help please: question about modelling photonic crystal fiber

I try to modify the program of author: Susan C. Hagness fdtd2d.m which
implements the finite-difference time-domain solution of Maxwell's curl equations over a two-dimensional Cartesian space lattice comprised of uniform square grid cells. To illustrate the algorithm, a 6-cm-diameter metal cylindrical scatterer in free space is modeled.

I try to modify this program to implement conventional fiber optics of
i make the following changes:
1- epsoln_r for glass to be 2.1 and 1 for air surrounding
2- sigma=0 for both air and glass fiber
3- the diameter of the cylinder = 2 micro m

is there is any other modifications?