JP2017024814A - Optical fiber winding method and optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber winding method in which tension control is facilitated, winding collapse hardly occurs in optical fiber transport, and increase of transmission loss can be suppressed.SOLUTION: A winding method of an optical fiber 10 is a method for winding the optical fiber 10 which is mainly formed of quartz glass to a bobbin 20, in which a winding tension of the optical fiber 10 is constant and in a range of 30 g or higher and 70 g or lower, and a ratio V/S of an actual volume V of the optical fiber 10 determined based on a cross section and length of the wound optical fiber 10, with respect to a volume S on a wound part 11 of the optical fiber 10 determined based on a winding radius t of the optical fiber 10 wound to a trunk 20a of the bobbin 20 and a radius r and a width w of the trunk 20a, becomes 58% or higher and 79% or lower, by setting a winding condition.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical fiber winding method and an optical fiber.

Patent Document 1 is an invention relating to a method of winding a plastic optical fiber, and discloses a preferable winding tension and winding pitch range for preventing the light transmission performance from being deteriorated by strain generated in the plastic optical fiber. Has been.
Patent Document 2 is an invention relating to a tension control method for winding an optical fiber, and discloses a method for reducing the winding tension as the winding of the optical fiber proceeds.
Patent Document 3 is an invention relating to an optical fiber winding method, in which a winding tension when winding an optical fiber having an outer diameter of approximately 250 μm on a bobbin is T (N), and a traverse pitch (an optical fiber is 1 on a bobbin). It is disclosed that T / P ² (N / mm ² ) is within a predetermined preferable range, where P (mm) is the bobbin or guide roller movement amount during circumferential winding.

JP-A-1-321259 JP-A-5-273416 JP 2014-97879 A

  The method described in Patent Document 1 is a method of winding a plastic optical fiber, and cannot be applied to silica-based optical fibers having different fiber characteristics. Further, in the method described in Patent Document 2, it is necessary to gradually change the winding tension, or to change the winding tension decreasing method according to the length of the fiber to be wound, and it is difficult to control the tension. there were. Further, even when the winding tension or traverse pitch is set within the range described in Patent Document 3 and the optical fiber is wound, the winding collapse may occur.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber winding method and an optical fiber that are easy to control tension, are less likely to collapse during transportation of an optical fiber, and can suppress an increase in transmission loss.

An optical fiber winding method according to the present invention includes:
A winding method for winding an optical fiber mainly composed of quartz glass on a bobbin,
The winding tension of the optical fiber is constant and is in the range of 30 g to 70 g;
The cross-sectional area of the wound optical fiber with respect to the volume S of the winding portion of the optical fiber obtained from the winding radius of the optical fiber wound on the bobbin barrel and the radius and width of the barrel. Winding is performed with the winding conditions set so that the ratio V / S of the actual volume V of the optical fiber determined from the length is 58% or more and 79% or less.

The optical fiber according to the present invention is
An optical fiber mainly composed of quartz glass wound around a bobbin,
Breaking of the wound optical fiber with respect to the volume S of the winding portion of the optical fiber determined from the winding radius of the optical fiber wound on the bobbin barrel and the radius and width of the barrel. The ratio V / S of the actual volume V of the optical fiber obtained from the area and length is 58% or more and 79% or less,
The winding thickness of the optical fiber determined from the difference between the winding radius of the optical fiber and the radius of the body portion is 15 mm or more,
The increase in transmission loss of the optical fiber due to being wound is 0.01 dB / km or less.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to control tension | tensile_strength, it is hard to generate | occur | produce winding collapse during optical fiber transport, and the winding method and optical fiber of an optical fiber which can suppress the increase in transmission loss can be provided.

It is a top view which shows the winding apparatus for performing the winding method of the optical fiber which concerns on one Embodiment of this invention. It is a graph which shows the relationship between the winding pitch of an optical fiber, and a winding density. It is a graph which shows the relationship between the winding tension | tensile_strength of an optical fiber, and a winding density. It is a graph which shows the relationship between the winding density of an optical fiber, and unwinding incidence.

<Outline of Embodiment of the Present Invention>
First, an outline of an embodiment of the present invention will be described.
An optical fiber winding method according to an embodiment of the present invention includes:
(1) A winding method for winding an optical fiber mainly composed of quartz glass around a bobbin,
The winding tension of the optical fiber is constant and is in the range of 30 g to 70 g;
The cross-sectional area of the wound optical fiber with respect to the volume S of the winding portion of the optical fiber obtained from the winding radius of the optical fiber wound on the bobbin barrel and the radius and width of the barrel. Winding is performed with the winding conditions set so that the ratio V / S of the actual volume V of the optical fiber determined from the length is 58% or more and 79% or less.
According to this configuration, it is possible to provide an optical fiber winding method that is easy to control tension, is less likely to collapse during transportation of the optical fiber, and can suppress an increase in transmission loss.

(2) An allowable value for increasing the transmission loss of the optical fiber is set, a winding tension of the optical fiber is calculated so as to satisfy the allowable value, and the volume S of the winding portion is calculated based on the winding tension. The winding pitch of the optical fiber is calculated so that the ratio V / S with the actual volume V of the optical fiber is maximized, and the winding condition is based on the calculated winding tension and the winding pitch. Is preferably set.
According to this configuration, it is possible to easily set a winding condition that does not collapse or increase loss based on the winding tension or winding pitch of the optical fiber.

In the winding method of the optical fiber,
(3) It is preferable that the winding thickness of the optical fiber obtained from the difference between the winding radius of the optical fiber and the radius of the body portion is 15 mm or more.
If the winding thickness of the optical fiber is greater than or equal to the above range, the winding method is likely to occur. Therefore, it is preferable to apply the winding method according to the present invention.

In the winding method of the optical fiber,
(4) It is preferable that the effective area Aeff of the optical fiber is 70 μm ² or more.
Since an optical fiber having a large Aeff tends to increase transmission loss due to side pressure, it is preferable to apply the winding method according to the present invention.

An optical fiber according to an embodiment of the present invention is:
(5) An optical fiber mainly composed of quartz glass wound around a bobbin,
Breaking of the wound optical fiber with respect to the volume S of the winding portion of the optical fiber determined from the winding radius of the optical fiber wound on the bobbin barrel and the radius and width of the barrel. The ratio V / S of the actual volume V of the optical fiber obtained from the area and length is 58% or more and 79% or less,
The winding thickness of the optical fiber determined from the difference between the winding radius of the optical fiber and the radius of the body portion is 15 mm or more,
The increase in transmission loss of the optical fiber due to being wound is 0.01 dB / km or less.
According to this configuration, it is possible to provide an optical fiber that is less likely to collapse during transportation and can suppress an increase in transmission loss.

The optical fiber is
(6) The effective area Aeff is preferably 70 μm ² or more.
An optical fiber having a large Aeff is preferably wound as described in (5) above.

<Details of Embodiment of the Present Invention>
Hereinafter, an example of an embodiment according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, the optical fiber 10 is made of, for example, quartz glass as a main component, and the outer periphery of a glass fiber having an outer diameter of 125 μm, for example, made of a core and a clad is coated with a resin. The outer diameter of the optical fiber 10 is, for example, 250 μm. The optical fiber 10 is bundled into an optical cable for use in optical communication, for example. As the optical fiber 10, for example, an optical fiber having an effective area Aeff of 70 μm ² or more is used. An optical fiber with a large Aeff is weak in lateral pressure, and when the bending occurs, the light guided inside tends to escape to the outside and the transmission loss increases, so the winding tension needs to be kept at a relatively low value. There is.

  The bobbin 20 that winds up the optical fiber 10 is made of a synthetic resin such as plastic, for example, and has a cylindrical body (winding part) 20a around which the optical fiber 10 is wound, and both ends of the body 20a. And a pair of disc-shaped flanges 20b, 20c provided on the surface. In this embodiment, the radius r of the trunk | drum 20a is 50 mm-100 mm, for example, and each radius R of a pair of collar parts 20b and 20c is 100 mm-200 mm, for example. Moreover, the width | variety w of the trunk | drum 20a is 100 mm-300 mm, for example.

  When the optical fiber 10 is wound around the bobbin 20, the optical fiber 10 needs to be wound evenly on the body 20a of the bobbin 20. Therefore, a winding device 21 as shown in FIG. 1 is used. The winding device 21 includes a drive shaft (drive unit) 22 that is rotationally driven, and the bobbin 20 is attached to the drive shaft 22. The bobbin 20 is fixed to the drive shaft 22 and rotated, for example, clockwise as viewed from the right side of FIG.

  The roller 19 that guides the optical fiber 10 is reciprocated in the direction of the rotation axis of the bobbin 20 (arrow A in FIG. 1) with respect to the bobbin 20 that is rotated by the drive shaft 22. As a result, the optical fiber 10 is wound around the body 20 a of the bobbin 20 while being reciprocated in the axial direction of the bobbin 20. That is, the winding device 21 fixes the position of the bobbin 20 in the rotation axis direction and winds the optical fiber 10 around the body 20a of the bobbin 20 by a method of reciprocating the optical fiber 10 (roller traverse method).

  In the present embodiment, the optical fiber 10 is wound around the bobbin 20 while the winding tension of the optical fiber 10 remains constant. If the winding tension is constant, it is easy to set the winding condition. Even if the optical fiber 10 is broken during winding, it is possible to set the winding condition again without resetting the winding condition. Can be resumed around the bobbin.

  Specifically, the winding tension of the optical fiber 10 is in the range of 30 g to 70 g, preferably 40 g to 50 g. If the winding tension is less than 30 g, the winding tension is too low to stabilize the winding tension, and the optical fiber 10 cannot be wound around the bobbin 20 at a desired winding pitch. On the other hand, when the winding tension exceeds 70 g, a side pressure is applied to the optical fiber 10 and the transmission loss of the optical fiber 10 becomes high.

  In the present embodiment, the ratio between the volume of the winding portion 11 of the optical fiber 10 that increases by winding the optical fiber 10 and the actual volume of the wound optical fiber 10 is defined as “winding density”. The preferred range of the winding density is set as follows.

Specifically, the winding is performed with respect to the volume S of the winding portion 11 of the optical fiber 10 obtained from the winding radius (radius of the winding portion 11) t of the optical fiber 10 and the radius r and width w of the body portion 20a. The winding conditions are set so that the ratio V / S of the actual volume V of the optical fiber 19 obtained from the cross-sectional area and length of the optical fiber 10 is 58% or more and 79% or less. That is, the volume S of the winding part 11 of the optical fiber 10 is obtained from the following equation (1).
S = (πt ² w) − (πr ² w) (1)

If the optical fiber 10 is wound up to the limit of the outer diameter of the flanges 20b and 20c of the bobbin 20, the winding radius t of the optical fiber 10 can be calculated by the radius R of the flanges 20b and 20c of the bobbin 20. Further, when the winding thickness of the winding portion 11 of the optical fiber 10 is T, the winding thickness T is determined by the difference tr between the winding radius t of the optical fiber 10 and the radius r of the body portion 20a. When the optical fiber 10 is wound up to the outer diameter of the flanges 20b and 20c of the bobbin 20, the winding thickness T is the difference R− between the radius R of the flanges 20b and 20c and the radius r of the body 20a. It can be calculated by r.
The actual volume V of the wound optical fiber 10 is calculated by the product of the cross-sectional area and the length of the wound optical fiber 10.

  When the winding density is high, the gap generated between the optical fibers 10 wound around the bobbin 20 is small, and the space in which the optical fiber 10 moves during transportation becomes small. Therefore, vibration, shock, and temperature change during transportation It is difficult for the material to collapse. Therefore, it is preferable that the winding density is high. If the optical fiber 10 is wound with the smallest gap and is densely wound, it is theoretically equivalent to 79%. The winding density is preferably as close as possible to the upper limit value. However, in practice, the gap between the optical fibers 10 increases due to the positional accuracy of the winding device, the vibration of the optical fiber 10 during winding, and the like. Is the actual upper limit.

In the present embodiment, the winding condition of the optical fiber 10 is set according to the following procedure.
Generally, transmission loss increases as the winding tension of the optical fiber is increased. Therefore, first, the winding tension is set so that the increase in the transmission loss of the optical fiber 10 is less than the allowable value. Next, based on the set winding tension, the ratio V / S of the actual volume V of the wound optical fiber 10 to the volume S of the wound portion 11 of the optical fiber 10 that is the winding density is maximized. Then, the winding pitch of the optical fiber 10 is calculated. Since the gap between the optical fibers 10 wound around the bobbin 20 changes depending on the winding pitch, the winding density also changes according to the change in the winding pitch. Finally, winding conditions are set based on the calculated winding tension and winding pitch.

  That is, the relationship between the winding pitch and winding tension of the optical fiber 10 and the winding density is examined, winding conditions are set based on the winding tension and winding pitch within a suitable range, and the bobbin 20 The winding density of the optical fiber 10 to be wound is adjusted so as to be in an optimum range. In the optical fiber 10 wound around the bobbin 20 under the above-described winding conditions, an increase in transmission loss due to being wound becomes 0.01 dB / km or less. If the increase in transmission loss of the optical fiber 10 after being wound around the bobbin 20 is 0.01 dB / km or less, it is a sufficiently acceptable range.

  In addition, about the optical fiber 10 wound up by the bobbin 20 as mentioned above, winding collapse | disintegration generate | occur | produced, so that the winding thickness T (refer FIG. 1) of the winding part 11 of the optical fiber 10 wound around the bobbin 20 becomes large. It's easy to do. If the winding thickness T of the optical fiber 10 is 15 mm or more, the rate of occurrence of winding collapse increases.

Generally, the optical fiber 10 is housed in a packing box (not shown) or the like while being wound around the bobbin 20 and shipped, and is conveyed by a truck, a ship, an airplane, or the like.
When the optical fiber 10 wound around the bobbin 20 is transported, if the winding tension when the optical fiber 10 is wound around the bobbin 20 is low, the optical fiber 10 is collapsed due to vibration or the like when transporting the optical fiber 10. May occur. Such unwinding of the optical fiber 10 causes disconnection when the optical fiber 10 is pulled out from the bobbin 20 to manufacture an optical cable. Therefore, the work of rewinding the optical fiber 10 is required, and workability is deteriorated. End up.
Further, when the winding tension is increased to prevent the optical fiber 10 from collapsing, the adjacent optical fibers 10 come into contact with each other, and the transmission loss of the optical fiber 10 increases due to the influence of the side pressure due to the contact between the optical fibers 10. End up.
Further, as described in Patent Document 3, even when T / P ² is set within a predetermined range when the winding tension of the optical fiber is T and the traverse pitch is P, collapse may occur. is there.

  In view of such problems, in the present embodiment, the inventor investigated the cause of the collapse of the optical fiber. As a result, even when wound at the same winding tension or traverse pitch, the case where it is wound closely In some cases, the “winding density” indicating whether the optical fiber 10 is densely wound, rather than the winding tension or traverse pitch, may be used as an index. It was found that it is effective in making it difficult to occur. By using the winding density as an index, it is possible to set a winding condition in which no winding collapse occurs without increasing the winding tension more than necessary. The reason why the winding density is effective is that, even with the same winding tension and traverse pitch, there are differences in the accuracy of tension control and traverse position due to differences in equipment, and the light that is wound around the bobbin. The effect of fiber vibration can be mentioned. In particular, when the vibration of the optical fiber is large, the optical fiber may run on the adjacent fiber wound immediately before, and may not be wound precisely.

  According to the winding method of the optical fiber 10 according to the present embodiment, the winding tension of the optical fiber 10 is constant and is in a range of 30 g or more and 70 g or less, and the optical fiber 10 wound around the body portion 20 a of the bobbin 20. The cross-sectional area and the length of the wound optical fiber 10 with respect to the volume S of the winding portion 11 of the optical fiber 10 obtained from the winding radius t of the optical fiber 10 and the radius r and width w of the body portion 20a. Winding is performed by setting the winding conditions so that the ratio V / S of the actual volume V of the optical fiber 10 obtained from this is 58% or more and 79% or less. That is, the condition is set so that the ratio V / S of the actual volume V of the wound optical fiber 10 to the volume S of the winding portion 11 of the optical fiber 10 becomes an appropriate value, and the optical fiber 10 is attached to the bobbin 20. Winding up. According to this condition, the winding tension of the optical fiber 10 is set within a constant and suitable range, so that the winding tension can be easily adjusted and an increase in transmission loss can be prevented. Further, by adopting an index “winding density” obtained from the ratio V / S of the actual volume V of the wound optical fiber 10 with respect to the volume S of the wound portion 11 of the optical fiber 10, the winding of the optical fiber 10 is performed. It is easy to set the removal conditions.

  Further, by setting the condition based on the “winding density”, it is possible to prevent the optical fiber 10 from being collapsed when transporting the bobbin 20 around which the optical fiber 10 is wound while suppressing an increase in transmission loss of the optical fiber 10 as much as possible. Can be prevented. Thereby, the disconnection of the optical fiber 10 accompanying the collapse of the optical fiber 10 after the conveyance can be suppressed, and the rewinding of the optical fiber 10 becomes unnecessary, so that the workability can be improved.

  In the present embodiment, an allowable value for increasing the transmission loss of the optical fiber 10 is set, the winding tension of the optical fiber 10 is calculated so as to satisfy the allowable value, and the winding of the optical fiber 10 is calculated based on the winding tension. The winding pitch of the optical fiber 10 is calculated so that the ratio V / S between the volume S of the winding portion 11 and the actual volume V of the optical fiber 10 is maximized, and based on the calculated winding tension and winding pitch. It is preferable to set the winding condition. This makes it possible to easily set a winding condition that does not collapse or increase loss.

  In the present embodiment, it is preferable that the winding thickness T of the optical fiber obtained from the difference between the winding radius t of the optical fiber 10 and the radius r of the body 20a of the bobbin 20 is 15 mm or more. When the wound thickness T of the wound optical fiber 10 is equal to or greater than 15 mm, the winding is likely to be collapsed. Therefore, the winding method according to the present embodiment that can prevent the collapse of the optical fiber 10 is provided. This is because it is preferable to apply.

Furthermore, in this embodiment, it is preferable that the effective area Aeff of the optical fiber 10 is 70 μm ² or more. Since the optical fiber 10 having an Aeff of 70 μm ² or more tends to increase the transmission loss due to the influence of the side pressure, the winding method according to this embodiment that can prevent the collapse without increasing the winding tension is applied. Is particularly preferred.

(Evaluation of the rate of collapse)
In order to evaluate the rate of occurrence of collapse of the optical fiber 10, first, the relationship between the winding pitch and winding tension of the optical fiber 10 and the winding density was evaluated.
FIG. 2 is a graph showing the relationship between the winding pitch and the winding density. In order to confirm the relationship between the winding pitch and the winding density, the winding tension is set to 45 g, for example, as a suitable winding tension for the allowable increase in the transmission loss of the optical fiber 10, and the winding pitch is set to 0.40 mm to Each winding density was measured by changing the thickness within a range of 0.60 mm. As a result, as shown in FIG. 2, it was confirmed that the winding density was maximized at a winding pitch of 0.45 mm. That is, by examining the relationship between the winding pitch and the winding density in advance, a suitable range of the winding pitch of the optical fiber 10 is calculated so that the winding density (ratio V / S) is maximized. be able to.

  Since the outer diameter of the optical fiber 10 is 0.25 mm, the winding density should increase as the winding pitch approaches 0.25 mm. However, when the winding pitch becomes smaller than 0.45 mm, the winding density is increased. Decrease. This is because the accuracy of the winding equipment and the vibration of the optical fiber are affected. When the winding pitch is reduced, the frequency of riding on the optical fiber wound immediately before increases, and the winding density decreases. Therefore, the winding pitch at which the winding density reaches a peak differs depending on equipment, winding conditions, fiber differences, and the like, but in this embodiment, the winding density is used as an index to obtain the optimum winding conditions. .

  FIG. 3 is a graph showing the relationship between the winding tension and the winding density. In order to confirm the relationship between the winding tension and the winding density, the winding tension is varied in the range of 45 to 75 g at a winding pitch of 0.45 mm at which the winding density is maximum, and the winding density at each winding tension is measured. did. As a result, it was confirmed that the winding density was 58 or more at any winding tension, and that the winding density increased as the winding tension increased. By examining the relationship between the winding tension and the winding density in advance, it is preferable to adjust the winding tension of the optical fiber 10 so that the winding density (ratio V / S) is maximized within a range where transmission loss does not increase. Range can be calculated.

Next, in order to evaluate the rate of occurrence of the collapse of the optical fiber 10, the ratio V / S (winding density) of the actual volume V of the wound optical fiber 10 to the volume S of the winding portion 11 of the optical fiber 10 is 56. It was changed in a range of ˜62%, and the occurrence rate of collapse of the optical fiber 10 at that time was confirmed. The result is shown in FIG.
As shown in FIG. 4, when the winding density is 58% or more, the rate of occurrence of winding collapse is suppressed to 0%, but when the winding density is less than 58%, the probability that the optical fiber 10 will collapse is increased. It was confirmed.

  From the above, it was confirmed that if the winding density was 58% or more, the optical fiber 10 did not collapse.

(Evaluation of payout and loss increase)
The pay-out property and loss increase of the optical fiber 10 were also evaluated as follows.
A single mode fiber (length 50 km) having an effective area Aeff of 70 μm ² and a fiber outer diameter of 250 μm is formed into a bobbin having a trunk radius r of 75 mm, a flange radius R of 150 mm, and a trunk width w of 150 mm. The winding tension was 45 g and the winding pitch was 0.45 mm. As a result, the winding radius was 120.4 mm. The ratio V / S of the actual volume V of the wound optical fiber to the volume S of the wound portion was calculated to be 58.7%. After applying vibration to the bobbin with a vibration tester, it was confirmed that the optical fiber could be drawn out. Moreover, when the loss of the optical fiber was measured in this state, the loss increase was as good as 0.003 dB / km. The increase in loss was obtained by comparing with a loss measured by applying 5 km from the upper opening of the bobbin and putting it into a bundle (cigarette) so that no side pressure is applied.

  While the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. In addition, the number, position, shape, and the like of the constituent members described above are not limited to the above-described embodiments, and can be changed to a number, position, shape, and the like that are suitable for carrying out the present invention.

DESCRIPTION OF SYMBOLS 10: Optical fiber 11: Winding part of optical fiber 20: Bobbin 20a: Trunk part 20b, 20c: Ridge part 21: Winding device 22: Drive shaft r: Radius of trunk | drum w: Width of trunk | drum R: Ridge part T: optical fiber winding radius T: optical fiber winding thickness S: volume of optical fiber winding V: actual optical fiber volume

Claims (6)

A winding method for winding an optical fiber mainly composed of quartz glass on a bobbin,
The winding tension of the optical fiber is constant and is in the range of 30 g to 70 g;
The cross-sectional area of the wound optical fiber with respect to the volume S of the winding portion of the optical fiber obtained from the winding radius of the optical fiber wound on the bobbin barrel and the radius and width of the barrel. An optical fiber winding method in which winding conditions are set so that the ratio V / S of the actual volume V of the optical fiber determined from the length is 58% or more and 79% or less.   An allowable value for increasing the transmission loss of the optical fiber is set, a winding tension of the optical fiber is calculated so as to satisfy the allowable value, and the volume S of the winding portion and the optical fiber are calculated based on the winding tension. The winding pitch of the optical fiber is calculated so that the ratio V / S with respect to the actual volume V is maximized, and the winding condition is set based on the calculated winding tension and the winding pitch. The method for winding an optical fiber according to claim 1.   The winding method of the optical fiber of Claim 1 or Claim 2 whose winding thickness of the said optical fiber calculated | required from the difference of the said winding radius of the said optical fiber and the said radius of the said trunk | drum is 15 mm or more. The winding method of the optical fiber as described in any one of Claims 1-3 whose effective cross-sectional area Aeff of the said optical fiber is 70 micrometers- ² or more. An optical fiber mainly composed of quartz glass wound around a bobbin,
Breaking of the wound optical fiber with respect to the volume S of the winding portion of the optical fiber determined from the winding radius of the optical fiber wound on the bobbin barrel and the radius and width of the barrel. The ratio V / S of the actual volume V of the optical fiber obtained from the area and length is 58% or more and 79% or less,
The winding thickness of the optical fiber determined from the difference between the winding radius of the optical fiber and the radius of the body portion is 15 mm or more,
An optical fiber, wherein an increase in transmission loss of the optical fiber due to being wound is 0.01 dB / km or less. The optical fiber according to claim 5, wherein the effective area Aeff is 70 μm ² or more.

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