Patent attributes
A problem to be solved is to make plural Ge PDs uniform in sensitivity by heating based on the Ge PDs with heaters photocurrent measurements taken by a current monitor, and thereby curb deterioration in a common-mode rejection ratio. A photodetector according to the present invention is a germanium photodetector (Ge PD) that uses germanium or a germanium compound in a light absorption layer, the photodetector including two or more Ge PDs placed to receive an input differential signal; a current monitor adapted to measure photocurrents of the two or more Ge PDs; resistors adapted to heat the respective Ge PDs; voltage sources connected to the respective resistors and capable of controlling voltage values independently of each other, wherein the voltage sources are connected with the current monitor, and the voltage sources manipulate voltages applied to the heaters such that current values output by the two or more Ge PDs will match each other.
