That's a brilliant idea. I have no idea of the sensitivity of the
method, but I would start with the following experiment. Take your
whole reel of optic fiber and see how well it transmits and preserves
the polarization of polarized light. A laser pointer will do as a
source, and you can use a polaroid on the output with some photo-
detector. If you can use the whole reel just pass a wire through the
center and ramp up the current. If you don't have immediate access to
the inner end of the fiber on the reel just wind it off onto another
reel, being careful to keep the end accessible.