WCA March 2012

Ineraction Plot for Pair 2 % Dev Data Means

Main effects Plot for Pair 2 % Dev Data Means

Mean

Mean of % Deviation from Target

Bow

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. ❍ ❍ Figure 7 : Main effects plot of set points and lay length

❍ ❍ Figure 8 : Interaction plot of set points and lay length

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 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 were swept to a frequency of 1.2 GHz. 2.2.1 FFT of the individual pair lays at cabling

Pair 1 Lay

Pair 2 Lay

Pair 1 Bow Pair 2 Bow Pair 1 Pretwist

Pair 2 Pretwist

❍ ❍ Figure 9 : FFT of pair ratio showing signatures of both pairs as well as other effects such as the cabler equipment

Cabler bow signature

Takeup Spool signature

❍ ❍ Figure 10 : FFT signature of cabling bow and takeup spool

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Wire & Cable ASIA – September/October 2007 March/April 2012