# In optical Multimode fiber MMF, what is the best pulse shaping filter that can be used to mitigate the ISI?

In telecommunications there are three pulse shaping filters:

Gaussian filter

raised-Cosine

Sinc filter

In fiber optics what is the most suitable pulse shaping filter that can be used to design the desired pulse shape to mitigate the Inter-symbol Interference (ISI)

The Gaussian filter is not a Nyquist filter. You know this because its impulse response is never zero, while a Nyquist filter must have its impulse response go to zero at all times $t = n T_0$. A Gaussian filter might be used in an MMF system because the MMF channel itself has a Gaussian response, so that a Gaussian filter is a channel-matching filter, optimizing received SNR, in these systems.