3D optical waveguide error

Hello everyone,

What I'm trying to do is basically simulate an optical fiber in 3D. I thought it would be a simple task but I'm running into an error.

I created an optical fibre with an air cladding. The fiber is very thin (.5 um radius).

I thought all I would have to do was create an input port and and exit port, perform a boundary mode analysis on both ports and then add the frequency domain study.
When I do this i get the following error:

Undefined value found.
- Detail: NaN or Inf found when solving linear system using SOR.

Does anyone know what I am doing wrong? Any input would be greatly appreciated.

Thank you,
Mark