Patent ID: 7366428

Claim:
An optical receiver for receiving signal light, comprising: an avalanche photodiode having a light-receiving area; a PIN photodiode having a light-receiving area and disposed separately from the avalanche photodiode; a half mirror for receiving the signal light and dividing the signal light into two signal-light components, the half mirror being optically coupled to the light-receiving area of the avalanche photodiode and the light-receiving area of the PIN photodiode such that one of the signal-light components is incident on the light-receiving area of the avalanche photodiode and the other signal-light component is incident on the light-receiving area of the PIN photodiode; and a control means for controlling, on the basis of an output current value obtained from the PIN photodiode, one or both of a supply voltage applied to the avalanche photodiode and a current which flows through the avalanche photodiode such that an avalanche multiplication factor of the avalanche photodiode is maintained at a predetermined value.