[Technical Field]
5 [0001]
The present invention relates to an optical cable and an
optical cable manufacturing method.
[Background Art]
[0002]
10 There is a known technique for forming an optical cable by
housing, inside a sheath, a plurality of optical fiber units each
being an optical fiber assembly formed by a plurality of optical
fibers brought together. PTL 1 describes placing a filling inside
a press-wrapping tape wrapping up a plurality of optical fiber
15 units in order to reduce occurrence of "untwisting" in which, when
the plurality of optical fiber units are twisted in an S-Z
configuration together, optical fibers move in untwisting
directions.
[Citation List]
20 [Patent Literature]
[0003]
[PTL 1] Japanese Patent Application Publication No. 2020-76915
[Summary of Invention]
[Technical Problem]
25 [0004]
In order to reduce "untwisting," it is desirable to decrease
voids inside an optical cable by placing many fillings around the
optical fiber units. However, more fillings inside an optical
cable means stronger lateral pressure acting on the optical fibers,
30 which may lead to more microbending losses. Thus, what is desired
is to meet conflicting goals of decreasing fillings and reducing
untwisting of optical fiber units.
[0005]
The present invention has an object to reduce untwisting with
35 less fillings.
3
[Solution to Problem]
[0006]
An aspect of the present invention to achieve the above
object is an optical cable comprising: a plurality of optical fiber
5 units each having a fiber group formed by a plurality of optical
fibers, wherein the plurality of optical fiber units are twisted
in an S-Z configuration, at least one optical fiber unit of the
plurality of optical fiber units has a filling, and the filling is
wrapped around an outer circumference of the fiber group.
10 [0007]
Other features of the present invention will become apparent
in the following description and the drawings.
[Advantageous Effects of Invention]
[0008]
15 The present invention has an object to reduce untwisting of
the optical fiber units with less fillings.
[Brief Description of Drawings]
[0009]
[Fig. 1] Fig. 1 is a diagram illustrating an optical cable 1.
20 [Fig. 2] Fig. 2A is a diagram illustrating an optical fiber unit
11. Fig. 2B is a diagram illustrating another optical fiber unit
11.
[Fig. 3] Fig. 3 is a diagram illustrating the placement of a filling
17A for a given optical fiber unit 11A.
25 [Fig. 4] Fig. 4 is a table showing evaluation results of easiness
of dismantling the optical cable 1.
[Fig. 5] Fig. 5 is a diagram illustrating a manufacturing system
40 for the optical cable 1.
[Fig. 6] Figs. 6A and 6B are diagrams illustrating a comber board
30 44.
[Fig. 7] Figs. 7A to 7C are diagrams illustrating how the comber
board 44 rotates.
[Fig. 8] Fig. 8 is a diagram illustrating a manufacturing system
40 of a modification.
35 [Fig. 9] Fig. 9A is a diagram illustrating how a compression rate
4
R is measured. Fig. 9B is a diagram illustrating how the crosssectional shape changes between before and after giving lateral
pressure.
[Fig. 10] Fig. 10 is measurement results of the compression rates
5 of fillings, a bundling member, and Kevlar.
[Fig. 11] Fig. 11 is a graph showing the relation between an applied
load P and the compression rate R.
[Fig. 12] Fig. 12 is a diagram illustrating the cross section of a
filling 17 in the optical cable 1.
10 [Description of Embodiments]
[0010]
At least the following matters will be become apparent from
the following description and the drawings.
[0011]
15 An optical cable will become apparent, comprising: a
plurality of optical fiber units each having a fiber group formed
by a plurality of optical fibers, wherein the plurality of optical
fiber units are twisted in an S-Z configuration, at least one
optical fiber unit of the plurality of optical fiber units has a
20 filling, and the filling is wrapped around an outer circumference
of the fiber group. According to such an optical cable, untwisting
of the optical fiber units can be reduced with less fillings.
[0012]
It is desirable that the optical fiber units each include a
25 bundling member bundling the plurality of optical fibers together.
This makes it possible for the optical fibers to be bundled together
and not to come apart.
[0013]
It is desirable that the filling is wrapped around an outer
30 side of the bundling member. This helps the filling come into
contact with the neighboring optical fiber units, and thus,
untwisting of the optical fiber units can be further reduced with
less fillings.
[0014]
35 It is desirable to further comprise the optical fiber units
5
having the filling and the optical fiber units not having the
filling. This helps decrease the fillings.
[0015]
It is desirable that an inner-layer unit is formed by the
5 optical fiber unit, an outer-layer unit is formed by
circumferentially placing a plurality of the optical fiber units
outside the inner-layer unit, and the optical fiber unit forming
the inner-layer unit has the filling. In this situation it is
desirable that the outer-layer unit includes the optical fiber
10 units having the filling and the optical fiber units not having the
filling. This makes it possible for untwisting of the optical
fiber units to be further reduced with less fillings.
[0016]
It is desirable that the optical fiber unit not having the
15 filling is placed between two of the optical fiber units having the
filling in the outer-layer unit. This makes it possible for
untwisting of the optical fiber units to be further reduced with
less fillings.
[0017]
20 It is desirable that P1/P2 is 0.1 or greater, where P1 is a
pitch of wrapping of the filling and P2 is a pitch of twisting the
plurality of optical fiber units. This improves easiness for
dismantling the optical cable.
[0018]
25 It is desirable that the filling is wrapped around the outer
circumference of the fiber group in an S-Z configuration without
being joined to other members. Not having to have a function to
bring the plurality of optical fibers together, the filling can be
wrapped around the outer circumference of the fiber group in an S30 Z configuration without being joined to other members.
[0019]
It is desirable that a compression rate R increases as a load
P increases when the load P is 1 N or greater, where P (N) is a
load applied to a winding member wound around an outer circumference
35 of the filling, and R is a compression rate of the filling when the
6
load P is applied to the winding member to give lateral pressure
to the filling. This makes it possible for untwisting of the
optical fiber units to be reduced.
[0020]
5 It is desirable that when the load P is in a range from 1.5
N to 2.0 N, the compression rate R increases as the load P increases.
This makes it possible for untwisting of the optical fiber units
to be reduced.
[0021]
10 It is desirable that α is 0.17 or greater, where α (N-1) is
a ratio of an amount of increase in the compression rate R to an
amount of increase in the load P when the load P is in a range from
1.5 N to 2.0 N. This makes it possible for untwisting of the
optical fiber units to be reduced.
15 [0022]
It is desirable that the filling is configured to deform such
that the compression rate R is 0.57 or greater, where P (N) is a
load applied to a winding member wound around an outer circumference
of the filling, and R is a compression rate of the filling when the
20 load P is applied to the winding member to give lateral pressure
to the filling. This makes it possible for untwisting of the
optical fiber units to be reduced.
[0023]
An optical cable manufacturing method will become apparent,
25 comprising: inserting fiber groups into a plurality of respective
insertion holes in a comber board; inserting a filling into at
least one of the insertion holes in the comber board; and
oscillating the comber board to wrap the filling around an outer
circumference of the fiber group. According to such an optical
30 cable manufacturing method, an optical cable can be manufactured
in which untwisting of the optical fiber units is reduced with less
fillings.

[Claim 1]
An optical cable comprising:
a plurality of optical fiber units each having a fiber group
5 formed by a plurality of optical fibers, wherein
the plurality of optical fiber units are twisted in an S-Z
configuration,
at least one optical fiber unit of the plurality of optical
fiber units has a filling, and
10 the filling is wrapped around an outer circumference of the
fiber group.
[Claim 2]
The optical cable according to claim 1, wherein
the optical fiber units each include a bundling member
15 bundling the plurality of optical fibers together.
[Claim 3]
The optical cable according to claim 2, wherein
the filling is wrapped around an outer side of the bundling
member.
20 [Claim 4]
The optical cable according to any one of claims 1 to 3,
further comprising:
the optical fiber units having the filling and the optical
fiber units not having the filling.
25 [Claim 5]
The optical cable according to any one of claims 1 to 4,
wherein
an inner-layer unit is formed by the optical fiber unit,
an outer-layer unit is formed by circumferentially placing a
30 plurality of the optical fiber units outside the inner-layer unit,
and
the optical fiber unit forming the inner-layer unit has the
filling.
[Claim 6]
35 The optical cable according to claim 5, wherein
32
the outer-layer unit includes the optical fiber units having
the filling and the optical fiber units not having the filling.
[Claim 7]
The optical cable according to claim 6, wherein
5 the optical fiber unit not having the filling is placed
between two of the optical fiber units having the filling in the
outer-layer unit.
[Claim 8]
The optical cable according to any one of claims 1 to 7,
10 wherein
P1/P2 is 0.1 or greater, where P1 is a pitch of wrapping of
the filling and P2 is a pitch of twisting the plurality of optical
fiber units.
[Claim 9]
15 The optical cable according to any one of claims 1 to 7,
wherein
the filling is wrapped around the outer circumference of the
fiber group in an S-Z configuration without being joined to other
members.
20 [Claim 10]
The optical cable according to any one of claims 1 to 9,
wherein
a compression rate R increases as a load P increases when
the load P is 1 N or greater,
25 where
P (N) is a load applied to a winding member wound
around an outer circumference of the filling, and
R is a compression rate of the filling when the load
P is applied to the winding member to give lateral pressure to the
30 filling.
[Claim 11]
The optical cable according to claim 10, wherein
when the load P is in a range from 1.5 N to 2.0 N, the
compression rate R increases as the load P increases.
35 [Claim 12]
33
The optical cable according to claim 10 or 11, wherein
α is 0.17 or greater, where α (N-1) is a ratio of an amount
of increase in the compression rate R to an amount of increase in
the load P when the load P is in a range from 1.5 N to 2.0 N.
5 [Claim 13]
The optical cable according to any one of claims 1 to 12,
wherein
the filling is configured to deform such that the compression
rate R is 0.57 or greater,
10 where
P (N) is a load applied to a winding member wound
around an outer circumference of the filling, and
R is a compression rate of the filling when the load
P is applied to the winding member to give lateral pressure to the
15 filling.
[Claim 14]
An optical cable manufacturing method comprising:
inserting fiber groups into a plurality of respective
insertion holes in a comber board;
20 inserting a filling into at least one of the insertion holes
in the comber board; and
oscillating the comber board to wrap the filling around an
outer circumference of the fiber group.