Optical fiber with double coating

Double-coated fiber optic refractive index profile for high power fiber lasers and amplifiers. c core, i inner shell, o outer shell.

The dispersion-compensating profile of the index of refraction in a double-coated optical fiber. c core, i inner shell, o outer shell.

Optical fiber with double coating ( born DCF, double-clad fiber ) is a type of optical fiber , which consists of three layers. The inner layer is called the core, the surrounding layer is called the inner shell, and the outer layer is the outer shell. All three layers have different refractive indices .

There are two different types of DCF. The first was developed in the early stages of the development of fiber technology and was intended to change the dispersion of optical fibers. In fibers of this type, the core conducts most of the luminous flux, and its shells change the waveguide signal dispersion. The second type of DCF was developed in the 1980s for use in fiber amplifiers and fiber lasers . In them, the core is doped with ions of rare-earth elements . The inner shell and the core form a light guide in which generation occurs, and the inner outer shell forms a light guide in which the pump radiation propagates. In laser and amplifier DCF, the refractive index decreases in steps with the distance from the center of the fiber. The outer shell is often made of polymeric materials .