high - speed driver circuits interface with and enhance the performance of vertical - cavity surface - emitting laser diodes used within fiber optic communication systems , according to embodiments of the invention . a reference diode is formed from a first transistor , and a first current mirror sets a modulation current through the reference diode for driving a light - emitting device . a second current mirror sets a reference biasing current to maintain a constant bias of the reference diode . a first capacitor , charged by a differential amplifier and coupled to the reference diode , supplies complementary charge to the reference diode during differential input voltage transitions . components of the driver circuit provide asymmetrical operation of the laser , allowing rapid light - emitting - device turn - on and turn - off .