hi jyoti raina…
i think this topic has already been discussed on the forum,so you should refer to the same for your query.
For your reference i am attaching a link which might be of some help to you.In this topic one of the forum master has suggested to use raman amplifier as it gives better results than other amplifiers and the reason maybe the gain flattering phenomena in raman amplifier and usage of external pump.
with regards…