Fig. 1 shows the total loss spectra of the N-doped fiber
samples before and after the first irradiation to 0.94 MGy.
Both H2- and D2- loaded fiber samples demonstrated a lower
loss at k1.30 pn than the gas-free sample. Unlike the H2-
loaded piece, the D2- loaded sample exhibited a lower induced
absorption at h=1.55 p than the gas-free sample. From Fig. 1
we may conclude that a more considerable induced loss
reduction is observed in the D2-loaded sample (by a factorof - 5 at the both wavelengths of interest). However, the
effects of H2 ~ and D2 -loading are not as tangible in the near-
IR region as they are in the visible region in the case of puresilica-
core fibers [6]. There are several factors preventing
significant induced loss reduction at 1.30 and 1.55 p in the
presence of the gases. In the case of H,-loaded fiber, these are,
first of all, OH- and NH-goup absorption bands at 1.38, 1.24,
and 1.50 p, which increase as the result of hydrogen
incorporation into the glass network under radiation. H2
molecules which survived the irradiation are responsible for
the narrow 1.24 pn band and for the intense bands of theFig.1. Total loss ofN-doped fiber samples before and after 0.94 MGy
irradiation.