For the FEXT
to be dimensionless, as the ratio of the noise voltage to the signal voltage, kf has to have units of nsec/in.
1000Base-T modeling on CAT 5 cabling has shown that ISI will be 104mV rms or approximately two orders of magnitude greater than NEXT and FEXT
at the input of the receiver (Source: Sailesh Rao, Level One Communications.
To achieve this, each component in the Enteraprise Category 6 line is designed and qualified to 250 MHz for NEXT, FEXT
, attenuation and return loss in component and channel testing.
The danger is that, ultimately, a switch supplier may have to produce a cabling manufacturer A Class E switch blade and a cabling manufacturer B Class E switch blade where the only difference will be the method of NEXT/ FEXT
(near-end/far-end crosstalk) cancellation within the interface socket
is similar but relates to the disturbance caused by one pair on another when measured at the far end.