urgent help:(FDTD questions)

Hi
Could any one help me in solving these questions?

I try to simulate waveguide propagation through conventional fiber using FDTD:

1- How to make the wave propagates through the high index core (Total internal reflection).

2- How to make the wave propagates through the low index core (Band gap effect).


plz heeeeeeeeeeeeeeelp me
Thanks

please if you found answers to your thess questions please i want to know it because i am also want to simulat optical fiber in FDTD

and if you have any materials relatede to this please put it here


with my best regards