Hi Aasif
I believe that if the program is regarding power coupling then it should work more properly in optigrating or optisytem. As i know about my program that i was trying to simulate in Matlab i could not get any result at all in Matlab But got the required results in Optisytem as it was meant to be for that. So i would suggest u to take the results of OptiGrating as the results u require. Rest I believe someone who has better knowledge of your query would answer it better.
Best Regards
Burhan