Abstract: The present invention has been made to realize an optical router capable of preventing optical signals from conflicting with each other and of efficiently allocating an optimum optical path.

Abstract: A system for measuring optical characteristics of a multiport optical device uses optical heterodyne detection and known port-specific transmission delays to simultaneously monitor multiple ports of the multiport optical device with a single receiver. An embodiment of a system includes a splitter configured to split a swept optical signal into a reference signal and a test signal and a test system input, connectable to the multiport optical device, for transmitting the test signal to the multiport optical device. The test system also includes an optical combiner and a receiver. The optical combiner is connectable to the multiport optical device to receive a first portion of the test signal having a first port-specific transmission delay and to receive a second portion of the test signal having a second port-specific transmission delay.

Abstract: A data compression device comprises at least two pulse generating devices (212, 222); a delay element (211, 221), modulating means (214, 224) and pulse compression element (215, 225) associated with each pulse generating device; and control means (240); whereby each modulated, compressed, pulse is multiplexed onto an optical fibre. The compression may be applied in the time domain or the spatial domain.

Abstract: An multiplex transmission apparatus that realizes a receiving system using a phased array antenna with high efficiency and low cost is provided. A delay controller 102 gives a time delay to a local oscillation signal outputted from a signal source 101. First and second optical transmitters 1031 and 1032 each converts the local oscillation signal and the delayed local oscillation signal into optical signals. A first optical multiplexer 104 multiplexes the optical signals for transmission. An optical separator 106 separates the multiplexed optical signal. A first multiplexer 1071 multiplexes first and second main element signals, while a second multiplexer 1072 multiplexes first and second sub-element signals. First and second optical modulators 1081 and 1082 each modulates the optical signal with multiplexed electrical signal group. A second optical multiplexer 109 multiplexes the modulated optical signals for transmission.

Abstract: A method and a device for receiving a broadband light pulse modified in the time and frequency domains, the light pulse comprising at least one frequency component. The method comprises receiving the light pulse at a particular moment, separating the frequency components of the light pulse from each other, converting each frequency component into an electrical pulse, performing a first comparison to compare the magnitude of each electrical pulse to a predetermined threshold value, performing a second comparison to compare said electrical pulses exceeding the threshold value at a particular moment, and deciding the bit value in response to the second comparison conducted.

Abstract: An arrangement and method for producing a predeterminable polarization mode dispersion by means of double refracting elements provides for the production of a second-order polarization mode dispersion. An element is envisaged which twists the polarization principal axes by an appropriate angle at the output of an arrangement for producing first-order PMD, and the light signal exiting this element is fed into an arrangement which is also an arrangement for producing first-order PMD to produce an output signal having both first- and second-order PMD.

Abstract: An optoelectronic pulse generator is provided that includes a thyristor detector/emitter device having an input port and an output port. The thyristor detector/emitter device is adapted to detect an input optical pulse supplied to the input port and to produce an output optical pulse (via laser emission) and an output electrical pulse in response to the detected input optical pulse. The output optical pulse is output via the output port. An optical feedback path is operably coupled between the output port and the input port of the thyristor detector/emitter device. The optical feedback path supplies a portion of the output optical pulse produced by the thyristor detector/emitter device to the input port, thereby causing the thyristor detector/emitter device to produce a sequence of output optical pulses and a corresponding sequence of output electrical pulses.

Abstract: An optical transmitter in accordance with the present intention consists of a light source and an interference unit. The interference unit consists of an optical power divider, an intensity modulator, a gain variation device, a phase shifter, an optical coupler, and a phase controller. In the optical transmitter, continuous-wave light emanating from the light source is bifurcated by the optical power divider. One of resultant continuous-wave rays has the intensity thereof modulated based on transmission data by the intensity modulator. The other continuous-wave light has the power thereof adjusted by the gain variation device, and then has the phase thereof shifted by the phase shifter. The optical coupler joins the light signals, whereby the phase of part of the modulated light signal is shifted. The gain variation device is realized with a combination of, for example, an optical amplifier and an optical attenuator. The phase shifter is realized for example, a phase modulator and an optical delay device.

Abstract: The optical sampling system realizes the optical sampling by detecting the interference effect which is a linear correlation between the signal lights and the optical pulses, so that it suffices for both the signal lights and the optical pulses to have relatively low intensities, and the reception sensitivity is high. Also, the pulse width of the optical pulses and the amount of delay given to the optical pulses are the only factors that limit the time resolution, so that it is possible to provide the optical sampling system with excellent time resolution and power consumption properties, and it is possible for the optical sampling system to monitor not only the intensity of the signal lights but also the frequency modulation component as well.

Abstract: An optical fiber emulator. The emulator receives a digitally-encoded optical signal; demodulates the optical signal to produce serial electrical pulses representative of the digital signal; converts the serial pulses to parallel pulses; propagates the parallel pulses through a shift register whose propagation time is less than or equal to the time of a length of fiber to be emulated. The emulator then converts the parallel pulses at the output of the shift register to serial pulses; modulates an optical carrier with the serial pulses from the shift register; and attenuates the modulated optical signal an amount corresponding to the length of the fiber being emulated to produce an output optical signal whose propagation time is substantially equal to that of a section of optical fiber to be emulated. The shift register may be tapped at any point to obtain an output delayed by a desired amount corresponding to a selected section of optical fiber.

Abstract: An optical transmission system includes an optical source for providing an input optical signal to an optical array having a plurality of delay lines, and by utilizing orthogonal code modulation for active optical wave component control, the optical signal split among the plurality of delay lines is phase and amplitude modulated for efficient transmission to a destination point.

Abstract: In a signal transmission system made up of a transmission section, a receive section and an optical fiber installed between the transmission section and the receive section, a harmonic producing circuit and a harmonic phase shifting circuit are provided on the downstream side of an FM modulator. The harmonic producing circuit superimposes a harmonic of an FM signal on the FM signal, and the harmonic phase shifting circuit shifts the phase of the harmonic. This arrangement compensates a group delay deviation occurring in system components when an AM signal or QAM signal is modulated into an FM signal or PM signal in a modulator and then transmitted to be demodulated in a demodulator, thereby improving transmission quantity.

Abstract: A method for synchronizing optical signals conducted via different optical waveguides to an optical network node, wherein the variations in propagation time of the optical signals are compensated by adjustable optical delay circuits of a synchronizing device. To set a new delay for one of the optical waveguides, one of the adjustable delay circuits, already switched into the passive state, is set at the desired delay. This delay circuit is then switched into the active state by means of a high-speed optical switch, and the previously active delay circuit is switched into a passive state.

Abstract: A communications network includes optical network terminations (ONTs) and an optical line termination (OLT) connected to a passive optical network (PON). The OLT measures round trip transmission delay expressed in time slot duration for each of the ONTs, and orders the ONTs in ascending order of respective delay modulo time slot duration. A desired reception time at the OLT is scheduled for each of the OLTs according to the ascending order and each ONT is commanded to transmit at a command time that leads the respective desired reception time by a respective delay integral time slot duration. The scheduling includes leaving a reception interval spare after the last ONT in ascending order. The ascending delay modulo slot protocol becomes more efficient as the number of time slots per frame increases. If the number of time slots per frame is N, then the efficiency of the protocol is (N−1)/N. Unassigned time required per transmission frame is thereby reduced.

Abstract: The present invention is a device to increase the bit rate and distance at which data can be transmitted by optical fiber. The device compensates the polarization dispersion of the line by processing a received optical signal with the use of a polarization controller, the generation of a differential group delay between two orthogonal polarization modes and a control unit for the polarization controller. The data that is sent is redundant to enable detection of errors affecting the data received and the control unit is adapted to minimize the error rate calculated in real time by using the redundant data. The application of the device is to long-haul optical transmission, in particular over stranded fibers.

Abstract: Methods and systems for higher-order PMD compensation are implemented by developing an effective mathematical model and applying economical design techniques to the model. By assuming a constant precession rate for a narrow band of frequencies in an optical signal, a simplified model of a higher-order PMD compensator can be derived. The model can be used produce an economical compensator by making multiple uses of selected optical components.

Abstract: A method and apparatus are disclosed for compensating for optical transmission delays in a synchronous mobile communication system. A Base Station Transceiver Subsystem (BTS) includes a Main Unit (MU) for processing a mobile communication signal and a plurality of Remote Units (RUs) connected to the MU by Synchronous Digital Hierarchy (SDH) transmission, for performing radio processing for communication with a Mobile Station (MS). The method comprises the steps of sequentially forming a loop on an optical transmission line to each of the RUs for optical transmission delay compensation test between the MU and each of the RUs; once a loop for the optical transmission delay compensation test is formed, transmitting a test SDH frame to a corresponding RU, and measuring a delay time until the test SDH frame is fed back; and transmitting data to the corresponding RU after compensating the transmission time by the measured delay time.

Abstract: The invention relates to a method of reducing the intensity distortion induced by cross phase modulation in a wavelength division multiplexed optical fiber transmission system comprising a transmission line made up of a plurality of optical fiber segments with repeaters interposed between successive optical fiber segments, the transmission system having N different wavelength channels, where N is an integer greater than unity. In each repeater interconnecting first and second consecutive fiber segments, a time offset is introduced between the channels in such a manner that compared with the inlet of the first optical segment, the (n+1)th and the nth channels are offset by &tgr;n at the inlet to the second fiber segment, where n is an integer less than or equal to N, where &tgr;n is selected to be greater than zero and less than a value that eliminates correlation between the intensity distortion contributions of each fiber segment.

Abstract: A laser-radar receiver comprising an array of optical fibres, wherein the opposite ends of the optical fibres are connected to at least one electromagnetic radiation detector, each of the optical fibres having differing physical characteristics which result in known delays in the transmission time of pulsed electromagnetic radiation.

Abstract: The invention consists of an apparatus or device for compensating for the chromatic and/or polarization mode dispersion of light waves in an optical communication system, and a method of using the device. The device is a feedback device wherein the feedback loop has a plurality of optical paths, and each of said optical paths has associated therewith a delay element which imparts a predetermined delay to a signal propagating through the optical path. The couplers/splitters in the device are configured to split an incoming optical signal among the plurality paths according to predetermined splitting ratios and to recombine the signal that have been delayed with incoming optical signal. The delays and splitting ratios may be predetermined and chosen to effect a specific change to said spectral profile.

Abstract: An optical transmission system capable of alleviating the non-linear optical effect from overhead portions of a bit pattern comprised of a plurality of bits, wherein a plurality of optical transmit devices input a clock signal of identical phase and frequency, and optical signals whose overhead positions are changed on each wavelength by respective variable delay lines under the control of a phase controller are sent to a transmit side WDM device. At the transmit side WDM device, these optical signals are multiplexed in a wavelength multiplexer and sent to the receive side WDM device. Receive side optical transmission devices receive the respectively isolated optical signals. A phase controller offsets the positions of the optical signals and sends them to the overhead on each wavelength so that the non-linear effect of the receive optical signal is suppressed and a satisfactory signal can be received.

Abstract: An optical delay unit comprises a periodic wavelength demultiplexer having M (M is a natural number) input ports including a signal input port, M output ports including a signal output port, and periodic input/output characteristics for wavelengths between the M input ports and the M output ports, and (M−1) optical paths to connect each of the (M−1) output ports in which the signal output port is excluded from the M output ports of the periodic wavelength demultiplexer with any of the (M−1) input ports in which the signal input port is excluded from the M input ports of the periodic wavelength demultiplexer.

Abstract: A time-spreading and wavelength-hopping optical encoder spreads each pulse in a modulated optical pulse signal into a predetermined pulse train including pulses with different wavelengths. The last pulse in the pulse train is delayed from the first pulse in the pulse train by an interval longer than the pulse period of the modulated optical pulse signal. Interference is avoided by dividing the pulse train into successive delay groups equal in length to the pulse period of the modulated data pulse signal, and having each wavelength appear in only one delay group. If encoders producing differently structured pulse trains are used in an optical multiplexer, interference is avoided by having the same wavelength appear only at different positions within the delay groups of different pulse trains. Long delays can be used to multiplex a relatively large number of channels, even at high transmission rates.

Abstract: A micro-optical delay element for a polarization time-division multiplexing scheme is disclosed wherein two light beams are provided to a polarization beam splitter/combiner (PBS/C) in the absence of optical fiber. At least one beam exiting a modulator is collimated and reaches the (PBS/C) unguided as a substantially collimated beam. In this manner the polarization state of the beam is substantially unchanged. This obviates a requirement for polarization controllers.

Abstract: An optical communication system comprising an apparatus to transmit at least a digital optical signal modulated with a first encoded sequence of optical dark pulses and with a second encoded sequence of optical phase, an optical transmission line and an apparatus to receive, the said optical signal having high spectral efficiency.

Abstract: A recirculating optical delay line 30 has a laser 32 controlled by wavelength control 33 so as to vary the wavelength of radiation over time to provide a first input 34 to an optical modulator 35. The modulator 35 modulates the intensity of the first input 34 with a pulsed electromagnetic frequency signal 36 to produce a pulsed modulated optical signal 39. The signal 39 passes through an optical coupler 40 into a delay loop 41 having a delay fibre 44 arranged to delay the signal 39 for a predetermined duration. The wavelength control 33 is arranged to vary the first input 35 so as to ensure that overlapping pulses of the signal 39 in the delay loop 41 are at different wavelengths, thereby inhibiting optical mixing effects between the overlapping pulses.

Abstract: Four optical interferometers are arranged in parallel. Optical path length differences of the optical interferometers are set to L, r×L, r×r×L, and r×r×r×L, respectively, where L is a unit optical path length difference (constant). A coefficient r by which the unit optical path length difference L is multiplied is any non-integer real number for example an irrational number. An irrational number is for example a surd ({square root}2, {square root}3, etc.), ratio of circumference D, or base e of a natural logarithm. When such optical path length differences are set in such a manner, a chaotic dynamical system, an addition theorem, and a chaotic map are not satisfied with respect to the intensities of light which is output from the optical interferometers. In other words, a thoroughly unpredictable sequence can be generated. The sequence is spectrum spread as spread codes.

Abstract: An optical stream is split into a primary optical stream and a secondary optical stream. The secondary optical stream is converted to an electrical signal. The electrical signal is processed to identify a particular portion of the optical stream. The primary optical stream is delayed to provide a delayed optical stream. The particular portion of the delayed optical stream is modified to provide a controlled impairment.