Hello Yang,
Since you are at the beginning level, did you consider the tutorials at the OptiSystem website from chapter “Doped Optical Fiber Amplifiers”? Here is the link for that: https://optiwave.com/resources/applications-resources/optical-system-automatic-control-simulation/ Or you can also take a look at more complex pumping techniques https://optiwave.com/resources/applications-resources/optical-system-optimizing-the-pump-power-and-frequencies-of-raman-amplifiers-for-gain-flatness/