JP4215943B2 - Manufacturing method of optical fiber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, an optical fiber bare wire 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 form a primary coating layer and a secondary coating layer. The present invention relates to a method of manufacturing optical fiber strands to be sequentially formed and a manufacturing apparatus used for the manufacturing method, and a transmission loss at a wavelength of 1.55 μm of the optical fiber strand by improving the cooling method of the bare optical fiber after melt spinning. Is reduced.
[0002]
[Prior art]
FIG. 4 is a schematic configuration diagram illustrating an example of a method for manufacturing an optical fiber.
The optical fiber preform 1 is heated at a high temperature in an inert gas atmosphere such as argon gas in a spinning furnace 2 and melt-spun, and the outer diameter of the bare optical fiber 3 is pulled down to 125 μm to obtain an bare optical fiber 3. The bare optical fiber 3 is cooled by a cooling device 4, then a resin is applied onto the bare optical fiber 3 by a resin coating device 5, and then the resin is cured by a curing device 6 to be primary coated. Form a layer. Further, a resin is applied on the primary coating layer by the resin coating device 7 and the resin is cured by the curing device 8 to form a secondary coating layer. The optical fiber 9 manufactured in this manner has its pass line changed by the turn pulley 10, passes through the take-up machine 11 and the dancer 12 in this order, and is taken up by the take-up device 13.
[0003]
By the way, in recent years, in the optical fiber melt spinning, the optical fiber bare wire 3 is drawn at a high speed for the purpose of increasing production efficiency.
When the lower end of the optical fiber preform 1 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 high speed, the conical shape of the neck-down portion of the optical fiber preform 1 becomes long, and before the outer diameter of the bare optical fiber 3 becomes 125 μm, the bare optical fiber 3 The wire 3 comes out of the spinning furnace 2, and the bare optical fiber 3 is rapidly cooled by the cooling gas in the subsequent cooling device 4.
[0004]
When the bare optical fiber 3 is rapidly cooled at the time of drawing, defects including a non-bridging oxygen hole center (Non Bonding Oxygen Hole Center, hereinafter abbreviated as NBOHC) in the bare optical fiber 3 are difficult to recombine. There is a problem that the transmission loss of the fiber strand 9 at a wavelength of 0.63 μm increases.
It is known that defects including NBOHC are generated when the optical fiber preform 1 is melted at a high temperature, and recombination easily occurs when the optical fiber preform 1 is gradually cooled during the melt spinning process of the optical fiber bare wire 3.
Further, it has been found that when the transmission loss of the optical fiber 9 at a wavelength of 0.63 μm increases, the transmission loss at a wavelength of 1.55 μm, which is a wavelength range for actual transmission, is also affected.
[0005]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a method for manufacturing an optical fiber having a small transmission loss at a wavelength of 1.55 μm by improving a method for cooling the bare optical fiber after melt spinning in the manufacturing process of the optical fiber. And providing an apparatus thereof.
[0006]
[Means for Solving the Problems]
In order to solve such problems, the present invention cools an optical fiber bare wire melt-spun from an optical fiber preform with a cooling device, and then coats the resin on the optical fiber bare wire, cures it, and sequentially coats the primary coating. In the manufacturing method of the optical fiber for forming the layer and the secondary coating layer,
When the optical fiber bare wire is gradually cooled between the optical fiber spinning furnace and the cooling device, and the optical fiber preform is heated by the heating device in the spinning furnace and reaches the maximum temperature in the spinning furnace A From 90 to 500 seconds, the melted portion of the optical fiber preform is drawn, and the melted portion is gradually cooled in the slow cooling device, and the time required until the point B when the optical fiber becomes a bare optical fiber having an outer diameter of 125 μm is obtained. An optical fiber manufacturing method is provided.
[0007]
In the optical fiber manufacturing method of the present invention , it is preferable that a slow cooling device is provided so as to extend the lower part of the optical fiber spinning furnace, and the bare optical fiber is slowly cooled by the slow cooling device.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
In the method for manufacturing an optical fiber according to the present invention, when a molten optical fiber preform is drawn by heating the optical fiber preform in an optical fiber spinning furnace, the glass portion with the optical fiber preform is spun. By introducing a slow cooling device for gradually cooling the bare optical fiber in the process from reaching the maximum temperature position in the furnace to the bare optical fiber having an outer diameter of 125 μm, light at a wavelength of 1.55 μm is introduced. The transmission loss of the fiber strand is reduced.
FIG. 1 is a schematic configuration diagram illustrating an example of an optical fiber manufacturing process using the optical fiber manufacturing method and manufacturing apparatus of the present invention. In the figure, the same reference numerals are assigned to the same devices as those shown in FIG.
[0011]
The bare optical fiber 3 melt-spun from the optical fiber preform 1 in the spinning furnace 2 is sent to the slow cooling device 14 and further sent to the cooling device 4 where it is cooled and sent to the resin coating device 5. Here, a resin is applied to the bare optical fiber 3, and then the resin is cured by the curing device 6 to form a primary coating layer. Further, a resin is applied onto the primary coating layer by the resin coating device 7, and the resin is cured by the curing device 8 to form a secondary coating layer. The optical fiber 9 manufactured in this manner has its pass line changed by the turn pulley 10, passes through the take-up machine 11 and the dancer 12 in this order, and is taken up by the take-up device 13.
[0012]
The slow cooling device 14 may be provided anywhere between the spinning furnace 2 and the cooling device 4, but in order to further increase the slow cooling effect, the lower part of the spinning furnace 2 may be extended. preferable.
[0013]
Although the external shape of the slow cooling apparatus 14 has a cylindrical shape, a polygonal shape, etc., it is not specifically limited. Moreover, although the internal shape through which the optical fiber bare wire 3 of the slow cooling apparatus 14 passes has a cylindrical shape, a polygon, a corrugated shape, etc., it does not specifically limit.
For example, when the outer shape of the slow cooling device 14 is cylindrical, the outer diameter is about 20 to 150 mm. When the outer diameter is less than 20 mm, the mechanical strength is insufficient. When the outer diameter exceeds 150 mm, workability at the time of drawing the optical fiber is lowered. Moreover, you may cover the outer periphery of the slow cooling apparatus 14 with a heat insulating material etc. suitably.
When the internal shape is also 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 narrow in terms of slow cooling. However, considering the contact of the optical fiber due to line blurring and the alignment of the optical fiber, a certain size is required.
[0014]
Further, the length of the slow cooling device 14 is required to be 100 mm or more in order to gently cool the bare optical fiber 3 melted in the spinning furnace 2, and the preferable length is appropriately determined according to the spinning wire speed. It is determined. If it is less than 100 mm, defects including NBOHC in the bare optical fiber 3 are recombined and cannot be sufficiently cooled slowly.
Moreover, the slow cooling device 14 has a detachable structure, and by removing this, the optical fiber strand manufacturing apparatus of the present invention can be used as a conventional optical fiber strand manufacturing apparatus. is there.
[0015]
In the slow cooling device 14, in order to further enhance the slow cooling effect, the slow cooling device 14 can be temperature controlled to about 50 to 1200 ° C. with a heater or the like, and the surroundings are a heat insulating material or the like. Covered with.
Further, the temperature of the slow cooling device 14 may be lowered stepwise in order from the one closer to the spinning furnace 2. In this case, from the side close to the spinning furnace 2, the slow cooling device 14 is divided into several parts so that the temperature can be controlled, and the temperature is lowered toward the outlet of the bare optical fiber 3. Through such a process, the bare optical fiber 3 can be cooled more slowly.
[0016]
When the drawing of the bare optical fiber 3 is performed at high speed, the conical shape of the neck-down portion of the optical fiber preform 1 becomes long, and the glass portion with the optical fiber preform 1 melted in the spinning furnace 2 is The distance from reaching the maximum temperature position in the spinning furnace to the bare optical fiber 3 having an outer diameter of 125 μm is also increased. Therefore, by providing the slow cooling device 14 as described above and forming the bare optical fiber 3 having an outer diameter of 125 μm while gradually cooling the conical shape of the neck-down portion in the slow cooling device 14, the optical fiber Defects including NBOHC in the bare wire 3 are more likely to recombine.
[0017]
As shown in FIG. 2, from the point A 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, the melted portion of the optical fiber preform 1 is drawn. The time required until the point B when the optical fiber bare wire 3 with an outer diameter of 125 μm is obtained while the molten portion is gradually cooled in the slow cooling device 14 as described above is defined as the deformation time of the optical fiber.
[0018]
The deformation time of this optical fiber is preferably 90 to 500 seconds, although it varies depending on the drawing speed of the bare optical fiber 3. Particularly preferred is 120 to 400 seconds.
If the deformation time is less than 90 seconds, the transmission loss of the optical fiber strand at a wavelength of 1.55 μm increases, and if it exceeds 500 seconds, the amount of fluctuation in the optical fiber strand speed increases.
[0019]
The bare optical fiber 3 formed to have an outer diameter of 125 μm by the slow cooling device 14 is cooled by the cooling device 4 to a temperature at which the resin as the primary coating layer can be applied. Next, a resin is applied onto 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 is formed on the primary coating layer. A resin is applied at 7 and the resin is cured by a curing device 8 to form a secondary coating layer, whereby an optical fiber 9 is obtained.
As the resin used for the coating layer, an ultraviolet curable resin is suitable.
[0020]
The method and apparatus for manufacturing an optical fiber of the present invention can be applied to any type of optical fiber such as a single mode optical fiber, dispersion shift, cut-off shift, and dispersion compensating optical fiber, but transmission at a wavelength of 0.63 μm. It is suitable for an optical fiber having a large loss, that is, absorption by NBOHC.
For optical fiber preforms produced by any method such as vapor phase method (VAD method), external method (OVD method), internal method (CVD method, MCVD method, PCVD method) or rod-in-tube method However, it can be applied regardless of its size and shape, but is suitable for a type in which it is difficult to reduce the amount of defects including NBOHC.
[0021]
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 this melted portion is a light having an outer diameter of 125 μm. The process up to the bare fiber 3 can be adjusted.
As a result, 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, it is suitable at a spinning linear speed of 30 to 1500 m / min.
[0022]
By the way, in the process until the lower end of the optical fiber preform 1 melted in the spinning furnace 2 is drawn and the melted portion becomes the bare optical fiber 3 having an outer diameter of 125 μm, the neck-down portion of the optical fiber preform 1 If the conical shape is too long, it becomes difficult to control the linear velocity when the bare optical fiber 3 is drawn. In addition, if the linear velocity fluctuation is large, the fluctuations in the coating diameters of the primary and secondary coating layers of the optical fiber 9 become large, making it difficult to apply a stable coating. As a result, uneven thickness occurs in the coating layer of the optical fiber 9 or a lateral pressure characteristic defect occurs.
Therefore, the temperature of the slow cooling device 14 is controlled, and the deformation time of the optical fiber is determined according to the drawing speed of the bare optical fiber 3. Thereby, an increase in transmission loss of the optical fiber 9, uneven thickness of the coating layer, poor side pressure characteristics, and the like can be reduced.
[0023]
Specific examples are shown below.
The optical fiber strand was manufactured with the manufacturing method of the optical fiber strand 9 of this invention. First, the optical fiber preform 1 is melt-spun from the spinning furnace 2, and the optical fiber bare wire 3 is gradually cooled by the slow cooling device 14 attached to the drawing port of the bare optical fiber 3 of the spinning furnace 2, and the outer diameter is 125 μm. The bare optical fiber 3 was melt-spun.
The optical fiber preform 1 used here is an optical fiber preform for wavelength multiplexing transmission.
As the slow cooling device 14, a cylinder having an inner diameter of 30 mm, an outer diameter of 80 mm, and a length of 500 mm was used.
Subsequently, a urethane acrylate 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 is formed in the same manner, and the coating diameter of the primary coating layer is 190 μm, An optical fiber 9 having a secondary coating layer with a coat diameter of 250 μm was produced.
[0024]
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 spinning the bare optical fiber 3. It was.
Ten optical fiber strands 9 thus obtained were taken with a length of 10 km, and 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.
Further, the fluctuation of the spinning speed in the spinning line of the bare optical fiber 3 at this time was recorded. The results are shown in FIG.
[0025]
From the results of FIGS. 3 and 4, in the manufacturing process of the optical fiber 9, when the spinning wire speed is 800 m / min, transmission at a wavelength of 1.55 μm is performed when the deformation time of the optical fiber is 200 to 400 seconds. It was found that the loss and the linear velocity fluctuation amount 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 was found that the deformation time of this optical fiber can be determined by the transmission loss at a wavelength of 1.55 μm and the allowable range of the amount of fluctuation in the spinning line speed, although the optimum time varies depending on the spinning line speed. .
[0026]
【The invention's effect】
As described above, in the method for manufacturing an optical fiber according to the present invention, an optical fiber bare wire melt-spun from an optical fiber preform is cooled by a cooling device, and then a resin is applied onto the optical fiber bare wire. In the method of manufacturing an optical fiber, in which a primary coating layer and a secondary coating layer are sequentially formed by curing, a bare optical fiber is gradually cooled between an optical fiber spinning furnace and a cooling device, and an optical fiber preform It takes 90 to 500 seconds from the time when a certain glass part reaches the highest temperature position in the spinning furnace until it becomes an optical fiber bare wire with an outer diameter of 125 μm, and therefore includes NBOHC of the bare optical fiber. Defects are easily recombined, transmission loss of the optical fiber at a wavelength of 1.55 μm can be reduced, and the amount of fluctuation of the optical fiber can be reduced even at a wide range of spinning speeds. .
[0027]
Further, the optical fiber manufacturing apparatus of the present invention includes a means for cooling an optical fiber bare wire melt-spun from an optical fiber preform by a cooling device, and applying and curing a resin on the optical fiber bare wire. In order to form a primary coating layer and a secondary coating layer in sequence, and a slow cooling device for the bare optical fiber between the optical fiber spinning furnace and the cooling device, the wavelength is 1.55 μm. It is possible to obtain an optical fiber having a small transmission loss and a small amount of fluctuation in the linear velocity.
[0028]
And since the optical fiber strand of this invention is manufactured by the manufacturing method of the optical fiber strand of this invention, there is no uneven thickness in a coating layer and it is excellent in the side pressure characteristic.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an example of a manufacturing process of an optical fiber according to the present invention.
FIG. 2 is a schematic view showing a deformation process of the optical fiber when the bare optical fiber is drawn.
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 amount of fluctuation in the spinning linear velocity.
FIG. 5 is a schematic configuration diagram showing an example of a manufacturing process of a conventional optical fiber.
[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 strand, 10 ... Turn pulley DESCRIPTION OF SYMBOLS 11 ... Take-out machine, 12 ... Dancer, 13 ... Winding device, 14 ... Slow cooling device, A ... Maximum temperature of optical fiber preform 1 B: Reach point of optical fiber preform 1 having outer diameter of 125 [mu] m

Claims (2)

An optical fiber in which 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. In the manufacturing method of
When the optical fiber bare wire is gradually cooled between the optical fiber spinning furnace and the cooling device, and the optical fiber preform is heated by the heating device in the spinning furnace and reaches the maximum temperature in the spinning furnace A From 90 to 500 seconds, the melted portion of the optical fiber preform is drawn, and the melted portion is gradually cooled in the slow cooling device, and the time required until the point B when the optical fiber becomes a bare optical fiber having an outer diameter of 125 μm is obtained. A method of manufacturing an optical fiber.   The optical fiber strand according to claim 1, wherein a slow cooling device is provided so as to extend a lower portion of the optical fiber spinning furnace, and the bare optical fiber is gradually cooled by the slow cooling device. Method.

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