  The temperature dependences of optical loss and luminescence spectra have
been measured in visible and NIR spectral range for Bi-doped silica and
Bi-doped germanosilicate fibers for the first time. The temperature dependence
of luminescence lifetime for Si-associated active bismuth centers in
germanosilicate fiber was measured. It has been revealed, that distribution of
Bi3+ ions across the fiber preform is essentially different as compared to that
of NIR active bismuth centers. Data received indicates that NIR-active centers
are associated with the low oxidation state of bismuth ion and/or oxygen
deficient center of the glass structure.
