Abstract: A tunable optical amplifier is used as a wavelength-selective high-gain element in a subcarrier-multiplexed fiber optic transmission system for providing a direct optical domain-to-baseband conversion of a selected optical channel. A high-speed diode laser optical transmitter is modulated by a plurality of independent information channels that are carried on separate, appropriately spaced carrier frequencies. An optical receiver, coupled to the transmitter by way of an optical fiber, includes a tunable narrow-bandpass semiconductor laser optical amplifier having a gain bandwidth smaller than wavelength distances between adjacent ones of the carrier frequencies, a photodetector coupled to the output of the amplifier, and polarization controlling means coupled to the fiber in front of the optical amplifier for maximizing gain in the optical amplifier.

Abstract: In a vector transform coding (VTC) scheme for image and video compression, a multi-layered codebook structure and a dynamic bit-allocation scheme in the vector transform domain are employed. The main advantage of this technique is that distortion is controlled by dynamically allocating more bits to vectors causing larger distortions and less bits to vectors causing smaller distortions.

Abstract: In a cellular system configuration, the location of a mobile station is determined from the acquisition of cellular network data pertaining to the mobile station, and the translation of such network data into a corresponding geographical position profile. The cellular system includes a mobile station locator entity for receiving from a mobile switching center the network data such as cell and/or sector ID and trunk group member number. The mobile station locator translates the network data into position information such as geographic coordinates (latitude and longitude), resolution (radius), and angle values for sectorized cells.

Abstract: A video coding scheme based on wavelet representation performs motion compensation in the wavelet domain rather than spatial domain. This inter-frame wavelet transform coding scheme preferably uses a variable-size multi-resolution motion compensation (MRMC) prediction scheme. The MRMC scheme produces displaced residual wavelets (DRWs). An optimal bit allocation algorithm produces a bit map for each DRW, and each DRW is then adaptively quantized with its respective bit map. Each quantized DRW is then coded into a bit stream.

Abstract: A Y-junction optical switch includes an input branch and two output branches optically coupled to the input branch at a junction. A single one of the output branches has an electrode. The two output branches are designed to have dissimilar optical refractive indices under a non-biasing condition.

Abstract: A cryptography-based entity authentication device (EAD) operated by a remote entity located at a subscriber site enables a telephone switch or computer system to identify and verify the authenticity of the entity. In one embodiment, the EAD encrypts a random digital sequence transmitted by a host facility and returns the encrypted signal to the host for comparison with another encryption signal generated locally by the host. If a match is detected, this serves as confirmation that the remote entity possesses the same encryption key as the host, therefore verifying the authenticity of the remote entity. Otherwise, the entity is deemed fraudulent and access is denied. In another embodiment, the host and subscriber site each include a respective time generation means which are maintained in relative time synchronicity. The EAD generates and encrypts a time signal for comparison with another encrypted time signal generated locally by the host.

Abstract: A network interface module operably connected to a subscriber's television receiver and to a switched broadband digital network includes a fiber-compatible digital transceiver. A downlink receiver in the transceiver detects video/audio/data information that is time-multiplexed within a serially transmitted digital signal optically transmitted by the switched digital network as a broadband digital downlink channel. The detected information is decoded into a parallel format of video/data samples, audio samples, and recovered sample clock that are applied to a digital switch in the television receiver.

Abstract: A novel variable-size block multi-resolution motion estimation (MRME) scheme is presented. The motion estimation scheme can be used to estimate motion vectors in subband coding, wavelet coding and other pyramid coding systems for video compression. In the MRME scheme, the motion vectors in the highest layer of the pyramid are first estimated, then these motion vectors are used as the initial estimate for the next layer and gradually refined. A variable block size is used to adapt to its level in the pyramid. This scheme not only considerably reduces the searching and matching time but also provides a meaningful characterization of the intrinsic motion structure. In addition, the variable-MRME approach avoids the drawback of the constant-size MRME in describing small object motion activities. The proposed variable-block size MRME scheme can be used in estimating motion vectors for different video source formats and resolutions including video telephone, NTSC/PAL/SECAM, and HDTV applications.

Abstract: An Asynchronous Transfer Mode (ATM) cell alignment assembly aligns an incoming ATM cell within an internal time slot of an ATM matrix by controllably time-delaying the cell before being switched by the matrix. The alignment assembly includes a 53-byte-wide shift register having a serial input receiving the incoming ATM cell, and fifty-three parallel outputs each coupled to a respective input of a 53.times.8 programmable crosspoint switching array. Each output of the array is coupled to an input of a shift register having eight parallel inputs and a serial output coupled to a respective input of the ATM matrix. The crosspoint switching array establishes only a single selected switching path through the array in accordance with the desired time delay, and is reconfigured upon the arrival of each incoming ATM cell.

Abstract: A broadband space switch matrix includes a parallel combination of individual switch modules each comprising a cascade of pass-transistor selectors, NAND gates, and inverters arranged into a multi-stage tree multiplexing configuration. The switching speed is increased by isolating each switching crosspoint from the stray capacitive loading in the matrix.

Abstract: A solder geometry for epi-down diebonding an optoelectronic component to a heat sink platform includes a solder deposition pattern having exposure windows to create gaps or diebond bridges in the solder pattern. The active regions of the components are disposably registered within the gaps of the solder pattern.

Abstract: A waferboard assembly incorporates mechanical registration features into a substrate platform to facilitate the passive alignment of lasers integrated on a chip to fibers in integral contact with the substrate. The waferboard includes two front pedestal structures and one side pedestal structure, and two vertical post structures within a mounting region defined by the pedestal struutures. The laser chip is mounted on the vertical post structures, and placed in concurrent abutting contact with the pedestal structures. The waferboard is fabricated by etching the substrate to form the front and side pedestal structures, and etching the substrate to define the grooves. In order to form the post structures, a polyimide material is deposited on the substrate using an appropriate mask.

Abstract: A junction field effect transistor, specifically a static induction transistor. The N-type source regions are formed as two zones. First, relatively lightly doped first zones are formed by ion-implanting doping material relatively deeply into the semiconductor material. Then relatively heavily doped second zones are formed by ion-implanting doping material to a relatively shallow depth within the first zones to leave portions of the first zones interposed between the second zones and the remainder of the semiconductor material. The resulting devices exhibit reduced gate-drain junction capacitance at low drain bias voltages thereby improving device capacitance linearity.

Abstract: Electrical circuitry of CMOS inverter circuits in cascade providing a compatible interface between ECL logic levels and CMOS logic levels. The ECL input is applied to the gate of the N-type transistor of the first inverter circuit. A threshold control circuit includes a CMOS inverter circuit with the gate of the N-type transistor connected to a reference voltage and the gate of the P-type transistor connected to its drain is connected to the gate of the P-type transistor of the first inverter circuit. The threshold control circuit adjusts the threshold voltage of the first inverter circuit so as to compensate for changes in current flow through the N-type or P-type transistors, thereby permitting operation over extreme variations in circuit parameters under situations of poor operating tolerances and wide temperature variations.

Abstract: A heterostructure device includes a ridge-waveguide laser monolithically integrated with a ridge-waveguide rear facet monitor (RFM). An integral V-groove etched directly into the device substrate enables passive alignment of an optical fiber to the active region of the laser. The laser and RFM facets were formed using an in-situ multistep reactive ion etch process.

Abstract: A base station in a cellular communications system is connected to a plurality of remote cellular sites by a communications link having a base terminal coupled to a remote terminal by two optical fibers. The base terminal receives RF downlink channels from the base station and optically transmits the RF channels as a non-overlapping composite signal to the remote terminal on a first fiber. The RF downlink channels are individually recovered at the remote terminal and distributed to disignated cell sites. The remote terminal also functions to receive RF uplink channels from the cell sites and optically transmit the RF channels as a non-overlapping composite signal to the base terminal on a second fiber. The RF uplink channels are indivicually recovered at the base terminal and forwarded to the base station.

Abstract: Electrical circuitry of CMOS inverter circuits in cascade providing a compatible interface between ECL logic levels and CMOS logic levels. The MOS transistors of the first inverter circuit of the series are approximately three times larger than the MOS transistors of the same type in subsequent inverter circuits of the series. The ECL input is to the gate of the N-type transistor of the first inverter circuit. A threshold control input is connected to the gate of the P-type transistor of the first inverter circuit. This configuration increases the operating speed of the first inverter circuit and permits controlling the threshold voltage in order to stabilize the output duty cycle.

Abstract: Apparatus and method for determining the concentration of NOx in a gas mixture. The gas mixture is supplied to two electrodes at which different NOx decomposition conditions are present. The electrodes may be of different materials or sizes or may be positioned in different gas enclosure environments. The NOx decomposes at different rates at the two electrodes and an emf is thus produced between the electrodes. The concentration of NOx in the gas mixture is determined from the measured emf.

Abstract: A method of fabricating a semiconductor heterostructure includes the growth of a quantum well active region that is highly lattice-mismatched relative to a substrate. A buffer layer having a thickness above a critical value is grown on the substrate whereby the stress due to a lattice constant mismatch between the buffer layer and substrate is relieved through the formation of misfit dislocations. A strained superlattice structure is grown on the buffer layer in order to terminate any upwardly-propagating dislocations. An unstrained barrier layer is subsequently grown on the superlattice structure. The fabrication method concludes with the growth of a quantum well structure on the unstrained layer wherein a lattice constant mismatch between the quantum well structure and the unstrained barrier layer is smaller than the lattice constant mismatch between the quantum well structure and the substrate.

Abstract: The present invention describes an apparatus and method for shutting off an electrodeless lamp such that it can be restarted instantaneously at any time. The method involves reducing the applied microwave power in a controlled way the moment the lamp is turned off. The reduction of power is accomplished by modulating the microwave power with an ever decreasing duty factor or a decrease of analog power. This reduction in power results continually in reduced light output and lamp cooling while maintaining partial ionization of the lamp fill. Circuitry to accomplish this is also presented.