HELLO SAHIL SINGH..
You must go through the tutorial of the opti-fiber tool..it will provide you with an option to design double clad fiber…The “Material Properties” allows the user to specify the Sellmeier and nonlinear coefficients of the fiber material. It also displays the material refr. index as a function of wavelength. For the dispersion model it is assumed that the fiber profile consists of regions with only the host material and doped regions. One of the dopants rises the refractive index, while the other dopant lowers it…Please try going through the optifiber tute..I hope it will, be of some help..
Thanks & regards