An optical amplification system includes: a first amplification module configured to amplify at least a conventional band (C band) optical signal; a second amplification module configured to amplify a longer wavelength band (L band) optical signal; an attenuator configured to attenuate at least the C band optical signal to obtain a first optical signal and a second optical signal, where the attenuator is further configured to output the first optical signal to the second amplification module and output the second optical signal to a wavelength division multiplexing module, which is configured to combine and output the C band optical signal and the L band optical signal.