This repo contain a Eye Diagram of a PCM M-ary, with a Raised Cosine Filter, Noise's Effect and Band Width Restrictions.
For M = 2, we have a Binary Comunication System, but for more symbols, we need M > 2.
For α (Roll-off) in [0 , 0.5 , 0.75 ,1]
your perfomance is:
With a Digital System without Noise, The ideal eye diagram don't have ISI and your perfomance will be clear.