Glass strands bounce light internally without losing photons

A closer look

You can treat light like water through a pipe if you trap it correctly. When a light beam enters an optical fiber, it hits the cladding boundary at a completely shallow angle. The difference in the refractive indices prevents the photon from crossing the barrier. Instead, it continuously ricochets off the internal walls in a state of absolute reflection, sprinting through miles of coiled glass without escaping or significantly dimming.