Gain saturation spectrum of backward-pumped broad-band Raman amplifiers.

The gain saturation of optical amplifiers due to changes in wavelength-division-multiplexed channel loading is characterized using a technique that determines the saturation effect on each channel. This channel gain saturation (CGS) measurement is applied to a broad-band backward-pumped Raman amplifier and used to study how the CGS spectral tilt is controlled by the relative contributions of the pump-to-pump and channel-to-channel interactions. The CGS is also used to measure the gain dependence on the channel add-delete pattern.