How Light Travels inside the Fiber

The fiber body is made from quartz glass and plastic. The center part (core) and periphery (cladding) are designed to have a different refractive index. A beam of light introduced into the core of the optical fiber travels while reflecting off the boundary surface between the core and the cladding. The core has a larger refractive index than the cladding. Along the boundary between materials with a different refractive index, light travels while changing direction.