Laser driving means
AssigneeAT&T Bell Laboratories
InventorsFridolin L. Bosch, Clarence B. Swan
Life of this patent
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Abstract
Disclosed is means for driving a laser whereby a dc bias current is supplied to keep the laser normally above threshold, and a modulation current brings the laser below threshold when a pulse appears. In one embodiment, a feedback controlled bias current source (11) and modulation current source (15) are coupled to the p-side terminal of the laser (10) while a constant voltage source (27) is coupled to the n-side terminal of the laser in a way which results in subtraction of the modulation current from the dc bias current. This mode of operation essentially eliminates laser overshoot and more nearly equalizes rise and fall times of the light pulses.
Claims12
A laser transmitter comprising a laser and circuit means for driving said laser in response to a data input signal, said circuit means comprising:
- circuit means including a constant current source for supplying a dc bias current to said laser sufficient to raise the current through said laser above its lasing threshold level;
- and
- circuit means including a constant current source for supplying to said laser a modulation current corresponding to said data input so that said modulation current is subtracted from said dc bias current and the appearance of a pulse in said modulation current lowers the current through said laser to below its lasing threshold level.
A method of operating a laser to produce optical pulses in response to a data input signal comprising the steps of:
- applying to said laser a dc bias current having a value exceeding the lasing threshold of the laser;
- and
- applying to said laser a modulation current corresponding to said data input so that said modulation current is subtracted from said bias current and the resulting current through the laser is below the threshold level whenever a pulse appears in said modulation current.
Dependencies are inferred from the claim text.