Optical amplification device and light amplification method

An optical amplification device comprising:

• a demultiplexer demultiplexing an optical wavelength multiplexed signal to be input into a first optical wavelength multiplexed signal having a first wavelength band and a second optical wavelength multiplexed signal having a second wavelength band located in a longer wavelength band than the first wavelength band;
• a first optical amplifier amplifying the first optical wavelength multiplexed signal;
• an excitation light controller controlling excitation light that amplifies the first optical wavelength multiplexed signal in the first optical amplifier;
• a second optical amplifier amplifying the second optical wavelength multiplexed signal;
• and
• a multiplexer multiplexing the amplified first optical wavelength multiplexed signal and the amplified second optical wavelength multiplexed signal, and outputting the multiplexed optical wavelength multiplexed signal to a Raman amplifier, wherein
• the first optical amplifier adjusts intensity of light of the first optical wavelength multiplexed signal in such a way that intensity of light in the second wavelength band is compensated for by a Raman effect in the Raman amplifier,
• the first optical amplifier causes, when loss in an optical fiber through which the optical wavelength multiplexed signal to be input passes increases, an amplification factor of the first optical wavelength multiplexed signal to be larger than a setting in a normal condition, and
• the excitation light controller controls the excitation light of the first optical amplifier, based on a control signal received from a monitoring device when loss in the optical fiber through which the optical wavelength multiplexed signal to be input passes increases.