Bell Telephone Laboratories

At&t Bell Laboratories

Clarence Burke Swan

Fridolin L Bosch

James Kevin Plourde

Gay Leon Dybwad

Donald Floyd Linn

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.

Laser driving means

A system for improving performance of lasers in optical digital systems. This is accomplished by superimposing a microwave modulation current on the normal digital signal input. In the case of single mode lasers, this results in essential elimination of modal noise without any eye margin degradation. In the case of multimode lasers, the superimposed signal obviates various nonlinearities in the light output versus current characteristic which can cause eye margin degradation.

Laser digital transmitter

An apparatus for stabilizing microwave oscillator circuits is disclosed. The apparatus comprises a dielectric resonator positioned in the vicinity of a microwave semiconductive device for completing a feedback path between two electrode circuits of the device. A dielectric spacer is positioned between the resonator and the electrodes for supporting the resonator and controlling the magnitude of coupling between the two electrode circuits. A folded mechanical structure is described wherein the oscillating device and the resonator are located at the fold for improving the frequency stability of the oscillator. The microwave semiconductive device may be a bipolar transistor or a field effect transistor.

Microwave oscillator having feedback coupled through a dielectric

An improved low-noise microwave amplifier comprises a circuit arrangement coupled in parallel with a GaAs FET amplifying stage for reducing transmission loss in case of dc power failure or amplifying stage failures. The circuit arrangement comprises two microwave circulators and a microwave isolator connected therebetween.

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Allentown, PA, United States of America

Clarence Burke Swan