<s>
Optical	B-Device
attached	I-Device
cable	I-Device
(	O
OPAC	O
)	O
is	O
a	O
type	O
of	O
fibre	B-Architecture
optic	I-Architecture
cable	O
that	O
is	O
installed	O
by	O
being	O
attached	O
to	O
a	O
host	O
conductor	O
along	O
overhead	O
power	O
lines	O
.	O
</s>
<s>
The	O
attachment	O
system	O
varies	O
and	O
can	O
include	O
wrapping	O
,	O
lashing	O
or	O
clipping	O
the	O
fibre	B-Architecture
optic	I-Architecture
cable	O
to	O
the	O
host	O
.	O
</s>
<s>
Installation	O
is	O
typically	O
performed	O
using	O
a	O
specialised	O
piece	O
of	O
equipment	O
that	O
travels	O
along	O
the	O
host	O
conductor	O
from	O
pole	O
to	O
pole	O
or	O
tower	O
to	O
tower	O
,	O
wrapping	O
,	O
clipping	O
or	O
lashing	O
the	O
fibre	B-Architecture
optic	I-Architecture
cable	O
in	O
place	O
.	O
</s>
<s>
Although	O
lashed	O
cable	O
systems	O
and	O
clipped	O
cable	O
systems	O
have	O
been	O
investigated	O
as	O
a	O
means	O
of	O
attaching	O
optical	B-Architecture
fibre	I-Architecture
cables	O
to	O
overhead	O
power	O
lines	O
,	O
wrapped	O
cables	O
were	O
the	O
first	O
type	O
to	O
be	O
developed	O
and	O
are	O
the	O
only	O
type	O
in	O
common	O
use	O
today	O
.	O
</s>
<s>
SkyWrap	O
is	O
the	O
most	O
successful	O
example	O
of	O
OPAC	O
and	O
is	O
used	O
together	O
with	O
more	O
familiar	O
optical	B-Architecture
fibre	I-Architecture
cables	O
such	O
as	O
OPGW	B-Device
and	O
All-dielectric	B-Device
self-supporting	I-Device
cable	I-Device
(	O
ADSS	O
)	O
to	O
build	O
communications	O
networks	O
for	O
power	O
utilities	O
.	O
</s>
<s>
OPAC	O
can	O
be	O
used	O
in	O
the	O
same	O
sense	O
as	O
the	O
nomenclature	O
"	O
OPGW	B-Device
"	O
and	O
"	O
ADSS	O
"	O
.	O
</s>
<s>
OPAC	O
refers	O
specifically	O
to	O
fibre	B-Architecture
optic	I-Architecture
cables	O
and	O
specifically	O
to	O
installations	O
where	O
the	O
host	O
conductor	O
is	O
part	O
of	O
the	O
electricity	O
supply	O
system	O
.	O
</s>
<s>
The	O
term	O
"	O
Ground-Wire	O
Wound	O
Optical	O
cable	O
"	O
(	O
GWWOP	O
)	O
is	O
sometimes	O
used	O
to	O
describe	O
wrapped	O
fibre	B-Architecture
optic	I-Architecture
cables	O
for	O
installation	O
on	O
power	O
lines	O
.	O
</s>
<s>
The	O
name	O
"	O
SkyWrap	O
"	O
is	O
one	O
of	O
three	O
related	O
brand	O
names	O
introduced	O
by	O
FOCAS	O
in	O
1990	O
to	O
describe	O
its	O
fibre	B-Architecture
optic	I-Architecture
cable	O
products	O
used	O
in	O
the	O
construction	O
of	O
power	O
utility	O
communications	O
networks	O
,	O
the	O
others	O
being	O
SkyLite	O
OPGW	B-Device
and	O
SkySpan	O
ADSS	O
.	O
</s>
<s>
Rayfos	O
is	O
a	O
portmanteau	O
name	O
constructed	O
from	O
"	O
Raychem	O
"	O
and	O
"	O
fibre	B-Architecture
optic	I-Architecture
system	O
"	O
.	O
</s>
<s>
Wrapped	O
optical	B-Architecture
fibre	I-Architecture
cable	O
technology	O
was	O
developed	O
independently	O
in	O
the	O
UK	O
and	O
Japan	O
in	O
the	O
early	O
1980s	O
.	O
</s>
<s>
The	O
initial	O
development	O
involved	O
an	O
all-dielectric	O
fibre	B-Architecture
optic	I-Architecture
cable	O
with	O
a	O
sheath	O
made	O
from	O
tracking	O
resistant	O
material	O
.	O
</s>
<s>
The	O
first	O
installation	O
was	O
carried	O
out	O
on	O
a	O
33kV	O
overhead	O
distribution	O
line	O
between	O
sub-stations	O
at	O
Hartley	O
and	O
Goudhurst	O
in	O
Kent	O
,	O
UK	O
in	O
December	O
1982.The	O
choice	O
of	O
a	O
33kV	O
line	O
indicates	O
the	O
expected	O
market	O
for	O
the	O
technology	O
–	O
building	O
communication	O
networks	O
over	O
local	O
distribution	O
lines	O
when	O
transmission	O
and	O
sub-transmission	O
lines	O
were	O
expected	O
to	O
be	O
equipped	O
with	O
OPGW	B-Device
.	O
</s>
<s>
Raychem	O
sold	O
the	O
wrapped	O
optical	B-Architecture
fibre	I-Architecture
cable	O
technology	O
to	O
Cookson	O
Group	O
plc	O
in	O
1987	O
.	O
</s>
<s>
BICC	O
also	O
had	O
a	O
technology	O
licence	O
from	O
Furukawa	O
,	O
but	O
carried	O
out	O
extensive	O
development	O
work	O
to	O
make	O
the	O
product	O
suitable	O
for	O
the	O
European	O
market	O
:	O
BICC	O
re-designed	O
the	O
cable	O
to	O
use	O
loose-tube	O
technology	O
and	O
so	O
provide	O
a	O
zero-strain	O
environment	O
for	O
the	O
optical	B-Architecture
fibres	I-Architecture
at	O
all	O
operating	O
conditions	O
of	O
the	O
overhead	O
line	O
;	O
the	O
tug	O
and	O
wrapping	O
machine	O
were	O
re-designed	O
to	O
reduce	O
the	O
overall	O
load	O
on	O
the	O
conductor	O
during	O
the	O
installation	O
process	O
.	O
</s>
<s>
The	O
wrapping	O
machine	O
is	O
self-balancing	O
with	O
the	O
fibre-optic	B-Architecture
cable	O
payload	O
held	O
on	O
a	O
pair	O
of	O
drums	O
arranged	O
one	O
on	O
either	O
side	O
of	O
the	O
host	O
conductor	O
and	O
therefore	O
on	O
either	O
side	O
of	O
the	O
axis	O
of	O
the	O
machine	O
.	O
</s>
<s>
A	O
second	O
Russian	O
company	O
,	O
Scientific	O
Innovations	O
,	O
introduced	O
a	O
more	O
conventional	O
design	O
of	O
wrapping	O
machine	O
in	O
the	O
mid-2000s	O
,	O
with	O
a	O
single	O
drum	O
of	O
fibre	B-Architecture
optic	I-Architecture
cable	O
and	O
a	O
counterbalance	O
arm	O
.	O
</s>
<s>
The	O
final	O
commercial	O
developments	O
of	O
wrapped	O
cable	O
systems	O
took	O
place	O
in	O
France	O
in	O
about	O
2005	O
when	O
RTE	O
,	O
the	O
national	O
electricity	O
transmission	O
utility	O
began	O
to	O
install	O
substantial	O
quantities	O
of	O
optical	B-Architecture
fibre	I-Architecture
cables	O
including	O
OPGW	B-Device
and	O
wrapped	O
cables	O
.	O
</s>
<s>
There	O
are	O
three	O
basic	O
technology	O
requirements	O
for	O
a	O
wrapped	O
cable	O
system	O
–	O
a	O
fibre	B-Architecture
optic	I-Architecture
cable	O
with	O
suitable	O
performance	O
for	O
installation	O
on	O
an	O
overhead	O
power-line	O
;	O
a	O
device	O
for	O
carrying	O
out	O
the	O
wrapping	O
operation	O
(	O
wrapping	O
equipment	O
)	O
and	O
the	O
appropriate	O
hardware	O
to	O
stabilise	O
and	O
complete	O
the	O
installation	O
.	O
</s>
<s>
Wrapped	O
fibre	B-Architecture
optic	I-Architecture
cable	O
must	O
provide	O
the	O
following	O
characteristics	O
:	O
</s>
<s>
Sufficient	O
strain-margin	O
to	O
protect	O
the	O
optical	B-Architecture
fibres	I-Architecture
at	O
the	O
extremes	O
of	O
the	O
overhead	O
line	O
operating	O
window	O
:	O
low	O
night-time	O
or	O
winter	O
temperatures	O
cause	O
the	O
host	O
conductor	O
to	O
shrink	O
,	O
high	O
day-time	O
or	O
summer	O
temperatures	O
cause	O
expansion	O
.	O
</s>
<s>
Strong	O
winds	O
and	O
built	O
up	O
layers	O
of	O
ice	O
will	O
cause	O
conductors	O
to	O
stretch	O
even	O
more	O
,	O
requiring	O
high	O
levels	O
of	O
strain	O
margin	O
in	O
the	O
fibre	B-Architecture
optic	I-Architecture
cable	O
design	O
.	O
</s>
<s>
These	O
characteristics	O
are	O
unique	O
to	O
OPAC	O
and	O
mean	O
that	O
wrapped	O
cables	O
are	O
designed	O
and	O
manufactured	O
specifically	O
for	O
the	O
application	O
:	O
generic	O
fibre	B-Architecture
optic	I-Architecture
cables	O
cannot	O
be	O
used	O
for	O
wrapped	O
cable	O
installations	O
.	O
</s>
<s>
Tight-buffer	O
cable	O
designs	O
do	O
not	O
provide	O
sufficient	O
strain	O
margin	O
and	O
the	O
optical	B-Architecture
fibre	I-Architecture
transmission	O
performance	O
is	O
compromised	O
under	O
strong	O
winds	O
,	O
heavy	O
ice	O
accretions	O
and	O
at	O
high	O
temperatures	O
.	O
</s>
<s>
In	O
cables	O
based	O
on	O
a	O
single	O
loose	O
tube	O
design	O
,	O
the	O
optical	B-Architecture
fibres	I-Architecture
have	O
too	O
much	O
freedom	O
of	O
movement	O
along	O
the	O
cable	O
axis	O
.	O
</s>
<s>
Consequently	O
,	O
mechanical	O
energy	O
in	O
the	O
form	O
of	O
wind-induced	O
vibration	O
of	O
the	O
host	O
conductor	O
causes	O
the	O
optical	B-Architecture
fibres	I-Architecture
to	O
move	O
gradually	O
‘	O
downhill’	O
and	O
allowing	O
the	O
excess	O
fibre	O
length	O
to	O
collect	O
in	O
the	O
low	O
point	O
of	O
the	O
span	O
.	O
</s>
<s>
In	O
order	O
to	O
cope	O
with	O
these	O
temperatures	O
,	O
the	O
sheath	O
of	O
a	O
wrapped	O
fibre	B-Architecture
optic	I-Architecture
cable	O
must	O
be	O
made	O
from	O
a	O
high-temperature	O
material	O
or	O
it	O
must	O
be	O
crosslinked	O
to	O
prevent	O
melting	O
.	O
</s>
<s>
The	O
installation	O
machinery	O
carries	O
a	O
drum	O
of	O
fibre	B-Architecture
optic	I-Architecture
cable	O
along	O
the	O
host	O
conductor	O
on	O
the	O
overhead	O
line	O
,	O
passing	O
the	O
drum	O
around	O
and	O
around	O
the	O
conductor	O
.	O
</s>
<s>
Motive	O
power	O
may	O
be	O
provided	O
by	O
a	O
petrol	O
engine	O
or	O
a	O
battery	B-Algorithm
pack	I-Algorithm
.	O
</s>
<s>
For	O
example	O
,	O
those	O
designs	O
using	O
electric	O
motors	O
tend	O
to	O
use	O
the	O
battery	B-Algorithm
pack	I-Algorithm
as	O
part	O
of	O
the	O
counterweight	O
system	O
.	O
</s>
<s>
Counterweights	O
are	O
required	O
for	O
two	O
separate	O
purposes	O
:	O
to	O
counter	O
the	O
turning	B-General_Concept
moment	I-General_Concept
of	O
the	O
wrapping	O
machine	O
and	O
to	O
balance	O
the	O
cable	O
drum	O
payload	O
.	O
</s>
<s>
The	O
turning	B-General_Concept
moment	I-General_Concept
arises	O
because	O
the	O
wrapping	O
machine	O
passes	O
a	O
heavy	O
drum	O
of	O
cable	O
around	O
the	O
machine	O
axis	O
so	O
as	O
to	O
wrap	O
the	O
fibre	B-Architecture
optic	I-Architecture
cable	O
onto	O
the	O
host	O
conductor	O
.	O
</s>
<s>
Wrapped	O
cable	O
systems	O
incorporate	O
several	O
unique	O
pieces	O
of	O
hardware	O
that	O
are	O
required	O
to	O
anchor	O
the	O
fibre	B-Architecture
optic	I-Architecture
cable	O
to	O
the	O
conductor	O
,	O
to	O
protect	O
the	O
cable	O
as	O
it	O
passes	O
over	O
or	O
around	O
supporting	O
poles	O
and	O
towers	O
of	O
the	O
overhead	O
line	O
,	O
and	O
to	O
control	O
electric	O
field	O
effects	O
in	O
installations	O
on	O
phase	O
conductors	O
.	O
</s>
<s>
There	O
are	O
two	O
variants	O
of	O
wrapped	O
optical	B-Architecture
fibre	I-Architecture
cable	O
systems	O
for	O
installation	O
on	O
overhead	O
electricity	O
power	O
lines	O
:	O
they	O
differ	O
in	O
the	O
nature	O
of	O
the	O
host	O
conductor	O
.	O
</s>
<s>
This	O
means	O
that	O
the	O
fibre	B-Architecture
optic	I-Architecture
cable	O
and	O
joint	O
closures	O
on	O
the	O
grounded	O
side	O
of	O
the	O
PTG	O
can	O
be	O
accessed	O
and	O
worked	O
on	O
safely	O
,	O
even	O
if	O
the	O
overhead	O
line	O
is	O
energised	O
to	O
full	O
system	O
voltage	O
.	O
</s>
<s>
This	O
process	O
typically	O
involves	O
lashing	O
one	O
or	O
more	O
copper	O
telephone	O
cable	O
,	O
co-ax	O
cable	O
TV	O
cable	O
or	O
fibre	B-Architecture
optic	I-Architecture
cable	O
to	O
a	O
pre-installed	O
steel	O
messenger	O
wire	O
using	O
a	O
steel	O
lashing	O
wire	O
and	O
a	O
device	O
called	O
a	O
'	O
spinner	O
 '	O
or	O
'	O
lasher	O
 '	O
.	O
</s>
<s>
OPAC	O
specifically	O
refers	O
to	O
fibre	B-Architecture
optic	I-Architecture
cables	O
attached	O
to	O
overhead	O
power	O
lines	O
where	O
the	O
host	O
conductor	O
is	O
part	O
of	O
the	O
overhead	O
electricity	O
system	O
.	O
</s>
<s>
This	O
is	O
an	O
attractive	O
concept	O
for	O
many	O
power	O
utilities	O
because	O
it	O
means	O
that	O
the	O
communications	O
network	O
is	O
under	O
their	O
own	O
control	O
and	O
can	O
be	O
tailored	O
to	O
meet	O
their	O
particular	O
requirements	O
with	O
suitable	O
attributes	O
such	O
as	O
redundancy	O
,	O
latency	O
and	O
bandwidth	B-Algorithm
.	O
</s>
<s>
Since	O
fibre	B-Architecture
optic	I-Architecture
cables	O
provide	O
very	O
high	O
bandwidth	B-Algorithm
-	O
much	O
more	O
than	O
a	O
power	O
utility	O
would	O
normally	O
require	O
-	O
many	O
power	O
utilities	O
are	O
able	O
to	O
generate	O
revenue	O
from	O
their	O
communications	O
networks	O
by	O
leasing	O
bandwidth	B-Algorithm
or	O
spare	O
optical	B-Architecture
fibres	I-Architecture
to	O
other	O
operators	O
such	O
as	O
mobile	O
phone	O
companies	O
or	O
ISPs	O
.	O
</s>
<s>
Three	O
different	O
types	O
of	O
fibre	B-Architecture
optic	I-Architecture
cable	O
have	O
been	O
developed	O
for	O
installation	O
on	O
overhead	O
power	O
utility	O
lines	O
:	O
Optical	B-Device
Ground	I-Device
Wire	I-Device
(	O
OPGW	B-Device
)	O
,	O
All-Dielectric	B-Device
Self-Supporting	I-Device
(	O
ADSS	O
)	O
cable	O
and	O
Optical	B-Device
Attached	I-Device
Cable	I-Device
(	O
OPAC	O
)	O
.	O
</s>
<s>
OPAC	O
cables	O
are	O
most	O
typically	O
used	O
when	O
access	O
to	O
the	O
overhead	O
line	O
is	O
difficult	O
(	O
for	O
example	O
,	O
in	O
remote	B-Protocol
areas	I-Protocol
or	O
,	O
conversely	O
,	O
in	O
crowded	O
urban	O
areas	O
)	O
or	O
when	O
an	O
overhead	O
line	O
is	O
structurally	O
too	O
weak	O
to	O
support	O
the	O
extra	O
weight	O
of	O
an	O
ADSS	O
cable	O
.	O
</s>
