On crosstalk mechanisms in cables composed of several unshielded twisted pairs

Reduction of near end crosstalk (NEXT) and far end crosstalk (FEXT) in data links is very important for reduction of error rate and link´s reliability. Three mechanisms of NEXT and FEXT may be distinguished in data communication links with cables incorporating several unshielded twisted pairs (UTP)s such as DM-to-DM coupling between UTPs running in the same cable, DM-to-CM and vice versa partial mode conversion in the same cable, DM-to-CM and vice versa partial mode conversion in interface circuits. This paper provides experimental evidence that mechanism DM-to-CM and vice versa partial mode conversion in the same cable and DM-to-CM and vice versa partial mode conversion in interface circuits may be dominant in a specific situations, dependent on factors, like cable quality, longitudinal balance of interface circuits, cable length etc.