JP2002160946A - Method for manufacturing optical fiber wire and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for manufacturing optical fiber wires having low transmission loss at 1.55 μm of wave length by improving a method for cooling optical fiber bare wires after melt spinning. SOLUTION: A device 14 for gradually cooling optical fiber bare wires is located between a spinning furnace 2 and a cooling device 4. It takes 90-500 seconds to make optical fiber bare wires with 125 μm of outer diameter after the temperature of glass parts of an optical fiber preform 1 rises in the maximum temperature in the spinning furnace 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cooling a bare optical fiber melt-spun from an optical fiber preform by a cooling device, and then applying a resin on the bare optical fiber and curing the resin to form a primary coating. Layer, a method of manufacturing an optical fiber in which a secondary coating layer is sequentially formed, and a manufacturing apparatus used in this manufacturing method, by improving the method of cooling the bare optical fiber after melt spinning, the optical fiber 1.55μm wavelength
Is to reduce transmission loss.

[0002]

2. Description of the Related Art FIG. 4 is a schematic diagram showing an example of a method for manufacturing an optical fiber. The optical fiber preform 1 is heated and melt-spun in an atmosphere of an inert gas such as argon gas in a spinning furnace 2 so that the outer diameter of the bare optical fiber 3 is 1 mm.
The optical fiber bare wire 3 is cooled down by a cooling device 4, a resin is applied on the bare optical fiber 3 by a resin coating device 5, and then cured. In the device 6, the resin is cured to form a primary coating layer. Further, a resin is applied on the primary coating layer by a resin application device 7 and the resin is cured by a curing device 8 to form a secondary coating layer. The optical fiber 9 thus manufactured has its pass line changed by a turn pulley 10, passes through a take-up machine 11 and a dancer 12 in this order, and is taken up by a take-up device 13.

In recent years, in the melt spinning of an optical fiber, the optical fiber bare wire 3 has been drawn at a high speed for the purpose of increasing production efficiency. Optical fiber preform 1
When the lower end is heated by the spinning furnace 2, softened and drawn, the lower end is gradually reduced in diameter to form a conical neck-down portion. By drawing the bare optical fiber 3 at a high speed, the conical shape of the neck-down portion of the optical fiber preform 1 becomes longer, and the outer diameter of the bare optical fiber 3 becomes 125 μm.
Before this, the bare optical fiber 3 goes out of the spinning furnace 2, and the cooling fiber 4 cools the bare optical fiber 3 in the subsequent cooling device 4.

When the bare optical fiber 3 is quenched during drawing, the non-crosslinked oxygen hole center in the bare optical fiber 3 (Non Bonding Oxygen Hole).
Center, hereinafter abbreviated as NBOHC. ) Becomes difficult to recombine, and the transmission loss at the wavelength of 0.63 μm of the optical fiber 9 increases. It is known that defects including NBOHC occur when the optical fiber preform 1 is melted at a high temperature, and when the optical fiber preform 1 is gradually cooled during the melt-spinning process of the bare optical fiber 3, recombination is likely to occur. It is also known that when the transmission loss at the wavelength of 0.63 μm of the optical fiber 9 increases, the transmission loss at the wavelength of 1.55 μm, which is the wavelength band actually transmitted, is also affected.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the method of cooling a bare optical fiber after melt-spinning in the process of manufacturing an optical fiber to thereby reduce transmission loss at a wavelength of 1.55 μm. Is to provide a method and an apparatus for producing an optical fiber having a small diameter.

[0006]

According to a first aspect of the present invention, there is provided a method for manufacturing an optical fiber, comprising the steps of: supplying a bare optical fiber melt-spun from an optical fiber preform to a cooling device; Then, a resin is applied onto the bare optical fiber, and then cured to form a primary coating layer and a secondary coating layer sequentially. Then, the bare optical fiber is gradually cooled.

According to a second aspect of the present invention, there is provided a method for manufacturing an optical fiber, wherein the glass portion having the optical fiber preform comprises:
The time from reaching the maximum temperature position in the spinning furnace to becoming a bare optical fiber having an outer diameter of 125 μm is set to 90 to 500 seconds.

According to a third aspect of the present invention, there is provided an apparatus for manufacturing a bare optical fiber, comprising: means for cooling a bare optical fiber melt-spun from an optical fiber preform by a cooling device; A means for applying a resin to the resin, curing and sequentially forming a primary coating layer and a secondary coating layer, and a device for gradually cooling the bare optical fiber is provided between the optical fiber spinning furnace and the cooling device. Is what it is.

An optical fiber according to a fourth aspect of the present invention is manufactured by the method for manufacturing an optical fiber according to the first or second aspect.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The method for producing an optical fiber strand according to the present invention comprises the steps of: heating an optical fiber preform in an optical fiber spinning furnace; thereby drawing a molten optical fiber preform; In the process from reaching the highest temperature position in the furnace to becoming a bare optical fiber having an outer diameter of 125 μm, light at a wavelength of 1.55 μm is introduced by introducing a slow cooling device for gradually cooling the bare optical fiber. This is to reduce the transmission loss of the optical fiber. FIG. 1 is a schematic configuration diagram showing an example of a process for manufacturing an optical fiber using the method and apparatus for manufacturing an optical fiber of the present invention. In the drawing, the same reference numerals are given to the same devices as those of the conventional device shown in FIG.

The bare optical fiber 3 melt-spun from the optical fiber preform 1 in the spinning furnace 2 is sent to a slow cooling device 14 and further sent to a cooling device 4 where it is cooled and sent to a resin coating device 5. Sent. Here, a resin is applied to the bare optical fiber 3, and then the resin is cured by a curing device 6 to form a primary coating layer. Further, a resin is applied on the primary coating layer by a resin application device 7 and the resin is cured by a curing device 8 to form a secondary coating layer. The optical fiber 9 thus manufactured has its pass line changed by a turn pulley 10, passes through a take-up machine 11 and a dancer 12 in this order, and is taken up by a take-up device 13.

The position of the cooling device 14 may be anywhere between the spinning furnace 2 and the cooling device 4, but in order to further enhance the cooling effect, the lower portion of the spinning furnace 2 is extended. Preferably, it is provided.

The external shape of the slow cooling device 14 includes a cylindrical shape and a polygonal shape, but is not particularly limited. The internal shape of the slow cooling device 14 through which the bare optical fiber 3 passes is as follows:
There are a cylindrical shape, a polygonal shape, a corrugated shape and the like, but there is no particular limitation. For example, when the external shape of the annealing device 14 is cylindrical, the outer diameter is about 20 to 150 mm. When the outer diameter is less than 20 mm, mechanical strength is insufficient.
When the outer diameter exceeds 150 mm, workability at the time of drawing an optical fiber is reduced. Also, the outer periphery of the slow cooling device 14
It may be covered with a heat insulating material or the like. When the internal shape is cylindrical, the inner diameter can be appropriately selected within a range of 10 to 125 mm. At the time of drawing the bare optical fiber 3, it is preferable that the inner diameter is small from the viewpoint of slow cooling, but a certain size is required in consideration of the contact of the optical fiber due to the deviation and the alignment of the optical fiber.

The length of the slow cooling device 14 is required to be 100 mm or more in order to slowly cool the bare optical fiber 3 melted in the spinning furnace 2, and the preferable length depends on the spinning speed. Is determined as appropriate. If it is less than 100 mm,
Defects including NBOHC of the bare optical fiber 3 cannot be sufficiently cooled to recombine. Further, the slow cooling device 14 has a removable structure, and by removing this, the apparatus for manufacturing an optical fiber of the present invention can be used as a conventional apparatus for manufacturing an optical fiber. is there.

The inside of the slow cooling device 14 is provided with a heater or the like to increase the slow cooling effect.
The temperature can be controlled to about 0 ° C., and the surrounding area is covered with a heat insulating material or the like. Further, the temperature of the slow cooling device 14 may be lowered step by step from the side closer to the spinning furnace 2. In this case, from the side closer to the spinning furnace 2, the annealing device 14 is divided into several parts so that the temperature can be controlled, and the temperature is reduced toward the outlet of the bare optical fiber 3. Through such steps, the bare optical fiber 3 can be cooled more slowly.

When the bare optical fiber 3 is drawn at a high speed, the conical shape of the neck-down portion of the optical fiber preform 1 becomes longer, and accordingly the glass with the optical fiber preform 1 melted in the spinning furnace 2. The distance from when the portion reaches the highest temperature position in the spinning furnace to when it becomes the bare optical fiber 3 having an outer diameter of 125 μm also becomes longer. Therefore, the slow cooling device 1 as described above
4 and the bare optical fiber 3 having an outer diameter of 125 μm is formed in the slow cooling device 14 while gradually cooling the conical shape of the neck-down portion, the NBOHC of the bare optical fiber 3 is obtained.
Defects more easily recombine.

As shown in FIG. 2, when the optical fiber preform 1 is heated by the heating device in the spinning furnace 2 and reaches the maximum temperature in the spinning furnace, a molten portion of the optical fiber preform 1 is started. While the molten portion is gradually cooled in the slow cooling device 14 as described above, the time required until the point B at which the bare optical fiber 3 having an outer diameter of 125 μm is obtained is defined as the deformation time of the optical fiber.

The deformation time of the optical fiber varies depending on the linear speed of the bare optical fiber 3, but is preferably 90 to 500 seconds. Particularly preferably, it is 120 to 400 seconds. If the deformation time is less than 90 seconds, the transmission loss of the optical fiber at a wavelength of 1.55 μm increases, and if it exceeds 500 seconds, the variation in the linear velocity of the optical fiber increases.

The bare optical fiber 3 formed to have an outer diameter of 125 μm by the slow cooling device 14 is cooled in the cooling device 4 to a temperature at which a resin to be a primary coating layer can be applied. Then
A resin is applied to the bare optical fiber 3 by a resin coating device 5, and then the resin is cured by a curing device 6 to form a primary coating layer. Further, a resin coating device 7 is formed on the primary coating layer.
Is applied, and the resin is cured by the curing device 8 to form a secondary coating layer, and the optical fiber 9 is obtained. As the resin used for the coating layer, an ultraviolet curable resin is preferable.

The method and apparatus for manufacturing an optical fiber according to the present invention include a single mode optical fiber, a dispersion shift,
It can be applied to any kind of optical fiber such as cut-off shift, dispersion compensating optical fiber, etc.
This is suitable for an optical fiber having a large transmission loss at the point, i.e., large absorption by NBOHC. Vapor phase attachment method (VA
D method), external method (OVD method), internal method (CVD method,
The method can be applied to an optical fiber preform manufactured by any method such as an MCVD method or a PCVD method or a rod-in-tube method regardless of the size or shape.
It is suitable for those types in which it is difficult to reduce the amount of defects including OHC.

As described above, by providing the slow cooling device 14 and controlling the temperature of this device, the lower end of the optical fiber preform 1 melted in the spinning furnace 2 is drawn, and the melted portion has an outer diameter. The process until the optical fiber bare wire 3 of 125 μm can be adjusted. Accordingly, the method and apparatus for manufacturing an optical fiber according to the present invention are effective for recombining defects including NBOHC in a bare optical fiber at a wide range of spinning speeds. Specifically, the spinning line speed is 30 to
Suitable at 1500 m / min.

By the way, the lower end of the optical fiber preform 1 melted in the spinning furnace 2 is drawn, and the melted portion has an outer diameter of 125 mm.
If the conical shape of the neck-down portion of the optical fiber preform 1 is too long in the process of forming the bare optical fiber 3 of μm, it becomes difficult to control the linear velocity when drawing the bare optical fiber 3. Also, if the linear velocity fluctuation is large, the fluctuation of the coating diameter of the primary and secondary coating layers of the optical fiber 9 becomes large, and it becomes difficult to apply a stable coating. As a result, the coating layer of the optical fiber 9 may be uneven in thickness, or may have poor lateral pressure characteristics. Therefore, the temperature of the slow cooling device 14 is controlled, and the deformation time of the optical fiber is determined according to the linear speed of the bare optical fiber 3. As a result, it is possible to reduce an increase in transmission loss of the optical fiber 9, uneven thickness of the coating layer, poor lateral pressure characteristics, and the like.

Hereinafter, specific examples will be described. The optical fiber was manufactured by the method for manufacturing the optical fiber 9 of the present invention. First, the optical fiber preform 1 is melt-spun from the spinning furnace 2, and the bare optical fiber 3 is gradually cooled by the slow cooling device 14 attached to the outlet of the bare optical fiber 3 of the spinning furnace 2.
A 5 μm bare optical fiber 3 was melt spun. The optical fiber preform 1 used here is an optical fiber preform for wavelength multiplex transmission. As the slow cooling device 14, the inner diameter of the cylinder is 30m.
m, an outer diameter of 80 mm, and a length of 500 mm were used. Next, a urethane acrylate-based ultraviolet curable resin is applied to the cooled bare optical fiber 3 and cured to form a primary coating layer, and then a secondary coating layer in the same manner as above, and a coating diameter of the primary coating layer of 190 μm. Coating diameter of secondary coating layer 250
An optical fiber 9 of μm was manufactured.

In the manufacturing process of the optical fiber 9, the spinning speed is set to 800 m / min, and the temperature of the slow cooling device 14 is changed to change the deformation time of the optical fiber, thereby forming the bare optical fiber 3. Spinning was performed. The optical fiber 9 thus obtained was set to have a length of 10 km, and 10 samples were taken. The transmission loss at a wavelength of 1.55 μm was measured in a bundled state or a free coil state. The results are shown in FIG. At this time, the fluctuation of the spinning line speed in the spinning line of the bare optical fiber 3 was recorded. FIG. 4 shows the results.

From the results shown in FIGS. 3 and 4, when the spinning speed is set to 800 m / min in the manufacturing process of the optical fiber 9, the wavelength 1. It was found that the transmission loss and the linear velocity fluctuation at 55 μm were small. Therefore, it was found that it is preferable to adjust the temperature of the slow cooling device 14 so that the deformation time falls within this range. From the above, it has been found that the deformation time of the optical fiber varies depending on the spinning line speed, but can be determined by the transmission loss at the wavelength of 1.55 μm and the allowable range of the spinning line speed variation. .

[0026]

As described above, in the method for producing an optical fiber according to the present invention, the bare optical fiber melt-spun from the optical fiber preform is cooled by a cooling device, and then the bare optical fiber is placed on the bare optical fiber. In a method for manufacturing an optical fiber in which a resin is applied and cured to form a primary coating layer and a secondary coating layer sequentially, the optical fiber bare wire is gradually cooled between an optical fiber spinning furnace and a cooling device. After the glass part with the optical fiber preform reaches the highest temperature position in the spinning furnace, the outer diameter is 125 μm.
Since the time required for the optical fiber bare wire to be 90 to 500 seconds is set to 90 to 500 seconds, defects including NBOHC of the optical fiber bare wire are easily recombined, and the transmission of the optical fiber bare wire at a wavelength of 1.55 μm is performed. The loss can be reduced, and the variation in the linear speed of the optical fiber can be reduced even at a wide range of spinning speeds.

Further, the apparatus for producing an optical fiber according to the present invention comprises means for cooling the bare optical fiber melt-spun from the optical fiber preform by a cooling device, and applying a resin to the bare optical fiber. A means for curing and sequentially forming a primary coating layer and a secondary coating layer, and a device for gradually cooling an optical fiber bare wire between an optical fiber spinning furnace and a cooling device. An optical fiber having a small transmission loss at 0.55 μm and a small fluctuation in the linear velocity can be obtained.

Since the optical fiber of the present invention is manufactured by the method of manufacturing an optical fiber of the present invention, the coating layer has no uneven thickness and has excellent lateral pressure characteristics. .

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one example of a manufacturing process of an optical fiber of the present invention.

FIG. 2 is a schematic diagram showing a deformation process of an optical fiber when drawing an optical fiber bare wire.

FIG. 3 is a graph showing the relationship between the deformation time of an optical fiber and the transmission loss at a wavelength of 1.55 μm.

FIG. 4 is a graph showing the relationship between the deformation time of the optical fiber and the fluctuation amount of the spinning line speed.

FIG. 5 is a schematic configuration diagram showing an example of a conventional optical fiber manufacturing process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical fiber preform, 2 ... Spinning furnace, 3 ... bare optical fiber, 4 ... Cooling device, 5, 7 ... Resin coating device, 6, 8 ... Curing device, 9 ... Optical fiber wire, 10 ... Turn pulley ,
11: take-up machine, 12: dancer, 13: winding device, 14: slow cooling device, A: highest point of temperature of optical fiber preform 1, B: point at which outer diameter of optical fiber preform 1 reaches 125 μm

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichi Harada 1440 Mutsuzaki, Sakura-shi, Chiba F-term in Fujikura Sakura Works (reference) 4G060 AA01 AA03 AC15 AD02 AD22 AD43 AD53 AD58 CB09

Claims (4)

[Claims] A bare optical fiber melt-spun from an optical fiber preform is cooled by a cooling device, and then a resin is applied onto the bare optical fiber and cured to sequentially form a primary coating layer and a secondary coating layer. A method for producing an optical fiber, wherein the bare optical fiber is gradually cooled between an optical fiber spinning furnace and a cooling device. 2. The method for producing an optical fiber according to claim 1, wherein the glass portion having the optical fiber preform becomes a bare optical fiber having an outer diameter of 125 μm after reaching a maximum temperature position in the spinning furnace. A method for producing an optical fiber, wherein the time until the production is 90 to 500 seconds. 3. A means for cooling a bare optical fiber melt-spun from an optical fiber preform by a cooling device, applying a resin on the bare optical fiber, curing the resin, and sequentially forming a primary coating layer;
An apparatus for producing an optical fiber, comprising means for forming a secondary coating layer, wherein a slow cooling device for bare optical fiber is provided between the optical fiber spinning furnace and a cooling device. . 4. An optical fiber strand produced by the method for producing an optical fiber strand according to claim 1.