Improvement of Raman amplifier gain flatness by broadband pumping sources

We propose the design of 100-km flat-gain backward-pumped Raman amplifier with four broad-linewidth 14XX-nm pumps with less than 0.2-dB gain-ripple in 1528-1584 nm bandwidth. We have found this pump scheme as a very efficient approximation for continuous pump spectrum with the similar Raman gain flatness parameters. Also, we present investigations of pump instability impact on resulting Raman gain flatness.