Hi mohammed hosni,
The problem that you are stating is very broad. Since there are different types of fibers existing (multi- and single mode: standard, dispersion shifted, non-zero dispersion shifted), and it’s known that each of them have a wide range of parameters, it is important to indicate the purpose of performed modeling first. Can you indicate yours, please? After that, can you tell about the software environment that you are planning to use for your models?