Systems and methods are provided for determining and compensating for the laser slope efficiency of a light source positioned in an optical transmitter in order to properly set a modulation current for the light source. In one embodiment, a method for setting a modulation current for the laser of an optical transmitter is disclosed, wherein data relating to the laser transmit power and laser bias current at a plurality of laser bias current levels are sensed. A processor is then employed to calculate a slope efficiency of the laser using the data. The processor then determines a desired modulation current for the laser using the slope efficiency. Then if needed, the modulation current of the laser is modified to match the desired modulation current.