JP2005326664A - Method of manufacturing optical fiber, twisting apparatus and primary coated optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a primary coated optical fiber by which a polarization mode dispersion in the optical fiber is reduced and failure such as the occurrence of crack or separation of the coated layer of the primary coated optical fiber is suppressed, to provide a twisting apparatus and to provide the primary coated optical fiber manufactured by the method. <P>SOLUTION: In the method of manufacturing the primary coated optical fiber including a twisting process in which a twist is given to the primary coated optical fiber 19 by allowing at least a pair of twisting rollers provided on the twisting apparatus 20 o abut on a part of the outer periphery of the primary coated optical fiber 19, the distance between the pair of rollers is controlled by controlling the pressure applied to the primary coated optical fiber 19 with the pair of the rollers so that the pressed quantity of the coated layer of the primary coated optical fiber 19 with the pair of the rollers becomes 20 μm to 70 μm. In the twisting process, the distance between the pair of rollers is controlled so that the pressed quantity of the coated layer of the primary coated optical fiber 19 becomes 20 μm to 70 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing an optical fiber, a twisting device, and an optical fiber, and in particular, a step of twisting an optical fiber preform in order to reduce polarization mode dispersion in the optical fiber The present invention relates to a method for manufacturing an optical fiber, to which the optical fiber is applied, a twisting device used in the method for manufacturing an optical fiber, and an optical fiber obtained by the method for manufacturing an optical fiber.

In general, an optical fiber is manufactured as follows.
FIG. 3 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, and Patent Document 3).

The twist applied to the optical fiber 109 being spun 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, Patent Document 2, Patent Document 3 and the like disclose the principle, method, and apparatus for twisting an optical fiber, a specific optical fiber using the same is disclosed. No manufacturing conditions are disclosed.

  2. Description of the Related Art Generally, twisting devices applied to the production of optical fiber strands are provided with at least a pair of twisting rollers that abut against the optical fiber strands and apply torque to the optical fiber strands.

  In such a twisting device, the optical fiber strand is twisted by the torque applied to the optical fiber strand by the periodic swinging of the pair of twisting rollers and the friction between the coating layer of the optical fiber strand and the twisting roller. Is added. 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, in order to increase the frictional force of the surface of the twisting roller against the coating layer, the friction coefficient of the surface of the twisting roller, the length of contact between the surface of the twisting roller and the optical fiber, the pressing force against the optical fiber by the twisting roller, etc. It seems to be effective to increase.

  However, if the pressing force applied to the optical fiber by the twisting roller is excessively increased, the coating layer of the optical fiber is crushed and the coating layer is broken, or the coating layer is broken at the interface between the bare optical fiber and the coating layer. May peel off. Due to such defects in the coating layer, the optical fiber has a problem that the transmission loss due to the microbend increases and the environment resistance and ironing resistance of the coating layer deteriorate. The ironing resistance is a property in which peeling or cracking of the coating layer of the optical fiber is difficult to occur when a side pressure is applied to the optical fiber.

On the other hand, if the pressing force of the twisting roller against the optical fiber strand is made too small to prevent the coating layer of the optical fiber strand from cracking or peeling off, the optical fiber strand will Torque is not applied. For this reason, slip occurs between the optical fiber and the twisting roller, and as a result, the optical fiber that is being spun has runout, resulting in coating failure such as uneven thickness of the coating layer.
Japanese Patent No. 2981088 Japanese Patent No. 3224235 JP 10-507438 A

  The present invention has been made in view of the above circumstances, and reduces the polarization mode dispersion in an optical fiber and suppresses the occurrence of defects such as cracking and peeling in the coating layer of the optical fiber. Provided are an element manufacturing method, a twisting device used in the optical fiber manufacturing method, and an optical fiber obtained by the optical fiber manufacturing method.

  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 the bare optical fiber formed by the spinning process is coated with a coating material. A coating step for forming an optical fiber, and at least a pair of twisting rollers provided in the twisting device in contact with a part of the outer periphery of the optical fiber formed by the coating step. A method of manufacturing an optical fiber, comprising: a twisting step of twisting a molten portion of an optical fiber preform by applying a twist to the optical fiber by moving a twisting roller in a translational or swinging manner. In the twisting step, a method of manufacturing an optical fiber strand is provided in which a distance between the pair of twisting rollers is controlled by controlling a pressure applied to the optical fiber strand by the pair of twisting rollers.

  In the method for manufacturing an optical fiber, in the twisting step, a distance between the pair of twisting rollers is controlled so that a cover layer of the optical fiber is crushed by the pair of twisting rollers between 20 μm and 70 μm. It is preferable to do.

  The present invention relates to a twisting device that is used for manufacturing an optical fiber and includes at least a pair of twisting rollers that abut against a part of the outer periphery of the optical fiber being spun and twist the optical fiber. And the outer diameter of a pair of said twist roller provides the twist apparatus which is 50 mm or more.

  In the twisting device, the friction coefficient of the surfaces of the pair of twisting rollers is preferably 0.2 μs or more.

  The present invention provides an optical fiber that is manufactured by the above-described method for manufacturing an optical fiber, wherein the amount of crushing of the coating layer is 20 μm to 70 μm, and the polarization mode dispersion is 0.2 ps / √km or less. To do.

  According to the optical fiber manufacturing method of the present invention, in the twisting step of twisting the optical fiber with at least a pair of twisting rollers provided in the twisting device, the pair of twisting rollers is added to the optical fiber. Since the distance between the pair of twisting rollers is controlled by controlling the pressure, an optical fiber with reduced polarization mode dispersion can be obtained, and the coating layer is not cracked and not peeled off. An optical fiber strand can be obtained.

  Furthermore, in the twisting process, if the distance between the pair of twisting rollers is controlled so that the amount of crushing of the coating layer of the optical fiber strand by the pair of twisting rollers is 20 μm to 70 μm, the polarization mode dispersion is 0.2 ps. An optical fiber strand of / √km or less can be obtained.

  According to the twisting device of the present invention, the outer diameter of at least a pair of twisting rollers that abuts a part of the outer periphery of the optical fiber strand being drawn and twists the optical fiber strand is 50 mm or more, The distance that the twisting roller contacts the optical fiber strand becomes longer than the collapse amount of the coating layer of the optical fiber strand, and the collapse amount of the coating layer of the optical fiber strand can be reduced. Thereby, the optical fiber strand which a coating layer does not crack and does not peel can be obtained.

  Further, if the friction coefficient of the surface of the pair of twisting rollers is 0.2 μs or more, it becomes difficult to slip between the optical fiber and the twisting roller. Thereby, the amount of crushing of the coating layer of the optical fiber can be reduced. As a result, it is possible to obtain an optical fiber that does not peel and does not peel off the coating layer.

  According to the optical fiber of the present invention, it is manufactured by the above-described optical fiber manufacturing method, the cover layer has a collapse amount of 20 μm to 70 μm, and the polarization mode dispersion is 0.2 ps / √km or less. Therefore, it is possible to realize an increase in transmission speed and an increase in transmission distance in optical communication.

Hereinafter, an optical fiber manufacturing method embodying 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 the method for manufacturing an optical fiber according to the present invention, 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. Then, the first coating material is cured by the ultraviolet rays irradiated from the UV lamp 16 to form a primary coating layer (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 the ultraviolet rays irradiated from the UV lamp 18 to form a secondary coating layer, thereby forming the optical fiber 19 (coating process).

  Further, the optical fiber 19 being spun is twisted by a twisting device 20 (twisting process), then turned in another direction by a turn pulley 21, and taken up via a take-up machine 22 and a dancer roll 23. The drum 24 is wound up.

  The twisting device 20 includes at least a pair of twisting rollers that contact 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 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 applying a twist that turns around the axis (hereinafter, such a device is referred to as “twist device A”).

  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 B”).

  As another example of the twisting device having a mechanism in which the twisting roller swings, for example, the rotating twisting roller and the optical fiber strand 19 are in contact, and the optical fiber strand 19 is periodically moved in a direction parallel to the spinning direction. By swinging (hereinafter referred to as “swinging motion”), torque is applied to the optical fiber 19 by periodically twisting the optical fiber 19 around its longitudinal direction. (Hereinafter, such a device is referred to as “twisting device C”).

Here, with reference to FIG. 2, the twisting device A will be described as an example of the twisting device used in the present invention.
The twisting device 20 of this example is generally configured by at least a pair of twisting rollers 31 and 31 that are in contact with a part of the outer periphery of the optical fiber 19 being spun and a support portion (not shown) that supports them. Yes.

  The twisting rollers 31, 31 are arranged so as to sandwich the optical fiber strand 19, and the longitudinal direction thereof is arranged to be substantially perpendicular to the spinning direction of the optical fiber strand 19. The twist roller 31 is rotatable about a central shaft 32 that is integral with the twist roller 31. Further, the twisting roller 31 is capable of translational movement along with the central shaft 32 in a direction perpendicular to the spinning direction of the optical fiber 19 (arrow direction in the figure).

  The twisting rollers 31, 31 are in contact with a part of the outer periphery of the optical fiber 19 being spun while rotating around the central axes 32, 32 in the direction of the arrow, Torque is applied to the optical fiber 19 by periodically translating in the direction perpendicular to the spinning direction. Torsion is applied to the optical fiber 19 being spun by the torque applied to the optical fiber 19 and the friction between the surface of the twisting rollers 31 and 31 and the coating layer (outer periphery) of the optical fiber 19. It is done.

Further, the distance between the twisting rollers 31 and 31 can be controlled. By adjusting this distance or pressing force, the twisting rollers 31 and 31 are formed on a part of the outer periphery of the optical fiber 19 being spun. Can be brought into contact with each other. Thereby, a part of the outer periphery of the optical fiber 19 is sandwiched between the twisting rollers 31 and 31, and an amount by which the coating layer of the optical fiber 19 is crushed (hereinafter referred to as “crush amount”) is adjusted. It is possible.
As a mechanism that makes it possible to control the distance between the twisting rollers 31 and 31 and the pressing force, for example, a support portion that supports one twisting roller 31 is fixed on the twisting device 20 and the other twisting roller 31 is supported. A mechanism that enables the support portion to move toward the one twisting roller 31 on the twisting device 20 is exemplified.

  Further, the twisting device 20 is provided with a measuring device for measuring the distance between the twisting rollers 31 and 31. As such a measuring device, for example, as described above, when the twisting device 20 is provided with a mechanism that can move the other twisting roller 31 with respect to the fixed one twisting roller 31, A laser displacement meter that measures the moving distance (displacement amount) of the twisting roller 31 is used.

  In order to measure the distance between the twisting rollers 31 and 31 using this laser displacement meter, first, the position where the twisting rollers 31 and 31 are in contact with the outer periphery of the optical fiber 19 is set as a reference point (0 point). To do. Furthermore, when the other twisting roller 31 is moved from the reference point toward the one twisting roller 31 and the coating layer of the optical fiber 19 is crushed, if the value indicated by the laser displacement meter is x μm, It is assumed that the amount of crushing of the coating layer of the optical fiber 19 is x μm.

  The outer diameter of the twisting roller 31 is preferably 50 mm or more, and practically about 100 mm to 200 mm is desirable. By setting the outer diameter of the twisting roller 31 to 50 mm or more, a predetermined amount of torque can be applied without increasing the amount of collapse of the optical fiber 19.

  Further, the surface of the twisting roller 31 is covered with a film made of aluminum, brass, urethane rubber or the like. The friction coefficient of the surface of the twisting roller 31 is preferably 0.2 μs or more, and practically about 0.25 μs to 0.4 μs is desirable. By setting the friction coefficient of the surface of the twisting roller 31 to 0.2 μs or more, the frictional force generated between the surface of the twisting rollers 31 and 31 and the coating layer (outer periphery) of the optical fiber 19 is set within a predetermined range. Thus, a predetermined amount of torque can be applied without increasing the amount of collapse of the optical fiber 19.

  By setting the outer diameter of the twisting roller 31 and the friction coefficient of the surface of the twisting roller 31 within the above ranges, a predetermined amount of twisting can be applied to the optical fiber 19 being spun.

  In the method for manufacturing an optical fiber according to the present invention, using such a twisting device, a pair of twisting rollers 31, 31 controls the pressure applied to the optical fiber 19 in the twisting process, thereby making a pair of twists. The distance between the rollers 31, 31 is controlled. Specifically, as a method of controlling the pressure applied to the optical fiber 19 by the pair of twisting rollers 31, 31, an air damper or the like is attached to one movable twisting roller base with respect to one fixed twisting roller, and air pressure A method of controlling the pressure by adjusting the pressure is used. With this pressure, the amount of collapse of the coating layer of the optical fiber 19 also changes.

  Further, in this twisting process, the distance between the pair of twisting rollers 31 and 31 can be controlled so that the amount of collapse of the coating layer of the optical fiber 19 by the pair of twisting rollers 31 and 31 is 20 μm to 70 μm. preferable.

  With the pressing force at which the crushing amount of the coating layer of the optical fiber 19 by the pair of twisting rollers 31 and 31 is less than 20 μm, the force that presses the optical fiber 19 by the twisting rollers 31 and 31 is too small. A sufficient torque is not applied to the wire 19. For this reason, slip occurs between the optical fiber 19 and the twisting roller 31, and as a result, the optical fiber 19 during spinning is oscillated, causing problems such as uneven thickness of the coating layer.

  On the other hand, when the pressing amount of the coating layer of the fiber strand 19 exceeds 70 μm, the force pressing the optical fiber strand 19 by the twisting rollers 31 and 31 is too large, and the coating layer of the optical fiber strand 19 is pushed. The coating layer may be crushed, and the coating layer may be peeled off at the interface between the bare optical fiber 13 and the coating layer. Further, due to such troubles occurring in the coating layer, in the optical fiber 19, transmission loss due to microbending increases, and the environment resistance and ironing resistance of the coating layer deteriorate.

  The optical fiber of the present invention manufactured by such a method of manufacturing an optical fiber has a crushing amount of the coating layer of 20 μm to 70 μm and a polarization mode dispersion of 0.2 ps / √km or less. It has become. Therefore, by using the optical fiber of the present invention, it is possible to increase the transmission speed and increase the transmission distance in optical communication.

  Hereinafter, the present invention will be described more specifically by experimental examples.

(Experimental 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 500 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. Further, as the pair of twisting rollers provided in the twisting device A, those having an outer diameter of 50 mm, the surfaces of which were coated with a coating made of aluminum (friction coefficient μs = 0.2) were used. Further, when twisting the optical fiber strand by the twisting device, the amount of collapse of the coating layer of the optical fiber strand was changed in the range of 5 μm to 90 μm.
The optical fiber strands during spinning were observed for the presence or absence of wire runout. The evaluation criteria were as follows. The results are shown in Table 1.
A: The runout width of the optical fiber strand immediately above the pair of rollers was 10.5 mm or less.
X: The runout width of the optical fiber strand immediately above the pair of rollers exceeded 10.5 mm.
Moreover, about 1 m was cut out from the obtained optical fiber strand, and it was set as the 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.
○: Abnormalities such as peeling and cracking of the primary coating layer were not observed at the interface between the bare optical fiber and the primary coating layer.
X: Abnormalities such as peeling and cracking of the primary coating layer were observed at the interface between the bare optical fiber and the primary coating layer.

  From the results shown in Table 1, it was confirmed that when the crushing amount of the coating layer of the optical fiber strand is 20 μm or more, the runout of the optical fiber strand during spinning is subsided. On the other hand, when the crushing amount exceeded 70 μm, it was confirmed that the coating layer was peeled off in the optical fiber after being immersed in warm water.

(Experimental example 2)
As the twisting device, an optical fiber was produced in the same manner as in Experimental Example 1 except that the twisting device B was used. As the pair of twisting rollers provided in the twisting device B, those having an outer diameter of 100 mm whose surfaces were coated with a coating made of brass (friction coefficient μs = 0.4) were used.
With respect to the optical fiber strand during spinning, the presence or absence of wire runout was observed in the same manner as in Experimental Example 1. The results are shown in Table 2.
Further, the obtained optical fiber was immersed in warm water at 60 ° C. for 12 hours in the same manner as in Experimental Example 1, and then the presence or absence of peeling or cracking of the coating layer was observed. The results are shown in Table 2.

From the results shown in Table 2, it was confirmed that if the crushing amount of the coating layer of the optical fiber strand is 15 μm or more, the runout of the optical fiber strand during spinning is subsided. On the other hand, when the crushing amount exceeded 70 μm, it was confirmed that the coating layer was peeled off in the optical fiber after being immersed in warm water.
Compared with Experimental Example 1, the amount of crushing of the coating layer in which the run-out of the optical fiber strands subsided decreased because the friction coefficient of the surface of the twisting roller was increased and the outer diameter of the twisting roller was increased. This is considered to be caused by an increase in the contact length between the twisting roller and the optical fiber wire due to the increase in the size.

(Experimental example 3)
As the twisting device, the above twisting device A is used, and as a pair of twisting rollers provided in the twisting device A, the surface is coated with a coating made of urethane rubber (friction coefficient μs = 0.6). An optical fiber was produced in the same manner as in Experimental Example 1 except that the one with a diameter of 200 mm was used.
With respect to the optical fiber strand during spinning, the presence or absence of wire runout was observed in the same manner as in Experimental Example 1. The results are shown in Table 3.
Further, the obtained optical fiber was immersed in warm water at 60 ° C. for 12 hours in the same manner as in Experimental Example 1, and then the presence or absence of peeling or cracking of the coating layer was observed. The results are shown in Table 3.

From the results shown in Table 3, it was confirmed that if the crushing amount of the coating layer of the optical fiber strand is 10 μm or more, the runout of the optical fiber strand during spinning is subsided. On the other hand, when the crushing amount exceeded 70 μm, it was confirmed that the coating layer was peeled off in the optical fiber after being immersed in warm water.
Compared with Experimental Example 1, the amount of crushing of the coating layer in which the run-out of the optical fiber strands subsided decreased because the friction coefficient of the surface of the twisting roller was increased and the outer diameter of the twisting roller was increased. This is considered to be caused by an increase in the contact length between the twisting roller and the optical fiber wire due to the increase in the size.

(Experimental example 4)
As the twisting device, an optical fiber was produced in the same manner as in Experimental Example 1 except that the twisting device B was used. As the pair of twisting rollers provided in the twisting device B, those having an outer diameter of 200 mm whose surfaces were coated with a coating made of aluminum (friction coefficient μs = 0.2) were used.
With respect to the optical fiber strand during spinning, the presence or absence of wire runout was observed in the same manner as in Experimental Example 1. The results are shown in Table 4.
Further, the obtained optical fiber was immersed in warm water at 60 ° C. for 12 hours in the same manner as in Experimental Example 1, and then the presence or absence of peeling or cracking of the coating layer was observed. The results are shown in Table 4.

From the results shown in Table 4, it was confirmed that if the crushing amount of the coating layer of the optical fiber strand is 15 μm or more, the runout of the optical fiber strand during spinning is subsided. On the other hand, when the crushing amount exceeded 70 μm, it was confirmed that the coating layer was peeled off in the optical fiber after being immersed in warm water.
In addition, compared with Experimental Example 1, the amount of crushing of the coating layer in which the runout of the optical fiber strands was reduced decreased because the outer diameter of the twisting roller was increased, and the twisting roller and the optical fiber strands were reduced. This is thought to be due to the increased contact length.

(Experimental example 5)
As the twisting device, an optical fiber was produced in the same manner as in Experimental Example 1 except that the twisting device C was used.
In this experimental example, since the twisting device C is used, the optical fiber strands are not crushed between the twisting rollers, so that the optical fiber strands being spun during spinning or the optical fiber strands after being immersed in warm water are used. No delamination of the wire coating layer was observed.

  As described above, from the results of Experimental Example 1 to Experimental Example 5, in the method of manufacturing an optical fiber strand by applying a torque by pressing a part of the outer periphery of the optical fiber strand being spun by at least a pair of twisting rollers. It was also confirmed that the amount of collapse of the coating layer of the optical fiber can be controlled also by changing the outer diameter of the twisting roller and the friction coefficient of the surface of the twisting roller. However, if the amount of crushing of the coating layer of the optical fiber strand is in the range of 20 μm to 70 μm, the optical fiber strand being spun is spun regardless of the outer diameter of the twisting roller or the friction coefficient of the surface of the twisting roller. Generation | occurrence | production of shake and peeling of the coating layer of an optical fiber strand were not observed, but it turned out that a favorable optical fiber strand is obtained.

  The manufacturing method of the optical fiber of the present invention is not only applied to reduce the polarization mode dispersion of the optical fiber, but also includes a gas phase axis method (VAD method) and an external method (OVD method). The present invention can also be applied to the production of an optical fiber by using an optical fiber preform produced by a production method such as an internal method (CVD method, MCVD method, PCVD method), rod-in-tube method or the like.

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 an example of the twist apparatus used by 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 ... Spinning furnace, 12 ... Optical fiber preform | base_material, 13 ... Bare optical fiber, 14 ... Cooling cylinder, 15 ... 1st coating material coating device, 16, 18 ... UV lamp, 17 ... second coating material coating device, 20 ... twisting device, 21 ... turn pulley, 22 ... take-up machine, 23 ... dancer roll, 24 ... winding drum, 31 ... twisting roller, 32 ... central axis.

Claims (5)

A spinning step of melt-spinning an optical fiber preform to form an optical fiber bare wire, a coating step of coating the bare optical fiber formed by the spinning step with a coating material to form an optical fiber strand, and In a state where at least a pair of twisting rollers provided in the twisting device is in contact with a part of the outer periphery of the optical fiber formed by the coating process, the pair of twisting rollers is translated or oscillated, A method of manufacturing an optical fiber with a twisting step of twisting the melted portion of the optical fiber preform by twisting the optical fiber,
In the twisting step, the distance between the pair of twisting rollers is controlled by controlling the pressure applied to the optical fiber by the pair of twisting rollers.   2. The distance between the pair of twisting rollers is controlled in the twisting step so that the amount of crushing of the coating layer of the optical fiber by the pair of twisting rollers becomes 20 μm to 70 μm. The manufacturing method of the optical fiber strand of description. A twisting device that is used for manufacturing an optical fiber and includes at least a pair of twisting rollers that abuts a part of the outer periphery of the optical fiber being spun and twists the optical fiber.
The twisting device characterized in that an outer diameter of the pair of twisting rollers is 50 mm or more.   The twisting device according to claim 3, wherein a friction coefficient of surfaces of the pair of twisting rollers is 0.2 μs or more. It is manufactured by the method for manufacturing an optical fiber according to claim 1, wherein the amount of crushing of the coating layer is 20 μm to 70 μm, and the polarization mode dispersion is 0.2 ps / √km or less. Fiber optic strands.

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