Hello,
I agree with you about the dependence of the amplitude of generated tones using FWM on the wavelength separation.
Could you please email me your OptiSystem project as zip file to check it? I need to check the setting of all other parameters in the layout.
you may email the zip file to ahmad.atieh@optiwave.com.
Also, please let me know the version of OptiSystem that you use?
Regards,
Ahmad