Patent ID: 7106768

Claim:
A control circuit for controlling a laser diode to emit light with a magnitude and an extinction ratio by supplying a bias current and a modulation current, the control circuit comprising: a load section for generating a signal that corresponds to an optical current generated by a light receiving element in accordance with the magnitude of the light emitted from the laser diode; a control section for selecting a combination of the bias and modulation currents based on a comparison of the signal with a reference value from a group of combinations, each combination including a pair of bias and modulation currents specified such that the light emitted from the laser diode exhibits a predetermined magnitude and the extinction ratio, and outputting a first and second control signals for controlling the bias and modulation currents, respectively, in accordance with the selected combination; a bias current circuit section for generating the bias current supplied to the laser diode in accordance with the first control signal, and a modulation current circuit section for generating the modulation current supplied to the laser diode in accordance with the second control signal.