Distributed gain monitoring in a Raman amplifier based on a germania-glass-core silica-glass-cladding optical fiber

Gain monitoring OTDR-technique recently demonstrated by some of us is now applied for characterizing a short Raman amplifier. Spectrum/power-pump/signal mapping of Raman gain profile in 100-m-long germania-glass-core fiber with a record gain ~260 dB/km/W is reported. (2 pages)