Ultra-broadband Raman amplification with spatially diverse pumps

Summary form only given. Distributed Raman amplification (DRA) with multi-wavelength pumping can provide flat gain over very large bandwidths 80-100 nm. However, the noise figure of such ultra-broadband amplifiers increases strongly for shorter-wavelength signal channels lying close to the pumps. In this paper we show that the noise figure spectrum can be flattened by optimizing the pump distribution along the fiber, while the gain spectrum is flattened by optimizing the pump spectral distribution. We describe the backward pumped DRA by a standard model including stimulated and spontaneous (Stokes and anti-Stokes) Raman scattering among all (pump and signal) waves.