use volterra series to get the nonlinear function from nonlinear system.
The result of simulation can be found at "Simple report in pdf/01-Simulation volterra series.pdf".
The code file is "Volterra series code.mlx"
Task02: Theory SER and Simulated SER for 2PAM, 4PAM, 8PAM, OOK. SER for 4PAM after MZM modulation, and the result after using Volterra series. code "main".