JP2005320191A - Method and apparatus for manufacturing optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the method for manufacturing an optical fiber by which the peeling or the crack of a coating layer which is caused by the Young's modulus is prevented and an apparatus for manufacturing the optical fiber. <P>SOLUTION: The method of manufacturing the optical fiber comprises a spinning step of melting and spinning an optical fiber preform 11 to form a bare optical fiber 13, a coating step of forming a primary coating layer on the bare optical fiber 13, applying a coating material on the outer periphery of the primary coating layer and curing the coating material by the irradiation with light from a crosslinking lamp provided on a 2nd crosslinking cylinder 18 to form a secondary coating layer to obtain the optical fiber 19 and a twisting step of twisting the optical fiber 19 by a twisting apparatus 22 to twist the molten part of the optical fiber preform 11. The secondary coating layer on the optical fiber 19 in the twisting by the twisting apparatus 22 in the twisting step is controlled to have 50-300 MPa Young's modulus and the temperature in the twisting is controlled to 50-130°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical fiber strand manufacturing method and an optical fiber strand manufacturing apparatus, and in particular, to reduce polarization mode dispersion in an optical fiber strand, the optical fiber preform is twisted. The present invention relates to an optical fiber manufacturing method and an optical fiber manufacturing apparatus to which an adding step is applied.

In general, an optical fiber is manufactured as follows.
FIG. 2 is a schematic diagram showing a schematic configuration of an optical fiber manufacturing apparatus used in a conventional optical fiber manufacturing method.

  In the production of an optical fiber, first, an optical fiber preform 101 containing silica glass as a main component is accommodated in a spinning furnace 102, and in an inert gas atmosphere such as argon (Ar) or helium (He). The tip portion is heated at a high temperature to about 2000 ° C. and melt-spun to obtain a bare optical fiber 103.

  Next, the bare optical fiber 103 is fed into the cooling cylinder 104. A cooling gas such as helium or nitrogen gas is supplied into the cooling cylinder 104, and the optical fiber bare wire 103 is rapidly cooled in the cooling cylinder 104 to a temperature suitable for forming the primary coating layer in the next process.

  Next, the bare optical fiber 103 cooled by the cooling cylinder 104 is covered with a primary coating layer made of an ultraviolet curable resin or the like by a coating material coating apparatus 105 for forming a primary coating layer and a UV lamp 106.

  Further, the bare optical fiber 103 provided with the primary coating layer is coated with a secondary coating layer made of an ultraviolet curable resin or the like by the coating material coating device 107 and the UV lamp 108 for forming the secondary coating layer. A fiber strand 109 is obtained.

  Further, the optical fiber 109 being spun is twisted by the twisting device 110 and then turned in another direction by the turn pulley 111, wound around the take-up drum 114 through the take-up machine 112 and the dancer roll 113. Taken.

  In recent years, in the production of an optical fiber, in order to reduce the polarization mode dispersion (hereinafter referred to as “PMD”) of the optical fiber, The optical fiber bare wire 103 is provided while twisting the heating and melting portion of the optical fiber preform 101 (the lower end portion of the optical fiber preform 101) by providing a twist device 110 and twisting the optical fiber 109. (For example, refer to Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, and Patent Document 6).

The twist applied to the optical fiber 109 during drawing by the twisting device 110 is transmitted to the heating and melting part of the optical fiber preform 101. For this reason, the optical fiber bare wire 103 is melt-spun while being twisted in the heating and melting portion of the optical fiber preform 101. Accordingly, the twist is fixed to the bare optical fiber 103 after spinning.
According to such an optical fiber manufacturing method, an optical fiber with reduced PMD can be obtained.

  However, although Patent Document 1 to Patent Document 6 disclose the principle, method, and apparatus for twisting an optical fiber, specific manufacturing conditions for the optical fiber using these are disclosed. Is not disclosed at all.

In general, in the methods disclosed in Patent Documents 1 to 6 and the like, the twist applied to the optical fiber after the secondary coating layer is formed by the twisting device is the secondary coating layer, the primary coating layer, and the optical fiber bare. It is transmitted in the order of the lines.
The twist is applied by, for example, torque applied to the optical fiber by a twist roller provided in the twisting device, and friction between the coating layer of the optical fiber and the twist roller.

  In order to efficiently apply torque to the optical fiber, the frictional force of the surface of the twisting roller against the coating layer of the optical fiber is a very important factor. Therefore, as a method of increasing the frictional force of the surface of the twisting roller against the coating layer, a method of pressing the optical fiber strand with the twisting roller while applying tension to the optical fiber strand, or an optical fiber element using at least a pair of twisting rollers is used. A method of sandwiching the line is used.

  However, if the force that presses the optical fiber with the twisting roller or the force that sandwiches the optical fiber with the twisting roller is too large, the Young's modulus of the coating layer when applying torque (mainly the outermost layer of the coating layer) Young's modulus: In a two-layer optical fiber made of a primary coating layer and a secondary coating layer, if the secondary coating layer has a high Young's modulus), the force applied to the optical fiber is generally Absorption is performed by the inner coating layer having a lower Young's modulus than the outermost layer of the coating layer (the primary coating layer in the case of a two-layer optical fiber). As a result, the inner coating layer may be crushed and the coating layer may be peeled off or the inner coating layer may be broken at the interface between the bare optical fiber and the inner coating layer. Due to such defects in the coating layer, the optical fiber has a problem that transmission loss due to microbending increases and the environmental resistance of the coating layer deteriorates.

  On the other hand, if the pressing force of the twisting roller against the optical fiber strand is made too small in order to prevent the coating layer of the optical fiber strand from peeling off or cracking, a sufficient torque is applied to the optical fiber strand. I can't. As a result, slippage occurs between the optical fiber and the twisting roller, and as a result, the optical fiber that is being drawn is shaken, resulting in coating defects such as uneven thickness of the coating layer.

  Therefore, as a method for preventing peeling at the interface between the bare optical fiber and the primary coating layer, and stably sticking the primary coating layer to the bare optical fiber, for example, immediately before being introduced into the coating material coating apparatus Examples include a method of controlling the temperature of the bare optical fiber within a predetermined temperature range (see, for example, Patent Document 7 and Patent Document 8).

  However, since the adhesion force of the coating layer to the bare optical fiber is determined by the maximum adhesion force of the coating material itself, it does not become larger than this maximum adhesion force. Even if the adhesion force of the coating layer to the bare optical fiber is increased, there is no effect in preventing the coating layer from cracking.

  In addition, as a method for preventing peeling at the interface between the bare optical fiber and the primary coating layer, the Young's modulus and glass transition point of the primary coating layer are adjusted by appropriately selecting the coating material forming the primary coating layer. And the method of making the primary coating layer absorb the external force applied to the secondary coating layer is mentioned (for example, refer patent document 9 and patent document 10).

  However, in an optical fiber manufacturing method using a process of twisting an optical fiber (hereinafter referred to as “twisting process”), rotational torque is always applied to the optical fiber as an external force. The primary coating layer cannot absorb the external force and cannot completely prevent peeling at the interface between the bare optical fiber and the primary coating layer. Further, the Young's modulus of the coating layer at room temperature and the Young's modulus of the coating layer when twisted are greatly different. In the production of an optical fiber, the Young's modulus of the coating layer when twisting is important, so the methods disclosed in Patent Document 9 and Patent Document 10 cannot be applied as they are.

  Further, the composition of the coating material for forming the primary coating layer is adjusted so that the adhesion force to the bare optical fiber, the ratio of Young's modulus to the secondary coating layer, and the adhesion force ratio are within a predetermined range. And a method of preventing the coating layer of the optical fiber from peeling off or cracking of the coating layer (see, for example, Patent Document 11 and Patent Document 12).

 However, the methods disclosed in Patent Document 11 and Patent Document 12 usually adjust the composition of the coating material at room temperature to obtain the properties (Young's modulus and adhesion) of the coating layer of the manufactured optical fiber. The purpose is to be within a predetermined range. In addition, in the method of manufacturing an optical fiber strand to which the twisting process is applied, an external force is applied to the optical fiber strand at a high temperature immediately after the coating material is cured. The Young's modulus of the coating material at the temperature at which the twist is actually applied affects the formation of the coating layer. For this reason, the methods disclosed in Patent Document 11 and Patent Document 12 cannot be applied to a method of manufacturing an optical fiber that applies a twisting process.

Moreover, when the optical fiber is manufactured by cooling the optical fiber to room temperature and then twisting with a twisting device, the Young's modulus of the secondary coating layer of the optical fiber is too high. Since all are absorbed by the primary coating layer, there is a problem that the primary coating layer peels off or the primary coating layer breaks.
Japanese Patent No. 2981088 Japanese Patent No. 3224235 Japanese National Patent Publication No. 10-507438 Japanese Patent No. 3070603 Japanese Patent No. 3070604 JP 2000-143277 A Japanese Patent No. 3401506 JP 2003-226559 A JP-A-2001-108874 JP-A-8-129119 Japanese Patent Application Laid-Open No. 9-5587 Japanese Patent Laid-Open No. 11-116282

  The present invention has been made in view of the above circumstances, and provides an optical fiber manufacturing method and an optical fiber manufacturing apparatus that prevent the peeling and cracking of a coating layer due to Young's modulus. For the purpose.

  In order to solve the above problems, the present invention provides a spinning process in which an optical fiber preform is melt-spun to form a bare optical fiber, and a coating material is applied to the bare optical fiber formed by the spinning process. The coating material is cured by light irradiated from a bridging lamp provided in a bridging cylinder to form a coating layer, and a coating process to form an optical fiber, and an optical fiber formed by the coating process, An optical fiber manufacturing method comprising a twisting step of twisting a molten portion of an optical fiber preform by applying a twist by a twisting device, wherein the twisting device applies a twist in the twisting step A method of manufacturing an optical fiber is provided in which the Young's modulus of the outermost layer of the coating layer of the optical fiber is 50 MPa to 300 MPa.

  In the twisting step, it is preferable that the temperature of the outermost layer of the coating layer of the optical fiber is 50 to 130 ° C. when twisting is performed by the twisting device.

  In the twisting step, it is preferable to control a distance between the bridging cylinder and the twisting device.

  In the twisting step, it is preferable to heat and / or cool the coating layer of the optical fiber strand before twisting the optical fiber strand.

  The present invention relates to a spinning furnace for melting an optical fiber preform, a coating material coating apparatus for coating a coating material on an optical fiber bare wire, and a bridge having a crosslinking lamp that cures the coating material by irradiating the coating material with light. An optical fiber manufacturing apparatus comprising a tube and a twisting device for twisting the optical fiber, wherein the twisting device is provided movably along the drawing direction of the optical fiber, and the bridge tube And an optical fiber manufacturing apparatus capable of controlling the distance between the twisting device and the twisting device.

  The present invention relates to a spinning furnace for melting an optical fiber preform, a coating material coating apparatus for coating a coating material on an optical fiber bare wire, and a bridge having a crosslinking lamp that cures the coating material by irradiating the coating material with light. An optical fiber manufacturing apparatus comprising a tube and a twisting device for twisting the optical fiber, wherein heating means and / or cooling means are provided between the bridging cylinder and the twisting device. An optical fiber manufacturing apparatus is provided.

According to the present invention, since the Young's modulus of the outermost layer of the coating layer of the optical fiber strand when twisting is applied by the twisting device can be reduced, even if an external force is applied to the optical fiber strand by the twisting device, Since it can be absorbed by the outermost layer of the coating layer and the coating layer inside the outermost layer, peeling of the coating layer from the bare optical fiber and cracking of the coating layer inside the outermost layer are prevented. be able to.
Therefore, in the optical fiber, an increase in transmission loss due to microbending caused by peeling and cracking of the coating layer can be suppressed. Moreover, since peeling and cracking of the coating layer of the optical fiber strand can be suppressed, an optical fiber strand excellent in environmental resistance can be manufactured.

  In addition, according to the present invention, since the torque can be applied to the optical fiber by the twisting device so that the twist can be effectively applied to the heating and melting portion of the optical fiber preform, the PMD is reduced. An optical fiber can be efficiently manufactured.

  Hereinafter, an embodiment of a method for manufacturing an optical fiber according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing a schematic configuration of an optical fiber manufacturing apparatus used in an optical fiber manufacturing method according to the present invention.
In FIG. 1, reference numeral 11 is an optical fiber preform, 12 is a spinning furnace, 13 is a bare optical fiber, 14 is a cooling cylinder, 15 is a first coating material coating device, 16 is a first bridging cylinder, and 17 is a first Two coating material coating devices, 18 is a second cross-linking tube, 19 is an optical fiber, 20 is a heating device, 21 is a cooling device, 22 is a twisting device, 23 is a turn pulley, 24 is a take-up machine, and 25 is a dancer roll. , 26 indicate winding drums, respectively.

  In the method of manufacturing an optical fiber according to this embodiment, first, an optical fiber preform 11 mainly composed of silica glass is attached to the spinning furnace 12 so as to be movable in the axial direction, and argon (Ar), In an inert gas atmosphere such as helium (He), the lower end portion thereof is heated to about 2000 ° C. at a high temperature and melt-spun to obtain a bare optical fiber 13 (spinning process).

  Next, the bare optical fiber 13 is fed into the cooling cylinder 14. A cooling gas such as helium or nitrogen gas is supplied into the cooling cylinder 14, and the bare optical fiber 13 is rapidly cooled in the cooling cylinder 14 to a temperature suitable for forming a primary coating layer in the next process.

  Next, the bare optical fiber 13 cooled in the cooling cylinder 14 is coated with a first covering material made of an ultraviolet curable resin so as to cover the outer periphery thereof in the first covering material coating apparatus 15 for forming the primary covering layer. Next, the first coating material is cured by light such as ultraviolet rays irradiated from a bridge lamp (not shown) made of a UV lamp or the like provided in the first bridge cylinder 16 to form a primary coating layer. Is formed (coating process).

  Further, the bare optical fiber 13 provided with the primary coating layer is a second coating made of an ultraviolet curable resin so as to cover the outer periphery of the primary coating layer in the second coating material coating apparatus 17 for forming the secondary coating layer. Then, the second coating material is cured by light such as ultraviolet rays irradiated from a bridge lamp (not shown) including a UV lamp provided on the second bridge cylinder 18. Then, the secondary coating layer is formed to form the optical fiber 19 (coating process).

  Further, the optical fiber 19 is twisted by a twisting device 22 (twisting process), and the direction is changed in another direction by a turn pulley 23, and is wound around a winding drum 26 through a take-up machine 24 and a dancer roll 25. Taken.

  In this embodiment, the twisting device 22 is movable along the drawing direction of the optical fiber 19 by a position adjusting mechanism provided in the optical fiber manufacturing apparatus. Thereby, the distance between the 2nd bridge | crosslinking cylinder 18 and the twist apparatus 22 can be adjusted arbitrarily.

  The twisting device 22 includes at least a pair of twisting rollers that abut a part of the outer periphery of the optical fiber 19 being spun, and a device having a mechanism in which the pair of twisting rollers translate, or a pair of twisting rollers A device having a mechanism that swings is used.

  As another example of a twisting device having a mechanism in which a pair of twisting rollers swing, for example, a pair of rotating twisting rollers and an optical fiber strand 19 are in contact with each other, and the optical fiber strand 19 is in a direction parallel to the spinning direction. By periodically twisting the optical fiber 19 by twisting it with the longitudinal direction as an axis, by periodically swinging the optical fiber (hereinafter referred to as “swinging motion”). And a device for applying torque (hereinafter, such a device is referred to as “twisting device A”).

  As a twisting device having a mechanism in which the pair of twisting rollers translate, for example, the optical fiber 19 is pressed between the peripheral curved surfaces of the pair of rotating twisting rollers, and the moving direction of the pair of twisting rollers is periodically changed. The optical fiber 19 is rolled back and forth in a direction substantially perpendicular to the spinning direction between the peripheral curved surfaces of the pair of twisting rollers by reversing or the like, and the spinning direction of the optical fiber 19 is periodically changed. A device that applies torque by adding a twist that turns around the axis (hereinafter, such a device is referred to as “twist device B”).

  As an example of the twisting device having a mechanism in which the pair of twisting rollers swings, the pair of twisting rollers are moved in different directions while pressing the optical fiber 19 between the peripheral curved surfaces of the pair of rotating twisting rollers, for example. The optical fiber 19 is periodically tilted obliquely with respect to the spinning direction, and a twist is applied to the optical fiber 19 to rotate about its longitudinal direction as an axis. Hereinafter, such a device is referred to as “twist device C”).

By the way, the Young's modulus of the coating layer of the optical fiber strand depends on the temperature, and generally, the Young's modulus of the coating layer decreases as the temperature increases and increases as the temperature decreases.
In the coating step, after the second coating material is applied to the bare optical fiber 13 on which the primary coating layer is formed, the second coating material is irradiated from the bridge lamp provided in the second bridge cylinder 18. The secondary coating layer is formed by being cured by light such as ultraviolet rays. The temperature of the coating layer rises and the Young's modulus decreases due to the reaction heat at the time of curing of the second coating material and the width radiation heat generated from the bridge lamp.

  Therefore, in this embodiment, by controlling the temperature of the secondary coating layer of the optical fiber 19 when twisting is performed by the twisting device 22 in the twisting process, the Young of the secondary coating layer of the optical fiber 19 is controlled. Set the rate within a predetermined range.

  Specifically, in the twisting process, the temperature of the outermost layer (here, the secondary coating layer) of the coating layer of the optical fiber 19 when the twisting device 22 is twisted is controlled within a range of 50 to 130 ° C. At this time, the Young's modulus of the outermost layer (here, the secondary coating layer) of the coating layer of the optical fiber 19 is set in the range of 50 MPa to 300 MPa. Preferably, the temperature of the secondary coating layer of the optical fiber 19 when twisting is performed by the twisting device 22 is controlled within a range of 70 to 100 ° C., and the secondary coating of the optical fiber 19 at this time is controlled. The Young's modulus of the layer is set in the range of 100 MPa to 200 MPa.

In this embodiment, in order to control the temperature of the secondary coating layer of the optical fiber 19 when the twist is applied by the twisting device 22 within the above range, a position adjusting mechanism provided in the optical fiber manufacturing apparatus. The twisting device 22 is moved by adjusting the distance between the second bridging cylinder 18 and the twisting device 22, and the optical fiber strand 19 is required to leave the second bridging cylinder 18 and reach the twisting device 22. Cool naturally with air.
In order to keep the temperature of the secondary coating layer of the optical fiber 19 when twisting is performed by the twisting device 22 within the above range, the distance between the second bridging cylinder 18 and the twisting device 22 is set to be equal to the optical fiber element. It is preferable to adjust appropriately according to the drawing speed of the wire 19 and the heat in the second bridging cylinder 18 and to match the temperature of the outermost layer (here, the secondary coating layer) of the coating layer of the optical fiber strand 19.

  When the temperature of the secondary coating layer of the optical fiber 19 when applying twist by the twisting device 22 is less than 50 ° C., the Young's modulus of the secondary coating layer is high, so that the external force applied by the twisting device 22 is applied to the primary coating. Cannot be absorbed by the entire layer and the secondary coating layer, causing separation at the interface between the bare optical fiber and the primary coating layer, and cracking of the primary coating layer, resulting in transmission loss due to microbending. Will increase. On the other hand, if the temperature of the secondary coating layer of the optical fiber 19 when twisting is performed by the twisting device 22 exceeds 130 ° C., the Young's modulus of the secondary coating layer is too low. When a torque is applied to 19, the secondary coating layer is peeled off, and the secondary coating layer adheres to a circumferential member such as a roller provided in the twisting device 22. As described above, when the peeled secondary coating layer adheres to the circumferential member, the twisting device 22 cannot apply a predetermined torque to the optical fiber 19, and as a result, the optical fiber This causes manufacturing defects.

  Further, when the Young's modulus of the secondary coating layer of the optical fiber 19 when twisting is performed by the twisting device 22 is less than 50 MPa, the Young's modulus of the secondary coating layer is too low. When the torque is applied, the secondary coating layer is peeled off, and the secondary coating layer adheres to a circumferential member such as a roller provided in the twisting device 22. As described above, when the peeled secondary coating layer adheres to the circumferential member, the twisting device 22 cannot apply a predetermined torque to the optical fiber 19, and as a result, the optical fiber This causes manufacturing defects. On the other hand, when the Young's modulus of the secondary coating layer of the optical fiber 19 when twisting by the twisting device 22 exceeds 300 MPa, the Young's modulus of the secondary coating layer is high, so that the external force applied by the twisting device 22 is increased. Transmission loss caused by microbending, which cannot be absorbed by the entire primary coating layer and secondary coating layer, causes separation at the interface between the bare optical fiber and the primary coating layer, and cracks in the primary coating layer. Will increase.

  Further, as described above, when the distance between the second bridging cylinder 18 and the twisting device 22 is adjusted and the optical fiber 19 cannot be naturally cooled, the second bridging cylinder 18 and the twisting device are used. One of the heating means 20 and the cooling means 21 or both the heating means 20 and the cooling means 21 is provided between the optical fiber strand 19 and the optical fiber 19 when the twisting device 22 is twisted. You may control the temperature of a coating layer in the range of 50-130 degreeC.

As the heating means 20, a heating cylinder provided with a heater such as a heating wire, a slow cooling tube in which an inert gas having a low heat transfer coefficient such as nitrogen gas or argon is flowed, and the like are used. Examples of the heating method by the heating means 20 include a method of heating the optical fiber 19 by adjusting the temperature of the heater. By using this heating means 20, the secondary coating layer of the optical fiber 19 is heated or slowly cooled, whereby the Young's modulus of the secondary coating of the optical fiber 19 when twisting is applied by the twisting device 22. It can be within a predetermined range.
Further, as the heating means 20, a bridge lamp provided in the second bridge cylinder 18 can also be used. When this bridge lamp is used, the coating layer of the optical fiber 19 is heated by radiant heat transfer generated from the bridge lamp.

As the cooling means 21, a cooling cylinder made of a cylinder in which helium gas having a high heat transfer coefficient flows and the periphery of the helium gas flow path is cooled is used. Examples of the cooling method by the cooling means 21 include a method of cooling the optical fiber 19 by adjusting the flow rate of helium gas and the length of the cooling cylinder.
The cooling means 21 is used to cool the secondary coating layer of the optical fiber strand 19, so that the Young's modulus of the secondary coating layer of the optical fiber strand 19 when twisting is applied by the twisting device 22 is within a predetermined range. Can be inside.

  In addition, in this embodiment, although the manufacturing method of the optical fiber strand which provides two coating layers was illustrated, this invention is not limited to this. The method for manufacturing an optical fiber and the apparatus for manufacturing an optical fiber of the present invention can also be applied when three or more coating layers are provided.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

Example 1
Using an optical fiber manufacturing apparatus as shown in FIG. 1, an optical fiber preform is melt-spun at a spinning line speed of 1000 m / min to form an optical fiber bare wire having an outer diameter of 125 μm. An optical fiber strand having an outer diameter of 250 μm is formed by sequentially providing a primary coating layer and a secondary coating layer obtained by curing a coating material made of urethane-acrylate UV curable resin on a bare optical fiber, followed by twisting. After twisting the optical fiber with the apparatus, the optical fiber was wound up.
As the twisting device, the twisting device A described above was used.
The distance between the second bridging cylinder and the twisting device was set to 0.3 m, and the cooling method for the optical fiber from the second bridging tube until reaching the twisting device was natural cooling.
Using an optical fiber thermometer, the temperature of the secondary coating layer of the optical fiber when the twist was applied by the twisting device was measured. The temperature of the secondary coating layer was 130 ° C.

(Example 2)
The distance between the second bridging cylinder and the twisting device is 0.7 m, and the method of cooling the optical fiber from the second bridging tube until it reaches the twisting device is forcibly cooled using the cooling tube. An optical fiber was produced in the same manner as in Example 1 except that.
Using an optical fiber thermometer, the temperature of the secondary coating layer of the optical fiber when the twist was applied by the twisting device was measured, and the temperature of the secondary coating layer was 50 ° C.

Example 3
The distance between the second bridging cylinder and the twisting device is set to 1.0 m, and the method of cooling the optical fiber from the second bridging cylinder until reaching the twisting device is gradually reduced using a slow cooling tube. An optical fiber was produced in the same manner as in Example 1 except that it was cooled.
Using an optical fiber thermometer, the temperature of the secondary coating layer of the optical fiber when the twist was applied by the twisting device was measured, and the temperature of the secondary coating layer was 70 ° C.

Example 4
As the twisting device, an optical fiber was produced in the same manner as in Example 1 except that the twisting device B was used and the distance between the second bridging cylinder and the twisting device was set to 0.5 m.
Using an optical fiber thermometer, the temperature of the secondary coating layer of the optical fiber when the twist was applied by the twisting device was measured, and the temperature of the secondary coating layer was 100 ° C.

(Example 5)
As the twisting device, the above-mentioned twisting device C is used, the distance between the second bridging cylinder and the twisting device is set to 0.8 m, and the optical fiber from the second bridging cylinder until it reaches the twisting device is used. An optical fiber was produced in the same manner as in Example 1 except that the cooling method of the strand was slow cooling using a heating cylinder and the temperature of the heating cylinder was set to 70 ° C.
Using an optical fiber thermometer, the temperature of the secondary coating layer of the optical fiber when the twisting was applied was measured, and the temperature of the secondary coating layer was 120 ° C.

(Comparative Example 1)
An optical fiber was produced in the same manner as in Example 1 except that the distance between the second bridging cylinder and the twisting device was 0.1 m.
Using an optical fiber thermometer, the temperature of the secondary coating layer of the optical fiber when the twist was applied by the twisting device was measured, and the temperature of the secondary coating layer was 150 ° C.

(Comparative Example 2)
The distance between the second bridging cylinder and the twisting device is 0.9 m, and the method of cooling the optical fiber from the second bridging tube until it reaches the twisting device is forcibly cooled using the cooling tube. An optical fiber was produced in the same manner as in Example 1 except that.
Using an optical fiber thermometer, the temperature of the secondary coating layer of the optical fiber when the twisting was applied was measured, and the temperature of the secondary coating layer was 40 ° C.

(Comparative Example 3)
As the twisting device, the above-mentioned twisting device B is used, the distance between the second bridging cylinder and the twisting device is 0.5 m, and the optical fiber from the second bridging cylinder to the twisting device is reached. An optical fiber was produced in the same manner as in Example 1 except that the cooling method of the strand was slow cooling using a heating cylinder and the temperature of the heating cylinder was 100 ° C.
Using an optical fiber thermometer, the temperature of the secondary coating layer of the optical fiber when the twist was applied by the twisting device was measured, and the temperature of the secondary coating layer was 150 ° C.

For Examples 1 to 5 and Comparative Examples 1 to 3, the following items (1) to (3) were evaluated.
(1) Measurement of Young's modulus of secondary coating layer of optical fiber strand The Young's modulus of the secondary coating layer of optical fiber strand when twisting was applied by a twisting device was measured by the following method.
First, the coating material forming the secondary coating layer is dropped onto the tray so that the thickness is 0.2 mm. Thereafter, the coating material was irradiated with ultraviolet rays having an intensity of 300 mJ / cm ² to cure the coating material, thereby preparing a sheet-like sample.
This sheet-like sample is held in a high-temperature environment (for example, in an atmosphere at 80 ° C. or in an atmosphere at 100 ° C.), and tensile force is applied to the sample in this high-temperature environment. The Young's modulus of the sample was calculated. The Young's modulus of this sample was regarded as the Young's modulus of the secondary coating layer of the optical fiber when the twist was applied by the twisting device. The results are shown in Table 1.

(2) Hot water immersion test of optical fiber strand About 1 m of the optical fiber strand was cut out and used as a test sample. The test sample was immersed in warm water at 60 ° C. for 12 hours. After 12 hours, the test sample was taken out of the warm water, and the presence or absence of peeling or cracking of the coating layer was observed with an optical microscope over 1 m in the longitudinal direction of the test sample within 5 minutes. The evaluation criteria were as follows. The results are shown in Table 1.
○: No peeling or cracking of the coating layer of the optical fiber.
X: There are one or more peeling and cracking of the coating layer of the optical fiber.

(3) Evaluation of the micro vent characteristics The optical fiber strands are converged and exposed to an environment where the temperature continuously changes in a temperature range of −60 ° C. to 85 ° C., and the transmission loss at this time is measured. The change of transmission loss of optical fiber due to bend was evaluated.
The evaluation criteria were as follows. The results are shown in Table 1.
○: The transmission loss at low temperature did not increase as the temperature changed compared to the transmission loss at normal temperature.
X: The transmission loss at low temperature increased as the temperature changed compared with the transmission loss at normal temperature.

From the results of Table 1, when Examples 1 and 2 and Comparative Examples 1 and 2 are compared, the temperature of the secondary coating layer of the optical fiber strand when twisting exceeds 130 ° C, and 50 ° C In the case of less than the above, it was found that the coating layer of the optical fiber was peeled off by hot water immersion, and the transmission loss of the optical fiber due to the microbend was increased.
This is because, when the temperature of the secondary coating layer of the optical fiber is less than 50 ° C. when the twist is applied by the twisting device, the Young's modulus of the secondary coating layer is high, so that the external force applied by the twisting device is applied to the primary coating. Cannot be absorbed by the entire layer and the secondary coating layer, peeling at the interface between the bare optical fiber and the primary coating layer, and cracking of the primary coating layer, resulting in an increase in transmission loss due to microbending. It is thought that it is from. On the other hand, if the temperature of the secondary coating layer of the optical fiber when the twist is applied by the twisting device exceeds 130 ° C., the Young's modulus of the secondary coating layer is too low, so that the torque is applied to the optical fiber by the twisting device. When added, the secondary coating layer is peeled off, and the secondary coating layer adheres to the roller provided in the twisting device. As described above, when the peeled secondary coating layer adheres to the circumferential member, a predetermined torque cannot be applied to the optical fiber by the twisting device, resulting in defective production of the optical fiber. It is thought to produce.
From this result, it was found that if the temperature of the secondary coating layer of the optical fiber strand when twisting is applied by the twisting device is in the range of 50 to 130 ° C., a good optical fiber strand can be obtained.

Further, in Example 3, an annealing tube is provided between the time when the second bridging cylinder is exited and the time when the twisting device is reached, the optical fiber is gradually cooled, and the optical fiber when twisting is applied by the twisting device. It has been found that a good optical fiber can be obtained by increasing the temperature of the secondary coating layer of the strand.
Furthermore, in Example 4, although the twisting device was changed, the temperature of the secondary coating layer of the optical fiber when the twisting was applied was set to 100 ° C., so that a good optical fiber could be obtained. I understood.

  In Comparative Example 3, a heating tube is provided between the time when the second bridge tube is exited and the time it reaches the twisting device, the optical fiber strand is gradually cooled, and the optical fiber strand when twisting is applied by the twisting device. By setting the temperature of the secondary coating layer to 150 ° C., when a torque is applied to the optical fiber with a twisting device, the secondary coating layer is peeled off, and the secondary coating layer is transferred to a roller provided in the twisting device. It was found that a good optical fiber could not be obtained due to the problem of adhesion.

  In Example 5, the twisting device is changed, and a heating tube is provided between the time when the second bridging tube is exited and the time when the twisting device is reached, the optical fiber is gradually cooled, and the twisting device is used to twist. Since the temperature of the secondary coating layer of the optical fiber strand at the time of addition is set to 120 ° C., the temperature of the secondary coating layer of the optical fiber strand is in the range of 50 to 130 ° C. even if a heating cylinder is used. Therefore, it turned out that a favorable optical fiber strand is obtained.

  From the above results, it is necessary to install a cooling cylinder, a slow cooling tube or a heating cylinder between the time when the second bridging cylinder is exited and the time when the twisting apparatus is reached. It has been found that when the temperature of the secondary coating layer is in the range of 50 to 130 ° C., a good optical fiber strand can be obtained regardless of the twisting method.

The optical fiber manufacturing method and the optical fiber manufacturing apparatus according to the present invention can be used not only to manufacture single-mode fibers, dispersion shifts, cut-off shift fibers, and dispersion compensation fibers, but also any kind of optical fibers. Although it can be applied, it is particularly suitable for a method of manufacturing an optical fiber strand to which a process of twisting the optical fiber strand is applied for the purpose of reducing PMD of the optical fiber strand.
In addition, the method for manufacturing an optical fiber and the apparatus for manufacturing an optical fiber according to the present invention include a vapor phase shaft attachment method (VAD method), an external attachment method (OVD method), and an internal attachment method (CVD method, MCVD). This method can also be applied to the case where an optical fiber is manufactured using an optical fiber preform manufactured by any manufacturing method such as a rod-in-tube method.

It is a schematic diagram which shows schematic structure of the manufacturing apparatus of the optical fiber strand used with the manufacturing method of the optical fiber strand which concerns on this invention. It is a schematic diagram which shows schematic structure of the manufacturing apparatus of the optical fiber strand used with the manufacturing method of the conventional optical fiber strand.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Optical fiber base material, 12 ... Spinning furnace, 13 ... Bare optical fiber, 14 ... Cooling cylinder, 15 ... 1st coating material coating device, 16 ... 1st 17 ... second coating material coating device, 18 ... second cross-linking cylinder, 19 ... optical fiber, 20 ... heating means, 21 ... cooling means, 22 ... Twisting device, 23 ... Turn pulley, 24 ... Take-up machine, 25 ... Dancer roll, 26 ... Take-up drum.

Claims (6)

A spinning process in which an optical fiber preform is melt-spun to form a bare optical fiber, and a coating material is applied to the bare optical fiber formed by the spinning process, and the coating material is provided in a bridging cylinder. A coating layer is formed by curing with light irradiated from the optical fiber strand, and an optical fiber preform is formed by applying a twist to the optical fiber strand formed by the coating step and a twisting device. A method of manufacturing an optical fiber comprising a twisting step of twisting a molten part of a material,
In the twisting step, the Young's modulus of the outermost layer of the coating layer of the optical fiber when the twist is applied by the twisting device is 50 MPa to 300 MPa.   2. The manufacturing of an optical fiber according to claim 1, wherein in the twisting step, the temperature of the outermost layer of the coating layer of the optical fiber is set to 50 to 130 ° C. when twisting by the twisting device. Method.   The method for manufacturing an optical fiber according to claim 1 or 2, wherein, in the twisting step, a distance between the bridging cylinder and the twisting device is controlled.   3. The method of manufacturing an optical fiber according to claim 1, wherein, in the twisting step, a coating layer of the optical fiber is heated and / or cooled before twisting the optical fiber. 4. . A spinning furnace that melts the optical fiber preform; a coating material coating device that coats the coating material onto the bare optical fiber; a bridge cylinder having a bridge lamp that irradiates the coating material with light to cure the coating material; An optical fiber manufacturing device comprising a twisting device for twisting a fiber strand,
The twisting device is movably provided along the drawing direction of the optical fiber, and the distance between the bridging cylinder and the twisting device can be controlled. apparatus. A spinning furnace that melts the optical fiber preform; a coating material coating device that coats the coating material onto the bare optical fiber; a bridge cylinder having a bridge lamp that irradiates the coating material with light to cure the coating material; An optical fiber manufacturing device comprising a twisting device for twisting a fiber strand,
An apparatus for manufacturing an optical fiber, wherein heating means and / or cooling means are provided between the bridging cylinder and the twisting device.

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