The Sources, Characteristics and Severity of Differential and Common Mode, Alien, Crosstalk

摘要

Alien crosstalk is an electrical phenomenon of interest to the cabling industry, and arises between pairs, each residing within separate cables, reactively coupling with each other. The reactive coupling between these two pairs causes signals from a disturbing pair in one cable to interfere with signaling in a disturbed pair residing in the separate cable. While most attention has been directed to the differential mode of alien crosstalk between disturbing and disturbed pairs, the alien crosstalk from common mode conversion and coupling can be worse than the differential mode of alien crosstalk between pairs and becomes more evident after connecting hardware is added to each end of the cable in a permanent link. Theory and test lab data confirm the existence and severity of alien-crosstalk attributed to common mode sources. The sources, characteristics and severity of differential and common mode, alien crosstalk are explored, and various methods for mitigating each are examined in detail.While many manufacturers have achieved levels of alien crosstalk mitigation as required by draft standard(s), alien crosstalk from links and channels might be worse than originally surmised, because of unbalance in the attached connecting hardware. We've explored the severity and characteristics of crosstalk from multiple sources within the cabling system, and report our findings herein. The sources and severity of differential crosstalk are examined in detail, and the affect on alien crosstalk from unbalance in the connecting hardware is explored.