Abstract: Disclosed is a semiconductor laser modulation control system, and a method thereof. The system includes a drive circuit (1) for supplying a drive current to a semiconductor laser (2) in accordance with an input data, to modulate the input data into an optical signal of the semiconductor laser (2). The optical signal is either at a high intensity state or a low intensity state in accordance with an input data of "1" or "0", in respective time slots of the input data. The system further includes a duty ratio conversion circuit (3) for converting the duty ratio of the input data in such a way that the low intensity state of the optical signal is returned to the high intensity state within each time slot of the input data, whereby the relaxation oscillation is suppressed.

Abstract: In a system in which a light emitting element such as a semiconductor laser, light emitting diode or the like is modulated directly by a drive current corresponding to an input modulation signal, the drive current is selected to correspond to an integrated value of the input modulation signal, thereby compensating for deterioration of the modulation characteristic based on a thermal effect in the light emitting element to obtain a desired optical output waveform.