Bell Telephone Laboratories

Charles Arthur Brackett

Richard G Smith

Stewart David Personick

A transitionally encoded data signal, which has a DC component and a bipolar AC component, is detected in an asynchronous receiver which includes a filter 16 for separating the AC and DC components into separate circuit paths, an amplifier 22 in the AC path, a feed-forward network 28 in the DC path for establishing a pair of threshold levels V.sub.th+ and V.sub.th- for detecting the positive and negative bipolar pulses, respectively, a dual comparator 26 for comparing the output of the amplifier with each of said threshold levels and for generating an output pulse whenever the thresholds are exceeded, and a set-reset flip-flop 34 responsive to the output pulses for reconstructing the binary signal which was transitionally encoded at the transmitter. Use of the receiver in a fiber-optic lightwave system is specifically described.

Asynchronous data receiver

Described is a stabilization circuit for reducing the sensitivity of a junction laser to variations in the amplitude of drive current pulses. The circuit comprises a transistor connected in common emitter configuration, a junction laser connected between the collector and emitter, a photodetector connected between a voltage node and the emitter, a nonlinear element, such as a switching diode, connected between the node and the base, means for coupling a portion of the laser radiation to the photodetector, and means for coupling an input signal (e.g., current pulses) between the base and emitter. In one embodiment the photodetector is an avalanche photodiode to provide gain and the nonlinear element is a switching diode. In another embodiment the nonlinear element is a switching transistor to provide gain and the photodetector is a PIN photodiode.

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Summit, NJ, United States of America

Charles Arthur Brackett