A method of amplifying a signal light includes initially multiplexing a signal
light and a pumping light, initially amplifying the signal light initially demultiplexing
so as to separately output the amplified signal light and the pumping light, and
modifying a waveform of the amplified signal light so as to compensate for waveform
distortion of the signal light along a transmission path of the signal light and
providing an output of a waveform modified signal light. Thereafter, the waveform
modified signal lights is secondarily multiplexed, secondarily amplified, and secondarily
demultiplexed with a waveform of amplified signal light being compensated for waveform
distortion of the signal light along a transmission path of the signal light and
providing an output of a waveform modified signal light.
