Fabrication of Yb-doped silica glass through the modification of MCVD process

A method to deliver Yb and Al compounds in vapor phase to the reaction/deposition zone has been devised for modified chemical vapor deposition (MCVD) process. By using this MCVD setup, we succeeded to prepare silica glass preforms presenting uniform dopants concentrations in the radial and longitudinal directions with good reproducibility. Preforms with a core diameter larger than 5 mm were easily prepared by depositing around 40 layers. By changing some parameters in the deposition step, such as carrier gases flow and temperatures of Yb(DPM)3 and AlCl3 furnaces, different concentrations of Yb and Al were incorporated into the core region of the silica glass preforms. By adjusting the Yb and Al concentrations, we succeeded to prepare preforms for large mode area (LMA) fiber with a change less than 10% of nominal refractive index.