Abstract: An optical transmission system enables launching at least 17 dBm of optical power at 1550 nm wavelength into an e.g. 50 km long span of standard telecommunications single-mode optical fiber, without incurring unacceptable penalties from stimulated Brillouin scattering, damage to optical phase modulators from excessive drive power or thermal effects, or signal degradations caused by the SBS suppression. High frequency modulation of the laser drive current is combined with lower frequency modulation of the phase of the laser output light that is itself varied over a range of approximately 25 MHz. This two tone modulation raises the SBS threshold to greater than 17 dBm in the 1550 nm wavelength region when the laser has a line width less than 10 MHz, under cw operation. By thereby dividing the task of spectral partitioning between the laser and the phase modulator, the RF input power level to the phase modulator is manageable and the laser operates in a regime that does not cause clipping.

Abstract: A transceiver (14) for recovering two different types of manchester coded, optical data signals from a photodiode is disclosed. The transceiver (14) includes a preamplifier (28) that receives and differentially amplifies the optical signal to reject power supply noise. The output of the preamplifier (28) is applied to an AC coupler (30) that extracts DC signal components using a switching circuit to produce a purely differential signal. A post amplifier/quantizer (34) receives the purely differential signal from the AC coupler (30) and generates a quantized signal therefrom. The quantized signal is applied to a data filter, clock recovery and control logic system 36 (36) that recovers a clock signal from the data signal that is synchronized by every data edge of the quantized signal.

Abstract: A photonic switching network includes input ports and output ports; a modulation device associated with the input ports modulates cells addressed to the same output port onto an optical carrier having a wavelength assigned to that output port. Q optical paths offer respective time-delays of 0, 1, . . . , Q-1 cell times between the input ports and the output ports so that, on being routed from an input port to an output port, cells are switched to one of the paths with time-delay so as to reach the same output port one by one. It further includes a plurality of additional output ports each connected to a controllable time-delay element the output of which can be coupled to a recirculation input port.

Abstract: An optical demultiplexer includes a first optical path that includes a first nonlinear optical element (NLE) which responds to a control pulse to induce a 180.degree. phase shift in an optical data signal propagating therethrough. The NLE responds rapidly to the control pulse but slowly reverts to a non-phase shift state. A second optical path is provided which includes a second NLE. An optical output coupler is connected to the first and second optical paths and responds to in-phase data pulses therefrom to output a data pulse on a first output. The optical output coupler is responsive to 180.degree. phase shifted data pulses to output a corresponding data pulse on a second output. An input data source concurrently couples a train of optical data pulses of wavelength .lambda. onto the first optical path and the second optical path. A control input induces a first control pulse of wavelength .lambda. onto the first optical path and a second control pulse of wavelength .lambda.

Abstract: A wavelength-interchanging cross-connect for use as an optical switch within a wavelength-division multiplexing (WDM) communications network in which multiple optical carrier signals at different optical wavelengths are switched in an all-optical process according to their wavelength. The cross-connect of the invention further allows the optical wavelength of the signal being switched to be changed to another WDM wavelength. The cross-connect includes a series of multi-wavelength 2.times.2 spatial optical switches. One serial path is directly connected between the spatial switches. The other serial path leads through intermediate wavelength-interchanging modules that interchange the carrier wavelengths of at least one pair of signals. Preferably, the wavelength interchanging is performed by difference frequency generation relying on second-order non-linear susceptibilities and a pump signal providing parametric gain.

Abstract: A method of determining Inter-Symbol Interference (ISI) in transmission systems first measures, for each of a plurality of received signal having different Signal-to-Noise (S/N) ratio, the minimum Bit-Error Rate (BER) as a function of the threshold level of a decision circuit at the system receiver. The measurements are then repeated on the system or on a simulated system where one or more segments of the transmission facility has been replaced with one or more non-ISI producing attenuators. The ISI levels for a given BER value is determined from the first and second sets of measurements. An alternate method measures minimum BER values of the system and the simulated system, as a function of the received signal power, for received signals having different S/N ratios. The ISI levels for a given BER value is then determined from these two sets of measurements.

Abstract: In a portable data terminal for infrared data communication, a light input/output section has a structure capable of varying the direction in which the data terminal emits and receives infrared rays.

Abstract: An output signal of an opto-electric conversion element 1 is amplified by a differential type pre-amplifier 3 to a predetermined level and input to an ATC circuit 5 as a positive phase signal and an inverted phase signal. These signals are held in respective peak holding circuits 51 and 52 of the ATC circuit 5. The positive phase signal held in the peak holding circuit 51 is added by an adder 57 to the inverted phase signal from the pre-amplifier 3 and the inverted phase signal held in the peak holding circuit 52 is added by an adder 58 to the positive phase signal from the pre-amplifier 3. Resultant sum signals are compared by a comparator 7 with a reference and discriminated as logical "1" and "0". The positive phase signal from the pre-amplifier 3 is input to a self-reset circuit 9 including a level detector 91, a reset pulse generator and a reset circuit 93. The level detector 91 detects a signal from the pre-amplifier 3.

Abstract: In a conference system of the present invention, a terminal modulates a sound signal taken by a micro-phone which is connected to the terminal, a coordinate information signal which is designated using a digitizer, and a video signal. The terminal converts the modulated signals to an optical signal by frequency multiplexing, and send the optical signal to the central device of the system. After the central device receives the optical signal, the device separates and extracts a sound signal, a coordinate signal, and a video signal from the optical signal. Each of these separated signals is sent to a corresponding demodulating circuit to be demodulated, outputted as sound or an image afterwards. Further, the coordinate information signal is processed, for instance, as a command data from a conference attendant.

Abstract: A communication system where a central module repetitively sends interrogation optical pulses to endpoint modules in order to determine operational state of the endpoint modules and of the two-way communication path to the central module. Those pulses also determine whether the endpoint module wishes to initiate communication with the central office. In the endpoint module, a modulator whose function is to send data from the customer's terminal is arranged to operate in two distinct modes. When it is "powered off", which is when the customer terminal is inactive, it allows central office signals to loop-back to the central office. In this state, the optical pulses sent by the central office serve the function of optical continuity checking. When an endpoint module wishes to establish a connection, i.e.

Abstract: A control unit provides unified control of various consumer electronic appliances such as a television, video cassette recorder, and home stereo system through remote control (e.g., infrared) signals. A receiver portion of an interface module positioned over the built-in remote control signal receiver of the appliance intercepts signals from a hand-held remote control operated by a user. The signals are routed to a control unit (such as a set-top television converter) where control logic determines a desired control action. A corresponding control action signal is routed back to a transmitter portion of the interface module and is received by the built-in remote control signal receiver of the appliance to be controlled, thereby resulting in the desired control action. The apparatus provides additional functions and increases user convenience and access to video, audio, and data signals provided via a cable television, direct satellite broadcast or similar service provider.

Abstract: The optical add/drop multiplexer has a pair of nominally identical interference filters, one of which carries out the function of extracting a carrier from a wavelength division multiplexed stream and the other the insertion function. The filters are arranged in parallel planes and are secured to opposite faces of a transparent plate so that the stream exits the device after having undergone reflection by both filters. The plate is mounted on a support which can be rotated in either direction to vary the tuning wavelength of the filters.

Abstract: An optical transmission system accomplishes optical transmission to a long distance by combining a multiplexing line terminal with optical amplifiers, linear repeaters, and regenerators with optical amplifiers combined together. The system also accomplishes the optical transmission to a short distance by directly connecting the linear terminals therebetween, with an electric-to-optic converter replaced by an electric-to-optic converter having a semiconductor amplifier, with an optic-toelectric converter by an optic-to-electric converter having an avalanche photodiode as light receiver, and with no use of any optical booster amplifier and optical preamplifier in the multiplexing line terminal. With these, the optical transmission system can be easily constructed depending on the transmission distance required.

Abstract: An optical correlator is disclosed that compares signals of interest with lected reference signals stored in holograms. The holograms are arranged so that the selected reference signals impinge onto the plane of the entrance of fiber optics arranged with an optical delay line and fiber optic amplifiers to form a delay line amplifier array. The optical delay line receives the signals of interest represented by light modulated pulses. The cooperative action from the light from the hologram and the light from the optical delay line produces signals that are proportional to the correspondence between the signals of interest and the stored reference signals.

Abstract: A fiber optic network comprises an optical fiber connection (one fiber or two) from a central office to an intelligent interface device in the subscriber's premises. The central office includes a serving node transceiver providing communication links to/from at least a narrowband switch and a broadband switch for providing narrowband and broadband service routing. The network includes at least one passive power splitter/combiner for passing all wavelengths on the optical fiber connection between the serving node transceiver and the intelligent interface devices. All wavelengths are provided to each customer and bandwidth on the optical fiber loop is dynamically allocated for individual services on demand through two-way wavelength division multiplexing and demultiplexing as well as any necessary signal format conversions. The network has media access control functionality and utilizes a dynamic media access control procedure for allocation of the bandwidth.

Abstract: An optical demultiplexor utilizes a single optical interference filter disposed between an input end and an output end of the device. The filter is preferably housed within a cavity in a glass block having an upstanding input end, endwall. The optical filter is a wavelength selective means having a wavelength characteristic dependent upon an angle of incidence. The device has a plurality of reflective surfaces disposed at the input end for reflecting light reflected from the filter, back to the filter at different predetermined angles. Each different predetermined incident angle allows a different predetermined wavelength of light to pass through the filter to an output end being spatially separated from other predetermined wavelengths that pass through the filter. The reflective surfaces are preferably formed in the upstanding endwall of the glass block. Sixteen channels can be separated by this demultiplexor.

Abstract: A method of proving the integrity of optical paths in an optical communication system wherein the same diagnostic optical signal is transmitted along each path from one end, and each path is provided at its other end with a grating pattern, for example, for producing a pattern of time spaced echoes of the diagnostic signal unique to that path. In one particular embodiment the diagnostic signal comprises an amplitude modulated optical signal and the echoes are produced at a time spacing such that the modulation components of the echoes are in-phase at a different frequency for each path.

Abstract: An optical communications system for transmission of optical signals using relaxation oscillation subcarrier, on-off keying modulation of the optical signals. Relaxation oscillation subcarrier on-off keying improves the signal-to-noise ratio of a receiver receiving the modulated optical signals and the data rate of the optical signal. A modulation device generates relaxation oscillations by pulsing a driving current for a transmitter between a first level below a threshold current and a second level above the threshold current. The optical communication system can further include a fiber optic link between the transmitter and the receiver. The optical communications system can further incorporate multiple frequency shift keying. The modulation device and modulation scheme can be used in all digital optical communications systems using a pulsed laser diode.

Abstract: A multiplex optical communication system transmitting a multiplex optical signal between terminal equipments each including converters producing optical signals combined to the multiplex optical signal, through repeater equipment including an optical amplifier, under controlling the amplifier so that when a converter is added or removed, a time constant of the amplifier is equal to a time constant of the added or removed converter, or the amplifier produces output under constant output level control before adding or removing the converter and after the amplifier produces final output and constant gain control during the added or removed converter increases or decreases output. The time constant control is performed to the amplifier by making the amplifier repeat start and stop of increasing or decreasing output step by step in accordance with prescribed objective values corresponding to half way output of the optical amplifier.

Abstract: An ultra-wideband signal processor, such as that employed for processing narrow time domain radar return pulses, includes a coherent acousto-optic Bragg cell channelizer having a plurality of IF outputs from which a plurality of IF output signals respectively representative of energy content of respectively different frequency portions of the RF input signal are derived. A summing circuit is coupled to sum the IF output signals to produce a summation signal representative of their average energy content. This average energy signal is compared with a threshold to determine if the input signal is a valid RF signal. A delay circuit delays a selected one of the IF output channels by a time sufficient to accommodate summation of the channelizer outputs and determining whether a valid RF signal is present. A digital signal processor processes the delayed selected output signal in response to the summation signal exceeding the threshold.