PREPARATION AND OPTICAL-PROPERTIES OF SILICA OPTICAL FIBERS WITH AN AL2O3-DOPED CORE

Preforms for drawing optical fibres, whose silica cores are doped with P2O5 and Al2O3 and codoped with Yb3+, Ex(3+), Nd3+ MgO or the newly studied codopants Cr3+ and Mn2+ are prepared by the extended modified chemical vapour deposition (MCVD) method. A novel approach to the MCVD preparation of porous layers doped with higher P2O5 levels, based on the deposition of this layer during the opposite traverse of the heating burner, is tested. The absorption spectra of the drawn fibres have been measured and the observed absorption bands have been identified as being due to the codopant Mn2+, Cr3+, Yb3+, Nd3+, Er3+ Or MgO.