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Wire & Cable ASIA – September/October 2007
104
March/April 2012
2.2 Pair Lays at Cabling Studies
Extending the experimentation of pair lays into the cabling
process was necessary to confirm previous findings of
individual pairs and to measure the lays of at least two
individual pairs going into the cabling process at the
same time.
Using the process set points described in Section 2.1.2,
a simple 2x2 test matrix was set up to compare the
signatures of various pairs at the chosen set points of
pretwist ratio and bow speed. Only two of the pairs in
the cable were subjected to the 2x2 test matrix while the
remaining two pairs were run under constant process
settings as control points. The crosstalk interaction of the
two pairs under study was the primary point of interest
although the interactions with control pairs were also
measured. Near End Crosstalk (NEXT) measurements
were swept to a frequency of 1.2 GHz.
2.2.1 FFT of the individual pair lays
at cabling
The basic form of the FFT graphs was consistent with what
was found at the rewind station also described in Section
2.1.3. In this case, the FFT is performed on the ratio of two
pairs measured at cabling. In the FFT plot in
Figure 9
, the
signatures are seen from both pairs in the one plot. The
FFT components previously mentioned can be seen for
primary lays, twinner bow speeds, and pretwist ratios in
both pairs. However, at lower frequencies there are other
signatures of interest. The measurement equipment is also
sensitive to mechanical variations in the manufacturing
equipment.
Figure 10
shows a strong component that is related to the
bow of the cabler. Also visible is a sloping signature that
is believed to be related to the rotation of the take up reel
in the cabler. The slope is due to the increase in the take
up reel barrel diameter during the run, decreasing the
spool rotation rate. The cabler bow speed is an extremely
strong and steady signal that is a measure of the effect
on the cabler bow on the short term cabling speed. For a
perspective on the amount of cabler induced variation, the
pairs entering the cabler had an 8% peak to peak variation
in instantaneous speed. It is likely that much of that speed
change is accommodated by short term stretching and
relaxing of the pair.
2.2.2 NEXT Response for Various
Process Set Points
As mentioned in Section 2.1.4, without replication
actual statistical significance of performance cannot
This means that how the lay length is affected by pretwist
ratio depends on what setting for bow speed has been
chosen. It should be noted that the amount of change in
lay length accounted for by the process pretwist ratio is
still very small. Normally this might not be considered
significant to crosstalk performance. Without replication
of the test matrix, statistical significance of this change
cannot be determined. But it does give initial indication
that there may be some cause and effect in this
relationship.
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❍
Figure 7
: Main effects plot of set points and lay length
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❍
Figure 8
: Interaction plot of set points and lay length
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❍
Figure 9
: FFT of pair ratio showing signatures
of both pairs as well as other effects such as
the cabler equipment
Pair 1 Lay
Pair 2 Lay
Pair 1 Bow
Pair 2 Bow Pair 1 Pretwist
Pair 2 Pretwist
❍
❍
Figure 10
: FFT signature of cabling bow and
takeup spool
Cabler bow signature
Takeup Spool signature
Main effects Plot for Pair 2 % Dev
Data Means
Ineraction Plot for Pair 2 % Dev
Data Means
Mean of % Deviation from Target
Mean
Bow