Dear Arjina,
please refer to the example (DP-16 QAM example with ADC.osd) located at the following link in OptiSystem Example Library for guidance on the ADC, which can be used for sampling and quantizing an analog signal.
C:UsersUSER NAMEDocumentsOptiSystem 18.0 SamplesComponent sample filesSignal Processing LibraryToolsElectrical
Regards,
Ahmad