Hello Love Kumar,
As far as your query is concerned i don’t think there is a way to calculate the crosstalk directly in optisystem. As such i have not found any component in the optisystem component library that could be used to measure crosstalk of any system that we design here. However, there are certain .osd files where there is mentioned something regarding crosstalk in a design. As mentioned by Hamza Ali Abbas Khan , you can refer to the link where there is a WDM ring architecture which you may find useful . For your convenience i will repost the link below. Try to refer to it and i hope you will get some idea about it.
Regards