Properties of ytterbium-doped double clad fiber made in China

The double clad fiber made in China was fabricated by the modified chemical-vapor deposition (MCVD) technique. The geometric, fluorescence, and laser characters of the fiber were measured. The fiber has a 16 ?m diameter Yb-doped core with a numerical aperture (NA) of 0.18,and the inner cladding has a 400/450 ?m diameter for the longer/shorter axis with a NA of 0.36. The fluorescence spectrum ranged from 1 000~1 140 nm, and the spectrum width at 1 030 nm is greater than 50 nm．When one end of the fiber was pumped by a high-power laser diode with the launched power of 61 W, 32 W laser output was obtained with the slope efficiency of 64%. There is no evidence of saturation at high pump powers, so the output power can be further improved by optimizing the parameters.