Jam192,
I think you could model this fiber with almost any light analysis program. I know you can with Zemax. If you want, you can download a trial version of Zemax and try to find an example that matches your scenario. You can also call Zemax and speak to them about your situation. I have had very good experience with them. Keep in mind that they are optical engineers over there and use optical engineering terms which you may or may not know. Good luck.