Gaze at the reflector while slowly moving the edge of a white piece of paper across your eye, and just before it blocks your vision, you'll see small white bits appear in the facets of the bicycle reflector. If you take apart a bicycle reflector, you'll find that the faceted back of the plastic is NOT a metal-coated mirror. When light within a transparent material strikes the inner surface of that material at a glancing angle, it reflects totally. Total Internal Reflection causes the surface of water to look silver when viewed from underwater. It causes the bottom of a glass cup to look silver except where you touch it with wet fingers.
Optical fibers are just reflective tubes.
Shine light down the tube, and it keeps going because it bounces from the walls. They look like transparent fishing line. I bet you're way ahead of me now. All rights reserved.