Abstract: A digital burst-mode packet data receiver receives high-speed burst-mode packet data signals superimposed on a lower frequency data signal. The receiver includes a first detector for detecting the received high-speed burst-mode packet data which is reset during the time period between consecutive bursts of the high-speed packet data signal. A second detector detects the lower frequency data signal during a predetermined portion of the time period between consecutive bursts of the high-speed packet data.

Abstract: A dc-coupled packet mode digital data receiver, for use with an optical bus uses peak detectors to adaptively establish an instantaneous logic threshold at the beginning of a data burst. A dc compensator, responsive to outputs of the peak detectors, shunts dc or low frequency currents, corresponding to "dark level" optical signals, from the input of the receiver.

Abstract: A dc-coupled packet mode digital data receiver, for use with an optical bus, uses a peak detector(s) to adaptively establish an instantaneous logic threshold at the beginning of a data burst. A reset circuit resets the peak detector(s) and other circuits of the receiver in response to an end-of-packet reset signal, thereby enabling the reception of closely-spaced burst date packets which have greatly differing power levels.

Abstract: Signal distortion in fiber optic systems is compensated for by forming decisions as to the transmitted information as a joint function of the received signal and of a feedback signal. The latter, in turn, is a function of decisions made for at least one signal transmitted over the fiber. The feedback signal determines the value of a threshold to which the received signal is compared in order to generate the decisions.

Abstract: A laser biasing stabilization circuit and method uses the second derivative of the optical light output of a laser with respect to the current through the laser, d.sup.2 L/dI.sup.2, in a feedback loop to control the laser bias current through the laser. The modulation current in the laser is controlled using a second, average power feedback loop.

Abstract: A burst mode digital data receiver automatically adjusts its logic reference voltage to be equal to one-half of the sum of the minimum and maximum excursions of a received data signal. The receiver includes a differential amplifier circuit which has a first input for receiving the data signal and a second input connected to a voltage reference circuit. The voltage reference circuit is responsive to an output signal from the amplifier circuit to produce the required logic reference voltage at the second input to the amplifier circuit by generating a feedback signal which causes the amplifier circuit to have a first gain value during the absence of the data signal and while the data signal is less than its peak amplitude and a second gain value approximately twice the first gain value for a predetermined time after the peak amplitude of the data signal is reached.

Abstract: A demultiplexer for demultiplexing a multiplexed input data signal into M output channels using M sequencer means clocked from an overlapping M phase system clock. The system clock operates at a frequency equal to the input data signal rate divided by M. Each sequencer means is clocked by a unique combination of the M phase system clock signals to select one data channel from the multiplexed input data signal. Since all sequencer means circuits are synchronized to the system clock, no variable delay lines are needed to align the timing between the circuit stages. A time delay latch is provided where needed in each sequencer means to enable all channels to output data concurrently. The demultiplexer includes a real-time data-framing capability to assure that the input data is correctly mapped to the proper output channels.

Abstract: A high data rate multiplexer (MUX) architecture includes front-end and rear-end MUXs clocked at a system clock rate equal to one-half of the MUX output data rate. The front-end MUX selects inputs under control of select signals derived from multiple phases of a select clock. The select clock is derived from the system clock. The number of select signals is equal to the multiplexing factor of the MUX.

Abstract: The novel technique for stabilizing an electronic device, e.g., a semiconductor laser, is disclosed. The technique can advantageously be used to stabilize the bias current of such a laser at or near the lasing threshold of the device. A preferred application of thus stabilized lasers is in optical communication systems. The inventive technique comprises determination of a derivative of a variable characteristic of the device operation, e.g., the voltage across a laser, with respect to a parameter, e.g., the laser bias current. The derivative is determined by a novel method. For the particular case of laser bias stabilization, the method comprises injecting one or more nonsinusoidal ac current components into the laser, and phase-sensitivity detecting the voltage changes at the ac frequencies. The method can, in principle, be used to determine derivatives of arbitrarily high order.

Abstract: An integrated array of pressure transducers capable of producing an analog output voltage representative of the applied pressure is proposed. The individual transducing elements (16) are defined by a three-layer structure including a thin layer of piezoelectric material (10) disposed between a reference potential plate (12) and a plurality of electrodes (15) contained in a silicon substrate (14). A force applied to a localized portion of the reference plate will cause a deflection of the piezoelectric material towards the electrodes on the substrate, inducing a capacitive charge on the electrode in the localized area. This capacitance is stores at a node A associated with the transducing element, and may be interrogated by a sensing circuit (18) located in the silicon substrate. Since the induced charge is directly proportional to the applied force, a measurement of the output voltage from node A will yield a direct indication of the localized force applied to the sensor.

Abstract: A substrate heating arrangement suitable for use in ultra-high vacuum MBE includes a filament responsive to a DC current for generating thermal energy, a metallic enclosure surrounding the filament and having an aperture at one end thereof, an intermediate semiconductor substrate parallel to and separated from a semiconductor growth substrate, and a substrate support mounted to the enclosure capable of holding the substrates in the prescribed relationship.The intermediate semiconductor substrate regulates the temperature on the surface of the semiconductor growth substrate to be less than or equal to a fixed temperature (approximately 1100.degree. C. for silicon) regardless of the DC current applied to the filament.

Abstract: A process for fabricating a high speed bipolar transistor is described wherein the collector, base and emitter layers are first grown using molecular beam epitaxy (MBE). A mesa etch is performed to isolate a base-emitter region, and a contact layer is grown using MBE over this isolated region to make contact with the thin base layer. The contact layer is selectively etched to expose the emitter layer, and metal is deposited to fabricate emitter, base and collector contacts.

Abstract: A molecular beam epitaxial method of fabricating a semiconductor device is disclosed wherein the dopant is implanted by establishing a plasma containing ions of the dopant and the ions are coupled through a drift chamber to impinge on the growing substrate surface. The plasma formed in the ion gun has ions of boron and arsenic and therefore the dopants selected for implantation can be determined by setting a mass filter present in the ion gun. A change to the dopant of the opposite conductivity type can be accomplished in seconds by simply readjusting the mass filter in the ion gun.

Abstract: A plurality of semiconductor lasers (431-434) and a photodetector (120) are mounted on a silicon substrate (100) having an integrated circuit (101) fabricated therein. The integrated circuit includes a biasing circuit (405) for establishing a threshold current level that is dependent on the output of the photodetector and a modulator circuit (404) for providing a modulation current that is dependent on the digital values in an input signal. A semiconductor switch (406) selects only one of the plurality of semiconductor lasers for activation by the biasing and modulator circuits. The integrated circuit also includes a circuit (408) that operates the semiconductor switch so as to selectively activate a different one of the plurality of semiconductor lasers in response to either a predetermined output from said photodetector or in response to an external supervisory signal.