Equalizer device, communication system, and equalization method

An equalization method in an equalizer device including:

• an optical matrix switch including a first terminal group including at least two first terminals and a second terminal group including at least two second terminals;
• an equalizer group including at least two equalizers, an input end of each of the equalizers being connected to one of the second terminals included in the second terminal group, and an output end of each of the equalizer being connected to one of the first terminals included in the first terminal group;
• and
• a variable attenuator being connected to one of the second terminals included in the second terminal group and attenuating an optical signal input to the optical matrix switch according to an amount of loss of the optical signal, the equalization method comprising
• changing a connection state between the first terminal and the second terminal,
• compensating for a tilt level of an externally input optical signal by setting an amount of attenuation by the variable attenuator according to an amount of loss of an optical signal input to the optical matrix switch and
• outputting a tilt-level-compensated optical signal as an optical output signal.