A simple method is provided for the performance comparison of the Raman-amplifie d optical-fiber transmission systems. The results show that, compared with conve ntional hybrid-Raman-amplification systems, the maximum transmission distance ca n be increased by about 10% and 30% separately, and the input signal power can b e decreased by about 6 dB for bidirectional-pumping all-Raman-amplification syst ems based on uniform or dispersion-managed transmission fibers.