JP5212331B2 - Optical fiber manufacturing method and manufacturing apparatus - Google Patents

Description

  The present invention relates to an optical fiber manufacturing method and manufacturing apparatus 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 group velocity between two orthogonally polarized waves 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. FIG. 10 is a diagram for explaining the outline of the twisting method disclosed in the above-mentioned Patent Document 1, FIG. 10 (A) is a schematic diagram of the whole, and FIG. 10 (B) is a diagram for explaining a swing guide roller. is there. As shown in FIG. 10A, the optical fiber preform 1 set in the drawing furnace 2a is heated and softened by the heater 2b, and the glass optical fiber 3 (hereinafter simply referred to as an optical fiber) is drawn. . The drawn optical fiber 3 is subjected to outer diameter measurement by the outer diameter measuring device 4 and is fed back to the drawing controller 5 so as to have a predetermined outer diameter (usually 125 μm) and the heating temperature and drawing speed of the heater 2b. Is controlled.

  The drawn optical fiber 3 is coated with a coating resin by the first and second resin coating dies 6a and 6b, and is cured by the first and second ultraviolet irradiation devices 7a and 7b. Thereafter, the coated optical fiber 3 'covered with resin is wound around the bobbin 8d through the bar roller 8a, the swing guide roller 9, the fixed guide rollers 8b and 8c, and the like.

As shown in FIG. 10B, when the rotation axis y of the swing guide roller 9 rotates by + θ around the drawing direction axis z, a lateral force is applied to the coated optical fiber 3 ′ by this rotation. Is applied, and the coated optical fiber 3 ′ rolls on the surface of the swing guide roller 9. This rolling imparts twist to the coated optical fiber 3 ′. Subsequently, when the swing guide roller 9 is rotated by −θ in the opposite direction, the coated optical fiber 3 ′ rolls on the surface of the swing guide roller 9 in the opposite direction. Thus, by repeatedly applying the rotation from + θ to −θ to the swing guide roller 9, clockwise and counterclockwise twists are alternately applied to the moving direction of the coated optical fiber 3 ′. Can do.
In addition to this, for example, various methods are considered for the swinging method such as a method in which the optical fiber 3 'is sandwiched between the pair of rollers 9a and 9b and twisted as shown in FIG.

  Further, Patent Document 2 discloses the twisting period and size of the swing guide roller, and the above-described twisting to the optical fiber is performed off-line (rewinding) in addition to performing on-line at the time of drawing. This is also disclosed.

JP-A-8-295528 US Patent Application Publication No. 2006/133551

  The application of twist to the optical fiber is usually performed at the time of drawing the optical fiber, and the twist is put in a form in which the glass fiber is permanently deformed in the heated and melted portion. Further, as disclosed in Patent Document 2, twisting is also performed when coloring or rewinding an optical fiber in a state where a protective coating is applied to the optical fiber once wound on a reel. . When twisting is applied when the latter optical fiber is rewinded, the swing guide roller is usually disposed between a capstan that is a take-up means of the optical fiber and a take-up bobbin. The reason for this is that, after twisting is applied to the optical fiber, the optical fiber is wound around the winding bobbin at a relatively early stage so that the twist is reduced.

  On the other hand, the PMD of the optical fiber is related to the twist amount (times / m) of the optical fiber, and the PMD can be reduced as the number of twists increases. In addition, the twisting amount of the optical fiber is related to the tension when it comes into contact with the swing guide roller. The larger the tension, the larger the twisting amount. If the tension is the same, the longer the free path length, the more the twisting amount. You can take more. However, due to equipment limitations, it is difficult to make the free path length so long, and the winding tension at the winding bobbin is relatively small (usually, in order to maintain fiber characteristics such as prevention of increased loss). 60 g or less). For this reason, there is a problem that the twist amount (turns / m) by the swinging guide roller disposed on the winding side is relatively small, and sufficient PMD reduction cannot be realized.

  The present invention has been made in view of the above-described circumstances, and even if it is difficult to take a long free path length due to equipment limitations, without affecting the winding tension in the winding bobbin, An object of the present invention is to provide an optical fiber manufacturing method and a manufacturing apparatus capable of increasing the twisting efficiency by giving a sufficient tensile tension to the optical fiber and reducing PMD of the optical fiber.

In the production of the optical fiber according to the present invention, the optical fiber is fed from the supply bobbin, taken by the take- up means, and taken up by the take- up bobbin. in the production method, without affecting the Ri winding of the winding bobbin, the provided capable interval applying winding tension higher tensile load of the take-up bobbin to the optical fiber, impart twist between said section, When the tension immediately before the twist applying portion is T (g), the free path length is L, the twist amount is R (times / m), and a and b are constants,
And setting "R = a × T × L ^b" tension as twisting amount R approximated is "2" or more in T, the free path length L. The twist amount R (times / m) is preferably “4” or more.

In addition, a high tension load means and a tension buffer means are provided in the front stage of the take-up means or in the subsequent stage of the take-up means, and the twist application by the high- tension load means . This is performed at a point where the tension is higher than the winding tension of . In addition, a torsion non-suppression roller is arranged between the torsion imparting portion and the torsion suppression roller provided on the upstream side of the torsion imparting portion to restrain the optical fiber from being twisted and rotated to extend the free path length. You may do it. Note that the twist imparting portion is composed of a swing guide roller, and the contact angle β of the optical fiber to the roller surface of the swing guide roller is preferably set to 40 ° to 160 °.

According to the present invention, without affecting the Ri winding of the winding bobbin, because from the take-up tension of the winding bobbin into the optical fiber provided which can apply a high tensile load path, facilities intended for example Even if the free path length cannot be increased due to the restriction, the tension in this section can be set to a predetermined tension, and a twist can be applied by applying a relatively large tension to the optical fiber. . As a result, the winding tension of the winding bobbin can be set to a value that is normally used, and the number of twists per unit distance can be efficiently given to the optical fiber to reduce PMD.

It is a figure explaining embodiment of this invention. It is a figure explaining other embodiment of this invention. It is a figure explaining other embodiment of this invention. It is a figure which shows the pass line of the twist provision part of an optical fiber. It is a figure which shows the relationship between the twist amount of an optical fiber, and PMD reduction rate. It is a figure which shows the relationship between the tension | tensile_strength of an optical fiber, and the amount of twist. It is a figure which shows the relationship between the free path length of an optical fiber, and the amount of twist. It is a figure which shows the correlation of the free path length and tension | tensile_strength with respect to the predetermined twist amount of an optical fiber. It is a figure which shows the relationship between the contact angle of an optical fiber, and the amount of twist. It is a figure explaining a prior art. It is a figure explaining other prior art.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an example in which twisting is applied to an optical fiber before the take-up means (capstan) during rewinding of the optical fiber, and FIGS. 2 and 3 are twists to the optical fiber after the take-up means. It is a figure which shows an example. 1-3, 10 is a supply bobbin, 11 is an optical fiber, 12 is a guide roller, 13 is a dancer roller, 14 is a bump detector, 15 is a torsion suppression roller, 16 is a torsion non-inhibition roller, and 17 is a tension detector. , 18 is a twist applying portion (twist applying roller), 19 is a twist suppressing roller, 20 is a capstan, 21 and 22 are guide rollers, 23 is a dancer roller, 24 is a winding bobbin, 25 is a tension detector, and 26 is a control. 27, a high tension loading means, and 28 a tension helper roller.

  In the rewinding of the optical fiber shown in FIG. 1, the optical fiber 11 delivered from the supply bobbin 10 is fed out with a predetermined tension by the guide roller 12 and the dancer roller 13. The fed optical fiber 11 can detect the presence or absence of bumps by, for example, a bump detector 14 disposed in the travel path. In addition, the tension detector 17 can detect the tension during travel of the optical fiber 11 immediately before the twist applying portion 18.

  The optical fiber 11 includes a twist imparting portion (hereinafter referred to as a twist imparting roller) 18 that imparts twist to the optical fiber 11 via a twist suppression roller 15, a twist non-suppression roller 16, and a capstan 20 via a twist suppression roller 19. It is picked up by the pick-up means. As the torsion imparting roller 18, for example, the swing guide roller 9 described with reference to FIG. 10B can be used, and the torsion suppressing rollers 15 and 19 are also V-groove type as shown in FIG. 10B. A fixed guide roller 8b can be used. The twist non-suppressing roller 16 is a roller having a wide roller width that allows the optical fiber to roll smoothly.

The optical fiber 11 taken up by the capstan 20 with a tension higher than the winding tension of the winding bobbin 24 (hereinafter referred to as high tension) is taken up by the winding bobbin 24 through the guide rollers 21 and 22 and the dancer roller 23. It is done. Moreover, the tension | tensile_strength of the optical fiber at the time of winding is detected by the tension | tensile_strength detector 25 as needed. The control device 26 controls the take-up speed of the take-up bobbin 24, etc. In addition, the control device 26 performs stop / reverse control by optical fiber bump detection and disconnection control, and tension according to tension detection by the tension detector 17. And control of the oscillation cycle of the torsion imparting roller 18 and the like.

  The rewinding of the optical fiber shown in FIG. 2 is an example in which a section for applying high tension is provided at the subsequent stage of the take-up means. The optical fiber 11 delivered from the supply bobbin 10 is fed out with a predetermined tension by the guide roller 12 and the dancer roller 13. The fed optical fiber 11 is taken up by a take-up means such as a capstan 20 while detecting the presence or absence of a hump by a hump detector 14 arranged in the traveling path.

  The optical fiber 11 taken up by the capstan 20 is loaded with high tension in the section from the capstan 20 to the high tension load means 27 by the high tension load means 27 disposed at the rear stage of the capstan 20. The high-tension load means 27 may be the same as the capstan described above, and may apply a tensile tension between the two capstans. An active motor or the like may be used to apply a predetermined tensile tension to the optical fiber. It may be given. In the section where the high tension is applied, the optical fiber 11 is a twist applying roller 18 for applying twist to the optical fiber 11 through the twist suppressing roller 15 and the non-torsion suppressing roller 16 as described with reference to FIG. Twist is imparted by the twist suppression roller 19. In addition, the tension detector 17 can detect the tension during travel of the optical fiber 11 immediately before the twist applying roller 18.

  The twisted optical fiber is relaxed by a tension helper roller 28 disposed downstream of the high-tension load means 27, and then wound by a winding bobbin 24 through a dancer roller 23 and a guide roller 22. If the high tension load means 27 can relieve the subsequent tension by itself, the tension helper roller 28 can be omitted. However, the tension tension roller 28 is provided with more winding tension. The influence on can be eliminated.

  Moreover, the tension | tensile_strength of the optical fiber at the time of winding is detected by the tension | tensile_strength detector 25 as needed. The control device 26 controls the take-up speed of the take-up bobbin 24, and the control device 26 also performs stop / reverse control by detecting optical fiber bumps and wire breakage, and tension according to tension detection by the tension detector 17. Control of the fiber tension by the high tension load means 27, control of the oscillation cycle of the torsion applying roller 18, and the like.

The rewinding of the optical fiber shown in FIG. 3 is an example using the tension loaded in the section between the high tension load means and the tension helper roller. The tension helper roller 28 relieves the high tension applied by the high tension load means 27, but a certain amount of high tension remains immediately after the high tension load means 27. When a predetermined high tension is obtained with the tension helper roller 28, twisting can be applied to the optical fiber as in the case of FIG. 2 described above.
In the rewinding of the optical fiber, a screening test may be performed by applying a high tension by the high tension load means 27. In this way, by separating the high tension load section and the torsion imparting section, the screening section It is possible to impart torsion without affecting.

  As described with reference to FIG. 2, the optical fiber 11 delivered from the supply bobbin 10 is fed out by the guide roller 12 and the dancer roller 13 with a predetermined tension. The fed optical fiber 11 is taken up by the capstan 20 while detecting the presence or absence of a bump by a bump detector 14 disposed in the traveling route, for example.

  The optical fiber 11 taken up by the capstan 20 is given a predetermined tension by the high tension load means 27 through the guide roller 21. The optical fiber 11 that has passed through the high-tension load means 27 is provided with a twist imparting roller 18 that imparts twist to the optical fiber 11 via the twist suppression roller 15, the twist non-suppression roller 16, and the like, as described in FIG. A twist is imparted by the roller 19. The twisted optical fiber is relaxed by the tension helper roller 28 and then wound by the winding bobbin 24 through the dancer roller 23 and the guide roller 22.

  FIG. 4 is a diagram showing an outline of a pass line of a twist applying portion of an optical fiber. The optical fiber is twisted by a pass line in which a twist non-suppression roller 16 is disposed between the twist imparting roller 18 and the twist restraining roller 15 disposed on the upstream side or between the twist imparting roller 18 and the twist restraining roller 15. It is applied by the twist applying roller 18. In addition, when the distance L1 + L2 between the torsion imparting roller 18 and the torsion suppression roller 15 is omitted and the torsion non-inhibition roller 16 is omitted, the distance L1 is referred to as a free path length L.

The relationship between the free path length L and the twist amount (times / m) indicating the number of twists per unit length that can be applied to the optical fiber is as follows. As shown in FIG. Many twists can be added.
When the free path length L cannot be sufficiently secured due to the equipment space, as shown in FIG. 4 and the like, the distance L2 between the twist suppression roller 15 and the twist suppression roller 15 is folded back by using the twist non-suppression roller 16. In addition, a predetermined free path length can be obtained by “L1 + L2”.

  The twist applying roller 18 applies a twist to the optical fiber by swinging the roller rotation shaft at a predetermined swing angle (± θ). For example, the twist applying roller 18 is the same as described with reference to FIGS. Any shape (swing guide roller) can be used, but the swing method is not particularly limited. That is, when the twist imparting roller 18 is swung in one direction (+ θ direction), a lateral force is applied to the optical fiber, and the optical fiber rolls on the surface of the twist imparting roller 18. Directional twist is imparted. Subsequently, when the twist imparting roller 18 is swung in the opposite direction (−θ direction), the optical fiber rolls in the opposite direction on the surface of the twist imparting roller 18 and the twist in the opposite direction is imparted. The As described above, the twist applying roller 18 is repeatedly controlled to swing in a predetermined range of swing angle and cycle, thereby alternately applying clockwise and counterclockwise twist in the moving direction of the optical fiber 11. Can do.

  Further, the twist imparting to the optical fiber 11 due to the swing of the twist imparting roller 18 is affected by a contact angle β (also referred to as a winding angle) at which the optical fiber 11 and the twist imparting roller 18 come into contact as will be described later. That is, if this contact angle is too small, the rolling of the optical fiber on the roller surface becomes insufficient, and a predetermined twist amount cannot be obtained. Also, if the contact angle is too large, the resistance when the optical fiber rolls on the roller surface increases and it becomes difficult to roll, so it is necessary to set an appropriate contact angle β.

  FIG. 5 is a graph showing the relationship between the twist amount R (times / m) of the optical fiber and the PMD reduction rate. Assuming that the PMD reduction rate is “1- (PMD after applying twist / PMD before applying twist)”, the amount of twist and the PMD reduction rate are approximately proportional as shown in the figure, and if the amount of twist increases, In proportion to this, the PMD reduction rate increases. That is, if the amount of twist increases, the PMD decreases in proportion thereto. For 10 to 40 Gbit transmission, the PMD is preferably 0.06 ps / √km or less, preferably 0.02 ps / √km, and the current general-purpose fiber has an ability of 0.01 to 0.2 ps / √km. In view of (average value 0.1 ps / √km), the PMD reduction rate is 0.4, preferably 0.8. In order to achieve this target PMD reduction rate, the twist amount R (times / m) needs to be “2” or more, preferably “4” or more.

  FIG. 6 is a diagram showing the relationship between the tension T (g) applied to the optical fiber and the twist amount R (times / m). Note that the twist amount R (turns / m) of the optical fiber has other requirements, but in this figure, the contact angle β described in FIG. 4 is 71 °, the roller diameter is 40 mm, the roller width is 30 mm, and the swing angle. Measures twist amount R (times / m) against tension T (g) applied to an optical fiber at a linear speed of 750 m / min when θ is 15 ° and free path lengths (L1 + L2) are 500 mm, 900 mm, and 1430 mm, respectively. It is a thing. As can be seen from this figure, the twist amount of the optical fiber depends almost linearly on the tension of the optical fiber.

  FIG. 7 is a diagram showing the relationship between the free path length L (mm) for imparting twist to the optical fiber described in FIG. 4 and the twist amount R (times / m). In this figure, the contact angle β, the roller diameter, the roller width, the swing angle θ, and the linear velocity are constant as described above, and the tension T of the optical fiber is 60 g, 150 g, 190 g, 240 g, and 310 g. In other words, the amount of twist for each free path length was measured.

FIG. 8 shows the actual values measured in FIG. 6 and FIG. 7, with a and b being constants and a tension T () so that the twist amount R (times / m) is constant at “2” and “4”. FIG. 5 is a graph showing the results of obtaining the relationship between g) and the free path length L (m) as an approximate curve. The approximate curve is “R = a × T × L ^b ”
In this case, a = 0.0235 and b = 0.90. These a and b are constants that change depending on factors such as ease of twisting due to the surface property of the roller and the period (speed) of rocking. For example, if a roller with good twisting performance is used, the value of a is growing.

  As is clear from this figure, in order to secure the twist amount R (turns / m) to “2” or more, it is sufficient that the tension T and the free path length L are on the right side of the graph of the twist amount R = 2. In order to ensure 4 "or more, it is sufficient if the tension T and the free path length L are on the right side of the graph of the twist amount R = 4. More specifically, for example, when the free path length is 1 m, in order to secure the twist amount R (times / m) of “2” or more, the tension T needs to be 80 g or more, and the twist amount R ( In order to secure “4” or more at times / m), the tension T needs to be 160 g or more. In addition, although the tension | tensile_strength of about 900g-1100g may be applied to the screening of an optical fiber, since the frequency of a cutting | disconnection increases, it is desirable to implement by the magnitude | size (for example, 500 g or less) below this.

  As described above, for example, by securing a tension of 160 g or more of the optical fiber and performing a swing, a twist amount of “4” or more is ensured, and an effect of reducing PMD is obtained. Since it is necessary to make it about 60 g, it is not possible to increase the tension where the winding tension of the winding bobbin is affected. In the winding equipment shown in FIG. 1, even if the tension is high before the capstan 20, the winding tension is not affected. Therefore, the twisting roller 18 is disposed in this portion to secure the necessary optical fiber tension. Like to do.

  On the other hand, in the winding facility of FIG. 2, a high-tension load means 27 is provided at the rear stage of the capstan 20 and the tension is relaxed by a tension relief means such as a tension helper roller 28. Thus, even if a high tension is applied between the capstan 20 and the high tension load means 27, the twisting roller 18 is disposed in the high tension portion as shown in FIG. 2 without affecting the winding tension. The necessary optical fiber tension is ensured. In FIG. 3, the necessary optical fiber tension is secured in the same manner as in FIGS.

  Further, when the free path length L is 500 mm, the twist amount (times / m) cannot be secured to “2” or more when the tension of the optical fiber is 150 g or less. On the other hand, when the optical fiber is run with a tension of 100 g or more, the free path length L needs to be 800 mm or more in order to secure the twist amount R (times / m) of “2” or more. If the space of the free path length L cannot be sufficiently taken into account in the configuration of the equipment, in addition to solving the problem by increasing the tension of the optical fiber, the twist non-suppressing roller 16 can be used as described in FIG. A predetermined free path length may be secured as the free path length including the return L2.

  FIG. 9 is a diagram illustrating the relationship between the contact angle β (°) of the optical fiber described with reference to FIG. 4 and the twist amount (times / m). In FIG. 9, the free path length, the roller diameter, the roller width, and the swing angle are the same as the measurement parameters in FIG. 6, and the twist amount when the contact angle β is changed with the free path length of 1430 mm and the tension of 150 g. R is measured. As a result, if the contact angle β is less than 40 °, it is difficult to secure the required amount of twist R (times / m), and if the contact angle β exceeds 160 °, the twist amount R (times / m). It becomes difficult to secure the required amount. Therefore, the contact angle β (°) of the optical fiber with respect to the twist applying roller is preferably 40 ° or more and 160 ° or less, and further, the twist amount R (times / m) is 50 ° or more that can secure “5”. It is preferable that it is 100 degrees or less.

  As described above, in order to reduce the PMD of the optical fiber by alternately twisting the optical fiber in an off-line process such as rewinding of the optical fiber, a predetermined twist amount (times / m) is required. It has been found that in order to give the optical fiber a predetermined twisting amount (for example, 2 times / m) or more, it is necessary to twist it as a tension or free path length exceeding a predetermined value. Therefore, in the present invention, even if it is difficult to take a long free path length due to equipment limitations, a high tension load is applied to the optical fiber so as not to affect the winding tension of the winding bobbin. High tension can be applied by using a tension relief means such as a tension helper roller even in a section where it is possible, for example, before the take-up means such as a capstan or after the take-up means. The torsion imparting portion is arranged at the place where the above is applied.

  As a result, even at the front stage of the take-up means such as the capstan and the rear stage of the take-up means, it is possible to load high tension by using a tension relief means such as a tension helper roller. It is possible to apply sufficient tension to impart twist to the optical fiber, and even if it is difficult to increase the free path length due to equipment limitations, the PMD value of the optical fiber can be reduced.

  When twisted before the take-up means (before the capstan), the twist imparted to the optical fiber is somewhat released in the path until it is wound by the take-up bobbin. It is also possible to apply a twist in anticipation. In addition, whether the twist is applied at the front stage or the rear stage of the capstan, the tension of the optical fiber on the winding bobbin side can be maintained while maintaining the same tension as that of the conventional one. Further, the twisting operation of the optical fiber is eliminated near the winding bobbin, and therefore, the winding state is eliminated and the winding state can be further improved.

DESCRIPTION OF SYMBOLS 10 ... Supply bobbin, 11 ... Optical fiber, 12 ... Guide roller, 13 ... Dancer roller, 14 ... Cobb detector, 15 ... Torsion suppression roller, 16 ... Torsion non-suppression roller, 17 ... Tension detector, 18 ... Torsion imparting part (Twist imparting roller), 19 ... Twist suppression roller, 20 ... Capstan, 21,22 ... Guide roller, 23 ... Dancer roller, 24 ... Take-up bobbin, 25 ... Tension detector, 26 ... Control device, 27 ... High tension Load means, 28 ... tension helper roller.

Claims (7)

Unwinding the optical fiber from the supply bobbin, in the path of winding by the winding bobbin me pulling by the take-up means, a method of manufacturing an optical fiber which imparts twist alternately by applying portion twist to the optical fiber,
Wherein without affecting to Ri winding of the winding bobbin, the optical fiber can be subjected to higher tensile loads than the winding tension of sections provided to impart twist in the section, immediately before the twist imparting portion When the tension at T is (g), the free path length is L, the twist amount is R (times / m), and a and b are constants,
The method of manufacturing an optical fiber , wherein the tension T and the free path length L are set so that the twist amount R approximated by “R = a × T × L ^b ” is “2” or more.   The method of manufacturing an optical fiber, wherein the twist amount R (times / m) is set to “4” or more. The method of manufacturing an optical fiber according to claim 1 or 2, characterized in that the twist imparted by the twist imparting portion in front of said take-up means. Wherein downstream of the take-up means is provided a high tension loading means and tension buffering means, the twist imparted by the twist imparting portion, in the high tension loading means by point which is set to a higher tension than the winding tension of the winding bobbin The optical fiber manufacturing method according to claim 1, wherein the optical fiber manufacturing method is performed.   A torsion non-suppression roller is disposed between the torsion imparting portion and a torsion suppression roller provided upstream of the torsion imparting portion to restrain the optical fiber from being twisted and rotated to extend the free path length. The method of manufacturing an optical fiber according to any one of claims 1 to 4.   5. The twist imparting portion comprises a swing guide roller, and the contact angle β of the optical fiber with respect to the roller surface of the swing guide roller is set to 40 ° to 160 °. The manufacturing method of the optical fiber of Claim 1. Unwinding the optical fiber from the supply bobbin in the winding bobbin me take-up by the take-up Ru pathway by take-off means, a manufacturing apparatus of an optical fiber to impart twist alternately by applying portion twist to the optical fiber,
Without affecting the Ri winding of the winding bobbin, said applying the winding high tensile loads than the winding tension of the bobbin provided capable section imparts twist in the section on the optical fiber, wherein When the tension immediately before the twist applying portion is T (g), the free path length is L, the twist amount is R (times / m), and a and b are constants,
The optical fiber manufacturing apparatus , wherein the tension T 1 and the free path length L are set so that the twist amount R approximated by “R = a × T × L ^b ” is “2” or more. .

Images