hi umer syed I think you have to rearrange your query because u have mentioned dispersion and dispersion..and I don’t feel there should be any difference as u have have used same terms.
if u mean distortion and dispersion then distortion is related to signal quality and dispersion is related to fiber..distortion is common term used technically for all types of signals but for optical signals we often use dispersionand there are various reasons for the cause of dispersion..i hope u will find better answer if you try to google it.
Thanks
regards