How To "Figure 8"
Cable for Intermediate Pulls in OSP Installations
On very long OSP runs (farther than approximately 2.5
miles or 4 kilometers), it may be necessary to
use an automated fiber puller at intermediate point(s)
for a continuous pull
or
pull from the middle out to both ends (midspan pull.)
When laying loops of
fiber on a surface during a pull, use “figure-8” loops
to prevent twisting the cable.
The figure 8 puts a
half twist in on one side of the 8 and takes it out on
the other, preventing twists.
Use
this procedure for pulling from one end:
1. Pull the cable out of the conduit or innerduct and
lay on the ground in a large "figure 8" pattern. The
size of the "8" will be determined by the size and
stiffness of the cable, but 6-12 feet (2-4 m) is a
common size. The end of the cable will be against the
ground - you might want a tarp or plastic sheet to keep
the cable clean. Pull slowly and carefully lay the cable
in the figure 8 pattern to keep it from becoming kinked.
2. Using several installers, pick up the cable and flip
it over so the end to be pulled to the next location is
on top.
3. Attach the end to the pull rope with appropriate
swivel pulling eyes and continue the pull.
For a "midspan pull," use these directions:
This
procedure eliminates having to flip the cable in the
Figure 8 on the ground over.
1. Place
the cable reel
a mid point on the long span (ensuring the maximum
pulling length in either direction would not be
exceeded).
2. Pull the one
end of cable through the conduit to one end of the
span.
3. Roll the
cable off the reel and Figure 8 the remaining cable on
the ground. The end on the cable will be on the
top of the figure 8.
4. Pull the
second end of the cable through the conduit to the
other end of the span.
A tech using "Figure
8" technique on a midspan pull in Kuala Lumpur,
Malaysia.
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