Title: Luminescence in germania-silica fibers in 1-2 μm region,
Abstract: We analyze the origins of the luminescence in germania-silica fibers with
high germanium concentration (about 30 mol. % GeO2) in the region 1-2 {\mu}m
with a laser pump at the wavelength 532 nm. We show that such fibers
demonstrate the high level of luminescence which unlikely allows the
observation of photon triplets, generated in a third-order spontaneous
parametric down-conversion process in such fibers. The only efficient approach
to the luminescence reduction is the hydrogen saturation of fiber samples,
however, even in this case the level of residual luminescence is still too high
for three-photon registration.