Hello Gurinder
I have read the discussion abut your system and use of sample file.I just want you to add WDM analyzer after total distance of your loop and run the system.Open WDM analyzer then scroll the under tab to extreme right ,here you go to see the OSNR at each wavelength.
Try it and let me know,i havent a access of optisystem 13 so i couldnt help you to do this.I will definately see your system file and will try to change if any possible modification required. Thank you