Abstract: Multistage Er-doped fiber amplifiers (EDFAs) advantageously use high numerical aperture (NA) fiber in the input stage, and low NA fiber in the output stage. The former typically is greater than 0.25, and the latter is less than 0.20. Such amplifiers can have high gain and low noise figure.

Abstract: An infrared collector for use in communications systems. The infrared collector employs a concentrator which concentrates infrared radiation received from some directions more than others. The concentrator is made of a dielectric material which is substantially transparent to infrared radiation and has a shape which is convex above a base plane determined by the top surface of an infrared radiation detector and in which any ray which connects any part of the top surface of the detector to any part of the concentrator above the base plane intersects the surface of the concentrator at an angle less than the critical angle for the material from which concentrator is made. The amount of concentration from a given direction is controlled by the curvature of the collector. The less a portion of the surface is curved, the less infrared radiation normal to the less-curved portion is concentrated.

Abstract: Heteroepitaxial growth of phosphorus-containing III/V semiconductor material (e.g., InGaAsP) on a non-planar surface of a different phosphorus-containing III/V semiconductor material (e.g., InP) is facilitated by heating the non-planar surface in a substantially evacuated chamber to a mass-transport temperature, and exposing the surface to a flux of at least phosphorus form a solid phosphorus source. This mass-transport step is followed by in situ growth of the desired semiconductor material, with at least an initial portion of the growth being done at a first growth temperature that is not greater than the mass transport temperature. Growth typically is completed at a second growth temperature higher than the first growth temperature. A significant aspect of the method is provision of the required fluxes (e.g., phosphorus, arsenic, indium, gallium) from solid sources, resulting in hydrogen-free mass transport and growth, which can be carried out at lower temperatures than is customary in the prior art.

Abstract: A system and method integrate mask layout tools to automate the generation of mask layouts for fabricating an integrated circuit corresponding to an input netlist and a timing specification. The mask layout is generated by the method including the steps of automatically sizing transistors specified in the netlist, clustering the sized transistors into cells, generating a cell library, and placing-and-routing the cells to generate the mask layout. The system includes associated memory and stored programs, including a plurality of mask layout tools; and a processor operated by an automatic mask layout generation program for sequentially applying the plurality of mask layout tools to generate the mask layout from the input data.

Abstract: A phase-shifting optical lithographic mask has a set of phase shifting features and a set of alignment marks, all having a common thickness and being made of a common material, such as chromium oxynitride, that is partially transparent to optical radiation used in an optical lithographic system. Both of these sets are located on a slab of quartz. An alignment shutter layer laterally intervenes between the alignment marks and the phase-shifting features, in order to suppress optical radiation leakage from the phase-shifting features to the alignment areas. A portion of the top surface of the alignment shutter layer and the entire top surface of the reinforced alignment marks are reinforced by an opaque layer, such as chrome. In addition, another similarly reinforced layer, a chip shutter layer, can be laterally located at an extremity of the reinforced alignment marks, in order to suppress optical radiation leakage from one chip area to another in step-and-repeat lithography.

Abstract: An overvoltage protection circuit using a diode bridge and a thyristor. The inputs to the bridge (first and second terminals) are coupled to a telephone line to be protected. The positive output of the bridge connects to a ground while the negative output of the bridge (intermediate node) connects through a thyristor to the ground. The thyristor is triggered into conduction when the voltage on the negative output of the bridge exceeds a reference voltage. The reference voltage is preferably the battery voltage for the telephone line.

Abstract: MSM-photodetectors are produced using implanted n-type Si and interdigitated electrodes deposited on the implanted surface. The implantation process decreases the carrier lifetime by several orders of magnitude. By implanting silicon with fluorine or oxygen, the bandwidth is increased relatively to unimplanted MSM photodetectors. Exemplary implanted photodetectors exhibited 3-dB bandwidths which were faster by an order of magnitude compared to their unimplanted counterparts. The detectors are thus compatible with multi-gigabit per second operation and monolithic integration with silicon electronics.

Abstract: An optical isolator includes an optical isolator unit including a main polarization discriminator in concatenation with a Faraday rotator, and an auxiliary polarization discriminator disposed in series with the optical isolator unit. One of the polarization discriminators initially divides an applied optical signal propagating in a forward direction along a reference axis into two polarized signals subsequently experiencing polarization dispersion and differential transverse deflection, while the other polarization discriminator eventually eliminates the polarization dispersion. The auxiliary discriminator includes a plate of a uniform thickness inclined at a tilt angle with respect to the reference axis selected so that the transverse deflection difference incurred during the passage through the one polarization discriminator is eliminated in the other polarization discriminator. This facilitates achieving very low polarization dependent loss in the isolator.

Abstract: An arrangement for generating and receiving standard telecommunications network signals on behalf of a terminal not equipped to generate or receive such signals. A controller shared by a plurality of such terminals receives signals from these terminals over a permanent virtual circuit (PVC) and uses the information received over the PVC to perform signaling. In a specific embodiment, the terminals are set top boxes, connected to a video cable, for controlling television sets. The controller controls signaling for establishing connections between the set top box and a video vendor system, and tunes the set top box to receive signals on the proper channel. Advantageously, such an arrangement significantly reduces the cost of the set top box while still allowing for a highly flexible signaling arrangement to the video vendor system.

Abstract: Acoustic echos are canceled by employing a first echo canceler having a comparatively short first impulse response synthesis capability which is connected between a transmit path and receive path for generating a first error signal and for canceling echo signals in the transmit path, and at least a second echo canceler having a comparatively long second impulse response synthesis capability connected in parallel with the first echo canceler between the transmit and the receive path. The second echo canceler is supplied with the first error signal from the first echo canceler and is adaptively operating simultaneously with but independent of the first echo canceler to further cancel echos in the transmit path. More specifically, the first echo canceler is intended to capture the direct path acoustic echo and any early arriving echos that are stable which are not time yawing. Since the direct path acoustic echo and the stable early arriving echos are not time varying, the adaptive adaptation rate, i.e.

Abstract: Transmission system comprising at least two links for connecting a transmitter and a receiver, and receiver suitable for such a system.Transmission system comprising at least two channels for connecting a transmitter and a receiver. The receiver comprises receiving circuits (20 and 31) for receiving the data coming from the channels, a coincidence providing circuit (30) for the data coming from said channels, formed by:detection circuit (66, 67) for detecting the shift between the data from the channels to produce shift information,a shifting circuit for shifting the data of at least one of said channels as a function of said shift information,a switching circuit (35) for connecting a user circuit to either of said channels.

Abstract: In a resonator in which a ground plane and a patch sandwich a dielectric, a slot in the patch concentrates emanation of radiation from the slot. Shorting conductors form the ends of the resonator. A dielectric cover over the slot matches the dielectric constant of the substrate to that of free space. Quarter-wave chokes at the ends of the resonator suppress currents in the ground plane.

Abstract: A line driver having two halves arranged in a push-pull configuration. Each half has a pass transistor, connected between a power supply rail and an output terminal, and an amplifier with an output coupled to the output terminal. Only one of the pass transistors conducts at any given time. A sense transistor, coupled between the power supply rail and the input of the amplifier, varies the output of the amplifier to compensate for variations in the conductivity of the conducting pass transistor. Preferably, the current density in the sense transistor is substantially the same as in the conducting pass transistor.

Abstract: An active pixel imaging system and method to generate an differential output signal consisting of the differences in a viewed image between adjacent detected flames. A buffered electrical charge storage capacity of the active pixel sensor is utilized to provide a system with reduced complexity and hardware requirements. In the imaging system, when a particular active pixel sensor is activated it generates a voltage signal corresponding to a previous frame's detect light intensity before the pixel is reset to generate a voltage signal corresponding to a present frame's detected light intensity. A differential output circuit is used to generate a differential output signal based on these two generated voltage signals.

Abstract: Methods and apparatus are disclosed for automatically establishing a conference call to a preselected list of prospective participants to the conference call. A subscriber to the conference calling service predefines one or more lists of participants, each list being associated with a different conference call. When the subscriber wishes to initiate a conference call, the subscriber accesses the network and requests that the call be set up. The network originates (e.g., dials) calls to each of the participants on a specified list. The network then bridges these individual calls to establish the conference call. The cost of the conference call can be billed to the subscriber or shared among the participants to the call.

Abstract: A connector assembly for coupling an optical fiber to an active optical device has a metal sleeve and an L-shaped alignment block having perpendicularly disposed reference surfaces. A resilient member on the sleeve biases an optical fiber terminating plug against the reference surfaces. The active optical device is attached to a ceramic sub-mount and the sub-mount is placed on one of the reference surfaces. The sub-mount is sized so that an optical port for the active optical device will become aligned with the central axis of the plug. To couple the optical fiber with the active optical device, the plug is slid into contact with the active optical device and is rotated until the fiber is substantially registered with the optical port. The sleeve may have a second resilient member for receiving another plug from the opposite end of the sleeve with a fiber in the other plug being coupled to a second optical port.

Abstract: An in-situ method is disclosed for highly accurate lattice matching using reflection high energy electron diffraction dynamics. The method includes the steps of providing a substrate of a first semiconductor material and initiating growth of a second semiconductor material thereon. The oscillation amplitude of intensity I of waveform cycles is monitored using reflection high energy electron diffraction. A maximum intensity I.sup.+ and a minimum intensity I.sup.- is determined over a predetermined number of waveform cycles. The intensity drop .DELTA.I from initial reflectivity to minimum reflectivity of the waveform cycles is determined and normalized figure of merit FM is calculated for the predetermined number of waveform cycles using the relationship: ##EQU1## The fluxes of the second semiconductor material are then adjusted to maximize FM and optimize matching.