Hello Samia,
The two effects XGM and XPM are different in their initiation conditions. Attached please find a reference on XGM in SOA. There are examples on XPM in OptiSystem example library located at the following link. You may check it for more information.
C:\Users\USER NAME\Documents\OptiSystem 16.1 Samples\Fiber analysis and design\Optical Fiber Nonlinearity
Regards,
Ahmad