Germania-glass-based core silica glass cladding single-mode fibers (Delta n up to 0.143) with a minimum loss of 20 dB/km at 1.9 µm were fabricated by the modified chemical vapor deposition (MCVD) method. The fibers exhibit strong photorefractivity with the type-IIa-induced refractive-index modulation of 2 × 10-3. The Raman gain of 300 to 59 dB /(km ... W ) was determined at 1.07 to 1.6 µm , respectively, in a 75 mol.% GeO2 core fiber. Only 3 m of such fibers are enough for the creation of a 10-W Raman laser at 1.12 µ m with a 13-W pump at 1.07 µm . Raman generation in optical fiber at a wavelength of 2.2 µm was obtained for the first time.
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