Micro fluorescence profiling of erbium doped fiber preforms

A micro-fluorescence technique for profiling the spatial distribution of erbium ions doped into optical fibre preforms is reported. Profiles have been compared using fluorescence at wavelengths of 0.553 and 1.5 µm to identify a critical erbium concentration of about 0.12 wt% Er3+, where the effects of clustering become apparent. The addition of core co-dopants has been studied and found to have no significant effect on the active ion distribution. The variation in 1.5 µm fluorescence lifetime with position across the core has been measured. A pronounced reduction (up to 66%) in this lifetime at the core extremities was observed and indicates the presence of local ion environment disordering.