Abstract: The disclosed method of making a mixed glass optical fiber exemplarily comprises providing a high-silica tube, and causing molten non-high silica glass to flow into the bore of the tube by application of a pressure differential. In order to prevent cracking, the tube desirably has an outer diameter/inner diameter ratio of at least 5, preferably about 10 or even more, and an inner diameter of at most 1 min. In a preferred embodiment, a conventional SiO.sub.2 tube is partially collapsed to an inner diameter less than 1 mm, a quantity of a non-high-silica glass is placed in a neck of the partially collapsed tube and heated such that molten glass communicates with the reduced-diameter portion of the bore and can be drawn into the reduced-diameter portion by means of a vacuum. The resulting mixed glass body is then further stretched to result in a core rod of core diameter at most 0.3 min. After overcladding the core rod with SiO.sub.2, fiber is drawn from the thus produced preform. A thus produced fiber with SiO.

Abstract: Semiconductor lasers are susceptible to harmful high currents or high voltage electrical transients. Semiconductor pump lasers are especially vulnerable to electrical transients under normal operation because of the large continuous wave current needed to drive the semiconductor pump laser to achieve a high optical power. A protection circuit for 980 nm pump lasers using a non-linear voltage-dependent resistance means which limits drive current based on a drive voltage powering a laser diode is demonstrated to be effective in guarding the laser against harmful electrical transients.

Abstract: The present invention provides a wireless communication system which employs Butler matrix combiners and circuit switching at transmitter and receiver antenna arrays to provide directive beamwidth capabilities. Such narrow beamwidths permit the communication system to determine and select the transmission path having an optimum signal quality. The antenna arrays are integrated in a multilayer construction which reduces power consumption, increases the coverage range, improves the efficiency of the antenna array, and which has lower fabrication costs.

Abstract: A fabrication technique for improved dielectric isolation of adjacent, electronic devices or electrically controllable optical devices provides an inter-device resistance in excess of 1 M.OMEGA.. Strips of a silicon oxide material, such as SiO.sub.2, are formed between the devices after device formation but prior to regrowth of an electrically conductive cap layer and subsequent metallization. The presence of the SiO.sub.2 strips prevents regrowth of the cap layer between the adjacent devices.

Abstract: A dispersion-balanced optical cable 90 reduces four-photon mixing in Wave Division Multiplexing (WDM) systems and is effective to reduce cumulative dispersion D substantially to zero. The dispersion-balanced optical cable 90 includes one or more optical fibers 90-1 having positive dispersion D.sub.1, and one or more optical fibers 90-2 having negative dispersion D.sub.2. The fibers are singlemode and are suitable for the transmission of optical signals in the 1550 nm region. At this wavelength, the positive-dispersion fibers have a chromatic dispersion of about +2.3 ps/nm.km, and the negative-dispersion fibers have a chromatic dispersion of about -1.6 ps/nm.km. The dispersion-balance optical cable preferably includes an equal number of positive- and negative-dispersion fibers in the same cable.

Abstract: Acoustic echos are canceled by employing a first echo canceler having a comparatively long 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 short 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. Specifically, the first echo canceler is intended to capture the substantially stationary and any slowly varying components of the echo path impulse response, and the second echo canceler is intended to capture the more time varying, i.e., dynamically varying, component of the echo path impulse response.

Abstract: A voltage-to-current converter comprises a first MOS transistor for receiving a voltage signal at a first gate and transferring a current signal between a first drain and a first source, a second MOS transistor for receiving a biasing voltage at a second gate and transferring the current signal between a second drain and a second source, and a biasing circuit for applying the biasing voltage of V.sub.C +V.sub.T +kV.sub.DS to the second gate such that the second transistor provides a substantially constant drain-to-source resistance of 1/.beta.V.sub.C, where V.sub.C is a constant voltage, V.sub.T is a threshold voltage for the second transistor, V.sub.DS is a drain-to-source voltage for the second transistor, k is a constant in the range of 1/3 to 2/3, and .beta. is a gain for the second transistor.

Abstract: Two separate electrooptic phase modulators are used in a modified Mach-Zehnder interferometer to vary the absolute and relative optical phases of two orthogonally polarized modes of an input signal independently of each other. A conventional Y-branch splitter on lithium niobate splits the input signal equally into the two waveguide phase modulators and an external polarization splitter recombines the two phase modulated signals in orthogonal polarization states. The polarization in the interferometer is maintained by connecting the outputs of the two phase modulators to polarization maintaining fibers. An alternate embodiment of the present invention uses an additional 3-dB directional coupler to mix the two phase modulated signals before they are combined in orthogonal polarization states.

Abstract: A waveguide mounting board having an array of ridge type waveguides on a surface thereof is automatically centered with an optical fiber board having a corresponding array of optical fibers by seating elongated alignment rails on the waveguide mounting board within alignment V-grooves in the fiber board. The alignment rails each comprises a short length of an optical fiber mounted on a pair of parallel alignment ridges. The alignment ridges are generally similar to the ridge type waveguides and are formed simultaneously therewith using a common photomask.

Abstract: A packet-based telecommunications architecture is disclosed that, like virtual-circuit networks, preserves the sequential order in which packets are presented to the network, but does not require node-by-node call set-up or tear-down, unlike virtual-circuit networks. Further, the packet switches which compose the architecture can be more simple than those used in datagram or virtual-circuit networks. An illustrative embodiment of the present invention comprises determining the topology of a network of packet switches that are connected by communication links, associating at least two names with at least one of the packet switches, and populating the router tables in the packet switches so that for each name the packet switches and communication links form a elemental network with the topology of a sink tree with the named packet switch at the root of the tree.

Abstract: Apparatus and methods for comparing a text with its translation. The apparatus uses cognates in the text and the translation to make a list of first positions in the text and second positions in the translation. The second position specifies a location in the translation which is in the neighborhood of the translation of the first position in the text. By means of the list, a given location in the text can be related to a location in the translation which is in the neighborhood of the translation of the given location. The list permits parallel displays of the text and the translation and easy production of full-context concordances, glossaries, and histograms. Graphs based on the list can be used to detect parts of the text which are not in the translation and vice-versa. The list is made using a technique which iteratively computes an alignment path in a graph which records the positions of matching 4-grams in the text and the translation.

Abstract: A wireless communication system for servicing personal communicators is connected to a a digital switch of a landline telephone network. The communication system includes a plurality of wireless communication base units, each having wireless circuitry enabling it to extract channel and setup information other from nearby wireless communication base units. Each unit measures the RSSI of channels of neighboring wireless communication base units and makes channel assignments to a base unit in response to RSSI measurements being compared to a threshold.

Abstract: A telephone network is modified so that callers making telephone calls can engage in a game of chance to win a prize without having had to specially dial the game processor, i.e., the telephone numbers of the telephone calls are independent of the game processor. In one embodiment of the invention, the game processor is part of the switch that processes calls through a telecommunications network. Upon conclusion of the game, the caller is supplied with an indication as to whether or not he is a winner and will receive a prize. The determination that a caller is a winner need be made only if the call was successfully completed, that is, routed to a destination at which the call is answered.

Abstract: A method and arrangement for characterizing features of a patterned material on an underlying layer is disclosed. According to the method, the patterned material is subjected to radiation including a range of wavelengths such that the patterned material absorbs more radiation than the underlying layer, and the underlying layer reflects more radiation than the patterned material. Zeroth order reflected radiation is measured and the reflectance measurement is expressed as a spectrum of the intensity of the reflected radiation as a function of the wavelength of the reflected radiation, or as an average reflectance over a range of wavelengths. The reflectance measurement can be correlated with features of the patterned material. An arrangement of equipment is disclosed for characterizing features of a patterned material according to the method.

Abstract: An architecture for a distributed CSMA/CD network using IEEE 802.3 protocol that is widely extended between transmitting and receiving nodes by placing some of the idle/busy/collision functions in one or more protocol control nodes which are located between the other nodes. The protocol control nodes do not perform resynchronization and are not bridge nodes, so their use does not cause any time delays. One application would be a cable TV system where the distant nodes would be the cable office node that is widely separated from a group of neighborhood local nodes. A protocol control node intermediately placed in close proximity to the local nodes provides the idle/busy/collision control functions while allowing the central office node to be located beyond the IEEE 802.3 maximum distance.

Abstract: Disclosed is an integrated circuit comprising a balanced set of inputs and a phase splitting circuit. The phase splitting circuit has a first input terminal that is coupled to the balanced set of inputs and a second input terminal that is coupled to the balanced set of inputs. The phase splitting circuit further comprises a balanced phase shifting network, a first set of output terminals, and a second set of output terminals. The balanced phase shifting network is coupled to the first: input terminal and the second input terminal. The first set of output terminals provides a voltage representative of a first voltage across a resistive portion of the balanced phase shifting network in response to an input voltage at the balanced set of inputs. The second set of output terminals provides a voltage representative of a second voltage across a reactive portion of the balanced phase shifting network in response to the input voltage at the balanced set of inputs.

Abstract: In external modulation, a modulated light signal is shaped to decrease pulse transition times resulting in less chirp. Accordingly, the modulated signal travels greater distances with less pulse distortion over an optical medium. For an integrated-type of external modulator, chirp is reduced further by using a laser modulator coupled to multiple complementary output ports.

Abstract: This invention relates to arrangements for interconnecting a plurality of stand-alone switches by data and communication channels (the latter typically used for communicating voice signals) in such a way as to make the plurality of switches act as if they were one switch. The invention further relates to arrangements for permitting groups of lines, the groups connected to different stand-alone switches, to be treated essentially as if they were connected to a single switch. Each switch of a symbiotic network (a group of stand-alone switches) or a virtual symbiotic network (the grouping of the groups of lines) accesses pertinent data in its own data base or the data base of one of the other switches of the symbiotic or virtual symbiotic network and treats the results of such data base accesses as if they were made internally in the switch.

Abstract: Described is a novel packaging of MCM tiles without wire-bond interconnections and in a total thickness which is reduced relative to conventional MCM packaging. The MCM tile includes a substrate with a plurality of peripheral metallizations and at least one chip flip-chip mounted on the substrate. The PWB is provided with an aperture which is smaller than the size of the silicon substrate but larger than the outside dimensions of the mounted chips. The substrate is positioned on the PWB so that its ends overlap areas of the PWB adjacent the aperture and the chips fit into the aperture. Peripheral metallizations on the substrate are interconnected to metallizations on the PWB by either solder reflow technology or conductive adhesive technology.

Abstract: Electronic devices include at least two electronic components in electrical contact by connector means, the components being at least partially encased by a molded resin. Preferably, the connector means is a compression connector and the molded resin maintains a compressive force on the connector to ensure that reliable contact is maintained.