Dear Uykra,
The PSK signal is represented by an amplitude and phase, which its field is defined as complex signal in OptiSystem. The amplitude is the square root of the intensity.
Please refer to the examples on PSK in OptiSystem Example Library located at the following link for guidance.
C:UsersUSER NAMEDocumentsOptiSystem 18.0 SamplesAdvanced modulation systemsPSK systems
Regards,
Ahmad