U.S. patent application number 14/251233 was filed with the patent office on 2016-06-09 for optical fiber ribbon and optical fiber cable housing optical fiber ribbon.
This patent application is currently assigned to NIPPON TELEGRAPH AND TELEPHONE CORPORATION. The applicant listed for this patent is FUJIKURA, LTD., NIPPON TELEGRAPH AND TELEPHONE CORPORATION. Invention is credited to Shinya HAMAGUCHI, Daisuke KAKUTA, Hisaaki NAKANE, Akira NAMAZUE, Naoki OKADA, Ken OSATO, Yusuke YAMADA.
Application Number | 20160161692 14/251233 |
Document ID | / |
Family ID | 48140853 |
Filed Date | 2016-06-09 |
United States Patent
Application |
20160161692 |
Kind Code |
A1 |
NAMAZUE; Akira ; et
al. |
June 9, 2016 |
OPTICAL FIBER RIBBON AND OPTICAL FIBER CABLE HOUSING OPTICAL FIBER
RIBBON
Abstract
Provided is an optical fiber ribbon capable of achieving higher
density and reduction in diameter and accurately placing optical
fibers in V-shape grooves in a fusion machine without failure. The
optical fiber ribbon 1 includes three or more of optical fibers 2
arranged in parallel and connecting portions 3 connecting adjacent
two optical fibers 2 together, the connecting portions 3 being
intermittently provided in each of a ribbon longitudinal direction
and a ribbon width direction. The connecting portions 3 are each
formed in such a manner as to fill resin into a gap S formed
between adjacent two optical fibers 2, and both surfaces of the
respective connecting portions 3 are each formed into a recess
having a concave shape curved toward a center of the gap S to
separate from lines 4,5 each connecting contact points of the
optical fibers 2 when being placed on a horizontal surface.
Inventors: |
NAMAZUE; Akira; (Edogawa-ku,
JP) ; OSATO; Ken; (Sakura-shi, JP) ; OKADA;
Naoki; (Yotsukaido-shi, JP) ; YAMADA; Yusuke;
(Tsukuba-shi, JP) ; KAKUTA; Daisuke; (Tsukuba-shi,
JP) ; NAKANE; Hisaaki; (Tsukuba-shi, JP) ;
HAMAGUCHI; Shinya; (Tsukuba-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJIKURA, LTD.
NIPPON TELEGRAPH AND TELEPHONE CORPORATION |
Tokyo
Tokyo |
|
JP
JP |
|
|
Assignee: |
NIPPON TELEGRAPH AND TELEPHONE
CORPORATION
Tokyo
JP
FUJIKURA, LTD.
Tokyo
JP
|
Family ID: |
48140853 |
Appl. No.: |
14/251233 |
Filed: |
April 11, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2012/076590 |
Oct 15, 2012 |
|
|
|
14251233 |
|
|
|
|
Current U.S.
Class: |
385/114 |
Current CPC
Class: |
G02B 6/4403 20130101;
G02B 6/443 20130101; G02B 6/4482 20130101; G02B 6/3636 20130101;
G02B 6/4489 20130101; G02B 6/2551 20130101; G02B 6/441 20130101;
G02B 6/2555 20130101; G02B 6/4404 20130101; G02B 6/448 20130101;
G02B 6/4405 20130101 |
International
Class: |
G02B 6/44 20060101
G02B006/44 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 18, 2011 |
JP |
2011-229066 |
Claims
1. An optical fiber ribbon comprising three or more of optical
fibers arranged in parallel and connecting portions connecting
adjacent two optical fibers together, the connecting portions being
intermittently provided in each of a ribbon longitudinal direction
and a ribbon width direction, wherein a gap is formed between
adjacent two optical fibers, the connecting portions are each
formed in such a manner as to fill resin into the gap, and both
surfaces of the respective connecting portions are each formed into
a recess having a concave shape curved toward a center of the gap
to separate from lines each connecting contact points of the
optical fibers when being placed on a horizontal surface.
2. The optical fiber ribbon according to claim 1, wherein an outer
diameter dimension of the optical fibers is set to smaller than or
equal to 220 .mu.m, and a distance between centers of the adjacent
two optical fibers is set to 250 .mu.m with a margin of plus or
minus 30 .mu.m.
3. The optical fiber ribbon according to claim 1, wherein an
outermost layer of the respective optical fibers is colored.
4. An optical fiber cable housing the optical fiber ribbon
according to claim 1 therein.
5. An optical fiber ribbon comprising three or more of optical
fibers arranged in parallel and connecting portions connecting
adjacent two optical fibers together, the connecting portions being
intermittently provided in each of a ribbon longitudinal direction
and a ribbon width direction, wherein a gap if formed between
adjacent two optical fibers, the connecting portions are each
formed in such a manner as to fill resin into the gap and cover a
periphery of the respective optical fibers with the resin, and both
surfaces of the respective connecting portions are each formed into
a recess having a concave shape curved toward a center of the gap
to separate from lines each connecting contact points of the
optical fibers when being placed on a horizontal surface.
6. The optical fiber ribbon according to claim 5, wherein an outer
diameter dimension of the optical fibers is set to smaller than or
equal to 220 .mu.m, and a distance between centers of the adjacent
two optical fibers is set to 250 .mu.m with a margin of plus or
minus 30 .mu.m.
7. The optical fiber ribbon according to claim 5, wherein a resin
thickness of the periphery covered with the resin is set to smaller
than or equal to 15 .mu.m.
8. The optical fiber ribbon according to claim 5, wherein an
outermost layer of the respective optical fibers is colored.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The application is a Continuation of PCT Application No.
PCT/JP2012/076590, filed on Oct. 15, 2012, and claims the benefit
of priority from the prior Japanese Patent Application No.
2011-229066, filed on Oct. 18, 2011, the entire contents of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to an optical fiber ribbon
having an intermittent fixing structure in which adjacent optical
fibers are intermittently connected together via connecting
portions, and relates to an optical fiber cable housing the optical
fiber ribbon.
[0003] There has been an increased demand for higher density and
reduction in diameter in the technical field of optical fiber
cables. As an example of a method for achieving higher density and
reduction in diameter, there is proposed a method for reducing the
outer diameter of optical fibers from 250 .mu.m, which is a
presently-used size, to 200 .mu.m or smaller (for example,
described in Japanese Patent No. 3058203 (Patent Literature 1). An
optical fiber ribbon using this method has a structure in which a
plurality of optical fibers each having the outer diameter of 200
.mu.m or smaller are arranged in parallel, and the entire
circumference of the optical fibers is covered with ultraviolet
curable resin.
[0004] With the optical fiber ribbon described in Patent Literature
1, however, an intermediate branching operation is difficult when
laying optical fibers into residences of subscribers. In order to
lay the optical fibers into the residences of subscribers, a cover
layer entirely covered with the ultraviolet curable resin is
required to be removed in the middle of the cable so that
particular optical fibers are only extracted from the plurality of
optical fibers. Since the entire circumference of the plural
optical fibers is covered with the ultraviolet curable resin, the
removal of the ultraviolet curable resin is difficult and the
particular optical fibers are not easily removed from the other
optical fibers. Further, in the optical fiber ribbon described in
Patent Literature 1, the entirely-covered cover layer increases the
thickness of the optical fiber ribbon by the thickness of the cover
layer, which decreases the packaging density thereof.
[0005] Japanese Patent No. 4143651 (Patent Literature 2) teaches an
optical fiber ribbon capable of solving these problems. This
optical fiber ribbon does not have a structure in which optical
fibers are entirely covered with resin, but has an intermittent
fixing structure in which adjacent two optical fibers of three or
more of optical fibers arranged in parallel are connected together
with resin. The intermittent fixing structure of the optical fiber
ribbon described in Patent Literature 2 contributes to easy
intermediate branching operation and has the advantage of higher
density since the number of connecting portions is smaller than
that in the structure of Patent Literature 1.
SUMMARY
[0006] However, when the optical fiber ribbon described in Patent
Literature 1 is fused and connected with another optical fiber
ribbon, bare optical fibers (glass optical fibers) from which the
cover layer made of resin is removed may be hard to be set in a
fusion machine having plural V-shaped grooves formed at a
predetermined pitch to be independently placed in the V-shaped
grooves. Failure in placing the optical fibers in the V-shaped
grooves in the fusion machine requires extra work to forcibly place
the optical fibers in the V-shaped grooves.
[0007] An object of the present invention is to provide an optical
fiber ribbon capable of achieving higher density and reduction in
diameter and accurately placing optical fibers in V-shape grooves
in a fusion machine without failure, and provide an optical fiber
cable housing the optical fiber ribbon.
[0008] Claim 1 recites an optical fiber ribbon comprising three or
more of optical fibers arranged in parallel and connecting portions
connecting adjacent two optical fibers together, the connecting
portions being intermittently provided in each of a ribbon
longitudinal direction and a ribbon width direction, wherein a gap
is formed between adjacent two optical fibers, the connecting
portions are each formed in such a manner as to fill resin into the
gap, and both surfaces of the respective connecting portions are
each formed into a recess having a concave shape curved toward a
center of the gap to separate from lines each connecting contact
points of the optical fibers when being placed on a horizontal
surface.
[0009] Claim 2 recites the optical fiber ribbon according to claim
1, wherein an outer diameter dimension of the optical fibers is set
to smaller than or equal to 220 .mu.m, and a distance between
centers of the adjacent two optical fibers is set to 250 .mu.m,
with a margin of plus or minus 30 .mu.m.
[0010] Claim 3 recites the optical fiber ribbon according to claim
1, wherein an outermost layer of the respective optical fibers is
colored.
[0011] Claim 4 recites an optical fiber cable housing the optical
fiber ribbon according to claim 1 therein.
[0012] Claim 5 recites an optical fiber ribbon comprising three or
more of optical fibers arranged in parallel and connecting portions
connecting adjacent two optical fibers together, the connecting
portions being intermittently provided in each of a ribbon
longitudinal direction and a ribbon width direction, wherein a gap
if formed between adjacent two optical fibers, the connecting
portions are each formed in such a manner as to fill resin into the
gap and cover a periphery of the respective optical fibers with the
resin, and both surfaces of the respective connecting portions are
each formed into a recess having a concave shape curved toward a
center of the gap to separate from lines each connecting contact
points of the optical fibers when being placed on a horizontal
surface.
[0013] Claim 6 recites the optical fiber ribbon according to claim
5, wherein an outer diameter dimension of the optical fibers is set
to smaller than or equal to 220 .mu.m, and a distance between
centers of the adjacent two optical fibers is set to 250 .mu.m with
a margin of plus or minus 30 .mu.m.
[0014] Claim 7 recites the optical fiber ribbon according to claim
5, wherein a resin thickness of the periphery covered with the
resin is set to smaller than or equal to 15 .mu.m.
[0015] Claim 8 recites the optical fiber ribbon according to any
one of claim 5, wherein an outermost layer of the respective
optical fibers is colored.
[0016] According to the present invention, a reduction in diameter
of the optical fibers is achieved and the optical fiber ribbon is
easily bent due to the intermittent fixing structure thereof in
which the connecting portions for connecting adjacent two optical
fibers are intermittently provided in each of the ribbon
longitudinal direction and the ribbon width direction and due to
the reduced outer diameter dimension of the optical fibers which is
set to smaller than or equal to 220 .mu.m. As a result, a larger
number of the optical fiber ribbons can be housed in the cable so
as to improve the packaging density.
[0017] According to the present invention, the distance between the
centers of adjacent two optical fibers is set to 250.+-.30 .mu.m,
which is equal to a distance between the centers of adjacent two
optical fibers of an optical fiber ribbon commonly distributed, so
as to accurately place the respective optical fibers in the
corresponding V-shape grooves in the fusion machine without falling
out of the V-shaped grooves.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is a top perspective view showing an example of an
optical fiber ribbon having an intermittent fixing structure
according to the present embodiment.
[0019] FIG. 2 is an enlarged cross-sectional view of a connecting
portion of the optical fiber ribbon of FIG. 1. FIG. 2(A) is a
structural example of the connecting portion, and FIG. 2(B) is
another structural example of the connecting portion.
[0020] FIG. 3 is an enlarged cross-sectional view of a connecting
portion of the optical fiber ribbon having another structure of
FIG. 1. FIG. 3(A) is a structural example of the connecting
portion, and FIG. 3(B) is another structural example of the
connecting portion.
[0021] FIG. 4 is a view showing a state where glass optical fibers
in the optical fiber ribbon according to the present embodiment
from which covering is removed, are placed in V-shaped grooves of a
fusion machine.
[0022] FIG. 5 is a cross-sectional view of a center tube-type
optical fiber cable housing the optical fiber ribbon according to
the present embodiment therein.
[0023] FIG. 6 is a cross-sectional view of an SZ-slotted optical
fiber cable housing the optical fiber ribbon according to the
present embodiment therein.
[0024] FIG. 7 is a cross-sectional view of a C-slotted optical
fiber cable housing the optical fiber ribbon according to the
present embodiment therein.
DESCRIPTION OF EMBODIMENTS
[0025] Hereinafter, a specific embodiment of the present invention
will be explained in detail with reference to the drawings.
[0026] FIG. 1 shows an example of an optical fiber ribbon having an
intermittent fixing structure according to the present embodiment,
and FIG. 2 shows an enlarged cross section of a connecting portion
of the optical fiber ribbon of FIG. 1. As shown in FIG. 1, the
optical fiber ribbon 1 according to the present embodiment has a
structure in which three or more of optical fibers 2 are arranged
in parallel, the adjacent two optical fibers 2 are connected
together via connecting portions 3, and the connecting portions 3
are intermittently located in each of a ribbon longitudinal
direction (in the X-arrow direction in FIG. 1) and a ribbon width
direction (in the Y-arrow direction in FIG. 1).
[0027] As shown in FIG. 1, the optical fiber ribbon 1 is composed
of the n optical fibers 2 in total, and the adjacent two optical
fibers 2 of the n optical fibers 2 are intermittently connected
together via the connecting portions 3 in each of the ribbon
longitudinal direction and the ribbon width direction. The
connecting portions 3 connecting the adjacent two optical fibers 2
together are formed in the ribbon longitudinal direction at a fixed
pitch P1, and have a shorter length than unconnected portions each
located therebetween. Namely, the length of each connecting portion
3 is shorter than that of each unconnected portion in the ribbon
longitudinal direction.
[0028] Further, only one connecting portion 3 is formed in the
ribbon width direction to connect the adjacent two optical fibers
2. The connecting portion 3 is not located on the same line in the
ribbon width direction as the other connecting portion 3 connecting
other adjacent two optical fibers 2 but located in the offset
position from the other connecting portion 3 in the ribbon
longitudinal direction. Therefore, the connecting portions 3 formed
in the optical fiber ribbon 1 are arranged in a zigzag manner as a
whole. Note that the arrangement of the connecting portions 3 is
not limited to that shown in FIG. 1 and may be other
configurations. The arrangement shown in FIG. 1 is merely an
example. Here, in addition to the arrangement in which only one
connecting portion 3 is provided in the ribbon width direction, two
or more connecting portions 3 may be formed in the ribbon width
direction in a manner such that at least one unconnected portion is
located between the connecting portions 3
[0029] As shown in FIG. 2(A), the connecting portion 3 connects the
adjacent two optical fibers 2 together in such a manner as to fill
the gap S between the adjacent two optical fibers 2 with resin (for
example, ultraviolet curable resin) and then cure it. Both surfaces
3a and 3b of the connecting portion 3 are respectively positioned
on the same lines as lines 4 and 5 each connecting the contact
points of the respective optical fibers 2 when being placed on the
horizontal surface. Therefore, the inner half circumferences of the
optical fibers 2 facing the gap S are covered with the resin
composing the connecting portion 3, but the outer half
circumferences on the opposite side of the gap S are not covered
with the resin.
[0030] The two surfaces 3a and 3b of the connecting portion 3 shown
in FIG. 2(B) are each formed into a recess having a concave shape
curved toward the center of the gap S to separate from the lines 4
and 5 each connecting the contact points of the respective optical
fibers 2 when being placed on the horizontal surface. In FIG. 2(B),
the amount of the resin composing the connecting portion 3 is
smaller than that in FIG. 2(A), and the resin is locally
concentrated in the central portion of the gap S between the two
optical fibers 2. The optical fiber ribbon connected with the
connecting portions 3 having such a configuration is more easily
bent since the amount of the resin used is smaller than that of the
connecting portion 3 shown in FIG. 2(A), so that the number of the
optical fiber ribbons to be housed in a cable further
increases.
[0031] Each of the optical fibers 2 includes a bare glass optical
fiber 6 provided in the center thereof, a first cover layer 7
covering the periphery of the glass optical fiber 6, and a second
cover layer 8 further covering the periphery of the first cover
layer 7. The glass optical fiber 6 has a diameter of 125 .mu.m. The
first cover layer 7 is a relatively soft resin layer to absorb
lateral pressure applied to the glass. The second cover layer 8 is
a relatively hard resin layer to protect against external damage.
The second cover layer 8 may be further covered with a colored
layer so that the respective optical fibers 2 can be discriminated
therebetween. The colored layer is formed as an outermost layer so
as to easily differentiate the respective optical fibers 2
visually.
[0032] According to the present embodiment, the outer diameter
dimension of the optical fibers 2 (the entire diameter including
the outermost layer) H is set to smaller than or equal to 220
.mu.m, and the distance L between the centers of the adjacent two
optical fibers 2 is set to 250.+-.30 .mu.m. The optical fiber 2 of
the present embodiment is a size smaller than the optical fiber 2
conventionally used which has the outer diameter dimension H of 250
.mu.m. In addition, the distance L between the centers of the
adjacent two optical fibers in the optical fiber ribbon
conventionally used is 250 .mu.m. The present embodiment sets the
distance L to 250 .mu.m with a margin of plus or minus 30
.mu.m.
[0033] The connecting portion 3 shown in FIG. 2(A) has a thickness
which is the same as the outer diameter dimension H of the optical
fibers 2. The connecting portion 3 shown in FIG. 2(B) has a
thickness which is smaller than the outer diameter dimension H of
the optical fibers 2.
[0034] The optical fiber ribbon 1 has an intermittent fixing
structure in which the connecting portions 3 are intermittently
provided in each of the ribbon longitudinal direction and the
ribbon width direction to connect the adjacent two optical fibers 2
together, and has a configuration in which the optical fibers 2
have the outer diameter dimension H of smaller than or equal to 220
.mu.m which is smaller than that of the conventionally-used optical
fibers, which contributes to decreasing the diameter of the optical
fibers 2 and easily bending the ribbon. As a result, a larger
number of the optical fiber ribbons 1 can be housed in a cable
compared with optical fiber ribbons having a conventional structure
so as to increase the packaging density thereof.
[0035] Further, since the optical fiber ribbon according to the
present embodiment has a configuration in which the optical fibers
2 have the outer diameter dimension H of smaller than or equal to
220 .mu.m which is smaller than that of the conventionally-used
optical fibers, the volume of the optical fibers can be reduced by
20% or greater compared with the optical fibers having a
conventional configuration. Accordingly, the entire diameter of the
optical fiber ribbon can be decreased so as to further increase the
packaging density thereof.
[0036] It should be noted that the connecting portions 3 are not
limited to the configurations shown in FIG. 2(A) and FIG. 2(B) in
which the connecting portions 3 are formed only in the gap S
between the adjacent two optical fibers 2, but may have the
configurations shown in FIG. 3(A) and FIG. 3(B). The connecting
portions 3 shown in FIG. 3 are formed in such a manner as to fill
resin into the gap S between the adjacent two optical fibers 2 and
cover the peripheries of the optical fibers 2 with the resin. The
resin thickness T on the outer half circumference of each optical
fiber 2 covered with the connecting portion 3 is set to smaller
than or equal to 15 .mu.m.
[0037] The example shown in FIG. 3, in which the outer half
circumference of each optical fiber 2 having the outer diameter
dimension of 220 .mu.m is covered with the resin, has no influence
on the bending performance of the optical fiber ribbon 1 since the
resin thickness T of the resin covering the outer half
circumference is as thin as 15 .mu.m or smaller. Therefore, such a
configuration does not prevent from improving the packaging density
in the cable.
EXAMPLE
[0038] Several types of optical fibers having different outer
diameter dimensions were used in which the distance between the
centers of adjacent optical fibers varied, so as to manufacture
optical fiber ribbons (4-core ribbons). The manufacture of
connecting portions and unconnected portions employed the method
disclosed in Japanese Unexamined Patent Application Publication No.
2010-033010 (Japanese Patent Application No. 2009-082778). The
pitch adjustment between the optical fibers employed the method
disclosed in Japanese Unexamined Patent Application Publication No.
08-146239 (Japanese Patent Application No. 06-163292). Note that
all optical fibers in one optical fiber ribbon have the same outer
diameter dimension.
[0039] Next, batch fusion splicing performance was evaluated when
one optical fiber ribbon thus obtained was entirely fused with the
other optical fiber ribbon. The operation process was as follows.
First, the optical fiber ribbon was held with a holder, the first
cover layers 7 and the second cover layers 8 covering the
respective optical fibers were removed by use of Hot Jacket
Stripper to obtain the bare glass optical fibers 6, and side
surfaces of the bare glass optical fibers 6 thus obtained were cut
with a fiber cutter. Subsequently, the respective glass optical
fibers 6 in the optical fiber ribbon held with the holder were
placed on a fusion machine 10 having V-shaped grooves 9 formed at a
fixed pitch P2 shown in FIG. 4. In this state, the evaluation was
performed in such a manner as to determine whether the respective
glass optical fibers 6 were placed in the corresponding V-shaped
grooves 9. The case where the glass optical fibers 6 were placed in
the V-shaped grooves 9 was defined as OK, and the case where the
glass optical fibers 6 deviated from the V-shaped grooves 9 was
defined as NG.
[0040] Hot Jacket Stripper used was HJS-02 manufactured by Fujikura
Ltd. The fiber cutter used was CT-30 manufactured by Fujikura Ltd.
The fusion machine used was FSM-60R also manufactured by Fujikura
Ltd. The pitch P2 between the respective V-shaped grooves 9 in the
fusion machine 10 is 250 .mu.m. The operation under the conditions
described above was repeated 10 times and the number of NG was then
counted. Table 1 shows the evaluation thereof.
TABLE-US-00001 TABLE 1 Outer Diameter of Distance between Centers
of Number of NG in Optical Fiber Adjacent Optical Fibers Batch
Fusion Splicing (.mu.m) (.mu.m) Performance 220 300 8 220 280 0 220
250 0 220 230 0 200 280 0 200 250 0 200 220 0 180 300 6 180 280 0
180 250 0 180 220 0 180 200 4
[0041] The results shown in Table 1 revealed that, when the
distance L between the centers of the adjacent optical fibers 2 of
the optical fiber ribbon 1 having an intermittent fixing structure
is set to 250.+-.30 .mu.m (220 .mu.m to 280 .mu.m), the glass
optical fibers 6 do not deviate from the V-shaped grooves 9 so as
to be concurrently fused with the corresponding glass optical
fibers of the other optical fiber ribbon. The number of NG
increased when the optical fiber ribbon did not meet the
above-described condition, and the glass optical fibers 6 could not
be placed in the V-shaped grooves 9 precisely.
[0042] [Optical Fiber Cable]
[0043] FIG. 5 shows an example of a center tube-type optical fiber
cable housing the optical fiber ribbon according to the present
embodiment therein. The center tube-type optical fiber cable 11 has
a configuration in which the optical fiber ribbon 1 of the present
embodiment is formed into a cable core 12 in a manner such that the
optical fibers 2 are rolled in the ribbon width direction and
assembled into a bundle as indicated by a dashed and double-dotted
line in FIG. 5, thermoplastic resin is extruded over the periphery
of the cable core 12 thus obtained so as to form a tube 13 thereon,
and the tube 13 is further covered with polyethylene so as to form
a sheath 14 thereon.
[0044] FIG. 6 shows an example of an SZ-slotted optical fiber cable
housing the optical fiber ribbon according to the present
embodiment therein. The SZ-slotted optical fiber cable 15 has a
configuration in which a plurality of slots 18 having a U-shape in
cross section are formed on the outer periphery of a slot core 17
including a tension member 16 in the center thereof extending in
the ribbon longitudinal direction, the optical fiber ribbon 1
according to the present embodiment is rolled in the ribbon width
direction into a bundle and housed in each of the slots 18, the
peripheral surface of the slot core 17 including the openings of
the slots 18 is covered with a press winding tape 19, and a sheath
20 is further formed thereon by extrusion.
[0045] FIG. 7 shows an example of a C-slotted optical fiber cable
housing the optical fiber ribbon according to the present
embodiment therein. The C-slotted optical fiber cable 21 has a
configuration in which the optical fiber ribbon 1 according to the
present embodiment is rolled in the ribbon width direction into a
bundle and housed in a slot groove 24 of a slot core 23 having a
C-shape in cross section including tension members 22 therein, and
the entire slot core is covered with a sheath 26 via a press
winding tape 25 interposed therebetween.
[0046] Although the optical fiber ribbon 1 shown in each of FIG. 5,
FIG. 6 and FIG. 7 according to the present embodiment is rolled in
the ribbon width direction into a bundle and housed in the cable,
the optical fiber ribbon 1 according to the present embodiment may
be folded in layers in the vertical direction and housed in the
cable. Alternatively, a plurality of the optical fiber ribbons 1
may be stacked on top of one another to have a stacked structure
and then housed in the cable.
[0047] The optical fiber cables 11, 15 and 21 according to the
present embodiment each use the optical fibers 2 having the reduced
outer diameter dimension of smaller than or equal to 220 .mu.m.
Therefore, a larger number of the optical fibers 2 can be housed in
the cable, compared with the conventionally-used optical fibers 2
having the outer diameter dimension of 250 .mu.m, so as to ensure
higher density. Further, the optical fiber cables 11, 15 and 21
according to the present embodiment can house the optical fiber
ribbon 1 having an intermittent fixing structure in any state in a
manner such that the optical fiber ribbon 1 is bent and rolled into
a cylindrical shape or folded to be stacked in any direction.
[0048] Further, the optical fiber cables 11, 15 and 21 according to
the present embodiment can easily separate the respective optical
fibers 2 from each other so as to improve single-core separation
workability at the time of terminal leading to extract the optical
fibers 2 from the terminals of the cable or at the time of
connecting operation to connect a connector to the extracted
optical fibers 2, since the optical fiber cables 11, 15 and 21 each
use the optical fiber ribbon 1 including the connecting portions 3
intermittently formed in each of the ribbon longitudinal direction
and the ribbon width direction to connect the adjacent two optical
fibers 2 together.
INDUSTRIAL APPLICABILITY
[0049] The present invention is applicable to the optical fiber
ribbon having an intermittent fixing structure to intermittently
connect the adjacent optical fibers together via the connecting
portions.
* * * * *