Optical fibers operate on the principle of total internal reflection, which keeps the light in the fiber core and guides it down the length of the fiber. Refraction refers to the bending of light as it passes from one substance to another. Light undergoes total custody within its cores. In comparison to free space optics considered so far, fibers confine light to a small volume, which prevents power loss by diffraction. As such, optical signals can propagate over large distances enabling, among others, fast and reliable communication all over the world. They consist of three elements as shown in Figure 1: a central core, cladding and a protective coating.
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