${\rm Er}^{3+}$ Concentration Effects in Commercial Erbium-Doped Silica Fibers Fabricated Through the MCVD and DND Technologies

Commercial Erbium doped silica fibers fabricated through the modified chemical vapor deposition and direct nanoparticle deposition processes where Er³⁺ concentration is varied in a wide range are characterized by means of analyses of Er³⁺ fluorescence decay kinetics and nonlinear absorption coefficient at 978-nm pumping. Through theoretical modeling of the results of the entire experiment, the values of key parameters for the concentration-related effects, i.e., homogeneous and inhomogeneous upconversion processes, are determined.