We propose a decomposition of bidirectionally pumped Raman-amplified long spans into two independent amplifiers. This decomposition leads to a simple optimization process of the transmission. An example of a 10-Gb/s wavelength-division multiplexed system, consisting of 14200-km spans, is described. It presents the optimization of cogain and countergain levels, including constraints from double Rayleigh backscattering and repeaters. We also generalize this procedure to other span lengths.