Simple thing to attach a fiber optic and collimating lens to a panel, with a spacer. we only had a few hundred microns of tolerance, but this centers the fiber. It's crude, but it works.
Made with OpenSCAD.
You probably want to change the screw hole locations for whatever you are trying to attach the fiber to. Print in a dark opaque plastic, or use a sharpie marker to prevent stray light. If you have warp to your printed thing, you might need to cut some black felt to act as a gasket to seal out stray light. Attach with screws, and screw in the collimating lens. The threads are so fine, they just cut into PLA.
The other object in the picture is http://www.thingiverse.com/thing:33222