hi dhiman sir..thanx for replying.
I hv taken an example from the optiwave samples for wdm systems.. it had 16 channels.. i changed it to 4 channels so that i could start frm basic..
when changing to 4 channel i got this waveform which is different from the one i got when i simulated the sample example..
now i ll try changing the filter as suggested by damian sir.. i hope it works well.. anyway thanx a lot