Whatever you do, don't use actual glass fiber optic cable. It's difficult to work with and dangerous. The fiber is too thin to provide adequate illumination for scale modeling anyway.
I bought some plastic fiber from these guys a few years ago...
www.fiberopticproducts.com
I know the site looks kinda cheesy, but I didn't have any trouble with my order. Here's a direct link to their plastic fiber page.
http://www.fiberopticproducts.com/Unjacketed.htm
Good luck! I'd love to see what you do with it.
m@