calculating pulse fidelity

Pulse replication will be based on bandwidth and group delay through which the pulse must pass. As bandwidth is reduced higher harmonics are attenuated which soften edges of pulse. Any filtering by the comm channel has some group delay versus frequency associated with it. If the delay varies across frequency then the Fourier components will be shifted in time adding to the distortion of the pulse.

(group delay is rate of change of phase versus frequency. A constant slope of phase versus frequency is a fixed and constant group delay.)

You can calculated the effect by doing Fourier series, act on series with comm channel mathematical description, and rebuild the result to see what the pulse distortion looks like. The definion of fidelity can be edge rounding, droop, ringing, intersymbol interference, just to name a few things. Commonly observed by 'Eye' diagram.