Patent ID: 7782916
Filing Date: 2010-08-24
Classification: H01S

Abstract:
1. A laser diode driver that controls a driving current in accordance with a transmitting signal, the driving current being supplied to the laser diode based on a monitored signal derived from a photodiode that monitors optical output power of the laser diode, comprising: a first comparator configured to compare the monitored signal with a first threshold; an integrator configured to integrate an output of the first comparator; a processing unit configured to generate, by receiving an output of the integrator, a control signal that includes information of a change mode and a change rate, wherein the processing unit includes a second comparator and a correlation unit, the second comparator being configured to compare the output of the integrator with a second threshold; the correlation unit having an adder, a subtractor and a delay unit and to generate an output corresponding to the change mode, the adder adding an output of the delay unit with the output of the second comparator, the subtractor subtracting a preset value from an output of the adder, the delay unit delaying an output of the subtractor, wherein the correlation unit changing the control signal by a preset amount within a preset time in accordance with the change mode; wherein the processing unit provides the output of the subtractor as the control signal; and a current source configured to generate the driving current in accordance with the control signal output from the processing unit, wherein the change mode of the control signal corresponds to a state whether the driving current is to be increased or decreased, and wherein the change rate of the control signal is kept constant by the processing unit.