1. Introducing multimode optical fibers

Optical fibers used in telecommunications are generally made of dielectric materials (in this article, glass or plastic) whose function is to confine and guide visible or infrared light over long distances. These optical fibers are made up of two concentric tubes of dielectric material, each with a different dielectric permittivity (and therefore a different refractive index). Under certain conditions, light is guided along the axis of revolution of the optical fiber into the material with the higher refractive index – in most cases, within the core of the fiber.