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A Small Optical Indoor Cable with PBO-FRPs

1.

INTRODUCTION

Recently, demand for leading optical fibers to subscribers’ homes has been increasing with the spread of FTTH
(Fiber To The Home), and optical indoor cables havebeen widely used for wiring in subscribers’ homes. Theseindoor cables are used between an outdoor optical distribution cabinet and an optical rosette installed in a wall ofthe room, and also used between an optical rosette andan ONU (Optical Network Unit) by wiring on a wall or afloor of the room. Therefore, the cables are required to bewired flexibly and practically unnoticeable in a room inorder not to disturb its beauty (Figure 1). Existing opticalindoor cables have been designed taking these points
into account. They are comparatively easy to be wired
because they are the smallest, the lightest and the mostflexible of all optical cables. Also, they are composed of
the coating materials with practically unnoticeable colors
such as white and ivory.
On the other hand, to promote leading and wiring optical fibers to subscribers’ homes further, optical indoor
cables that are easier to be wired and that also are smaller, lighter, and more flexible with the minimum disturbance to the beauty compared to the existing opticalindoor cables, are required. However, there were problems with the tension members used in the existing optical indoor cables, such as steel cables and aramid fiber
FRPs (Fiber Reinforced Plastics). Because steel cables
are heavy, they are comparatively inflexible. Aramid fiber
FRPs have difficulty in further downsizing in terms of their
allowable tensile force because their tensile elasticity
rates are low.
To counter such a situation, we have developed a small
optical indoor cable using PBO (Poly-pphenylenebenzobisoxazole) fiber FRPs. PBO fibers arewhat we have been considering to implement into practical use. That will be described in the following.

Optical distribution cabinet

PCONU

Optical drop cable
Opticalrosette

Optical indoor cable

Figure 1

2.

Installation of optical indoor cable.

CHARACTERISTICS OF THE DEVELOPED PRODUCT

2.1 Cable Structure
Figure 2 shows the structures of the existing cable andthe developed cable. Figure 3 shows the comparison of
their appearances. By using PBO fiber FRPs which have ahigh tensile elasticity rate, the tensile strength is equivalent to the existing aramid fiber FRPs, also the external
diameter of the tension member can be smaller.
Moreover, we have tried to reduce the diameter of thecable to the extent of holding its mechanical characteristics.

Tension member

Coat(Non-halogen flame resisting)Tension member
Coat（PBO-FRP） (Non-halogen flame resisting)

Optical fiber(R15 mm)Existing productFigure 2

Optical fiber(R15 mm)Developed product

Cable structure.

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A Small Optical Indoor Cable with PBO-FRPs

low bend restitution, wiring with small radius bending
inside an optical rosette and an optical distribution cabinet, and wiring along the corners of walls and desks
become easy.

Existing product

Table 3  Bend restitution.
Developed product

Existing product Developed product
Bend restitution (N)IEC60794-1-2 compliant
Bend radius 15 mm

1.9 *10.15

1.3 *2*1 ： The tension member is a steel cable.

Figure 3*2 ： The tension member is an aramid fiber FRP.

Cable appearance.

2.2 Cross Sectional Areas of the Cable
Table 1 shows the cross sectional areas of the existingproduct and of the developed product. The cross section2
al area of the developed product is 1.9 mm , which is
reduced to 30% of the existing product. Consequently, it
brings advantages that not only cables are practicallyunnoticeable in a room but also lightweight and flexible.

2.5. Cable Characteristics
Table 4 shows the cable characteristics of the small optical indoor cable. This cable has good transmission,mechanical, temperature and flame resisting characteristics.
Table 4  Cable characteristics.
Test item

Table 1Existing product Developed product
Cross sectional area (mm2)

6.2

1.9

Relative value of crosssectional area

1.0

0.3

2.3. Cable Weight
Table 2 shows the weights of the existing cables and ofthe developed cable. The weight of the developed product per unit length is 3 g/m, which is lightweight to a great
extent. Compared with the existing product made of asteel cable, it accomplished the reduction of about 70%of the weight. Compared with the existing product madeof an aramid fiber FRP, it accomplished the reduction ofabout 60% of the weight.
Table 2Test conditionCharacteristic

Test wavelength
λ=1.31 μm

Less or equal to 0.35dB/km

Test wavelength
λ=1.55 μm

Less or equal to 0.21dB/km

Tensile150 N

Less or equal to 0.1 dBBending

R = 15 mm × 10 cycles

Less or equal to 0.1 dB

Crush1200 N/25 mm

Less or equal to 0.1 dB

ImpactWeight 2.94 N, Height 1 m

Less or equal to 0.1 dB

Temperature
characteristic－30 to ＋70℃

Less or equal to0.05 dB/km

Flame resisting

JIS C3005 inclination

Self inflammation

Cross sectional area.

Cable weight per unit length.

Existing productDeveloped product1Weight (g/m)

10 *8*2

3*1 : The tension member is a steel cable.
*2 : The tension member is an aramid fiber FRP.

Transmissionloss※Test wavelength of mechanical test and temperature test: λ = 1.55 μm※The characteristic values in the table are the representative values, notguaranteed values.

2.6. Wiring Example
Figure 4 shows the statuses that the existing product andthe developed product are wired along the wall startingfrom an optical rosette. Compared with the existing product, the developed product can be wired easily along awall and the cable itself is practically unnoticeable
because of its thinness and flexibility. In addition, it iseasy to handle because of its lightweight. Consequently,
it contributes to the facilitation of the installation work.

2.4. Flexibility (Bend Restitution)
Table 3 shows the bend restitutions of the existing products and of the developed product. When bent to 15 mm
radius, the existing product made of a steel cable showed
the bend restitution of 1.9 N, and the existing productmade of an aramid fiber FRP showed the bend restitutionof 1.3 N. On the other hand, the bend restitution of thedeveloped product showed 0.15 N, which is low. With thisFurukawa Review, No. 42201213

A Small Optical Indoor Cable with PBO-FRPs

Optical rosette

Closeup

CloseupExisting productFigure 43.

Optical rosette

Developed product

Wiring example.

CONCLUSION

We have developed a small optical indoor cable using
PBO fiber FRPs. This cable enables easy wiring inside ahome because it is small, lightweight and flexible.
Moreover, because it is practically unnoticeable, opticalfibers can be wired without disturbing the beauty of aroom.
For more information, please contact:
Engineering Department
Optical Fiber & Cable Division
Telecommunications Company
TEL: +81-436-42-1857 FAX: +81-436-42-1678
E-mail: optcom@ho.furukawa.co.jp

Furukawa Review, No. 42

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