and 3, which respectively show other examples of the side surface shape of the splicing end portion of one optical fiber preform 11, the splicing surface 14 has an outer diameter of the optical fiber preform 11. For example, it is processed into a tapered truncated cone shape that is about ⅕ (see FIG. 2), or the central portion that becomes the joint surface 14 has a convex curved surface that protrudes from the outer peripheral edge by about 0.001 to 0.1 mm, for example. It is also possible to process (see FIG. 3). As described above, by appropriately processing the shapes of the bonding surfaces 14 and 16 in advance, the bonding time by the diffusion bonding method can be shortened and the bonding surfaces 14 and 16 can be bonded without entrapping air bubbles. The quality can be improved.

The shapes of the bonding surfaces 14 and 16 are not limited to the above-mentioned shapes, and it is of course possible to adopt other shapes as long as drawing is possible.

In this case, it is also possible to preliminarily process a short optical fiber preform processed as shown in FIGS. 2 and 3 to the optical fiber preforms 11 and 15 as joint ends. .

In order to confirm the effect of the present invention, the joint end portion of the optical fiber preform having a diameter of 3 cm and a length of 1 m is shaped into a truncated cone having a taper angle of 30 °, and the diameter of this joint surface is 1 The center line average roughness Ra was set to 0.5 cm and finished to 100 Å or less. Then, 20 of the optical fiber preforms were prepared and the bonding heating unit 18 was used by using the drawing apparatus shown in FIG.
Pre-heating by and the bonding heating by the diffusion bonding method
When the pressing force at the time of butting the optical fiber preforms was set to 1 kg / cm ² or more, the optical fiber having a diameter of 125 μm could be continuously drawn out over 1000 km. It was also found that the joint before drawing under these conditions had a strength that did not break even under a tensile load of 50 kg. In this case, in order to minimize the influence of the disturbance, the drawing work of the joint and the joining work of the new optical fiber preform were adjusted at the same time.

Generally, in the case of an optical fiber with very few cracks on the surface, for example, in the case of an optical fiber of 125 μm,
It has a strength that does not break under a load of more than kg, which corresponds to a tensile strength of about 400 kg / mm ² . That is, assuming that the joint part of the optical fiber preform with very few cracks can be formed, the diameter of the joint surface used in the confirmation test is further reduced. be able to. For example,
When the tensile strength of the optical fiber is allowed to be about 40 kg / mm ² , the area of the joint surface is 1.
Even about 25 mm ² (equivalent to a diameter of about 0.63 mm),
Theoretically, continuous drawing is sufficiently possible.

Further, when the light transmitted through the optical fiber preform is irradiated from the side of the optical fiber preform to detect the position of the core portion constituting the optical fiber preform, It is possible to align the core portions of the pair of optical fiber preforms that are joined to each other, and it is possible to draw an optical fiber having continuous transmission characteristics even with an alignment accuracy of about 1 μm.
In this case, it is advisable to retreat the bonding heating unit 18 to another place during the alignment work of the bonding surfaces.

The above-mentioned base material gripping and feeding means 19, 20 are
Although it moves up and down by itself to feed the optical fiber preforms 11 and 15, at least three rotations are required in order to avoid the possibility of interference with other members as they are moved up and down. It is also possible to use rollers.

As shown in FIG. 4 showing the schematic structure of another embodiment of the present invention and FIG. 5 showing the sectional structure taken along the line V--V, the lower end of the preceding optical fiber preform 11 is Above the drawing heating portion 13 provided with the annular heater 12 for heating and melting, the upper end joining surface 14 of the preceding optical fiber preform 11 and the lower end joining of the new optical fiber preform 15 to be drawn next. The surface 16 and the surface 16 are preheated apart from each other by a certain distance, while the pair of optical fiber preforms 11 and 1 are preheated.
A joining heating unit 18 is provided which is provided with an annular heater 17 for abutting and joining together 5 by a diffusion joining method.

Immediately below the joining heating section 18, there is provided a lower preform holding and feeding means 19 for grasping the upper end of the optical fiber preform 11 being heated and melted and sending it to the drawing and heating section 13 side. There is. Similarly, above the joining heating section 18, an upper preform holding and feeding means 20 is provided which holds the upper end of a new optical fiber preform 15 to be heated and melted next and sends it to the joining heating section 18 side. Has been.

Each of the base material gripping and feeding means 19, 20 has a set of four rotary rollers 23 to 26, and these four rotary rollers 23 to 26 are used as the optical fiber base material 11, respectively.
It is arranged so as to surround 15 at equal intervals. Then, these outer peripheral surfaces are in a state of being pressed against the outer peripheral surfaces of the optical fiber preforms 11 and 15, and along with this, the outer peripheral surfaces of the rotating rollers 23 to 26 are formed into the optical fiber preforms 11 and 1.
The curved concave surface has a curvature corresponding to the diameter of 5.
In addition, two of these adjacent rotating rollers 23, 2
The rotation shafts 27 and 28 of the No. 4 are fixed in position so that they cannot be displaced in the direction opposite to the optical fibers 11 and 15, but these two rotation rollers 23 and 24 and the optical fiber preform The rotary shafts 29 and 30 of the remaining two rotary rollers 25 and 26 facing each other with the optical fiber 1 and the optical fiber 1 facing each other.
It is held so that it can be displaced in the direction facing the optical fibers 1 and 15 and is always urged in the direction facing the optical fibers 11 and 15 by springs 31 and 32, respectively. That is, the optical fiber preforms 11 and 15 are held by the four rotating rollers 23 to 26 by the spring force of the springs 31 and 32. One of the rotary rollers 23, 24 in which the positions of the rotary shafts 27, 28 are fixed.
A roller driving means (not shown) is connected to the rotary shaft 27 of the rotary roller 27, and the rotary driving of the rotary roller 23 can be performed at an arbitrary speed by the roller driving means. Feed is given.

Since the structure other than this is the same as that of the embodiment shown in FIG. 1, the members having the same functions as those shown in FIG. I shall.

[0048]

According to the present invention, by bonding the optical fiber preforms to each other using the diffusion bonding method, the optical fiber preforms can be joined at 1700 ° C. or below without causing thermal deformation. The joining heater for this purpose can be designed easily and the equipment can be made compact. Especially 1550
In the case of solid-phase bonding at a temperature equal to or lower than 0 ° C., the deformation of the optical fiber preform can be reduced, so that it is possible to reduce the number of defective portions of the optical fiber obtained by drawing the bonded portion.

Further, before the upper end joining surface of the optical fiber preform which is being heated and melted and the lower end joining surface of the new optical fiber preform to be next heated and fused are butt-joined and integrally joined, these heating and fusion are carried out. The upper end joint surface of the optical fiber preform and the lower end joint surface of the new optical fiber preform are preheated with a certain distance, and the outer peripheral edge of the joint end of the optical fiber preform is removed. In the case where the diameter is removed by entanglement to reduce the diameter, or when it is curved in a convex shape, the time required for diffusion bonding can be shortened, and bubbles can be prevented from being mixed during bonding.

Similarly, the holding portion of the optical fiber preform by the first preform holding feed means and the second preform holding feed means and the joint portion of the optical fiber preform by the diffusion joining method are respectively flame-polished. When the means is provided between the first preform holding and feeding means and the drawing heating part, it is possible to remove cracks generated on the outer peripheral surface of the preform for optical fiber, and to join the preform for optical fiber. It is possible to reduce the surface area to shorten the time required for diffusion bonding, and it is possible to draw out a high-strength optical fiber. In particular,
If the joint surface of the optical fiber preform is flame-polished immediately before the start of the joint, the joint surface can be cleaned and the joint quality can be improved.

Further, after the upper end joint surface of the optical fiber preform which is being heated and melted and the lower end joint surface of a new optical fiber preform to be subsequently heat-melted are butted and integrally joined, a joint strength confirmation test is conducted. When confirming the joint strength of the joint portion, it is possible to prevent the disconnection accident of the optical fiber after drawing.

On the other hand, a step of heating and melting the joint portion of the optical fiber preform by the diffusion joining method to draw out the optical fiber,
In the case where the step of joining the upper end joint surface of the optical fiber preform during heating and melting and the lower end joint surface of the new optical fiber preform by butting and integrally joining them at the same time is performed, The yield of continuously drawn optical fibers can be improved.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a schematic structure of an embodiment of an optical fiber drawing apparatus capable of realizing an optical fiber drawing method according to the present invention.

FIG. 2 is a side view showing an example of a structure of a joint end portion of a base material for an optical fiber.

FIG. 3 is a side view showing another example of the structure of the joint end portion of the optical fiber preform.

FIG. 4 is a conceptual diagram showing a schematic structure of another embodiment of the optical fiber drawing device according to the present invention.

5 is a sectional view taken along the line VV in FIG.

[Explanation of symbols]

 11 Optical Fiber Base Material 12 Heater 13 Wire Drawing Heating Section 14 Upper End Joining Surface 15 Optical Fiber Base Material 16 Lower End Joining Surface 17 Heater 18 Joining Heating Section 19 Lower Base Material Holding Feeding Means 20 Upper Base Material Holding Feeding Means 21 Optical Fiber 22 Healing burner 23-26 Rotating roller 27-30 Rotating shaft 31, 32 Spring

Claims (20)

[Claims] 1. An optical fiber drawing method in which a lower end portion of an optical fiber preform is melted by heating so that an optical fiber is drawn out. As a straight line with the optical fiber preform, the upper end joining surface of the optical fiber preform being heated and melted and the new lower end joining surface of the new optical fiber preform are butted and integrated by a diffusion joining method. The optical fiber drawing method is characterized in that the optical fiber is drawn continuously with respect to a plurality of optical fiber preforms by continuously joining the optical fibers and continuously drawing out the joined portion. 2. A temperature at a portion where the upper end joining surface of the optical fiber preform during heating and melting and the lower end joining surface of the optical fiber preform to be subsequently heated and abutting are butted and integrally joined by a diffusion joining method. Is in the range of 1100 ° C. or higher and 1700 ° C. or lower. 3. The optical fiber drawing method according to claim 1, wherein 3. The pressing force between the upper end joint surface of the optical fiber preform which is being heated and melted and the lower end joint surface of a new optical fiber preform to be subsequently heated and melted is continuously detected, and this pressing force is continuously detected. The joint surfaces are abutted against each other so that is always greater than or equal to a predetermined value.
The optical fiber drawing method described in. 4. The upper joint surface of the optical fiber preform during heating and melting and the lower joint surface of a new optical fiber preform to be subsequently heated and melted are butted against each other with a pressing force of 50 g / cm ² or more. The optical fiber drawing method according to claim 3, wherein 5. The heating and melting of the upper end joining surface of the optical fiber preform which is being heated and melted and the lower end joining surface of a new optical fiber preform to be next heated and fused prior to butting and integrally joining them. The method further comprises the step of preheating the upper end joint surface of the optical fiber preform and the lower end joint surface of the new optical fiber preform by a predetermined distance.
Alternatively, the optical fiber drawing method according to claim 2, claim 3, or claim 4. 6. The upper end joint surface of the optical fiber preform which is being heated and melted and the lower end joint surface of the new optical fiber preform are butted against each other and integrally joined by a diffusion joining method, and then the joined portion is gradually removed. The temperature of the cold point or higher is maintained for 5 minutes or more to remove the strain of the joint portion. 6. The method according to claim 1, 2 or 3, or 4 or 5. Optical fiber drawing method. 7. The upper end joint surface of the optical fiber preform which is being heated and melted and the lower end joint surface of a new optical fiber preform are butted against each other and integrally joined by a diffusion joining method, and then the joined portion is gradually removed. 3. The optical fiber is drawn after maintaining the temperature at the cold point or higher for 5 minutes or more, and further cooling the joint portion to a temperature at the slow cooling point or lower. The optical fiber drawing method according to claim 3, claim 4, or claim 5. 8. An upper end joint surface of an optical fiber preform which is being heated and melted and a lower end joint surface of a new optical fiber preform which is to be subsequently heated and melted are butt-joined to each other and then integrally joined. The bonding strength confirmation test for confirming the bonding strength of (1), (2), (3), (4), (5), (6), or (7) according to claim 7 is performed. Fiber drawing method. 9. The joint strength confirmation test is to apply a tension, which is equal to or more than the own weight of a new optical fiber preform to be joined to the optical fiber preform being heated and melted, to the joint. The optical fiber drawing method according to claim 8. 10. The position of the core portion at the upper end of the optical fiber preform during heating and melting and the position of the core portion at the lower end of the new optical fiber preform to be heated and melted next are detected by optical means. , Thereby aligning the core portion and then aligning the upper end joint surface of the optical fiber preform that is being heated and melted with the lower end joint surface of the new optical fiber preform to be heated and melted, and integrally. The present invention is characterized in that it is joined to the above. 1. Claim 1 or Claim 2 or Claim 3 or Claim 4 or Claim 5 or Claim 6 or Claim 7 or Claim 8
Alternatively, the optical fiber drawing method according to claim 9. 11. Before joining the upper end joining surface of the optical fiber preform during heating and melting and the lower end joining surface of a new optical fiber preform to be heated and fused next to each other and integrally joining them. The surface is flame-polished. Claim 1 or Claim 2 or Claim 3 or Claim 4 or Claim 5 or Claim 6 or Claim 7 or Claim 8 or Claim 9 or Claim Item 10. The optical fiber drawing method described in Item 10. 12. The diameter of the joint ends of a pair of optical fiber preforms to be joined to each other is reduced by removing the outer peripheral edge portions of the bases. The optical fiber drawing method according to claim 2 or claim 3 or claim 4 or claim 5 or claim 6 or claim 7 or claim 8 or claim 9 or claim 10 or claim 11. 13. The center line average roughness Ra of the region of at least 10% of the diameter of these optical fiber preforms is 3 from the center of the joining surface of the pair of optical fiber preforms that are mutually joined.
It is less than or equal to 00Å. Claim 1 or Claim 2 or Claim 3 or Claim 4 or Claim 5 or Claim 6 or Claim 7 or Claim 8 or Claim 9 or Claim 10 or Claim Item 11 or Claim 12
The optical fiber drawing method described in. 14. A pair of optical fiber preforms which are joined to each other are integrally joined with a short optical fiber preform which has been preliminarily processed into a predetermined shape, and which constitutes a joint end portion. The optical fiber drawing method according to claim 12, wherein 15. A step of heating and melting a joint part of a base material for an optical fiber by a diffusion bonding method to draw out an optical fiber, an upper end joint surface of the base material for an optical fiber being heated and melted, and a new base material for an optical fiber. 6. The step of abutting the lower end joint surface of the above and integrally joining them by a diffusion joining method is performed at the same time. Alternatively, the optical fiber drawing method according to claim 6 or claim 7 or claim 8 or claim 9 or claim 10 or claim 11 or claim 12 or claim 13 or claim 14. 16. A drawing heating unit for heating and melting the lower end of the optical fiber preform to draw out the optical fiber, and a drawing heating unit provided above the drawing heating unit for gripping the optical fiber preform. A first preform holding and feeding means for sending to the drawing heating part side, an upper end joint surface of the preform for the optical fiber which is provided above the first preform holding and feeding means and is being heated and melted, and then heat and fusion. A joining heating part for abutting the lower end joining surface of the new optical fiber preform to be joined integrally by diffusion joining method, and the new optical fiber mother provided above the joining heating part. An optical fiber drawing apparatus comprising: a second base material holding and feeding means for holding a material and sending it to the joining heating section side. 17. The preform holding and feeding means presses the outer peripheral surface of the preform for optical fiber against the outer peripheral surface of the preform for optical fiber at a predetermined pressure from at least two directions orthogonal to the feeding direction of the preform for optical fiber. 17. The device according to claim 16, further comprising at least three rotatable rollers, one roller of which is connected to a driving means to adjust a feed speed of the optical fiber preform. Optical fiber drawing device. 18. A means for flame-polishing the holding portion of the optical fiber preform by the first preform holding feed means and the second preform holding feed means and the joining portion of the optical fiber preform by the diffusion joining method, respectively. The optical fiber drawing apparatus according to claim 16 or 17, wherein is provided between the first preform holding and feeding means and the drawing heating section. 19. The flame polishing means is movable in the conveying direction of the optical fiber preform, and is used for a new optical fiber to be heated and fused next to the upper end joint surface of the optical fiber preform being heated and fused. The optical fiber drawing device according to claim 18, which is also used for flame-polishing the lower end joint surface of the base material. 20. The optical fiber drawing device according to claim 16, 17 or 18 or 19, wherein the joining heating section is retractable.