Hi Sahil.
Well in my opinion You can improve the quality factor of your system by increasing the input power of your system,but not so high because at high powers the non-linearity effects come into existence.
Also you can use DCF( dispersion compensating optical fiber) and optical gain amplifiers to increase the quality factor as well as transmission distance of your system.
For the problem of change in results i am attaching a link for your reference which might help you.