Dear Muhammad,
you may check the examples in OptiSystem Example Library on the different topics and use them as guidance to build your desired design. Check the locations:
C:UsersUSER NAMEDocumentsOptiSystem 18.0 SamplesMetro and access systemsPON and CDMA systems
C:UsersUSER NAMEDocumentsOptiSystem 18.0 SamplesAdvanced modulation systemsOFDM systems
Regards,
Ahmad