Optical amplification apparatus

An optical amplification apparatus comprising:

• a wavelength demultiplexing section which receives an input WDM signal light, which separates the input WDM signal light into n signal lights with different wavelengths between which spacing is widened, and which outputs the n signal lights;
• n optical amplification sections each including:
• a first semiconductor optical amplifier which amplifies a signal light after the separation;
• an optical filter which performs filtering of an output light outputted from the first semiconductor optical amplifier at the time of the signal light after the separation being a WDM signal light by a transmission characteristic which is a product of a transmission characteristic that reduces a gain tilt in a wavelength direction that occurs at the time of the first semiconductor optical amplifier exercising auto level control of the output light and a transmission characteristic which compensates in advance for a gain tilt that occurs in a second semiconductor optical amplifier;
• and
• the second semiconductor optical amplifier which amplifies a transmitted light outputted from the optical filter, and
• a wavelength multiplexing section which combines n signal lights outputted from the n second semiconductor optical amplifiers.