This article has some really good descriptions of what's going on as the light interacts with the atoms in the fibers. [https://en.wikipedia.org/wiki/Refractiv

This article has some really good descriptions of what's going on as the light interacts with the atoms in the fibers. [https://en.wikipedia.org/wiki/Refractive_index https://en.wikipedia.org/wiki/Refractive_index]