Thank you very much Sam Sung for your replies. I have designed my networks as in the attached file like the sample of [FWM validation], I’ve added 2 more channels so now 4 channels entering the MUX. Channels frequencies are in THz (193.0, 193.1, 193.2, and 193.3). I got the result of optical spectrum analyzer before and after entering the fiber as shown in the attached files. I am new in this filed so I’m not sure how to analyze the results. I see new lines with some signals in the before file and then 2 lines with channels 193.2 and 193.3. Is this FWM signals, how can I change the channel spacing value? I tried to save the design as new project but
