Abstract: An intrusion detection optical communication system modifies the original data signal to include a synchronizing periodic waveform. The receiver generates an inverted synchronizing periodic waveform signal corresponding with the transmitted signal to null the same under normal operation. When an intrusion in the optical system arises, power is extracted from the system and the nulled condition is disrupted. The disruption is detected and activates an alarm circuit when the disruption is above a threshold value.

Abstract: In an optical heterodyne homodyne detection apparatus, signal light and local oscillation light are combined, and the combined light is received in an optical detector to produce intermediate frequency signal which is then demodulated thereby producing base band signals. The frequency sweep of the intermediate frequency signal is performed so that the frequency of the intermediate frequency signal becomes a predetermined value. During the frequency sweep, at least one polarization of the signal light and the intermediate frequency signal is scrambled, and is stopped when the frequency becomes the predetermined value. Thereafter, polarizations of the signal light and the local oscillation light are coincided with each other in accordance with the polarization angle control.

Abstract: An optical interface which is adapted for use in a local area network is provided. The optical interface comprises an optical transmitter section and an optical receiver section. The optical transmitter section receives data in a non-return to zero inverted (NRZI) format from a LAN controller which the optical interface is part of a remote node. The optical transmitter section converts the non-return to zero inverted data to an alternate mark insertion (AMI) format. An LED driver circuit smooths out and extends the alternate mark insertion data and uses it to drive an LED. The LED driver alternately drives the LED from a fifty percent reference output level to zero percent output and one hundred percent output corresponding to alternate positive-going and negative-going transition of the data. The optical receiver section has a light sensitive detector and preamplifier which receives optical signals encoded with digital data and generates corresponding electrical signals.

Abstract: The Invention provides a locally distributed crossbar switch to optically connect many computer processors and memories in arbitrary permutation an without interruption. A process or and an associated memory can be packaged together, taking advantage of the fact that the distributed crossbar switch employs local switching. At the same time, processor-memory pairs can be physically separated from other such processor-memory pairs, and by great distance.

Abstract: Disclosed is a direction sensing apparatus employed with universal connectors at the data units located along a data transmission cable. Each connector includes an optical source and an optical detector and the connecting segments cable between units each includes two fiberoptic conduits. One is for the transmission of control signals in a direction away from a master station and the other is for the transmission of the data signals toward the master station. Logic circuitry within each unit determines the presence of the first light source detected at the unit and switches the signals modulated thereon to the command channel within the unit. This switching also applies the signals modulated on the second-in-time light source detected at the unit to be applied to the data channel within the unit. Hence, it makes no difference which of the two connections at each data unit is used for connecting with the preceding station or with the succeeding station.

Abstract: One or more infrared receiver units communicate by carrier current to an infrared transmitter unit in order to extend the operational range of an infrared remote control device that normally operates an electrical or electromechanical apparatus. The receiver converts the infrared radiation pattern produced by an infrared remote control device into a signal at a suitable frequency that is injected onto the carrier current of a facility. The transmitter, located adjacent the apparatus, converts the signal on the carrier current back into the original infrared signal used to operate the apparatus.

Abstract: An optical network comprises a plurality of transmitting (T.sub.n) and receiving (R.sub.n) terminals; and cross-coupling means (2), the transmitting (T.sub.n) and receiving (R.sub.n) terminals being optically coupled with the cross-coupling means whereby modulated carrier signals transmitted from each transmitting terminal (T.sub.n) are fed to each receiving terminal (R.sub.n) via the cross-coupling means (2). A plurality of first sources (4, 7) of optical signals are grouped together remotely from and optical coupled with the transmitting (T.sub.n) and receiving (R.sub.n) terminals to supply carrier signals and tuning signals to the transmitting and receiving terminals respectively.

Abstract: An optical packet switching system is disclosed in which a routing signal is composed of a wavelength-multiplexed optical signal and an information part and a packet end code are also composed of optical signals. In accordance with the present invention, a switching network is formed by a multi-stage combination of light triggering switches which are closed depending on the presence or absence of a particular wavelength in the wavelength-multiplexed optical signal.

Abstract: An optical frequency synthesizer and/or sweeper, whereby a coherent optical output light is obtained by using a wavelength stabilized laser and an optical phase locked loop wherein the frequency of the output has the characteristics of high accuracy, high stability and narrow spectral line width. The optical phase locked loop comprises a tunable laser, an optical frequency multiplier, an optical frequency shifter and an optical heterodyne detector, wherein the optical phase locked loop is capable of precisely outputting an arbitrary wavelength by feeding back an output optical frequency.

Abstract: Orthogonal optical signals on a common waveguide are obtained by power splitting a light signal into a split waveguide, modulating at least one of the split signals and recombining the signals. The orthogonal signals may be obtained by separating the signals in frequency or by quadrature encoding. Frequency translation may be obtained by continuously varying an applied voltage to vary the dielectric constant of a leg of the split waveguide. One of the signals may also be frequency, phase or amplitude modulated. This split waveguide may serve as the frequency shifter and modulator in a three-frequency heterodyne system.

Abstract: The present invention relates to optical repeaters in a two-way optical line link, e.g. one included in a teletransmission system. The optical repeaters are implemented such as to provide a system which, inter alia in fault localizing, utilizes the line link transmission capacity optimally by completely optical through-connection of signals on the optical fibre cables. In fault localizing, one repeater at a time is checked, by an end terminal in the link transmitting a test signal including an address for selecting a repeater for testing and a test pattern. An optical amplifier amplifies the test signal in every repeater through which the signal passes, and when it reaches the repeater indicated by the address, a control circuit controls an optical switch such that the test signal is switched (loop connected) and is returned to the transmitting terminal where fault analysis takes place.

Abstract: The system comprises a laser transmitter/receiver set which transmits laser radiation and processes the radiation received by retro-reflection and a remotely-placed retro-reflecting and modulating set which modulates the laser radiation and sends it back to the receiver. These two sets are mechanically separated, and one can be placed on board an aircraft and the other on the ground, for example. The modulation is done by a frequency-controlled acousto-optical deflector to obtained the operating conditions of diffraction according to Bragg's law. The laser radiation, after crossing the deflector, is sent back by a catadioptric device along its original path. The double passage through the deflector, on the way out and back, produces a shift in the frequency of the laser radiation, the value of the said shift being equal to twice the control frequency of the deflector. A double axis or single axis optical scanning device is added on, for functioning in a wide field.

Abstract: A wireless optical short-range communication system adapted for use as an intercom system. The system can be used in fast food restaurants and similar commercial institutions. The communication system includes a base station to interconnect via optical communication a group of substantially similar physically spaced-apart, remote units. Each one of the remote units and the base units includes an optical emitter to transmit an optical message-carrying beam to the base station, and an optical receptor to receive an optical message-carrying beam from the base station. The base station includes a receptor for receiving the optical beam transmitted by the optical emitters of all of the remote units, and an optical emitter to relay the received optical beam to the optical receptors of all the remote units.

Abstract: A beam failure alarm and protection circuit for a laser communications link. In order to distinguish a true beam failure from a mere absence of data to be transmitted, an alternate signal is produced in the transmitter whenever no data is available for transmission. The alternate signal is of a much higher frequency than true signals and is bandpass filtered. Its absence is used at the receiver to shut down the data output and trigger an alarm if the receiver senses no alternate signal within the maximum time that a typical burst of data would terminate.

Abstract: A microphone/pickup system employing a digital signal throughout. There are a plurailty of digital microphone/pickup devices each comprising, a microphone/pickup element for sensing sound vibrations and for producing an analog electrical signal reflecting the sound vibrations at an output thereof. An analog to digital converter is directly connected to receive the analog electrical signal at an input thereof and produce a digital signal reflecting the sound vibrations at an output thereof, the output of the analog to digital converter being the output of the microphone/pickup device. Preferably, there is a support structure carrying each microphone/pickup element and its associated analog to digital converter in combination as well as a plurality of user devices disposed at a location removed from the support structure and operatively connected to receive and use the digital signal from respective ones of the digital microphone/pickup devices.

Abstract: The device of the present invention provides a signal modulation system. The system has a first station communicatively connected to at least first and second optical fibers. The first station has a transmitter to produce an unmodulated light carrier signal through the first optical fiber and a receiver to convert a modulated light signal from the second optical fiber to a demodulated electrical signal for output. The system also has a second station communicatively connected to the first and the second optical fibers. The second station has an amplifier and power source which receive input carrier modulating signals, a modulation circuit, and an electro-optical modulator constructed and arranged to modulate transmission of the light carrier signal from the first optical fiber to the second optical fiber.

Abstract: An optical signal regenerator includes an optical coupler having a first input for an optical information signal, a second input for optical clock pulses and an output for a combined signal. A resonant laser amplifier is located downstream of the output of the coupler and arranged to receive the combined signal and, in use, output a regenerated optical information signal. The bias current applied to the laser amplifier, in use, biases the amplifier to a level below its lasing threshold, and the power of the optical clock pulses is just below the bistable threshold of the amplilfier, so that, when an optical information signal is fed into the first input during the application of an optical clock pulse to the second input, the bistable threshold of the amplifier is exceeded causing a sudden jump in the power of the optical output of the amplifier to provide a regenerated optical information signal.

Abstract: A bidirectional optical communications system is described using a multiple quantum well structure as both a photodetector and light modulator.

Abstract: A fiber optic hub (10) for local area networks (15, 35) and other data communication systems including an internal self-diagnostic and cable test capability for permitting off-line testing of the hub (10) and of fiber optic cables connected to the hub (10). The hub (10) includes a plurality of optical interfaces (30a-30p) each having an optical receiver section (36) and an optical transmitter section (37) and hub-processing circuitry (32) connected to the optical interfaces (30a-30p) for processing data signals received by the optical receiver sections (36) and for providing the processed data signals to the transmitter sections (37) to be transmitted back through the network (15, 35) thereby.

Abstract: A wavelength division optical switching system comprises a plurality of terminals each generating a light signal on a particular wavelength division multiplexed channel and an optical multiplexer connected to the terminals for multiplexing the light signals from the terminals. A processor identifies the channel of a source terminal requesting a connection and the channel of a destination terminal. A reference light generator generates a plurality of reference lightwaves of different wavelengths. A wavelength switch is provided for switching multiplexed channels by selecting the light signal of the identified source terminal channel and modulating the intensity of one of the reference lightwaves with the selected light signal so that the identified channel of the source terminal is switched to the identified channel of the destination terminal.