Tm/Ho profiled co-doped core area optical fiber for emission in the range of 1.6-2.1 µm.

Double-clad optical fiber with a multi-ring core profile doped with thulium and holmium fabricated by Modified Chemical Vapor Deposition Chelate Doping Technology (MCVD-CDT) is presented. The measured TmO and HoO complexes' weight concentrations were 0.5% and 0.