Dear Zahid,
Currently, OptiSystem doesn’t support probabilistic shaping. However, you may use the Matlab component in OptiSystem to add your code to shape the transmitted pulse.
Examples on how to use the Matlab component are found at the following link.
C:\Users\USER NAME\Documents\OptiSystem 17.0 Samples\Software interworking\MATLAB co-simulation
We are in process of adding this feature in the coming main release 18.0.
Regards,
Ahmad