40G Certifier NEXT/PSNEXT Graph

Knowledge Base - Solution

How do I interpret the NEXT or PSNEXT results graph on my Viavi 40G Certifier?
NEXT is near end crosstalk and is defined as the different in amplitude between a transmitted signal and the crosstalk received on another pair. As NEXT is near end, it is referring to crosstalk received at the same end of the cable as the transmitted signal. As we do not want a lot of crosstalk, the bigger the difference between the levels the better. The Y axis maps with a small value at the top and larger on the bottom so a passing signal will plot below the limit line. PSNEXT is Power Sum NEXT and is the summed effect of three pairs causing crosstalk on one pair and a passing value would again map below the limit line.