Abstract: The invention relates to a heterodyne receiver, preferably for multichannel reception, especially for the reception of optical signals, in which the received signal is mixed with an oscillator signal of an oscillator in a mixing stage, to generate an intermediate frequency in an intermediate frequency stage (IF stage). According to the invention, the frequency (f.sub.LO) of the oscillator is tuneable discontinuously in jumps (Sp1, Sp2), and the intermediate frequency stage is tuneable continuously.

Abstract: An optical switching system for optical wavelength-division and time-division multiplexed signals includes a plurality of tunable wavelength filters each of which selects a signal having a desired wavelength from an optical wavelength-division and time-division multiplexed signal, a plurality of optical memory elements each of which is supplied with an output signal of each of the plurality of tunable wavelength filters. Each optical memory element memorizes a light intensity of the output signal by being applied with a first control voltage and supplies an output port with the output signal which is converted to have a predetermined wavelength in a desired time slot. The tunable wavelength filters and optical memory elements may by replaced by wavelength filters and tunable wavelength optical memories.

Abstract: In an optical communication system, there are provided an optical transmission path, a terminal, and a transmitter. The transmitter includes at least one light source, a plurality of external light modulators for modulating respective lights from the at least one light source according to a signal from the terminal, and a coupler means for combining modulated lights from the external light modulators into a single light to transmit this single light to the optical transmission path. As a result, the present invention can preferably be applied to a multi-value digital optical communication system, and therein a complicated modulation control device is unnecessary for obtaining a signal light intensity accurately modulated in a multi-valued form.

Abstract: A network head-end station (1) is arranged to receive an upstream TDMA frame comprising interleaved optical signals from a plurality of terminations (2) connected to the head-end station (1) by a fibre network (3). The upstream TDMA frame includes a quiet phase during which none of the terminations transmit. The station (1) includes an opto-electronic receiver (4), a DC clamping circuit (10) for the opto-electronic receiver (4) and a clamping pulse generator. The clamping pulse generator is arranged to generate a pulse at a predetermined time falling within the quiet phase to operate the DC clamping circuit to clamp signals received during the remainder of the TDMA frame to a DC reference level received during the quiet phase.

Abstract: Optical communications system for the subscriber area with optical amplifiers.The system according to the invention is used to distribute information signals, particularly telephone signals, from a center to a plurality of subscribers and to make possible a bidirectional transmission of telephone and data signals between the center and the subscribers. According to the invention, the network used for this purpose is a multistar fiber-optic network in which fiber-optic amplifiers (10, 11) are present between successive branch points. The information signals to be distributed are transmitted via the fiber-optic network with a first wavelength (.lambda..sub.1) to the subscribers, and the subscriber-specific information signals to be transmitted from the center (1) to the subscribers (T.sub.i) are converted by frequency modulation to a different frequency band (FB.sub.

Abstract: A coherent optical communications system with continuous polarization scrambling, wherein such scrambling is obtained by combining orthogonally polarized radiations at different frequencies emitted by two independent sources. The two sources may be employed to build the transmitted or the local oscillator of the system.

Abstract: A light input energizes an optical transmitter providing a light output to a waveguide indicating a process variable. The transmitter has a process variable sensor generating a sensor output. An electrical circuit receives the sensor output and generates an electrical transmitter output indicating the process variable adjusted by a changeable parameter stored in the electrical circuit. The electrical circuit has an input energizing the circuit. An LED converts the electrical transmitter output to the light output. A gallium arsenide photodiode converts a first portion of received light into electrical energy provided to the energization input and converts a second portion of the received light into an electrical output controlling the stored parameter.

Abstract: A semiconductor device for driving a light emitting element used in high speed optical communication. The semiconductor device comprises circuitry for delaying a clock signal and producing first and second delay signals. The second delay signal has a delay time different from that of the first delay signal. The first delay signal controls flip-flop circuitry which receives a data signal and outputs a signal indicative of the data signal. The first delay signal also controls a first latch circuit to receive the signal from the flip-flop circuitry and output a signal with the delay time of the first delay signal. The second delay signal controls a second latch circuit to receive the signal from the flip-flop circuitry and output a signal with the delay time of the second delay signal. The signals output from the first and second latch circuits are logically combined by logic circuitry. The logic circuitry is either AND or OR circuitry.

Abstract: A parallel optical data transmission device has an optical signal emitting unit, an optical signal reception unit and a parallel optical signal transmission cable for optically coupling therebetween. The optical signal emitting unit has an array of semiconductor lasers, whereas the reception unit has an array of semiconductor photodetectors of the same number. The transmission cable essentially consists of optical fibers bundled together. In the optical signal emitting unit, electrical drive signal transfer lines for the lasers have a stair-step bending pattern such that their transmission lengths sequentially vary.

Abstract: A fiber optic subscriber loop architecture is disclosed. The architecture utilizes a double star configuration comprising a Central Office and a plurality of Remote Nodes. Illustratively, in the Central Office, one bank of N lasers supplies wavelengths .lambda..sub.1, .lambda..sub.2 . . . .lambda..sub.N in a first wavelength band to form channels on which downstream information will be transmitted to subscribers. In one embodiment, a second bank of N lasers operating at wavelengths .lambda..sup.N+1, .lambda..sub.N+2 . . . .lambda..sub.2N in a second wavelength band is used to form unmodulated channels to be delivered to subscribers for use in subsequent upstream transmissions. Groups of N wavelength channels are combined via WDM techniques at the Central Office before being transmitted over feeder fibers to the Remote Nodes.

Abstract: A satellite system for optical communications such as a multi-access laser transceiver system. Up to six low Earth orbiting satellites send satellite data to a geosynchronous satellite. The data is relayed to a ground station at the Earth's surface. The earth pointing geosynchronous satellite terminal has no gimbal but has a separate tracking mechanism for tracking each low Earth orbiting satellite. The tracking mechanism has a ring assembly rotatable about an axis coaxial with the axis of the field of view of the geosynchronous satellite and a pivotable arm mounted for pivotal movement on the ring assembly. An optical pickup mechanism at the end of each arm is positioned for optical communication with one of the orbiting satellites by rotation of the ring.

Abstract: A block of amplitude modulated television channel signals frequency modulates an optical communication path. In one embodiment, the AM modulated channel signals FM modulate an RF subcarrier which, in turn, is used to intensity modulate an optical carrier for transmission. Frequency modulation of the RF subcarrier by the amplitude modulated channel signals is advantageously performed at microwave frequencies. The FM modulated subcarrier signal is then converted down to a frequency range compatible with transmitter and receiver components used in the system. The frequency modulation and conversion can be performed by a pair of voltage controlled oscillators coupled in a push-pull mode of operation. The outputs of the oscillators are combined in a double balanced mixer to down convert the FM signal spectrum. In another embodiment, the optical frequency of an optical carrier is FM modulated by the block of AM signals. Receivers for the FM modulated band of AM channel signals are also disclosed.

Abstract: An electronic presentation system is presented utilizing a wireless remote for controlling a digital computer, one or more display or storage/playback devices and an audience response system. A Terminate and Stay Resident (TSR) program within the digital computer manages the wireless remote. The digital computer running the TSR program enables the wireless remote to operate any applications program, as well as to use the computer to add spontaneously certain special effects to the presentation and to control an audience response system. In addition, the computer downloads into the wireless remote control, via a wireless communications link, data commands and signalling parameters such as modulation scheme and communications protocol with which to enable the wireless remote to generate the correct signalling to operate predefined display or storage/playback device.

Abstract: Methods and apparatus for operating an optical communications system having at least two communicating entities (10,12). In accordance with a method of the invention a first step transmits communication link control information from a first entity to a second entity over a first optical channel having a first data bit rate. Responsive to the transmitted communication link control information, a second step of the method transmits data information from the second entity to the first entity over a second optical channel having a second data bit rate that is greater than the first data bit rate. The first optical channel is preferably a relatively low-bandwidth diffuse transmission infrared radiation channel. The second optical channel is preferably a relatively high-bandwidth infrared channel. One of the entities is a network adapter coupled to a wired network. The network adapter is preferably ceiling mounted. The other entity may be a mobile data processor.

Abstract: A remote controller capable of learning and later transmitting infrared signals transmitted by any other remote controller. The remote controller determines which of four modes of transmission a signal is transmitted in, including carrier mode, pulse mode, frequency shift keying mode and continuous wave mode. Once the type of signal is determined the controller learns each signal, saves them and later replays them to control a remote device.

Abstract: In a wavelength division switching system having m.sub.1 inlet highways and m.sub.2 outlet highways, m.sub.1 splitters are coupled respectively to the inlet highways to split each multiplex signal into m.sub.2 .times.n output signals for coupling to respective inputs of m.sub.2 .times.n optical switches. Each optical switch is responsive to a switching control signal for coupling one of its inputs to one of m.sub.2 .times.n tunable wavelength filters capable of passing one of n different wavelengths, in response to a wavelength selecting signal, to one of m.sub.2 .times.n fixed wavelength converters which are organized into m.sub.2 groups. These wavelength converters provide conversion of the input signals so that the converted wavelength is unique in each of the m.sub.2 groups. An array of m.sub.2 combiners are respectively associated with the groups of the fixed wavelength converters and with the outlet highways.

Abstract: In an optical fiber telecommunication transmission system, a remote terminal interfaces a high-rate optical fiber feeder line and a plurality of lower rate optical fiber distribution lines. The remote terminal includes a plurality of interfacing and signal cross-connecting devices which interface and cross-connect lower rate telephony signals with higher rate telephony signals. The plurality of interfacing and cross-connecting devices are interconnected with high-rate transmission lines so that telephony signals from under-utilized optical fiber distribution lines may be concentrated onto the high-rate optical fiber feeder line for efficient use of the feeder line.

Abstract: An optical electronic multiplexing reflection sensor system for a plurality of Bragg sensors connected in series spaced relation in a plurality of single mode fiber optic cable buses. In each of the buses a unique address is provided each sensor function by wavelength selection. Each of a plurality of monochromators is coupled to a corresponding one of the buses and has a control connected to it for controlling the operation of the monochromator. A tunable laser source is coupled to each of the buses. A wavelength sweep generator is coupled to the laser source and provides outputs to the controls of the monochromators. Each of a plurality of photodetector receivers receives the output of a corresponding one of the monochromators and each has an output providing output signals indicating individual wavelengths of the Bragg sensors coupled to it. Each if a plurality of analog to digital converters is connected to the output of a corresponding one of the photodetector receivers.

Abstract: A plurality of transmitting signal lights are supplied from a semiconductor laser light source which is modulated by a current having adjusted amplitude and phase injected thereinto in an optical transmitting apparatus. The signal lights are modulated in intensity by a plurality of external modulators, and a time-difference is applied among the signal lights. Thus, the signal lights are combined to provide a transmitting signal light which is propagated through a transmission line. At this time, a frequency component having a low transmission speed is supplied to the transmission line earlier than a frequency component having a fast transmission speed in compliance with a wavelength dispersion property of the transmission line.

Abstract: The monitoring system of the conduction of a low voltage A.C. mains system comprises at least one measuring module creating a D.C. current component between two mains system conductors. The measuring module computes a value representative of the line resistance of the mains system which is proportional to the ratio between the measurement of the D.C. component of the voltage at its terminals and the measurement of the D.C. component of a voltage at the terminals of a resistor through which the D.C. current flows. An increase in this measured value indicates a loss of conduction and, therefore, such an increase is detected and indicated as soon as it exceeds a preset thereshold. A servo module delimits, may also be provided for delimiting the portion of the mains system to be monitored enabling looping of the D.C. current component and regulating the D.C. component of the voltage at its terminals to zero.