What is the role of total external reflection in optical fibers?

Total internal reflection is a critical phenomenon that enables optical fibers to effectively guide light along their length. When light travels through the core of the fiber, it encounters a boundary with the surrounding cladding. If the angle of incidence is greater than the critical angle specific to the core-cladding boundary, the light cannot pass through; instead, it reflects entirely back into the core. This process keeps the light bouncing within the fiber regardless of bends or twists, allowing it to travel significant distances with minimal loss of intensity.

The efficiency of total internal reflection is what makes optical fibers suitable for applications such as telecommunications and medical instruments. It enables the fibers to transmit data over long distances without substantial weakening of the signal, as the light remains confined to the core. This is in contrast to mechanisms such as allowing light to escape or changing the diameter of the fiber, which do not contribute to the fiber's primary function of light transmission. The role of color change is also irrelevant in this context, as the focus is on maintaining the integrity of the light signal rather than altering it.