The two fundamental components that allow a fiber to confine light are the core and the
cladding. Most of the light travels from the beginning to the end inside the core. The
cladding around the core provides confinement. The diameters of the core and cladding
are shown in this illustration, but the core diameter can vary for different fiber types. In
this case, the core diameter of 9 μm is very small—the diameter of a human hair is about
50 μm. The outer diameter of the cladding is a standard size of 125 μm. Standardizing the
size means that component manufacturers can make connectors for all fiber-optic cables.