TECHNICAL FIELD
The present invention relates to an optical fiber twisting apparatus that, when
melting and drawing an optical fiber preform so as to form an optical fiber, causes the
optical fiber to oscillate while a twisting roller is placed against a portion of an outer
circumference of the optical fiber so that a twist is imparted to the optical fiber, thereby
imparting a twist to a molten portion of the optical fiber preform that is positioned on an
upstream side of the optical fiber. The present invention also relates to a method of
manufacturing an optical fiber in which an optical fiber is manufactured using this
optical fiber twisting apparatus, and to an optical fiber that is manufactured using this
method of manufacturing an optical fiber.
Priority is claimed on Japanese Patent Application No. 2003-432264, filed
December 26,2003, the contents of which are incorporated herein by reference.
BACKGROUND ART
Conventionally, an optical fiber twisting apparatus is known in which in order
to reduce polarization mode dispersion (PMD) in an optical fiber there is provided a
twisting roller that, when an optical fiber is being manufactured by melting and drawing
an optical fiber preform, imparts a twist to the molten portion of the optical fiber preform
that is positioned on the upstream side of the optical fiber by oscillating while in a state

of contact with the optical fiber.
In this optical fiber twisting apparatus, melting and drawing of an optical fiber
preform is performed while a twist is imparted to a suitable location while the optical
fiber preform is being wiredrawn, for example, to a portion of the optical fiber preform
that is melted in a drawing furnace by installing an optical fiber twisting apparatus and
imparting a twist to the optical fiber using the twisting roller of the optical fiber twisting
apparatus in a process that is performed after the optical fiber preform has been melted
and wiredrawn, then cooled, then primarily coated and secondarily coated (see, for
example, Patent Document 1).
The twist that is imparted to the molten portion of the optical fiber preform by
this optical fiber twisting apparatus is brought about by friction between the optical fiber
twisting roller and the coated portion of the optical fiber. In order to efficiently impart a
twist to the optical fiber, it is possible to extend the length of the contact portion between
the surface of the optical fiber twisting roller and the optical fiber. In order to extend
this contact length, it is possible to increase the contact angle of the optical fiber relative
to the optical fiber twisting roller, or, if a large diameter optical fiber twisting roller is
used, it is possible to further increase the winding force from the optical fiber twisting
roller on the coated portion of the optical fiber. (Patent Document 1: Japanese Patent
No. 3224235).
However, if the contact angle is increased, or if a large diameter optical fiber
twisting roller is used, then due to the effects of the accuracy and the like with which the
optical fiber twisting roller has been assembled, when the optical fiber twisting roller is
being swung, the pressing force of the optical fiber twisting roller on the coated portion
of the optical fiber changes which results in a non-uniform force being applied to the
optical fiber during the drawing process. Consequently, problems arise such as the

movement of the optical fiber that is rolling over the optical fiber twisting roller
becoming irregular, and line distortion occurring such as the optical fiber moving to the
left and right over the optical fiber twisting roller so that it becomes ho longer possible to
consistently coat the optical fiber with the primary coated portion and the secondary
coated portion. As a result, there are large variations in the outer diameter of the optical
fiber, and the thickness of the coated portion of the optical fiber varies in the longitudinal
direction of the optical fiber.
Moreover, when the optical fiber twisting roller is being swung in order to
impart a twist to the optical fiber, damage is imparted to portions of the coated portion of
the optical fiber where the optical fiber twisting roller makes contact due to the effects of
the accuracy and the like with which the optical fiber twisting roller has been assembled.
Moreover, delamination occurs at a boundary face between the optical fiber glass (i.e.,
the bare optical fiber) and the primary coated portion, and, if the optical fiber is put in a
low temperature environment after it has been laid, the problem arises that the
attenuation of the optical fiber is increased by this delamination of the coated portion.
The present invention was conceived in view of the above described problems
and it is an object thereof to provide an optical fiber twisting apparatus that prevents line
vibration occurring in an optical fiber as it is undergoing a drawing process, that makes it
possible to coat a bare optical fiber with consistency, and that prevents damage being
imparted to portions of the coated portion of the optical fiber where the optical fiber
twisting roller makes contact. It is also an object of the present invention to provide a
method of manufacturing an optical fiber in which an optical fiber is manufactured using
this optical fiber twisting apparatus.
DISCLOSURE OF INVENTION

In order to achieve the above objects, the present invention is an optical fiber
twisting apparatus that includes: a twist roller that, by imparting a twist to an optical fiber,
imparts a twist to a molten portion of an optical fiber preform that is positioned on an
upstream side of the optical fiber; and a support portion that supports the twist roller,
wherein an accuracy of an outer circumference of the twist roller when the twist roller is
forming a part of the twist roller apparatus is 15 µm or less.
According to this invention, it is possible to prevent line distortion occurring in
an optical fiber as it is undergoing a drawing process, and it is possible to consistently
coat a bare optical fiber, and to prevent damage being imparted to portions of the coated
portion of an optical fiber where the optical fiber twisting roller makes contact. It is
also possible to prevent any increase in attenuation of an optical fiber that is caused by
delamination of the coated portion of the optical fiber even when the optical fiber is
installed in a low temperature environment.
The present invention is also a method of manufacturing a optical fiber that
includes: a drawing step in which a bare optical fiber is formed by melting and then
drawing an optical fiber preform; a coating step in which the bare optical fiber that was
formed in the drawing step is coated so as to form an optical fiber; and an optical fiber
twisting step in which the aforementioned optical fiber twisting apparatus is placed
against a portion of an outer circumference of the optical fiber that was formed in the
coating step and is made to oscillate, so that a twist is imparted to the optical fiber,
resulting in a twist being imparted to the molten portion of the optical fiber preform.
The present invention is also an optical fiber that has been manufactured using
this method of manufacturing an optical fiber.
According to the present invention, it is possible to prevent line distortion
occurring in an optical fiber as it is undergoing a drawing process, and it is possible to

consistently coat a bare optical fiber, and to prevent damage being imparted to portions
of the coated portion of an optical fiber where the optical fiber twisting roller makes
contact. It is also possible to prevent any increase in attenuation of the optical fiber that
is caused by delamination of the coated portion of the optical fiber even when the optical
fiber is installed in a low temperature environment.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG 1 is a schematic view showing a drawing apparatus according to an
embodiment of the present invention.
FIG. 2 A is a view illustrating the measurement of the accuracy of an outer
circumference of a twisting roller according to an embodiment of the present invention.
FIG 2B is a view illustrating the measurement of the accuracy of an outer
circumference of a twisting roller in a state in which it is forming the twist roller
apparatus of an embodiment of the present invention.
FIG 3 A is a view illustrating the measurement of the accuracy of an outer
circumference of a twisting roller according to an embodiment of the present invention.
FIG. 3B is a view illustrating the measurement of the accuracy of an outer
circumference of a twisting roller according to an embodiment of the present invention.
FIG. 3C is a view illustrating the measurement of the accuracy of an outer
circumference of a twisting roller according to an embodiment of the present invention.
FIG 4A is a view illustrating the measurement of the accuracy of an outer
circumference of a twisting roller according to an embodiment of the present invention.
FIG. 4B is a view illustrating the measurement of the accuracy of an outer
circumference of a twisting roller according to an embodiment of the present invention.
FIG. 4C is a view illustrating the measurement of the accuracy of an outer

circumference of a twisting roller according to an embodiment of the present invention.
FIG 4D is a view illustrating the measurement of the accuracy of an outer
circumference of a twisting roller according to an embodiment of the present invention.
FIG 5 is a view illustrating the measurement of the accuracy of an outer
circumference of a twisting roller according to an embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will now be described with reference
made to the drawings.
FIG. 1 shows a drawing apparatus 3 that manufactures an optical fiber 2 using
the optical fiber twisting apparatus 1 according to an embodiment of the present
invention.
The drawing apparatus 3 according to an embodiment of the present invention is
provided with a drawing furnace 5 (i.e., a drawing furnace) that heats an optical fiber
preform 4 that is formed from quartz based glass or the like so as to melt and wiredraw
this optical fiber preform, a cooling jacket 7 that is provided on a downstream side of the
drawing furnace 5 and cools a bare optical fiber 6 that has been formed by drawing, a
first primary coater 8 that is provided on a downstream side of the cooling jacket 7 and
applies a primary coating material to the bare optical fiber 6 that has been cooled by the
cooling chamber 7, a first bridging cylinder 9 that irradiates ultraviolet rays so as to cure
the coated primary coating material, a second primary coater 10 that applies a secondary
coating material to the optical fiber that has received a primary coating, a second
bridging cylinder 11 that irradiates ultraviolet rays so as to cure the coated secondary
coating material, an optical fiber twisting apparatus 1 that is provided on the downstream

side of the second bridging cylinder 11 and imparts a twist to the portion of the optical
fiber preform 4 that has been melted in the drawing furnace 5 by applying a twist to an
optical fiber 2 that is formed by the optical fiber that has received a secondary coating, a
turn pulley 12 that is provided downstream from the optical fiber twisting apparatus 1
and changes the direction of movement of the optical fiber 2, a conveying tool 13
(described below) that has the function of pulling the optical fiber preform 4, a dancer 14
that adjusts the revolution number of a winding tool 15 (described below), and the
winding tool 15 onto which the optical fiber 2 is wound. Note that a coating
mechanism 16 is formed by the first primary coater 8, the first bridging cylinder 9, the
second primary coater 10, and the second bridging cylinder 11.
The optical fiber preform 4 that is used in an embodiment of the present
invention may be manufactured using a number of methods such as a vapor axis
deposition method (i.e., a VAD method), an external deposition method (i.e., an OVD
method), an inner deposition method (i.e., a CVD method, a MCVD method, or a PCVD
method), or a rod-in-tube method or the like.
The optical fiber 2 that is manufactured using the optical fiber manufacturing
method according to an embodiment of the present invention may be one of a variety of
optical fiber such as a single mode optical fiber, a dispersion shifted optical fiber, a
cut-off shifted optical fiber, and a dispersion slope compensating optical fiber and the
like.
The optical fiber twisting apparatus 1 that is used in an embodiment of the
present invention may be an optical fiber twisting apparatus of the type that is described
in, for example, Japanese Patent No. 3224235, FIGS. 1. 4. and 6.
The optical fiber twisting apparatus that is described in FIG. 1 of Japanese Patent
No. 3224235 (referred to below as Apparatus A) is formed by a single twisting roller

apparatus 25 such as that shown in FIG. 2B. This twisting roller apparatus 25 is
provided with a trestle 20 that has a top surface that serves as a reference surface 19, a
support portion 21 that extends in a perpendicular direction from the reference surface 19,
and a single twist roller 22 that is supported by the support portion 21 and that, when
drawing the optical fiber preform so as to form an optical fiber, oscillates while being in
a state of contact with a portion of the optical fiber so as to impart a twist to the molten
portion of the optical fiber preform. By causing the rotation shaft 23 of the twist roller
22 to oscillate, the twist roller 22 is made to oscillate while in a state of contact with the
optical fiber and thereby impart a twist to the optical fiber as it is undergoing a drawing
process.
The optical fiber twisting apparatus that is described in FIG. 6 of Japanese Patent
No. 3224235 (referred to below as Apparatus B) is provided with a pair of the same twist
roller apparatuses 25 as those in Apparatus A and imparts a twist to an optical fiber that is
sandwiched between the pair of twist rollers 22 of the pair of twist roller apparatuses 25.
As a result of each of the pair of twist rollers 22 rotating, the optical fiber is pulled
towards the downstream side, and a pair of trestles 20 of the pair of twist roller
apparatuses 25 each oscillate in a direction that is perpendicular to the direction in which
the optical fiber extends and also in the opposite direction from each other. Accordingly,
as a result of the pair of twist rollers 22 also oscillating while in a state of contact with
the optical fiber, the optical fiber is rotated and a twist is generated in the optical fiber.
The optical fiber twisting apparatus that is described in FIG. 4 of Japanese Patent
No. 3224235 (referred to below as Apparatus C) imparts a twist to an optical fiber that is
sandwiched between the pair of twist rollers 22 of the pair of twist roller apparatuses 25
in the same way as in Apparatus B. This pair of twist rollers 22 rotate in the direction in
which the optical fiber extends and also move in the opposite direction from each other.

A measurement of the accuracy of the outer circumference of the twist roller (i.e.,
a twist roller unit) 22 in an embodiment of the present invention is shown in FIG. 2A.
Namely, the length of the outer diameter of the twist roller 22 is measured over
the entire outer circumference of the twist roller 22, and a maximum value measured for
the length of the outer diameter is set as a, while a minimum value measured for the
length of the outer diameter is set as b. Note that in the case of an elliptical twist roller,
the minimum value b is taken as the length of the outer diameter of the twist roller in a
direction that is perpendicular to the outer diameter when the maximum value a is
measured. However, the twist roller is not limited to having an elliptical shape and
there may also be cases when the outer diameter when the maximum value a is measured
and the outer diameter when the minimum value b is measured are not in a perpendicular
direction. In addition, |(a-b) / 2| is taken as the accuracy of the outer diameter of the
twist roller of the twist roller 22.
Next, a description will be given of the measurement of the accuracy of the
outer circumference of the twist roller 22 of the present embodiment when it forms the
twist roller apparatus 25 of an embodiment of the present invention with reference made
to FIGS. 2B, 3A to 3C, 4A to 4D, and 5.
As is shown in FIG. 3 A, a minimum value of the length of the outer diameter of
the twist roller (i.e., a twist roller unit) 22 is taken as d", while a length of this outer
diameter that is projected onto a surface that is perpendicular to the reference surface is
taken as d. As is shown in FIG 3B, when the twist roller apparatus 25 is constructed
with precision, namely, when the support portion 21 is positioned in a direction that is
perpendicular to the reference surface 19, and when the rotation shaft 23 is positioned in
a direction that is perpendicular to the support portion 21 (i.e., in a horizontal direction
relative to the reference surface 19), and when the twist roller 22 is positioned in a

direction that is perpendicular to the rotation shaft 23 (i.e., in a horizontal direction
relative to the support portion 21), then d = d'. Namely, the term "surface that is
perpendicular to the reference surface", such as is described above, refers to a surface
that is orthogonal to the rotation shaft 23 when, as is described above, the twist roller is
constructed with precision (namely, when the rotation shaft 23 is set in a horizontal
direction relative to the reference surface 19). However, as is shown in FIG. 3C, in
cases when the twist roller apparatus 25 is not constructed with precision, such as when,
due to reasons such as the rotation shaft 23 not being attached perpendicularly relative to
the support portion 21, the twist roller 22 is not set perpendicularly relative to the
reference surface 22, then d < d'. Note that the value of d' becomes a smaller value as
the tilt of the twist roller 22 increases, such as when the angle 91 of the twist roller 22
relative to a direction that is perpendicular to the reference surface 19 increases.
As is shown in FIGS. 4A to 4D, a maximum value of the length of the outer
diameter of the twist roller (i.e., a twist roller unit) 22 is taken as c\ while a length of this
outer diameter that is projected onto a surface that is perpendicular to the reference
surface is taken as c. As is shown in FIG 4B, when the twist roller apparatus 25 is
constructed with precision, then c = c'. However, due to reasons such as, as is shown in
FIG. 4C, the twist roller 22 not being perpendicular relative to the reference surface 22, or,
as is shown in FIG 4D, the support portion 21 not being attached with precision relative
to the trestle 20, then c < c'. Note that the value of c becomes a smaller value as the tilt
of the twist roller 22 increases, such as when the angle θ2, which is the angle of the twist
roller 22 relative to a direction that is perpendicular to the direction in which the
reference surface 19 extends, increases.
Note that the maximum value c and the minimum value d of the length of the
outer diameter of the twist roller 22 that is projected onto a surface that is perpendicular

to the reference surface are determined by the maximum value c' and the minimum value
d' of the length of the outer diameter of the twist roller (i.e., a twist roller unit) 22, and by
the tilt of the twist roller 22 and the like.
Moreover, normally, at a position where the length of the outer diameter of the
twist roller (i.e., the twist roller unit) 22 is at the minimum value, the length d of the outer
diameter of the twist roller 22 that is projected onto a surface that is perpendicular to the
reference surface is also at the minimum value, and at a position where the length of the
outer diameter of the twist roller (i.e., the twist roller unit) 22 is at the maximum value,
the length c of the outer diameter of the twist roller 22 that is projected onto a surface
that is perpendicular to the reference surface is also at the maximum value.
Due to the reason described above, the accuracy of the outer circumference of
the twist roller 22 when it is forming a part of a twist roller apparatus 25 such as that
described below cannot be said to be the same as the accuracy of the outer circumference
of the twist roller 22 unit.
In addition to the above, due to discrepancies in the accuracy of the outer
circumference of the twist roller 22 unit or to looseness in the various bearings or the like,
(the position on) the surface of the outer circumference of the twist roller 22 that is in
contact with the optical fiber 2 changes. Therefore, as is described below, the accuracy
(e - f) / 2 of the outer circumference of the twist roller 22 after it has been assembled and
is forming a part of the twist roller apparatus 25 is measured in the following manner (see
FIG 5).
Namely, firstly, a micro gauge 26 is set in the reference surface 19.
Next, a measuring needle 27 of the micro gauge 26 is set to the same height (i.e.,
distance) from the reference surface 19 as the height (i.e., distance) of the rotation shaft
23 from the reference surface 19, and is matched to the center of the direction towards

the rotation shaft 23 of the twist roller 22, and is also matched to the zero point.
Next, the twist roller 22 is rotated and the width of the oscillation (which is in a
transverse direction when viewing FIG. 5) of the measuring needle 27 of the micro gauge
26 is measured. The maximum value of this oscillation is taken as el, while the
minimum value thereof is taken as fl. (el - fl) / 2 is then prescribed as being the
accuracy at the center of the outer circumference of the twist roller 22 when it is forming
a part of the twist roller apparatus 25.
Next, in addition to the center thereof, the oscillation width of the measuring
needle 27 of the micro gauge 26 is measured at both ends in the direction of the rotation
shaft 23 of the outer circumferential surface of the twist roller 22. The maximum value
at one end is taken e2 and the minimum value at this end is taken as f2, while the
maximum value at the other end is taken as e3 and the minimum value at this other end is
taken as f3. (e2 - f2) / 2 is then prescribed as being the accuracy at the one end of the
outer circumference of the twist roller 22 when it is forming a part of the twist roller
apparatus 25, while (e3 - f3) / 2 is then prescribed as being the accuracy at the other end
of the outer circumference of the twist roller 22 when it is forming a part of the twist
roller apparatus 25.
The largest value of the above described (el - fl) / 2, (e2 - f2) / 2, and (e3 - f3)
/ 2 is then determined as being the accuracy (e - f) / 2 of the outer circumference of the
twist roller 22 when it is forming a part of the twist roller apparatus 25.
[Examples]
Results of various experiments that were performed for three optical fiber
twisting apparatuses (Apparatuses A, B, and C) are shown in Table 1 as the Examples of
the present invention.
Table 1

Note that the conditions that were common to all three optical fiber twisting
apparatuses (i.e., Apparatuses A, B, and C) are described below.
(Common conditions)
Optical fiber outer diameter: 125 µm
Coating material: Urethane acrylate based ultraviolet curable resin (both primary and
secondary coatings)
Coating diameter (Optical fiber outer diameter): 250 µm

Drawing line speed: 1200 m/min
Twist roller diameter: 100 mm
Oscillation angle when twist roller is oscillating: 10°
Note that delamination of the coated portion was confirmed by immersing one
meter of the manufactured optical fiber for 12 hours in warm water at 60°C, and then,
within five minutes after extraction, observing the extracted one meter of optical fiber
using an optical microscope.
(Example 1)
Using the optical fiber twisting apparatus described in FIG. 1: of Japanese Patent
No. 3224235 (i.e., Apparatus A), by adjusting the optical fiber twisting apparatus and
using twist rollers in which the values of the accuracy of the outer circumference (a - b) /
2 of the twist roller were 5, 10, and 15 µm, the accuracy of the outer circumference of the
twist roller when it was forming a part of the twist roller apparatus was set such that (e -
f) / 2 was 5,10, and 15 µm. In addition, when the actual drawing was performed and
the line distortion was confirmed and also the warm water delamination of the
manufactured optical fiber was observed, as is shown in Example 1 in Table 1, no line
distortion occurred in the optical fiber during the manufacturing of the optical fiber,
which resulted in a consistent coating being provided. Moreover, excellent results were
obtained in the warm water delamination test of the manufactured optical fiber.
(Comparative example 1)
Using Apparatus A, (e - f) / 2 was set so as to be 20, 30, and 45 µm by adjusting
the optical fiber twisting apparatus. In addition, when the actual drawing was
performed and the line distortion was confirmed and also the warm water delamination
of the manufactured optical fiber was observed, as is shown in Comparative example 1 in
Table 1, irrespective of whether the twist roller having a value for (a - b) / 2 of 5, 10, 15,

or 20 µm was used, if (e - f) / 2 exceeded 15 µm, then it became easier for line distortion
in the optical fiber to be generated when the optical fiber was being manufactured, which
resulted in a consistent coating not being able to be provided. Note that, in Apparatus A,
in the warm water delamination test of the manufactured optical fiber using a single twist
roller, delamination of the coated portion of the optical fiber was not observed.
(Example 2)
Using the optical fiber twisting apparatus described in FIG. 4 of Japanese Patent
No. 3224235 (i.e., Apparatus B), when experiments were performed under the same
conditions as in Example 1 (i.e., (e - f) / 2 was 5,10, and 15 µm), in the same way as in
Example 1, excellent results were obtained for line distortion and warm water immersion
delamination.
(Comparative example 2)
Using Apparatus B, when experiments were performed under the same
conditions as in Comparative example 1 (i.e., (e - f) / 2 was 20, 30, and 45 µm), in the
same way as in Comparative example 1, line distortion tended to occur easily.
Moreover, in Apparatus B, in the warm water delamination test of the manufactured
optical fiber using a pair of twist rollers, delamination of the coated portion of the optical
fiber was observed.
(Example 3)
Using the optical fiber twisting apparatus described in FIG. 6 of Japanese Patent
No. 3224235 (i.e., Apparatus C), when experiments were performed under the same
conditions as in Example 1 (i.e., (e - f) / 2 was 5,10, and 15 µm), in the same way as in
Example 1, excellent results were obtained for line distortion and warm water immersion
delamination.
(Comparative example 3)

Using Apparatus C, when experiments were performed under the same
conditions as in Comparative example 1 (i.e.,"(e- f) / 2 was 20, 30, and 45 µm), in the
same way as in Comparative example 2, line distortion tended to occur easily.
Moreover, in the warm water delamination test, delamination of the coated portion of the
optical fiber was observed.
As is clearly evident from the results shown in Table 1, in all of the apparatuses
A, B, and C, when the accuracy (e - f) / 2 of the outer circumference of the twist roller
when it formed a part of the twist roller apparatus was 15 µm or less, excellent results
were obtained for both the line distortion and the warm water immersion delamination
test. Note that, here, describing the result of the line distortion as being excellent infers
the following. Namely, in Apparatus A, because a single twist roller is oscillated and
the optical fiber is rolled over the top of the twist roller, line distortion is generated
because of the mechanism adjacent to the twist roller. A pulley (because this pulley is a
line distortion inhibiting pulley, it is formed in a V groove shape) is installed directly
above the twist roller in order to inhibit this line distortion. In this case, line distortion
is essentially inhibited by this V groove-shaped pulley. However, if the precision with
which the twist roller has been assembled is poor, then the optical fiber vibrates directly
above the line distortion inhibiting pulley in a direction that is perpendicular to the
drawing direction of the optical fiber with the pulley acting as a projection. If the
amplitude of this vibration is within two optical fibers (for example, 0.5 mm in the case
of optical fibers having a diameter of 250 µm) on an optical fiber position detector, then
it is determined to be Good with no line distortion. If the vibration amplitude is greater
than this, then it is determined as being Bad with poor line distortion. For Apparatuses
B and C, the line distortion inhibiting pulley that was used in Apparatus A was not used.
When the amount of oscillation in a direction that is perpendicular to the drawing

direction of the optical fiber directly above a pair of twist rollers was within two optical
fibers, then it was determined to be Good, while in all other cases, it was determined to
be Bad. In the case of the results of the warm water immersion delamination test, if
delamination was not observed in the observation of the optical fiber after it had been
immersed, then it was determined to be Good, while if delamination was observed in one
or more locations then it was determined to be Bad.
Moreover, if the accuracy (e - f) / 2 of the outer circumference of the twist roller
when it forms a part of the twist roller apparatus and the accuracy (a - b) / 2 of the outer
circumference of the twist roller are both 15 µm or less, then extremely excellent results
are obtained for the line distortion and the warm water immersion delamination test.

WE CLAIM:
1'. An optical fiber twisting apparatus comprising:
a trestle comprising a reference surface;
a support portion extending from the reference surface of the trestle;
a twist roller which is supported by the support portion
wherein an accuracy (e - f) / 2 of an outer circumference of the twist roller when
the twist roller is supported by the support portion is 15 urn or less, where e is the
maximum value of an oscillation of a measuring needle of a micro gauge when the
twist roller is rotated and measured using the micro gauge, while f is the minimum
value of the oscillation of the measuring needle of the micro gauge when the twist
roller is rotated and measured using the micro gauge.
2. A method of manufacturing an optical fiber comprising the steps of:
a drawing step in which a bare optical fiber is formed by melting and then
drawing an optical fiber preform;
a coating step in which the bare optical fiber that was formed in the drawing
step is coated so as to form an optical fiber; and
an optical fiber twisting step in which the optical fiber twisting apparatus as
claimed in claim 1 is placed against a portion of an outer circumference of the
optical fiber that was formed in the coating step and is made to oscillate, so that a
twist is imparted to the optical fiber, resulting in a twist being imparted to the molten
portion of the optical fiber preform.
3.' An optical fiber that has been manufactured using the method of
manufacturing an optical fiber as claimed in claim 2.

ABSTRACT

OPTICAL FIBER TWISTING DEVICE, METHOD OF
MANUFACTURING OPTICAL FIBER, AND OPTICAL FIBER
The invention discloses an optical fiber twisting apparatus (25) comprising: a) a
trestle (20) comprising a reference surface (19); b) a support portion (21) extending
from the reference surface of the trestle; c) a twist roller which is supported by the
support portion, wherein an accuracy (e - f) / 2 of an outer circumference of the twist
roller when the twist roller is supported by the support portion is 15 µm or less,
where e is the maximum value of an oscillation of a measuring needle of a micro
gauge when the twist roller is rotated and measured using the micro gauge, while f is
the minimum value of the oscillation of the measuring needle of the micro gauge
when the twist roller is rotated and measured using the micro gauge.
The invention is also for a method of manufacturing optical fiber using this
apparatus and the optical fiber so made
Fig.2B