WCA March 2012

be determined. However, repeated samples were taken from the trial to validate qualitative findings noted below. Distinct differences can be seen in some of the set points mainly in the form of spikes in the NEXT graphs. At one combination of pretwist ratio and bow speed an obvious spike appears in the NEXT graph at 80 MHz. By changing only the pretwist ratio for both pairs, this spike is reduced or eliminated. At the opposite setting of bow speed, the change in pretwist ratio has a similar effect on a spike that is seen at about 125 MHz. 3 Conclusion As a result of this study there were a number of important findings. It has been shown that the high speed measurement technology used in this study provides an accurate and repeatable method for measurement of lay length value of twisted pairs. The use of this technique over long lengths along with real time data collection of the speed of the pair provides insight, through FFT analysis, into the stability of, and patterns within, the twinning process. Mainly, lay variation signatures are found at the fundamental pair lay length, the twinner bow speed and the pretwist speed. The nominal lay length values are affected by changes in process set points, specifically pretwist ratio and its interaction with bow speed. Quantitatively, these changes are relatively small. But there appears to be a relationship between the inputs and the lay lengths that would require further validation for statistical significance. An additional and potentially larger impact to the nominal lay length can be seen between machine types. Subsequent processes can add to or have an impact on the variation signatures. This was evident in the measurement of pairs at cabling. Additional signatures for cabler bow speed and take up spool diameter were seen. Finally, and most importantly, crosstalk performance is significantly affected by the process changes in these experiments. Investigation into the changes in lay length values as well as changes in the variation signatures are needed to verify the contribution from each factor. It is reasonable to assume that there are other process inputs that could have an impact to the lay variation as there are other unexplained signatures seen at both twinning and cabling. Their impact to crosstalk performance would require further investigation.

❍ ❍ Figure 11 : Spike at 80 MHz in one trial

❍ ❍ Figure 12 : Spike missing at 80 MHz after pretwist changes

❍ ❍ Figure 13 : Spike reduced at 125 MHz after pretwist changes

Kenneth E Cornelison Beta LaserMike Dayton, Ohio USA Email : ken.cornelison@betalasermike.com Website : www.betalasermike.com

Stephen Pearson Tyco Electronics Greensboro , North Carolina USA Email : shpearson@te.com Website : www.te.com

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Wire & Cable ASIA – September/October 2007 Wir & Cable ASIA – March/April 12