Hello Dhiman. Greetings.
Well i completely agree with you when you are saying that we need to modulate as your wish of type like QAM, DQPSK, BPSK etc but most importantly we need to modulate the optical signal before you apply to add drop multiplexer, and accordingly extract the signal of definite wavelength at the receiver side. Undoubtedly.
I was able to change the modulation format of both the signals and got the desired results. Thank you anyway for your interest.
Regards
Atul Sharma