Impact of Cable Length on NEXT

REFERENCE NUMBER: C24-IWCS2018

AUTHORS: J. Poltz

VENUE: Presented at the 67th IWCS Conference/International Cable & Connectivity Symposium, October 14-17, 2018, Providence, RI, USA

ABSTRACT - Two pairs with varied lay length values were simulated in the presence of a ground wire, as components of a category cable core and finally as elements of an F/UTP cable in order to determine the impact of cable length on NEXT. The lay length values were selected intentionally to demonstrate NEXT resonance within the 1 MHz to 1 GHz frequency range used for testing the samples. The paper also describes the simulation environment used in the investigation. The study uses a set of different length samples (from 1 m to 100 m) to establish the impact of the sample length on NEXT. It is pointed out, that the samples behavior is strongly dependent on the presence of other cable components (core, screen). In isolated pairs, the increase of sample length leads generally to increase of crosstalk. In an isolated cable core, the crosstalk levels are very similar for all cable length samples. However, in the F/UTP model the shortest, 1 m long, sample of the cable demonstrated the worst crosstalk. There is also a discussion related to origins of the NEXT resonance and the approach used for automated generation of lay values that can be used to push NEXT resonance above the required spectrum.

NEXT simulation between pairs 1-3 with strong NEXT resonance at 666 MHz

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