How can I tell the difference between jitter and cable loss in an eye diagram?

How can I tell the difference between jitter and cable loss in an eye diagram?

Jitter can be differentiated from cable loss because jitter is not really changed over long lengths of cable whereas other signal parameters such as rise-time, fall-time and amplitude are severely impacted by long runs of cable. If you see an eye diagram that has the eyes "closed" but the rise/fall time and amplitude are within normal ranges then you most likely have a lot of jitter. The opposite situation is if you have a closed eye diagram with normal jitter values but stretched out rise/fall times and reduced amplitude, this is most likely the result of long cable lengths.