Light inside the glass thread

Light bounces along the walls

The request has now become light that flashes on and off very fast. On and off stand for the numbers 1 and 0. The light races through the middle of a glass thread as thin as a hair. When it hits the wall at a slant, it does not leak out. It bounces back inside. So even when the thread bends, the light follows it all the way.

Why?If you are underwater in a swimming pool and look up at the surface at a slant, it looks like a mirror. The light cannot get out, so it bounces back. The middle and outer layers of the glass thread trap light in the same way.

Learn moreThe glass thread is called an "optical fiber," and the bouncing is called "total internal reflection." The zigzag in the picture is simplified. The thread is so thin that real light travels almost straight. The light it uses is invisible (infrared), and many different colors of light share one thread (the three colors in the picture).

Time

7.6 ms → 9 ms

Simplified route · light in glass at about 200,000 km per second