Abstract: An optical receiver circuit is provided which is able to receive optical signals having a variable transmission rate, without loss of data. The optical receiver circuit according to the present invention has a light-receiving section for converting an optical signal with a variable transmission rate into an electric signal. A recovery section recovers a plurality of different clock signals and data corresponding to possible transmission rates. These data are stored into a plurality of memories and at the same time a decision section decides the transmission rate. A switch section reads data from one of the memories selected according to the result of the decision.

Abstract: A demodulator comprises an input splitter, optical device sets, and couplers. The input splitter splits an input signal comprising symbols to yield a number of signals. A first optical device set directs a signal of along a first path. A second optical device set directs another signal along a second path to yield a delayed signal. At least a portion of the second path is in free space. A path length difference between the first path and the second path introduces a symbol delay between the first signal and the second signal. A coupler receives a portion of the signal and a portion of the delayed signal to generate interference, where the interference indicates a phase shift between a phase corresponding to a symbol and a successive phase corresponding to a successive symbol.

Abstract: A spread spectrum waveform generator has a photonic oscillator and an optical heterodyne synthesizer. The photonic oscillator is a multi-tone optical comb generator for generating a series of RF comb lines on an optical carrier. The optical heterodyne synthesizer includes first and second phase-locked lasers, where the first laser feeds the multi-tone optical comb generator and the second laser is a single tone laser whose output light provides a frequency translation reference. At least one photodetector is provided for heterodyning the frequency translation reference with the optical output of the photonic oscillator to generate a spread spectrum waveform. A receiver pre-processor may be provided to operate on the spread spectrum waveform.

Abstract: A timing jitter measurement system and method is provided that acquires the timing jitter in an all-optical fashion, by extracting the timing jitter probability distribution function using auto-correlation and cross-correlation data. This makes the system and method of the present invention particularly useful for ultra-high bit rates, where power spectrum analysis cannot be applied. The resolution of the timing jitter measurement system and method is higher than the actual pulse width, and depends on the time resolution of the correlator. The system and method of the present invention facilitates the identification of deterministic or random timing jitters or combinations thereof, and therefore can be used to identify the origins of timing jitters within the optical network and to provide feedback to the optical network that can be used to actively control the timing jitter.

Abstract: A method and apparatus for implementing an RF photonic transversal filter that utilizes tap apodization and wavelength reuse to obtain a high side lobe suppression together with narrow and configurable passbands. Several taps are obtained from one wavelength by using dispersive optical delay lines such as chirped fiber gratings that introduce a delay between successive wavelengths. A selected subset of the input wavelengths is utilized to generate multiple taps per wavelength. Some of the taps are apodized to generate various filter transfer functions that yield a high side lobe suppression ratio.

Abstract: An optical transmitter for an optical communication system is provided. Included in the transmitter is a first optical delay element configured to generate a second optical signal from a first optical signal. A second optical delay element is configured to generate a fourth optical signal from a second optical signal. An optical multiplexer is configured to combine the third and fourth optical signals to produce a fifth optical signal. Also included is an optical modulator configured to alter a pulse width of the fifth optical signal to generate a sixth optical signal. An optical delay controller is configured to control the first optical delay element and the second optical delay element based on the sixth optical signal.

Abstract: An optical signal transmission control apparatus that controls transmission of optical signals transmitted via a plurality of redundant routes. The optical signal transmission control apparatus includes a delay difference adjusting unit that adjusts a transmission delay difference between the optical signals of each route by converting a wavelength of the optical signal and making the optical signal with a converted wavelength pass through a waveguide in which a transmission delay of the optical signal changes continuously depending on the wavelength, and a waveform degradation compensating unit that compensates degradation of a waveform of the optical signal, while maintaining the transmission delay difference adjusted by the delay difference adjusting unit.

Abstract: An optical transmitter generates a transmission signal having a frame as a unit, the frame including a signal pilot signal with fixed amplitude and phase and two data bits to output the generated signal into a transmission line. In a receiver, a splitter splits the signal light from the transmission line. An optical delay delays the signal light for a 1-bit period. A first combiner combines the signal light from the transmission line and the output signal light from the optical delay. A photodetector converts the combined light into an electrical signal. A 3-bit optical delay, a second combiner, a BPF, and an oscillator generate a frame-timing signal. A gate separates a data from the output from the photodetector under the control of a gate control unit. A binary discriminator binary-discriminates the output signal from the gate.

Abstract: A method for receiving an optical signal is included where an ingress signal is split into a first portion and a second portion. A relative delay is induced between the first portion and the second portion, which are optically interfered to generate at least one interfered signal. Quality criteria of a monitored signal at least based on the at least one interfered signal is monitored so that a relative delay based in the quality criteria may be adjusted.

Abstract: A RF-synchronization system includes a laser that creates pulse trains for synchronization. A modulation means transfers the timing information of the pulse train into an amplitude modulation of an optical or electronic system. A synchronization module changes the driving frequency of the modulation means until it reaches a phase-locked state with the pulse train.

Abstract: An optical apparatus comprises a phase comparator detecting a phase shift between a changing point of data transmitted through an electro/opto converter and a changing point of data received through an opto/electro converter, a delay controller and a variable delay circuit controlling a delay of the transmitted data so that the phase shift detected becomes equal to a value which minimizes a receiver sensitivity degradation due to crosstalks between a transmitter portion and a receiver portion.

Abstract: The present invention provides a method for reducing spreading of a pulse in a transmission line, said spreading being as a result of polarization mode dispersion, comprising inducing predetermined polarization rotations of particle or wave components of the pulse in the transmission line.

Abstract: The present invention provides an apparatus and method for preserving a frame sequence and distributing traffic in a multi-channel link, which efficiently distributes frame traffic while preserving the transmission sequence of frames in a link composed of multiple channels, and to a multi-channel transmitter using the apparatus and method. The present invention determines whether the preservation of a sequence of frames is required using information about received frames, predicts a frame transmission service finish time on the basis of the length of frames if the sequence preservation is required, determines a sequence preservation service time (SPST) on the basis of the predicted transmission service finish time, stores the frames in a sequence preservation buffer for the SPST, and distributes the frames to idle transmitters at a termination point of the SPST, thus maximizing the efficiency of channel use.

Abstract: A technique for generating variable pulse delays uses one or more nonlinear-optical processes such as cross-phase modulation, cross-gain modulation, self-phase modulation, four-wave mixing or parametric mixing, combined with group-velocity dispersion. The delay is controllable by changing the wavelength and/or power of a control laser. The delay is generated by introducing a controllable wavelength shift to a pulse of light, propagating the pulse through a material or an optical component that generates a wavelength dependent time delay, and wavelength shifting again to return the pulse to its original wavelength.

Abstract: In an optical detection method that requires a reference light such as homodyne detection, a signal light and the reference light must be equal to each other in the wavelength, and the phase relation between them must be maintained constant. In order to satisfy this requirement, the signal light and the reference light are extracted from the same light source and made equal to each other in the wavelength. The signal light and the reference light are transmitted so as to be temporally superimposed on each other with orthogonal polarizations to the same optical path, thereby making the external environments equal to each other to maintain the constant phase relation.

Abstract: Optical transmission equipment, capable of electrically adjusting the delay difference between a plurality of digital signal paths to be connected to a multilevel optical modulation unit or demodulation unit, having multiplexing circuits connected to the digital signal paths and a delay adjustment unit inserted in one of the digital signal paths to adjust delay of N-bit-parallel low-speed digital signals with the timing unit of a bit period of a high-speed serial digital signal to be outputted from multiplexing circuit.

Abstract: One embodiment of the invention relates to producing optical pulses for use on a transmission link. A light source is configured to produce an optical signal. A pulse generator is coupled to the light source. The pulse generator is configured to receive, for a first channel, the optical signal and a clock signal. The pulse generator is also configured to modify the optical signal based on the clock signal to produce an optical pulse having a predetermined pulse shape. The clock signal is associated with the predetermined pulse shape. The predetermined pulse shape being based on a transmission characteristic of the transmission link.

Abstract: An apparatus and method for use in an adaptive optical equalizer including, in one embodiment an optical equalizer having an input and output coupled to receive an incoming optical signal and configured to generate an output optical signal by phase modulation and/or amplitude modulation of the receive optical signal in response to electronic control signals. A photodiode is configured to receive the output optical signal and generate an representative current signal. A control signal generator is configured to generate the electronic control signals in accordance with predetermined criteria and in response to the representative current signal from the photodiode. An interferometer is connected to receive the incoming and output optical signal from the optical equalizer, the differential amplifier is configured to receive electronic versions of outputs from the interferometer for generating a difference signal and supplying the difference signal to the control signal generator.

Abstract: Method and apparatus for demodulating one or more channels of an optical differential phase shift keyed (DPSK) signal with a symbol rate of SR using an athermal optical delay interferometer with a free spectral range (FSR) of 50 GHz/2N, and (0.8×SR)<FSR<(1.3×SR), where N=0, 1, 2 . . . .

Abstract: The present invention includes apparatus and method of a variable step size dithering control algorithm for polarization mode dispersion controllers (PMDCs). The dithering step size of the PCs is adjusted according to the feedback signal including degree of polarization (DOP).

Abstract: A receiver for an OTDM/PDM pulse train (10) in which the pulses (12) have alternating polarizations (P1, P2) has a polarization insensitive optical switch (16; 161, 162, 163, 164) for isolating optical pulses (10?) within the pulse train (10), and a polarization selective element (17) for separating from the isolated pulses (10?) at least one component that has a single polarization. This allows to considerable relax the constraints posed on the switch since components in the isolated pulses that result from interchannel interference can, at least to a large extent, be eliminated by the subsequent polarization selective element (17).

Abstract: An optical receiving apparatus sets, efficiently and optimally, a delay interferometer and a variable wavelength dispersion compensator in the apparatus.

Abstract: An optical data transmission system and a method of communicating data. In one embodiment, the transmission system is part of an optical data communication system that includes: (1) an optical pulse transmitter configured to generate amplitude-modulated optical pulses at a fixed repetition rate, (2) an optical filter coupled to an output of the optical pulse transmitter, having a transmission notch at the fixed repetition rate and configured to filter the optical pulses and (3) an optical detector coupled to an output of the optical filter and configured to produce an output electrical signal representative of intensities of the optical pulses provided by the optical filter.

Abstract: A transmitting and receiving device, in which the received signal which is produced by the receiving device has only a small amount of crosstalk. This object is achieved by providing a transmitting and receiving device having a transmitting device for producing a transmission signal, a receiving device for producing a received signal, and a compensation device which is connected to the transmitting device and to the receiving device and which at least reduces any crosstalk which is produced by the transmitting device in the receiving device.

Abstract: Systems and methods for compensating transitions in a data stream to account for jitter including laser jitter. Transitions in the data stream are delayed or advanced depending on the laser jitter and/or whether the previous transition is a rising or falling transition. The compensation of transitions is non-linear such that compensation applied to a rising transition is not necessarily the same as compensation applied to a falling transition. A history of more than one or more bits or transitions of the data stream can be used to further adjust the compensation of transitions in the data stream. When a transition is detected, the bit following the detected transition is peaked either positively or negatively such that the following transition is accordingly delayed or advanced.

Abstract: In an optical communication-use receiving circuit of the present invention, the pulse width of the received pulse which is a binary signal corresponding to the signal optical pulse is specified by using an integration circuit and a trigger generating circuit. If the pulse width of the received pulse is not shorter than a predetermined value, a signal having a fixed pulse width is outputted as an output signal from a one-shot pulse generating circuit, so that a pulse having a constant pulse width corresponding to the specified communication speed is outputted. Accordingly, if the pulse width deriving from the signal optical pulse is larger than a certain value, the communication is deemed as a low-speed communication, and a pulse having a constant pulse width corresponding to the communication speed is outputted. As a result, it is possible to realize a small-size receiving circuit and a small-size electronic device which require no external switching-over terminal.

Abstract: A squeezed light generator comprises an arbitrary optical fiber, a means for temporally separating two linearly polarized components, two Faraday rotators and a high-reflection mirror. Pulse lights that are temporally separated into two orthogonally polarized components at an intensity ratio of 50:50 are reciprocatively propagated in the optical fiber, and the polarized light is rotated by 90° in an outward transmission. Since those two polarized components pass through the optical paths which are accurately equal to each other in the outward and homeward transmissions, those two polarized components interfere with each other accurately at 50:50 after reciprocation through the fiber. The interfered beam is separated by a polarizing beam splitter that is high in an extinction ratio. When the polarized lights before inputting the fiber and after reciprocating coincide with each other, it is unnecessary to maintain the polarization in the fiber propagation, and an arbitrary fiber can be used.

Abstract: A group delay compensation equalizer is disclosed that employs a single channel four-port WDM device for compensating the group delay experienced by a plurality of wavelengths transmitted over different paths. The transmission differential between two wavelengths is compensated by transmitting the two wavelengths through two different paths where the fiber length in reflecting the second wavelength is equal to the transmission time difference between the two wavelengths. The single channel four-port group delay equalizer effectively provides a unidirectional signal flow, as compared to the conventional equalizer that transmits optical signals bi-directionally. The present invention reduces the cost of a group delay equalizer by simplifying the use of multiple three-port WDM devices into a single channel four-port WDM device.

Abstract: A DQPSK optical signal is split by the splitter 1 into Data 1 and Data 2 systems. For each system, a phase-modulated optical signal is converted into an intensity modulated electric signal, and clock reproduction and data reproduction are independently carried out for each system. While a phase difference occurs between the data of each system, a clock signal having an intermediate phase of the reproduced clock of each system is generated to latch data of both systems by using the clock signal. This results in the data of both systems having the same phase.

Abstract: A wavelength converter for binary optical signals includes an interferometer structure (110) for generating an output signal by modulating a received local signal (LS) according to the modulation of a fUrther received first input signal (IS 1). When such interferometer structures (110) are operated in a standard mode it is known in the art to control the power of the input signal such that the extinction ratio of the output signal is kept minimal. The invention also controls the power of the input signals to achieve the minimal extinction ratio when the wavelength converter and in particular the interferometer structure (110) is operated in a differential mode receiving two input signals.

Abstract: A method for transmitting traffic in an optical communication system comprising separating the input traffic into a plurality of data signals, parameter encoding the data signals, transmitting each of the data signals on a separate optical channel, receiving the data signals on the channels, parameter decoding the data signals, and combining the plurality of data signals from the channels into output traffic corresponding to the input traffic.

Abstract: An electrical return to zero (RZ) encoder converts non-return to zero (NRZ) data, into of RZ data patterns with a flexibility for duty cycle adjustment so that any RZ data pattern may be provided for a specific application's need. A duty cycle of>50% or<50% may be achieved by selecting between a clock signal or its complement and adjusting its delay.

Abstract: An optical code division multiplexing communication method includes the steps of: producing a multi-wavelength optical pulse train from wavelength multiplexing pulse; transmitting the multi-wavelength optical pulse train through a transmission line using a time-spreading/wavelength-hopping method; decoding wavelength multiplexing pulse from the multi-wavelength optical pulse train transmitted through the transmission line; compensating delay time differences between individual optical pulses of the multi-wavelength optical pulse train, the delay time differences occurring in the step of transmitting the multi-wavelength optical pulse train through the transmission line; and compensating optical pulse spread in a time direction, which occurs in each of the optical pulses of the multi-wavelength optical pulse train in the step of transmitting the multi-wavelength optical pulse train through the transmission line.

Abstract: An optical receiver for receiving a transmission light signal which is subjected to an optical phase modulation based on a data signal to be transmitted and has a dither signal superposed thereon includes a delay interferometer to which the transmission light signal having the dither signal superposed thereon is applied and which converts the transmission light signal into a light intensity modulation signal based on a control signal, a photodetector for converting two light outputs of the delay interferometer into an electric signal, two current detecting sections for differentially detecting a photocurrent flowing to the photodetector as a detection voltage, a data clock reproducing section for outputting the data signal and a clock signal based on an output of the photodetector, two filter sections for extracting dither signal components of the differential detection voltages respectively, and a control section for determining the control signal and applying the control signal to the delay interferometer i

Abstract: A demodulator includes: a Michelson interferometer having: a half-mirror which splits an optical signal, emits a first split light to a first optical path, and emits a second split light to a second optical path; a first reflector which reflects the first split light to the half-mirror; and a second reflector which reflects the second split light to the half-mirror, wherein the half-mirror recombines the first split light and the second split light, and emits a recombined optical signal while splitting the recombined optical signal; and an balanced optical detector which receives the recombined optical signals from the Michelson interferometer, and generates a demodulated signal based on the two recombined optical signals. The length difference between the first optical path and the second optical path is set so that the second split light has a delay time equal to a one-bit period, with respect to the first split light.

Abstract: Method and apparatus for compensating for first-order Polarization Mode Dispersion in an optical transmission system. An apparatus has a polarization controller for transforming polarization components of an optical signal carried by the optical fiber into orthogonal polarization states, a variable delay line for introducing a variable differential time delay between the polarization states and for producing an output optical signal that is compensated for PMD in the optical fiber, and a feedback unit for adjusting the polarization controller and the variable delay line to compensate for variations in the PMD of the optical fiber, the feedback unit including apparatus for generating a plurality of independent control signals to independently control actuators of the polarization controller and the variable delay line. The invention provides for a reduction in response time of the actuators and a reduction in complexity of an algorithm used to control the apparatus.

Abstract: A method and apparatus for dispersion management in hybrid data rate long haul mesh networks are provided. The apparatus comprises a dispersion compensator for fully compensating the residual dispersion of a fiber link in the mesh network. A de-interleaver is coupled to the dispersion compensator for de-interleaving odd and even channels of wavelength division multiplexed (WDM) signals transmitted across the fiber link. A delay device is coupled to the de-interleaver for introducing a delay to the odd channels or the even channels of the WDM signals to decorrelate the odd and even channels and substantially reduce inter-channel cross-phase modulation.

Abstract: An agile spread spectrum waveform generator comprises a photonic oscillator and an optical heterodyne synthesizer. The photonic oscillator comprises a multi-tone optical comb generator for generating a series of RF comb lines on an optical carrier. The optical heterodyne synthesizer includes first and second phase-locked lasers; the first laser feeding the multi-tone optical comb generator and the second laser comprising a rapidly wavelength-tunable single tone laser whose output light provides a frequency translation reference. A photodetector is provided for heterodyning the frequency translation reference with the optical output of the photonic oscillator to generate an agile spread spectrum waveform.

Abstract: The inventors propose herein a switch fabric architecture that allows broadcasting and fast channel access in the ns-range. In various embodiments of the present invention, 10 Gb/s receiver modules are based on a novel heterodyne receiver and detection technique, which is tolerant to moderate wavelength drifts of a local oscillator. A gain clipped electrical amplifier is used in the novel receiver as a rectifier for bandpass signal recovery.

Abstract: Optical transponders with reduced sensitivity to PMD and CD are described. In one embodiment, an optical transponder comprises a differential group delay (DGD) mitigator integrated within the transponder and optically coupled to an optical input port of the optical transponder, an optical receiver integrated within the optical transponder and optically coupled to the DGD mitigator and to an electrical output port of the transponder, and a multi-level transmitter integrated within the optical transponder, where the multi-level transmitter is electrically coupled to an electrical input port and optically coupled to an optical output port of the transponder.

Abstract: A method and system is provided for compensating polarization mode dispersion (PMD) in an optical communications system includes a controller designed to control a broadband PMD compensator to differentially delay light at each one of a plurality of selected wavelengths. At least one of the selected wavelengths lies between an adjacent pair of channel wavelengths of the optical communications system. A performance parameter value indicative of PMD is measured at each channel wavelength of the optical communications system. An estimated performance parameter value is then calculated at each selected wavelength, and an error function calculated as a function of wavelength based on the estimated performance parameter values. The broadband PMD compensator is then controlled to minimize the value of the error function.

Abstract: A method of reducing correlation between channels in an optical communication network. A transmission characteristic of first data on a first channel is altered to reduce correlation between the first data and second data on a second channel. The reduction in correlation reduces crosstalk. The transmission characteristic may be one or more of time delay, scrambling, inversion or modulation.

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: To resolve problems, with the invention, an optical transmitter comprises an encoder for generating an optical signal obtained by encoding multi-wavelength pulses corresponding to sending data by use of a method of time spread/wavelength hopping in accordance with an encoding pattern of the encoder itself. The encoder concurrently executes time delay for every wavelength component at encoding, and time delay due to pre-compensation processing to pre-compensate for difference in propagation time for every wavelength component, occurring due to chromatic dispersion characteristics of a transmission line by ?%. An optical receiver comprises a decoder for decoding the optical signal transmitted by the optical transmitter in accordance with a decoding pattern of the decoder itself.

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: A system and method is disclosed for mitigating the scintillation and fading effects of baseband wireless, radio frequency wireless, optical wireless and satellite communication links. The system uses a space-time channel model to derive an optimal processing architecture for signal recovery through a scintillation channel. The signal power is collected by space-time sampling within the four dimensional volume of the spatial and temporal spread. Consequently, the space-time equalizer can effectively recover the lost signal power induced by the spreading effects of atmospheric scintillating medium. The advantages of this invention include a decrease in link outages resulting in higher link availability and more reliable data network services.

Abstract: A demodulator comprises an input splitter, optical device sets, and couplers. The input splitter splits an input signal comprising symbols to yield a number of signals. A first optical device set directs a signal of along a first path. A second optical device set directs another signal along a second path to yield a delayed signal. At least a portion of the second path is in free space. A path length difference between the first path and the second path introduces a symbol delay between the first signal and the second signal. A coupler receives a portion of the signal and a portion of the delayed signal to generate interference, where the interference indicates a phase shift between a phase corresponding to a symbol and a successive phase corresponding to a successive symbol.

Abstract: A method for transmitting digital data includes splitting a coherent optical carrier having a subcarrier into mutually coherent optical carriers, producing corresponding sequences of phase shifts in each of the mutually coherent optical carriers, and then, interfering the mutually coherent optical carriers. The interfering produces an output optical carrier whose subcarrier has modulated inphase and quadrature components with a corresponding sequence of pairs of values. The pairs of values of the modulated inphase and quadrature phase components produced by the interfering correspond to a sequence of coordinate pairs for the signal points the 4-PSK 2D, 16-QAM 2D, or 16-PSK 2D constellation.

Abstract: A method, apparatus, and system for optical communications. An optical transmit signal is generated in response to an electrical transmit signal. The optical transmit signal is coupled into a single communication link for transmission there over. An optical receive signal is received from the single communication link, and in response an electrical receive signal is generated.

Abstract: Embodiments of the present invention are directed to dual stage modular optical devices with insert digital diagnostics components. A first portion of a leadframe couples a first fabricated package including a light source and/or light detector to a second fabricated package with first opening for receiving inserts. A second portion of the leadframe couples the second fabricated package to a third fabricated package with a second opening for receiving inserts. A first component insert is coupled to the second fabricated package such that components of the first component insert can electrically interoperate with the light source and/or light detector. A second component insert is coupled to the third fabricated package such that components of the second component insert can electrically interoperate with components of the first component insert to implement digital diagnostics functions.