Optical apparatus and optical receiving method

An optical apparatus comprising:

• an attenuator configured to attenuate input signal light that has been input;
• an extractor configured to extract a first signal light having first modulation component of a target channel and a second signal light having a second modulation component of a target channel by making local oscillation light interfere with the signal light;
• a first photoelectric converter configured to convert the first signal light into a first electric signal;
• a second photoelectric converter configured to convert the second signal light into a second electric signal;
• a first amplifier configured to adjust a first gain of the first electric signal;
• a second amplifier configured to adjust a second gain of the second electric signal;
• and
• a processor configured to:
• detect a monitor value of respective the first modulation component and the second modulation component of target channel from an output signal of the first amplifier and the second amplifier,
• calculate a power value of the target channel from the detected monitor values,
• calculate a difference value between the power value and a target power value of the target channel,
• calculate a set attenuation amount by adding a current attenuation amount, which is currently set to the attenuator, to the difference value,
• control the first gain of the first amplifier and the second gain of the second amplifier so that the difference value of the target channel is minimized when the set attenuation amount is less than zero, and
• set the set attenuation amount to the attenuator when the set attenuation amount is zero or more.

An optical receiving method being performed by an optical apparatus, the method comprising:

• detecting a monitor value of a target channel from an output signal of an amplifier included in the optical apparatus,
• calculating a power value of the target channel from the detected monitor value,
• calculating a difference value between the power value and a target power value of the target channel,
• calculating a set attenuation amount by adding a current attenuation amount, which is currently set to an attenuator included in the optical apparatus, to the difference value,
• controlling the gain of the amplifier so that the difference value of the target channel is minimized when the set attenuation amount is less than zero, and
• setting the set attenuation amount to the attenuator when the set attenuation amount is zero or more.