Hello Gaganpreet kaur
If you are working on more number of channels and dense channel spacings as you mentioned earlier.You can mitigate the effects of non linearities by using following things
1. Low input power
2. Use of low factor of gamma of fiber
3. you can use DSP to compensate the effects of non linearities
5. Broad band amplification
6. Correct frequency band
Also matlab will be the best solution to your system