Abhishek Shrama Hi,
You are trying to make NZDSF in Optisystem.
It is NOT possible in Optisystem software.
For Modelling, simulation, and design of single mode fiber designs such as Corning SMF-28, dispersion flattened or shifted fibers and multimode optical fibers, you can use OptiFiber software. It uses numerical mode solvers and other models specialized to fibers for calculating dispersion, losses, birefringence, and PMD.