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Small-diameter High-strength Optical Drop and Indoor Cables
with PBO-FRP Strength Member

1.

With the growing demand for optical communications,demands for installation of optical fiber cables to subscribers' households are increasing. For such opticalcable installations, currently, the fiber element portion ofan optical drop cable or optical fiber indoor cables areused. Conventional optical cables using metallic strength
member have problems such that although they have sufficient strength they are conductive of lightning currents,
and that they are rigid in bending thus leading to difficultyin cabling. On the other hand, non-metallic cables havesuch advantages as being non-conductive of surge currents and low in bending rigidity, but they are low in tensile strength compared with metallic cables.
Accordingly, we have recently developed optical drop
and indoor cables using a new strength member made ofpoly-paraphenylene-benzobisoxazole (PBO) reinforced
FRP. PBO fiber has a tensile strength more than twice thatof aramid fiber, and the PBO strength member combines
the advantages of both the metallic and non-metallicstrength members.

2.

Table 1

GENERAL DESCRIPTION

Strength membersize (mm)Cable size(mm)Allowable tensilestress of cable(N)PBO-FRP

φ0.52×3130

Single steel wire

φ0.4

2×3150PBO-FRP

φ0.27

1.2×2.4

40

Aramid FRP

φ0.52×335

Cable type

2.2 Low Bending Rigidity
The cables using PBO-FRP have been successful in lowering their bending rigidity in comparison with conventional cables. Table 2 shows the bending rigidity of thenew cable using selected sizes of strength members. Fordrop cables, only the fiber element portion is taken intoaccount.
It can be seen that the bending rigidity of a cable usinga PBO-FRP of φ0.5 mm is not more than one half that of acable using a single steel of φ0.4 mm, and that of a flat
cable measuring 1.2 x 2.4 mm using a PBO-FRP of φ0.27
mm is one third that of a cable using an aramid FRP of
φ0.5 mm.

FEATURES

2.1 High Strength
PBO fiber is manufactured by the fiber spinning methodof liquid crystal polymers, and combines the highest-ranking levels among organic fibers of tensile strength, i.e.
more than twice that of aramid fiber, and elastic modulus.
The strength member was fabricated by impregnating thePBO fiber with a thermo-setting resin, followed by heating
for thermo-setting to make an FRP.
Table 1 compares the size and tensile strength of thenew cable using selected sizes of strength members withthose of conventional cables. For drop cables, only thefiber element portion is taken into account.
It can be seen that a PBO-FRP of φ0.5 mm can achieve,
regardless of being non-metallic, an allowable tensilestress comparable to that of a single steel of φ0.4 mm.
Meanwhile, a PBO-FRP of φ0.27 mm can reduce the cablecross-sectional area by half, while obtaining an allowabletensile stress comparable to that of an aramid FRP of φ0.5mm.

Size and tensile strength of cables.

Table 2
Cable type

Size and bending rigidity of cables.
Strength member
size (mm)φ0.5
PBO-FRP

φ0.27

Cable size(mm)Bending rigidity at
D=20 mm (N) *2×3

1.5

1.2×2.4

0.48

φ2.4

1.3

Single steel wire

φ0.42×3

3.5

PBO-FRP

φ0.52×31.5* Measured in compliance with IEC 60794-1-2 Method E17C.

3.

STRUCTURE

Figure 1 shows the cross-sectional structures of thecables. For each type of cable, the FlexiWave fiber that iscapable of reducing the conventional allowable bending
radius by half, i.e. from 30 mm to 15 mm, has been
applied. As for small-diameter types, a round cable has
been added to the product lineup in addition to conventional flat type cables.

Furukawa Review, No. 29

200631Small-diameter High-strength Optical Drop and Indoor Cables with PBO-FRP Strength Member

φ 1.2-mm galvanized steel wire
φ 0.5-mm PBO-FRP
Flame-retardant
halogen-free polyolefin
φ 0.25-mm FlexiWave fiber
High-strength drop cable (2 x 5 mm)

High-strength indoor cable (2 x 3 mm)

φ 0.27-mm PBO-FRP

Small-diameter indoor cable (flat type) (1.2 x 2.4 mm)

Figure 1

Cross-sectional structures of cables.
Table 3

Test item
Transmission characteristics

Mechanicalcharacteristics
at λ=1.55µm

4.

Cable characteristics.

Test condition

High-strengthdrop

High-strengthindoor

Small-diameterindoor (flat)

Small-diameterindoor (round)at 1.31µm, the maximum0.34 dB/km

0.34 dB/km

0.34 dB/km

0.34 dB/km

at 1.55µm, the maximum

0.21 dB/km

0.21 dB/km

0.21 dB/km

0.21 dB/km<0.01 dB

<0.01 dB

<0.01 dB

<0.01 dB

Tensile strength(of element portion)

High-strength: 130 N

Squeezing

700 N, R=300 mm, 90°<0.01 dB———

Reversed bending

R=15 mm x 10 cycles<0.01 dB

<0.01 dB

<0.01 dB

<0.01 dB

Indoor: 40 N

Winding

R=15 mm x 10 turns<0.10 dB

<0.10 dB

<0.10 dB

<0.10 dB

Lateral pressure

1200 N/25 mm x 1 min.

<0.01 dB

<0.01 dB

<0.01 dB

<0.01 dB

Twist50 N, ±180°/m x 10 cycles<0.01 dB

<0.01 dB

<0.01 dB

<0.01 dB

Impact0.3 kg x 1-m height<0.01 dB

<0.01 dB

<0.01 dB

<0.01 dB

Drop: -30~70°C<±0.02 dB/km<±0.03 dB/km<±0.03 dB/km<±0.03 dB/km

Temperature characteristics
Flame resistance

Small-diameter indoor cable (round type) (•2.4φmm)

Indoor: -10~40°C
JIS C 3005, slanted

CABLE CHARACTERISTICS

Table 3 shows the cable characteristics, which are excellent and are comparable to those of conventional cables.

Self-extinguishing Self-extinguishing Self-extinguishing Self-extinguishing

For more information, please contact:
Transmission Engineering Dept.,
Telecommunications Co.
TEL: +81-3-3286-3397
FAX: +81-3-3286-3190

Furukawa Review, No. 29

200632