Luminescence in germania–silica fibers in a 1–2 μm region

We analyze the origins of the luminescence in germania–silica fibers with high germanium concentration (about 30 mol.% GeO2) in the region of 1–2 μm 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 downconversion 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.