Apparatus and method for controlling semiconductor laser module

Abstract

Disclosed is an apparatus for controlling a semiconductor laser module wherein despite an increase in laser driving current owing to aging of the laser module, temperature control can be performed accurately so as to render constant the actual temperature of the laser module and prevent a change in lasing wavelength that accompanies a change in temperature. The apparatus includes a photodiode for sensing optical intensity of the laser; an APC circuit for controlling driving current of the laser in accordance with an output from the photodiode; a thermistor for sensing the temperature of the laser module; an ATC circuit for driving an electronic laser-cooling device in accordance with an output from the thermistor; and a current-quantity sensing circuit, which is connected to the APC and ATC circuits, for sensing the driving current of the laser output from the APC circuit. Data obtained by measurement of actual temperature of the laser module in relation to the laser driving current is stored in the ATC circuit in advance. The data obtained by measurement, laser driving current information output from the current-quantity sensing circuit and temperature information output from the thermistor are compared and the driving current of the cooling device is set, based upon the result of the comparison, in such a manner that the actual temperature of the laser module is rendered constant.