HELLO DHIMAN..
You have correctly mentioned it we cannot increase the launching power or keep it very high.. it needs to be on optimum side and as per the ITU-T guidelines. However in some cases just like FSO the launching power needs to be on higher side as it has to transmit wirelessly..
and u are right Nonlinear effects in optical fibers occur due to change in the refractive index of the medium with optical intensity but i don’t have any idea how to simulate that change.. Anyways it was a healthy discussion.
Thanks & regards