Dear Ngoc,
You can’t load OptiSystem Project to the forum. You may load it as Zip file.
There are few examples in OptiSystem example library located at the following address that can provide guidance on PONs. Please check them out. If the problem persists, please email me the file as zip file to ahmad.atieh@optiwave.com and let me know the version of OptiSystem that you use & the university that you study at.
C:UsersUSER NAMEDocumentsOptiSystem 19.0 SamplesMetro and access systems
Regards,
Ahmad