Hello Atul Sharman, Good Afternoo,
I was referring to modulation that you need to modulate as your wish of type (eg. QAM, DQPSK, BPSK etc.) but most importantly you 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 and apply respective demodulation and thats all, in this case you need to be very much careful while demultiplexing the signal at the WDM demux (i.e. central wavelength and bandwidth).
from your reply “the functionality of the add component it simply adds a wavelength into the transmitted signal from the CW Laser” this does not mean that you need to apply directly CW laser output to the OADM component. can do modulation as per your wish and then apply.
Regards,
Dhiman