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We used to use thick fishing line, it's not perfect of course but it worked. a lot of homes have fibre optics ornaments and christmas.

Well what I know about Optical fibers is that they are a wave guide for the light. And the light is coupled into the fiber so that it undergoes total internal reflection at the boundary of the fiber. I think Optical fibers are made from silica. You can check the Wikipedia link.

In terms of construction:

Optical fibers typically include a transparent core surrounded by a transparent cladding material with a lower index of refraction.