  The fabrication of Er-doped ZrO2-based nanocrystalline phase-separated silica
optical preforms by the MCVD and solution doping techniques is presented.
Fabricated preform cores are nearly transparent and contain phase-separated
rare-earth doped nanocrystalline particles with diameters mainly in a range
from 20 to 80 nm. High concentrations of erbium and aluminium in preform cores
of about 0.3 and 14 mol%, respectively have been achieved without defects on
the core-cladding interface. Spectral losses in a range 800-1600 nm and
fluorescence spectra of erbium ions around 1550 nm measured on a fibre drawn
from the preform are reported.
