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SPECIFICATION OF JAPAN CABLE
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Development of the Small Size Low-Friction Indoor Cable
Katsuyoshi Endoh, Tadayoshi Sayama, Daiki Takeda, Shimei Tanaka, Masashi Ohno, Satoru Shiobara, Naoki Okada and Matsuhiro Miyamoto
Optical Fiber Cables R&D Dept, Optical Cable System R&D Center, Fujikura Ltd.
1440 Mutsuzaki, Sakura, Chiba, Japan
Abstract In Japan, it is required to construct indoor cables in existing
multiple dwelling units for FTTH network development.
However, some existing multiple dwelling units have no conduit
unit for optical cables and it is difficult to add new conduit lines
because of expensive construction cost. So, we have to use
existing metal telephone cable conduits for realizing additional fibers installation. Therefore we developed the small size low-
friction indoor cable. It has low coefficient of friction and suitable
for pushing-installation without utilizing any rod into conduits
crowded with existing cables.
Keywords: FTTH; small size low-friction indoor cable; multiple
dwelling units; installation
1. Introduction For constructing FTTH in multiple dwelling units, the optical fiber
cable usually is laid out from MDF (Main Distribution Frame) into
each floor of multiple dwelling units. Most of the existing multiple
dwelling units have no conduit unit for optical cables, and it is
difficult to add new conduit lines for optical cables because of
expensive construction cost. To solve this problem, we use existing
conduits meant for metal telephone wires. Using conventional
indoor optical cables, only a few cables can be installed. The reason
is because of high friction between a conventional cable and conduit
inner surface or other existing cables. As a result, high tension is
required to pull the conventional cable. In addition, we can have a
shorter installation time if we could push a cable into a conduit unit
directly. Therefore we developed a small size low-friction indoor
cable which is suitable for not only pulling-installation but also
pushing-installation through existing conduit lines.
2. Cable design Cross-section and structure of the development products are shown
in Fig.1 and characteristics comparison in Table.1. To realize
pushing-installation into conduit units, we examined three factors.
They are improvement of cable sheath characteristic, size reduction
and bending stiffness.
Figure 1. Cross-section of a conventional indoor cable
and small size low-friction indoor cables
Table 1. Comparison between conventional cable and
small size low-friction indoor cable (relative value)
Item Conventional
cable
Small size low-
friction indoor
cable
Cross section area 1 Approx. 1/2
Weight 1 Approx. 2/3
Friction coefficient 1 1/7 or less
Abrasion resistance 1 100 or above
Stiffness 1 Approx. 2
2.1 Cable sheath characteristic To realize smooth pushing-installation, friction between indoor
cables and other cables or inner wall of conduits must be reduced[1].
Therefore we chose a new plastic resin as a base polymer for low
friction characteristics. Compared with conventional polyolefin resin,
it is harder.
In order to evaluated friction coefficient of trial cables, we
established test method as shown in Fig.2. The friction coefficient
is calculated by followed equation.
0/ FF (1)
In this equation, F is the force to pull out testing cable and 0F is
the weight.
With a new resin, we examined three types of low friction treatment
whose results are shown in Fig.3. In this figure, coefficients of
friction are relative values. All treatments are effective. Since
treatment A and C are the most effective, we chose these two
Flame retardant polyolefin resin Low friction, abrasion
resistant and flame retardant
polyolefin resin
Conventional indoor cable
Single fiber type Double fibers type
Small size low-friction indoor cable
Strength member
φ0.25mm Optical fiber
treatments and investigated the friction coefficient reliability of
treatment A & C with aging. The results are shown in Fig.4. At this
experiment, the aging environment was high temperature and high
humidity. Throughout aging time, friction coefficient of treatment A
gradually increased but treatment C is relatively constant.
Considered these results, we decided to adopt treatment C for small
size low-friction indoor cable sheath.
To verify abrasion resistance property, we measured abraded
thickness of cables after abrasion resistance test as shown in Fig.5
and the test results are shown in Fig.6. The amount of abraded
sheath of the small size low-friction indoor cable was 100 times less
than the conventional indoor cable.
Figure 2. Experiment of friction measurement
Figure 3. Comparison of different kinds of treatment in
order to reduce coefficient of friction
0.1
0.12
0.14
0.16
0.18
0.2
1 10 100
Aging time[day]
Fri
ctio
n c
oef
fici
ent
(rel
ativ
e v
alu
e)
Treatment A
Treatment C
Figure 4. Comparison coefficient of friction between
treatments A & C with aging time
Figure 5. Abrasion resistance test method
Figure 6. Results of abrasion resistance tests
2.2 Size Reduction Reducing the cable cross-section area enable us to install cables
into conduit easily. However, by reducing the size, it will weaken
its mechanical characteristic. Thus, we used the new resin, above
mentioned, as the sheath of small size low-friction indoor cable.
By using low friction, abrasion resistant and flame retardant
polyolefin resin, the cross-section of cable could be reduced into
half compared with the conventional indoor cable without
compromising its mechanical characteristics. The reduction makes
the weight of small size low-friction indoor cable to be 2/3
smaller than conventional cable.
2.3 Bending stiffness When we push a cable into a conduit, cable stiffness is an important
factor. High cable stiffness enables installer to easily push the cable
into the conduit but it makes installation in an small optical rosette
more difficult. We tested a relation among types of strength member,
cable stiffness and difficulty to put in an optical rosette. The result is
Weight 0F
Cables
Cables
Generator Weight
Cable
Abraded thickness
0.00
0.10
0.20
0.30
0.40
Con
vent
iona
l cab
le
No
treatm
ent
With
trea
tmen
t A
With
trea
tmen
t B
With
trea
tmen
t C
Fri
cti
on
co
eff
icie
nt
(rela
tiv
e v
alu
e)
Low friction, abrasion resistant
and flame retardant polyolefin resin
1.00
0
0.02
0.04
0.06
0.08
0.1
Conventional indoor cable Small size low-friction
indoor cable
Abra
ded
thic
knes
s (r
elat
ive
val
ue)
,
0.01
100 times lesser
1.00
Pull out a testing cable
(Force F )
shown in Table.2. Cable stiffness B was calculated by following
equation.
2
2
rFB (2)
In this equation, F is measured force and r is the bend radius
of cable at final jaw separation as shown in Fig.7. These are
measured using method E17C, the method from IEC 60794-1-2[2].
Fig.8 shows a small size low-friction indoor cable installed in an
optical rosette. According to table 2, strength member C has high
stiffness and yet can be installed easily in an optical rosette.
Table 2. Relation among strength member, cable
stiffness and optical rosette installation properties
Strength member type A B C D
Cable Stiffness (relative value;
Conventional cable’s stiffness is 1)
1 1.5 2 7
Installation in an optical rosette
Figure 7. Stiffness measurement method
Figure 8. Cable installation in the optical rosette
3. Installation characteristic We evaluated small size low-friction indoor cables to install into
the conduit. The test conduit description is shown in Table.3. In
this experiment, we set 30 small size low friction indoor cables as
a target which is the same number of pairs installed metal
telephone cable.
Table 3. Conduit line for cable installation test
Item Description
Conduit inner diameter φ22 mm
Corners 90 °×5 corners
Length 20 m
Existing cable 30-pair of metal telephone
cable (9mm diameter)
3.1 Pulling-installation with a rod We tested pulling-installation method using small size low-
friction indoor cables and conventional indoor cables. These
results are shown in Fig.9. 5 pieces of conventional indoor cable
could be installed; on the other hand we were able to install more
than 30 pieces of small size low-friction indoor cable. Fig.10
shows the conditions of cable installation at the conduit line exit.
Though there is much unused space after installation of
conventional cable, we couldn’t install anymore because of high
pulling force which is caused by high friction inside the duct.
Unlike conventional cable, even though there is little space
available for more installation, small size low-friction indoor
cables can still be installed easily. After installing 30 pieces
installation of low-friction indoor cable, we measured force to
pull out a cable randomly. These results are shown in Fig.11.
Small size low-friction indoor cables could be pulled by lower
force than conventional indoor cables. It is evidence that small
size low-friction indoor cable has superior installation
characteristic.
0
5
10
15
20
25
30
35
Conventional cable Small size low-friction
indoor cable
Inst
alle
d p
iece
nu
mb
er,
Figure 9. Result of cable pulling-installation tests
Final jaw separation
Cable
Optical rosette
Small size low-
friction indoor
cable
Above 30 pieces
5 pieces
Adapter
Greatly increased
Figure 10. Conditions of cable installation at the exit
of conduit line
Figure 11. Pulling-installation force and pulling out
force between conventional cable and small size low-
friction indoor cable
3.2 Pushing-installation method When we operate pushing-installation, we bend the tip of a cable
in order to prevent cable from getting stuck inside the conduit
since the conduit surface is in corrugated shape. It is shown in
Fig.12. In this method, small size low-friction indoor cable could
be installed over 30 pieces, but conventional cable couldn’t be
installed at all as shown in Fig.13. Based on these results,
installation performance was dramatically improved by using
small size low-friction indoor cable than using conventional cable.
Figure 12. Pushing-installation procedure by making a
bend of cable tip
0
5
10
15
20
25
30
35
Conventional cable Small size low-friction
indoor cable
Inst
alle
d p
iece
nu
mb
er,
Figure 13. Result of cable pushing-installation tests
4. Cable characteristics We show other test results for small size low-friction indoor cable
in Table.4. Temperature cycling test was based on IEC60794-2-20
in a range of -20 degrees to +60 degrees[3]. Mechanical tests were
carried out with IEC60794-1-2[1]. In these test, loss increase was
not detected. Flame retardant test method was 60 degree flaming
test from JIS C 3005 as shown in Fig.14[4]. With the new resin
applied, the cable can extinguish the fire by itself.
Table 4. Results of mechanical tests, temperature
cycling test and flame retardant test
Test item Test condition Result
Transmission loss 1310 nm
1550 nm
< 0.35 dB/km
<0.25 dB/km
Temperature
cycling* -20 ˚C～+60 ˚C <0.05 dB/km
Impact* 1200 N/25 mm 1min <0.05 dB
Bending* R= 15 mm ±180 ° <0.05 dB
Crush* 3 J <0.05 dB
Torsion* ±90 ° <0.05 dB
Flame retardant JIS C 3005, 60 degree Pass
*Wave length 1550 nm
Figure 14. Flame retardant test method
Conduit line
Small size low-
friction indoor
cable
Conventional
indoor cable
Telephone cable
(30 pairs)
0
50
100
150
200
Pulling-
installation of
conventional
indoor cable
Pulling-
installation
Pulling out
Fo
rce[
N]
Small size low-friction indoor cable
Above 200N
10N or less 10N or less
A bend of cable tip Pushing-installation
No piece could be installed.
Above 30 pieces
Improved dramatically
Flame
Cable
60 degree
5. Reelex® packing
Small size low-friction indoor cable was packed with Reelex®
packing. We show the packing example in Fig.15. Reelex® packing
enable installer to install the cable from the package directly,
therefore other tools were not needed. Also during installation, small
working space is required for Reelex® packing. In addition, cable
could be pulled out by low force. Furthermore, the size of 1000m
scroll packing box is a half of 300m LAN cable packing.
Figure 15. Reelex® packing box and conventional cable
reel
6. Conclusions We successfully developed the small size low-friction indoor cable.
This cable has 1/2 the size and 1/7 friction coefficient of
conventional indoor cable. Because of these characteristics, we can
install this cable by pushing into the existing conduit line easily. It is
expected that using small size low-friction indoor cable, installation
of optical fiber cable in multiple dwelling units is greatly improved.
7. References [1] Yukitoshi Takeshita, Seizo Sakata, Hiroyuki Saito, Takashi
Sawada, Takao Handa, Shinichi Niwa, Keiichiro Sugimoto,
Ryuichi Nishio, and Shinji Tsuru, “Influence of Various
Factors on Indoor Cable Friction Properties and
Measurement Trial at High Drawing Speed in Actual
Environment”, OSA/OFC/NFOEC 2009 JThA85.
[2] IEC60794-1-2: 2003, Generic specification– Basic optical
cable test procedures.
[3] IEC60794-2-20: 2003, Indoor cables- Family specification for
multi-fibre optical distribution cables.
[4] JIS C 3005: 2000, Test methods for rubber or plastic insulated
wires and cables.
8. Pictures of Authors
Katsuyoshi Endoh
Optical Fiber Cable R&D Dept.
Fujikura Ltd.
1440, Mutsuzaki, Sakura, Chiba,
285-8550, Japan
Katsuyoshi Endoh was born in 1981. He joined Fujikura Ltd after
his graduation from Tokyo Institute of Technology in 2007 with
M.E. degree and has been engaged in research and development
of optical fiber cables. He is now an engineer in Optical Fiber
Cable R&D Dept.
Tadayoshi Sayama
Optical Fiber Cable R&D Dept.
Fujikura Ltd.
1440, Mutsuzaki, Sakura, Chiba,
285-8550, Japan
Tadayoshi Sayama was born in 1968. He joined Fujikura Ltd after
his graduation from Muroran Institute of Technology in 1993 with
B.E. degree and has been engaged in research and development of
optical fiber cables. He is now an engineer in Optical Fiber Cable
R&D Dept.
Daiki Takeda
Optical Fiber Cable R&D Dept.
Fujikura Ltd.
1440 Mutsuzaki, Sakura, Chiba,
285-8550, JAPAN
Daiki Takeda was born in 1978. He joined Fujikura Ltd after his
graduation from Muroran Institute of Technology in 2002 with
M.E. degree and has been engaged in research and development
of optical fiber cables. He is now an engineer in Optical Fiber
Cable R&D Dept.
Reelex®
packing box Conventional cable reel
Small size low-friction
indoor cable
Conventional indoor cable
Reel
Shimei Tanaka
Telecommunication Cable System Dept.
Fujikura Ltd.
1-5-1, Kiba, Koto-ku, Tokyo, 135-8512,
JAPAN
Shimei Tanaka was born in 1975. He joined Fujikura Ltd after his
graduation from Chiba University in 2000 with M.E. degree and
has been engaged in research and development of optical fiber
cables. He is now an engineer in Telecommunication Cable
System Dept.
Masashi Ohno
Optical Fiber Cable R&D Dept.
Fujikura Ltd.
1440, Mutsuzaki, Sakura, Chiba, 285-8550,
Japan
Masashi Ohno was born in 1969. He joined Fujikura Ltd after his
graduation from Tohoku University in 1993 with B.E. degree and
has been engaged in research and development of optical fiber
cables. He is now an engineer in Optical Fiber Cable R&D Dept.
Satoru Shiobara
Optical Fiber Cable R&D Dept.
Fujikura Ltd.
1440, Mutsuzaki, Sakura, Chiba, 285-8550,
Japan
Satoru Shiobara was born in 1967. He joined Fujikura Ltd after
his graduation from Ibaraki University in 1989 with B.E. degree
and has been engaged in research and development of optical
fiber cables. He is now a manager in Optical Fiber Cable R&D
Dept.
Naoki Okada
Optical Fiber Cable R&D Dept.
Fujikura Ltd.
1440, Mutsuzaki, Sakura, Chiba,
285-8550, Japan
Naoki Okada was born in 1964. He joined Fujikura Ltd. in 1986
after graduation from Chiba University with B.E. degree, and has
been engaged in research and development of optical fiber cables,
and optical fiber production engineering. He is now a manager in
Optical Fiber Cable R&D Dept.
Matsuhiro Miyamoto
Optical Cable System R&D Center
Fujikura Ltd.
1440, Mutsuzaki, Sakura, Chiba,
285-8550, Japan
Matsuhiro Miyamoto was born in 1953. He joined Fujikura Ltd.
in 1978 after graduation from Tokyo Institute of Technology with
M.S. degree, and has been engaged in research, development and
production engineering of optical fiber cables, and optical fiber.
He is now a manager in Optical Cable System R&D Center.
