INFOCOMMUNICATIONS

Ultra-High-Density Optical Cable with Rollable Ribbons
for Simple Installation and Cost Reduction
Kentaro TAKEDA*, Masakazu TAKAMI, Shigehisa ISHIGAMI, Yoshiaki NAGAO, Masashi OKAand Dai SASAKIThis paper describes a newly developed ultra-high-density optical fiber cable containing rollable 4-fiber ribbons with afiber adhesive part and a single-fiber part. The 24-fiber cable is an aerial distribution cable that has sheath
configurations similar to a conventional optical thinner drop cable and can therefore be drastically downsizedcompared with a conventional aerial non-slotted core cable. The cable also has multiple notches on the sheath, withstrength members, plastic tapes and yarns surrounding the rollable ribbons, offering easy fiber ribbons extraction fromthe cable. Moreover, we have also adopted 24MPO optical connectors for joint boxes and on both ends of the cable,
which simplifies cable installation and reduces installation time and cost.
Keywords: rollable ribbon, ultra-high-density, cable downsizing

1. Introduction
The number of the fiber to the home (FTTH) subscribers in Japan has already reached 23 million and is forecast to increase at a consistent rate. As shown in Fig. 1, thetypical FTTH cabling network is connected from the telecombuilding to underground cables, aerial cables and dropcables. Recently, to construct a FTTH network more economically, several studies for new aerial distribution cablewith thinner diameter and higher density have been carried out. Easy cable connection and branching workability
are also much in demand.

cable which has two strength members at both sides of the6 rollable fiber ribbons and rectangular jacketing, with theintention of downsizing the cable. This configuration results in drastically reducing the size by 70% and weight by
55%, while retaining the equivalent cable characteristics ofconventional aerial non-slotted core cable.

Fig. 2. Cable cross-section

Fig. 1. Common wiring system in Japan
Table 1. Cable configurations

Item

2. Cable design
2-1 Features of ultra-high-density optical fiber cableconfigurations
To construct a FTTH network, distribution cables withribbon fibers are installed in advance, and then drop cables
with a single fiber can be routed from any mid-span point
upon requests for the FTTH service. We decided that thenew cable’s design would be more suitable for mid-spanaccess.
The configurations of the new 24-fiber cable withrollable 4-fiber ribbons are shown in Fig. 2 and Table 1.
We kept similar configurations to the conventional drop

Conventionalcable

New cable

Self-supporting type
Supporting wire7/1.4 mm

Fiber
Strength member
Wrapping

Cross section
Size (main cable)
Weight－a single mode fiber
0.7 mmPlastic tapeJacketDiameter

2.6 mmsupportingtype

0.5 mm

0.7 mmPlastic tapes & Soft yarns
Polyolefin

8.5 × 17 mm

3 × 10.5 mm

3 × 5.5 mm

10.3

0.3

0.16 kg/km

0.07 kg/km

0.02 kg/km

72 · Ultra-High-Density Optical Cable with Rollable Ribbons for Simple Installation and Cost Reduction

2-2 Rollable ribbon
As shown in Fig. 3, rollable ribbon consists of a fiberadhesive part and a single-fiber part. In addition, rollable
ribbons can be connected by fusion splicing like conventional 4-fiber ribbons.

position using the blade on the special tool. Furthermore,because the ribbons are circumscribed on all four sides by
the plastic tapes and yarns, ribbons can be extracted safely
without the fibers being left in the polyolefin jacket.

Fig. 3. Rollable ribbon
Fig. 5. Fiber extracting proceduresThis configuration also enables the ribbons to change
shape in order to reduce stress to the fibers in the cable.
Thus, the cable will have a high tolerance against external
stress, with the result that the fiber density inside it will behigher and the cable will be thinner and lighter.

With conventional cables, it can take more than 3 minutes to take out the fibers, but with this new cable, the handling process is very simple and it takes less than 30
seconds. With this method, the fibers can be taken out very
easily at any location after cables are installed in a very
short time.

3. Improvement for Cable Jointing
3-1 Application to mid-span accessFigure 4 shows how to dissect the conventional cables
to extract the fibers. First of all, peel off the sheath with atool like a peeler. As you continue to peel, the rip cord appears. By taking out the rip cord, the jacket is pulled apartand the inside core can be taken out. After taking out thecore, remove the thread and core wrap wrapped in a spiralmanner, and then finally the optical fibers appear.
The handling procedures to extract rollable ribbons
from the cable are shown in Fig. 5. The new cable has fournotches on the rectangular jacket. By using these notches
as guide grooves, we can accurately slit at any longitudinal

Fig. 6. Working time to extract fibers

3-2 Connecting method for the new cable
To construct the FTTH more economically, more simplified construction methods and products are required.
To do so we attached 24MPO optical connectors on bothends of the new cable and each cable with 24MPO connectors is jointed in a newly developed “Joint Box.”
The assembled configuration of the new 24-fiber cablewith Joint Box is shown in Fig. 7. Special skills are notneeded to connect the two new 24-fiber cables.
Fig. 4. Dissection of conventional cable

SEI TECHNICAL REVIEW · NUMBER 79 · OCTOBER 2014 · 73

Appearance of the Joint Box

Fig. 7. New 24-optical cable with Joint Box

3-3 24MPO connector
To realize easy connection in the field, we selected the24MPO optical connector. MPO optical connectors havebeen used worldwide over ten years, the reliability in thefield is proven, and it is possible to connect all of opticalfibers in new cable in one operation. The configuration of24MPO optical connector is shown in Fig. 8 and the 24fiber cable’s terminal with a 24MPO connector is shown inFig. 9, respectively.

Fig. 10. Joint Box

the supporting wire; the third is connecting the opticalfibers.
3-5 Procedures to assemble the Joint Box
The procedures to connect to a Joint Box are shown inFig. 11. All operations can be carried out within 3 minutes
without using special tool.

1. Open the Joint Box
1
2. Fix supporting wireAppearance

End face

Fig. 8. 24MPO optical connector

3. Fix optical cable2

4. Connect 24MPO connector
5. Put away surplus optical fiber
6. Install the waterproof parts

Supporting wire3

7. Close the Joint Box
24MPO connector

8. Lay cables
Fig. 9. Cable terminal

3-4 Design of the Joint Box
The Joint Box is connected to one end of the cable asshown in Fig. 10. For outdoor and long term use, the Joint
Box has to be robustly designed: the outer configurationsof the Joint Box adhere fundamentally to conventional aerial closure which is waterproof and resistant to ultraviolet
light. A 24MPO connector is also attached on the opposite
end of new cable.
The Joint Box consists of three main parts as shown in
Fig. 10: the first is holding the cable; the second is holding

4567

Process 1-7 carry out on the ground.
Fig. 11. Procedures of jointing

74 · Ultra-High-Density Optical Cable with Rollable Ribbons for Simple Installation and Cost Reduction

Table 3. Tests results of 24MPO Connector

4. Characteristics
4-1 Cable characteristics
Table 2 shows the transmission, temperature and mechanical characteristics of the newly developed cable. Allof the test results were positive. In the test cable, a single
mode fiber complying with ITU-T G.657 class A1 was used.

Table 2. Transmission and mechanical performance

Test item

Methods

Test Results

Insertion Loss

Vs. Master plug connector

Avg. 0.22 dB
Max. 0.57 dB

Return Loss

Vs. Master plug connector> 60 dB

Durability100 times< 0.19 dB

Vibration

1.5 mm PP 10~55 Hz 3 axis
2 hours< 0.02 dB
No damage

ItemMethods

Test Results

Impact100 G 6ms, 5 times< 0.18 dB
No damage

Attenuation
Coefficient

IEC60793-1-40
λ = 1,550 nm< 0.25 dB/km

Proof (90˚)

0.5 N 10times< 0.17 dB
No damage

Temperature
Cycling

IEC60794-1-2-30 ~ +70 degrees C,
3 cycles λ = 1,550 nm< 0.10 dB/km

Proof (0˚)

5.9 N

< 0.19 dB
No damage

Crush

IEC60794-1-2
1960N/100 mm λ = 1,550 nm< 0.05 dB

Temperature Cycle-40~70 degrees C10 cycle< 0.11 dB

Impact

IEC60794-1-2
300 g, 1 m , λ = 1,550 nm< 0.05 dB

Temperature andHumidity Cycle-10~25~65 degrees C
93% at 65 degrees C10 cycles< 0.04 dB

RepeatedBending

IEC60794-1-2
Bending radius:100mm
10 cycles, λ = 1,550 nm< 0.05 dB

High Temperature

70 degrees C
240 hours< 0.04 dB

Low Temperature< 0.05 dB-40 degrees C
240 hours< 0.08 dB

Torsion

IEC60794-1-2+/-90 degrees/1 m
λ = 1,550 nm
700N, R=250 mm
λ = 1,550 nm(self-supporting type)

Salt Spray< 0.05 dB
No damage< 0.05 dB

35 degrees C
5% salt water
24 hours

Continuous Temperature Humidity
Cycle

85 degrees C, 336 hours
95%/ at 60 degrees C
336 hours-40~23~75 degrees C
42 cycles< 0.10 dB

Bending undertension

4-2 Connector characteristics
We have conducted various mechanical and environmental tests on the 24MPO connectors in the Joint Box
shown in Fig. 12 and Table 3. As representative results, theinsertion loss when using a master connector plug was
0.22dB average, 0.57dB max and the insertion loss fluctuation during the environmental tests (Temperature cycle,Temperature and humidity cycle, High temperature, Lowtemperature, Salt spray, Continuous temperature Humidity cycle) were within 0.11dB. All other test results were positive.

5. Conclusion
We have developed an ultra-high density 24-fiber cablewith rollable 4-fiber ribbon. This cable results in drasticallyreducing the size by 70% and weight by 55%, while retaining the equivalent cable characteristics of conventional aerial non-slotted core cable.
Furthermore, we have created a Joint Box with 24MPOconnectors which will contribute to simplifying installation
work saving installation time and cost.

(1)

(2)
Fig. 12. Insertion loss results of 24MPO connector(3)

References
Y. Yamada et al, “Ultra-High-Density Optical Fiber Cable with Rollable
Optical Fiber Ribbons,” The Institute of Electronics, Information andCommunication Engineers (2008), p. 292
Y. Yamada et al, “High-Fiber-Count and Ultra-High-Density OpticalFiber Cable with Rollable Optical Fiber Ribbons,” The Institute ofElectronics, Information and Communication Engineers (2009),p. 503
M. Takami et al, “Design of Ultra-High-Density Optical 24-FiberCable with Rollable 4-Fiber Ribbons for Aerial Deployment”

SEI TECHNICAL REVIEW · NUMBER 79 · OCTOBER 2014 · 75

Contributors (The lead author is indicated by an asterisk (*).)

K. TAKEDA*• Assistant Manager, Optical Fiber & CableDivision

M. TAKAMI• Assistant General Manager, Optical Fiber &Cable Division

S. ISHIGAMI• Manager, Optical Fiber & Cable Division

Y. NAGAO• Manager, Optical Fiber & Cable Division

M. OKA• Connector Production Department, SEI
Optifrontier Co., LtdD. SASAKI• Assistant Manager, Optical Communications R&D Laboratories

76 · Ultra-High-Density Optical Cable with Rollable Ribbons for Simple Installation and Cost Reduction