JP2010132468A - Method for producing optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an optical fiber where PMD is reduced by imparting twisting to the optical fiber and certain twisting is imparted even if the travelling velocity of the optical fiber is varied. <P>SOLUTION: In the method for producing the optical fiber where the optical fiber is twisted in alternate directions by rocking a guide roller 56 to guide the travelling of the optical fiber 51, it is characterized by that the travelling velocity of the optical fiber 51 is detected, the rocking revolution numbers of the guide roller is controlled according to detected travelling velocity and then the number of the times of twisting per a unit length of the optical fiber becomes constant. When the travelling of the optical fiber is reversed, twisting imparted at the travelling is canceled by reversing the rocking direction of the guide roller. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing an optical fiber used as a transmission line for optical communication.

  In the production of an optical fiber, it is difficult to form the core portion and the clad portion in a perfect circle and concentric shape, resulting in a slightly elliptical or distorted circular shape. For this reason, the refractive index distribution in the cross-sectional structure of the optical fiber is not uniform. As a result, there is a difference in the group velocity between two orthogonal polarizations in the cross section of the optical fiber, and there is a problem that polarization mode dispersion (PMD) increases. As a method for reducing this PMD, it is known to impart twists in an alternating direction to an optical fiber.

  As a method for imparting twist to an optical fiber, for example, Patent Document 1 discloses a method using a swing guide roller. 4A and 4B are diagrams for explaining the outline of the prior art disclosed in the above-mentioned Patent Document 1. FIG. 4A is an overall schematic diagram, and FIG. 4B is a diagram for explaining a swing guide roller. . As shown in FIG. 4A, the optical fiber preform 10 set in the drawing furnace 11 is heated and softened by the heater 12, and the glass optical fiber 13 (hereinafter simply referred to as an optical fiber) is drawn. . The drawn optical fiber 13 is subjected to outer diameter measurement by the outer diameter measuring instrument 14 and fed back to the drawing controller 15 so that the heating temperature and the drawing speed of the heater 12 are adjusted to a predetermined outer diameter (usually 125 μm). Is controlled.

  The drawn optical fiber 13 is coated with coating resin materials 17a and 17b by the first and second resin coating dies 16a and 16b, and is cured by the first and second ultraviolet irradiation devices 18a and 18b. Thereafter, the coated optical fiber 13 ′ covered with resin is wound around the drum 10 through the guide roller 19, the swing guide roller 20, the fixed guide rollers 21 and 22, and the like.

  As shown in FIG. 4B, when the rotation axis y of the swing guide roller 20 is rotated by + θ around the drawing direction axis z, a lateral force is applied to the coated optical fiber 13 ′ by this rotation. The coated optical fiber 13 ′ rolls on the surface of the swing guide roller 20. This rolling imparts twist to the coated optical fiber 13 '. Subsequently, when the swing guide roller 20 is rotated by −θ in the opposite direction, the coated optical fiber 13 ′ rolls on the surface of the swing guide roller 20 in the opposite direction. In this way, by repeatedly applying the rotation from + θ to −θ to the swing guide roller 20, clockwise and counterclockwise twists are alternately applied to the moving direction of the coated optical fiber 13 ′. Can do.

  The fixed guide roller 21 at the next stage of the swing guide roller 20 is installed directly beside the swing guide roller 20, and the coated optical fiber 13 ′ comes into contact with the circumferential surface of the swing guide roller 20, and then the fixed guide roller 21. Move to 21. The fixed guide roller 21 is provided with a V-shaped narrow groove so that the coated optical fiber 13 ′ does not roll on the roller surface. The coated optical fiber 13 ′ is prevented from rolling on the surface of the fixed guide roller 21, and the twist is alternately applied to the coated optical fiber 13 ′ by the rotation of the swing guide roller 20. The twist imparted to the coated optical fiber 13 'is transmitted to the heating and melting position of the optical fiber 13 in a free state.

Further, Patent Document 2 discloses that the swing angle or swing speed of the swing guide roller described above is varied to impart a random twist to the optical fiber. Patent Document 3 discloses the relationship between the number of twists per unit length and PMD, and the relationship between the inversion period in the twist direction and PMD.
Japanese Patent Laid-Open No. 9-243833 JP 2003-292334 A JP 2006-522369 A

  In each of the above-described configurations for imparting twist to the conventional optical fiber, the traveling speed of the optical fiber (also referred to as linear velocity) and the swing period of the swing guide roller (period in which the twist direction of the optical fiber is reversed) , Each is set separately. For this reason, when the traveling speed of the optical fiber is slowed while the swinging guide roller is swung at a constant cycle, the number of twists per unit length of the optical fiber increases. As the speed increases, the number of twists per unit length of the optical fiber decreases.

  The PMD decreases as the number of twists per unit length of the optical fiber increases, and the PMD increases as the number of twists per unit length of the optical fiber decreases. Normally, the swing of the swing guide roller is set at a predetermined cycle. However, when the traveling speed of the optical fiber varies, the PMD also varies due to the variation, and the PMD value varies depending on the position in the longitudinal direction of the optical fiber. There was a problem that PMD deteriorated as a whole. In addition, when twisting is applied at the time of rewinding the optical fiber, there is a problem that the twisting state of the optical fiber becomes discontinuous when the optical fiber is rewound by detecting the bump.

  The present invention has been made in view of the above-described circumstances, and in the manufacture of an optical fiber that imparts twist to the optical fiber to reduce PMD, even if fluctuations occur in the traveling speed of the optical fiber, a constant twist is imparted. An object of the present invention is to provide a method for manufacturing an optical fiber.

  The method of manufacturing an optical fiber according to the present invention detects the traveling speed of an optical fiber by manufacturing an optical fiber that swings a guide roller that guides the traveling of the optical fiber and applies twist in the alternate direction to the optical fiber. It is characterized in that the number of rotations of the guide roller is controlled according to the detected traveling speed, and the number of twists per unit length of the optical fiber is made constant. Further, when the traveling of the optical fiber is reversed, the swinging direction of the guide roller is reversed to eliminate the twist applied during the traveling.

  According to the present invention, the twist applied to the optical fiber is uniform in the longitudinal direction, so that the PMD value can be uniform over the entire length of the optical fiber. Also, when returning the traveling of the optical fiber (reverse running), since the twist can be returned according to the backward running speed of the optical fiber, when the transition to the steady running state next, the twist is given again. A continuous and uniform PMD value can be obtained without twisting or becoming discontinuous.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating an example in which twisting of an optical fiber is applied in an optical fiber rewinding process. In the figure, 30 is a supply reel, 31 is an optical fiber, 32 is a guide roller, 33 is a dancer roller, 34 is a bump detector, 35 is a fixed guide roller, 36 is a twisting roller, 37 is a fixed roller, and 38 is a control device. , 39 is a capstan, 40 is a linear velocity detector, 41 is a guide roller, 42 is a dancer roller, 43 is a winding guide roller, and 44 is a winding drum.

  The rewinding of the optical fiber is, for example, rewinding the optical fiber wound around the supply reel 30 to the winding drum 44 as shown in FIG. At the time of rewinding the optical fiber, it is possible to detect a fiber coating bump generated during drawing of the optical fiber.

  In the example of rewinding the optical fiber shown in FIG. 1, the optical fiber 31 delivered from the supply reel 30 is fed out with a predetermined tension by a guide roller 32 and a dancer roller 33. The fed optical fiber 31 can detect the presence or absence of bumps by, for example, a bump inspection device arranged in the travel route. The application of twist to the optical fiber 31 is performed by a guide roller 36 (hereinafter referred to as a twist application roller) similar to the swing guide roller 20 described in FIG.

  The twist imparting roller 36 that imparts twist to the optical fiber 31 can be installed between the fixed guide roller 35 and the fixed roller 37, for example, before the capstan 39. The optical fiber 31 taken up by the capstan 39 is taken up by the take-up drum 44 from the guide roller 41 and the dancer roller 42 through the take-up guide roller 43. In the rewinding of the optical fiber, the twist applying roller 36 for applying twist to the optical fiber 31 may be installed on the rear stage side of the capstan 39 using a fixed guide roller.

  As shown in FIG. 1B, when the twist applying roller 36 swings in one direction (+ θ), a lateral force is applied to the optical fiber 31, and the optical fiber 31 rolls on the surface of the twist applying roller 36. To do. This rolling imparts twist to the optical fiber 31. Subsequently, when the twist applying roller 36 is swung in the opposite direction (−θ), the optical fiber 31 rolls on the surface of the twist applying roller 36 in the opposite direction. As described above, the twist applying roller 36 repeatedly imparts swinging from + θ to −θ, so that clockwise and counterclockwise twist can be alternately applied to the moving direction of the optical fiber 31.

  The twist imparting roller 36 is controlled by the control device 38 so that the swing cycle becomes a predetermined value. The swinging period is a twisting roller 36 that swings in one direction and rolls in one direction on the surface of the roller on which the optical fiber is tilted, and is twisted several times in one direction. The period when the application roller 36 swings in the opposite direction and the optical fiber rolls on the roller surface in the opposite direction and is twisted several times in the opposite direction is defined as one cycle. That is, the swing of the twist imparting roller 36 is set to one cycle (one swing rotation) in one reciprocation.

  The application of twist to the optical fiber 31 is controlled by the control device 38 so that the rotational speed of rotation becomes a predetermined value. The traveling speed of the optical fiber 31 can be detected in real time by the linear speed detector 40 from the rotation of the capstan wheel of the capstan 39, for example. The detected traveling speed of the optical fiber 31 is input to the control device 38, and the rotational speed of the twist applying roller 36 is controlled in accordance with the traveling speed.

  When the rotational speed of the twist applying roller 36 is controlled at a constant value, the number of twists per unit length of the optical fiber increases as the traveling speed of the optical fiber 31 decreases. Therefore, in this case, control is performed so as to reduce the number of rotations of rotation so that the number of twists per unit length of the optical fiber does not increase. On the other hand, as the traveling speed of the optical fiber 31 increases, the number of twists per unit length of the optical fiber decreases. In this case, the number of times of twisting per unit length of the optical fiber is not reduced by controlling the number of rotations to be increased.

  Further, when a bump is detected on the optical fiber coating by the bump detector 34, in order to verify the state of the bump, the traveling of the optical fiber may be temporarily stopped and rewound. In this case, the information on the bump detection is input to the control device 38, and the direction of the torsion applying roller 36 is reversed in synchronization with the unwinding of the optical fiber, and the rotation speed is adjusted according to the unwinding speed of the optical fiber. Control to be.

  As a result, the twist imparted to the optical fiber in the winding direction is eliminated by rewinding, and it is possible to return to a state where no twist is imparted. Thereafter, the occurrence of bumps is verified, and when the optical fiber is run again in the winding direction, twist is applied again from the point where the optical fiber is rewound. As a result, the direction of twisting and the number of twists can be continued from the unwinding point of the optical fiber, and the uniformity of the PDM can be maintained.

  FIG. 2 is a diagram illustrating an example in which twisting is applied to the optical fiber during the fiber drawing process. In the figure, 50 is an optical fiber preform, 51 is a drawing furnace, 52 is a heater, 53 is an optical fiber (glass optical fiber), 53 'is an optical fiber (coated optical fiber), 54 is a cooling device, and 55 is a resin coating die. , 56 is a liquid resin, 57 is an ultraviolet irradiation device, 58 is a twist applying roller, 59 is a fixed guide roller, 60 is a fixed roller, 61 is a control device, 62 is a capstan, 63 is a linear velocity detector, and 64 is a dancer roller. , 65 is a winding guide roller, and 66 is a winding drum.

  In the production of an optical fiber through winding from drawing in the present invention, the optical fiber preform 50 set in the drawing furnace 51 is sequentially heated and melted by the heater 52 in the same manner as described in FIG. A fiber 53 (hereinafter simply referred to as an optical fiber) is drawn. The optical fiber 53 immediately after drawing is cooled to a predetermined temperature by a cooling device 54, and thereafter, an ultraviolet curable liquid resin 56 is applied by a resin coating die 55. Next, the coating resin is cured by the ultraviolet irradiation device 57 to obtain a coated optical fiber 53 ′. Note that the coating of the optical fiber is formed of one layer or two layers, and when it is formed of two layers, the resin coating die 55 and the ultraviolet irradiation device 57 are provided in two stages as in FIG.

  The coated optical fiber 53 ′ is taken up by a capstan 62 through a fixed guide roller 59, a twist applying roller 58, and a fixed roller 60. The optical fiber 53 ′ taken up by the capstan 62 is taken up by the take-up drum 66 from the dancer roller 64 through the take-up guide roller 65. The twist imparting to the optical fiber 53 ′ is performed by a guide roller (twist imparting roller) 58 similar to the swing guide roller 20 described in FIG.

  Also in this example, the traveling speed of the optical fiber 53 ′ can be detected in real time by the speed detector 63 that detects the rotation of the capstan wheel of the capstan 62, as in the example of FIG. 1. The detected traveling speed of the optical fiber 53 ′ is input to the control device 61, and the swinging rotational speed of the twist applying roller 38 can be controlled in accordance with the traveling speed.

  When the rotational speed of the twist applying roller 58 is controlled at a constant value, the number of twists per unit length of the optical fiber increases when the traveling speed of the optical fiber 53 ′ decreases from the steady speed. Therefore, in this case, the number of times of twisting per unit length of the optical fiber is not increased by controlling the number of rotations to be small. On the other hand, when the traveling speed of the optical fiber 53 ′ increases from the steady speed, the number of twists per unit length of the optical fiber decreases. In this case, the number of times of twisting per unit length of the optical fiber is not reduced by controlling the number of rotations to be increased.

  The rotation speed of the torsion imparting rollers 36 and 58 can be proportional to the traveling speed of the optical fiber, for example. Control for making the swing rotation speed proportional to the traveling speed of the optical fiber can be easily performed by the control devices 38 and 61, and by this control, the number of twists of the optical fiber per unit length is made constant over the entire length. be able to. As a result, even when the twist is uniformly applied over the entire length of the optical fiber and is cut into a predetermined length, the PMD value per unit length can be reduced and uniform quality can be achieved. .

  The twisting to reduce the PMD value of the optical fiber is not limited to the above-described rewinding to divide the long optical fiber into a predetermined winding amount, and when the colored optical fiber is applied to the optical fiber in addition to the drawing of the optical fiber. Can also be done. In this case as well, as described with reference to FIGS. 1 and 2, the PMD value per unit length is reduced by controlling the swing rotation speed of the twist applying roller according to the traveling speed of the optical fiber. Uniform quality is possible.

  FIG. 3 is a diagram illustrating the above-described traveling state of the optical fiber and the control state of the twist applying roller. 3A shows the relationship between the traveling speed (m / min) of the optical fiber and the traveling time (T), and FIG. 3B shows the rotation speed (rpm) and the traveling time (T). Shows the relationship. As shown in FIG. 3 (A), for example, the traveling speed of the optical fiber is gradually increased from the traveling start speed 0 to the steady speed state b, and then the speed is decreased for some reason. c. After that, when a bump is detected, for verification, when the vehicle travels from a state d where the traveling speed is reduced to rewind the optical fiber to a stop state e and then goes through a state f where the traveling direction is rewound at a low speed. To do. Further, after the bump verification, in order to run the optical fiber again in the winding direction, it is assumed that the running speed is gradually increased through the stop state g and then the steady speed state i is set. To do.

  When the traveling speed of the optical fiber fluctuates as shown in FIG. 3A, the rotation speed of the torsion imparting roller is controlled in a form corresponding to the traveling speed of the optical fiber as shown in FIG. Proportional control). That is, when the traveling speed of the optical fiber fluctuates with the states a, b, and c, the swing rotation speed of the twist applying roller is controlled to be the states a ′, b ′, and c ′. Further, in response to the traveling speed fluctuating with the states d, e, and f due to the unwinding of the optical fiber, the swinging rotation speed of the torsion imparting roller is changed to the states d ′, e ′, and f ′, and the swinging direction is reversed. . When the traveling speed is changed to the states g, h, i by causing the optical fiber to travel again in the winding direction, the swinging rotation speed of the torsion imparting roller is set to the states g ′, h ′, i ′.

  The PMD value was 0.0942 (ps / √km) when the travel speed of the optical fiber was 1000 m / min and the rocking by the twist applying roller was not performed by rewinding the optical fiber of FIG. At this time, assuming that the rotation speed of the torsion imparting roller is 50 rpm and the swing angle is 15 °, and detecting the bump, once the optical fiber runs backward, the torsion imparting roller swings as shown in FIG. The PMD value when the rotational speed was reversed and followed was 0.044 (ps / √km). When the optical fiber was run backward, the PMD value was 0.066 (ps / √km) especially when the twist imparting roller was not allowed to follow.

It is a figure explaining embodiment of this invention. It is a figure explaining other embodiment of this invention. It is a figure explaining the control state of the twist provision roller in this invention. It is a figure explaining a prior art.

Explanation of symbols

30 ... Supply reel, 31, 53 '... Optical fiber (coated optical fiber), 32, 41 ... Guide roller, 33, 42, 64 ... Dancer roller, 34 ... Cobb detector, 35, 59 ... Fixed guide roller, 36, 58 ... Twisting roller, 37, 60 ... Fixed roller, 38, 61 ... Control device, 39, 62 ... Capstan, 40, 63 ... Linear velocity detector, 43, 65 ... Winding guide roller, 44, 66 ... Winding Removable drum, 50 ... Optical fiber preform, 51 ... Drawing furnace, 52 ... Heater, 53 ... Optical fiber (glass optical fiber), 54 ... Cooling device, 55 ... Resin coating die, 56 ... Liquid resin, 57 ... Ultraviolet irradiation device .

Claims (2)

A method of manufacturing an optical fiber that swings a guide roller that guides the traveling of the optical fiber and imparts twists in an alternating direction to the optical fiber,
Light that detects the traveling speed of the optical fiber, controls the swing rotation speed of the guide roller in accordance with the detected traveling speed, and makes the number of twists per unit length of the optical fiber constant. Fiber manufacturing method.   2. The method of manufacturing an optical fiber according to claim 1, wherein when the optical fiber runs backward, the swing direction of the guide roller is reversed to eliminate the applied twist. 3.

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