Hi,
As Eye Opening Penalty (EOP) is defined as twice the average signal level
divided by the smallest value of a one sample minus the largest value of a
zero sample. The EOP is not a power penalty. So it has nothing to do with
the fiber light loss budget. It shows the posibility of choosing a decision
threshold and should be less than 1 dB. So, if twice the average signal level
divided by the smallest value of a one sample is less than the largest value of a
zero sample, then eye-opening penality will be negative .
Eye Opening is related to pulse smearing. Pulse smearing is due to
optical dispersion of the fiber (among other things).