Thanks a lot for your inputs.
To FvM:
This output pulse, however, is result from symmetrical ideal pulse with rising and falling time of 5 ps.
Then the question is, if it is happened due to the dispersion, why do we have asymmetrical behavior between rising and falling edge? rising edge should also experience this dispersion behavior.
In addition, in my opinion, even if dispersion distorts the signal, non-linearity should partially cancel the distortion effect (soliton)
Gaussian pulse response would not experience this asymettrical behavior by its definition and its mathematical model. FFT of gaussian shape in time domain would result in gaussian shape frequency response. This is already implying that both of rising and falling edge of gaussian behavior are symmetric.
1st order Low-pass filter behavior would not mimic this effect as well because both of rising and falling time is exponentially increasing & decreasing (we can prove this mathematically using differential equation).
My question is to answer the reason why the non mirror-symmetrical pulse response appears as a long tail in the edge shape... not to see the rising and falling time.
But you've got the good point: S-parameter channel description are presuming a linear model and don't involve non-linear signal distortion.
What if the s-parameter file I am using is generated based on somewhat non-linear channel characteristics? would it be the cause of this problem?