Gain transients in copumped and counterpumped Raman amplifiers

Gain transients in both copumped and counterpumped distributed Raman amplifiers were investigated as a function of signal launch power, fiber type, and surviving signal wavelength for the first time. We found that gain transients are much more pronounced in a copumping scenario than in a counterpumping scenario for the same operating conditions. We also found that the dependency of gain transients on signal launch power, fiber type, and surviving channel wavelength follows the pump-depletion theory. A simple transient suppression technique with better than 0.2-dB ripple capability was also demonstrated.