Influence of the Substrate tube Quality on TSL Features of Yb-doped Silica Preforms of Optical Fibres

We have demonstrated by spectral analysis of thermally stimulated luminescence that depending on the quality of the substrate-tube used during the MCVD technique, Ybdoping of silica preforms might be responsible for both the formation of the non-bridging hole centres (NBOHC) and their amount within the final preform. If these centres as well as those originating from the substrate tube are still present even after drawing, they will give rise to absorbing defects and thus a detrimental effect – like photo-darkening on the performance of the ytterbium-doped optical fibres serving as amplifier (YDFA) or in high-power fibre lasers. To describe the TSL of Yb-doped preforms, we also propose a mechanism based on the oxidation/reduction process involving hole traps and Yb impurities as recombining centres. PACS