Double cladding optical fiber

The utility model relates to a double cladded optical fiber used for high power optical-fiber laser, consisting of a fiber core 1, an inner cladding 2, a boundary 3, and an outer cladding 4. The boundary 3 which is formed on the inner cladding 2 is composed of a plurality of circle arcs a [n]; the radius R [3] of each circle arc a [n] is different from others, presenting asymmetrical distribution. The boundary 3 consists of a plurality of tangential paths b [n], too; the length L [n] of each tangential path is different from others and presenting asymmetrical distribution. The utility model provides a double cladded optical fiber used for high power optical-fiber laser to resolve the background technical problems and adopts the inner cladding structure of the asymmetric boundary to make the local area stable state of the pump light in the inner cladding disappear during the transmitting process, increase the number of the pump light traveling through the fiber core, enhance the coupling efficiency of the pump light and the fiber core, enhance the absorption efficiency of the double cladded optical fiber and reduce the length of the optical fiber. Because the absorption efficiency is enhanced and the gain of the optical fiber is increased, the threshold value of the laser is lowered; because the rest pump light is less, the stability of the laser output is enhanced.