Hi sahil,
If you will use advanced modulation formats like CSRZ, DRZ, MDRZ, DPSK AND QPSK , it will give propagate over larger distance for appreciable Q-factor and minimum BER.
I have designed 8 channel wdm system using different advanced modulation format mentioned above. I think MDRZ IS best of csrz and drz.
Here, i am uploading osd file of WDM SYSTEM USING MDRZ modulation format.
HOPE THIS will help you to understand things more properly.