Channel Operating Margin (COM) for PAM-4 links with support for TX non-linearity and time skew.
Reading time: 4 minutes
COM (Channel Operating Margin) is a copper link margin and pass/fail tool popular in PAM-2 and PAM-4 25 Gb/s and faster standards. COM relies on a number of simplifications in which the non-linearity of the link is considered to be part of the penalty. But as the link technology develops past the earlier COM usage, dividing the non-linearity assumption offers a path to link improvement: some of the transmitter non-linearity can be an advantage, rather than a penalty. In this white paper, the authors consider a number of modifications to COM which make it applicable to non-linear PAM-4 links.