The basic, well-known of the fiber task is to transmit the optical signal along an optical fiber. To achieve this, you should reduce energy losses which result from reflections on the border of core - clad. However, in some cases, the light output can be derived by side surface the fiber. Luminous flux through side surface of optical fiber is realized in many ways. It is possible to change local shape of cylindrical fiber or scattering light on border between core and clad. Side optical fiber with helical spiral core have a different way of side emission. It is the result of controlled scattering inside the optical fiber .