Abstract: A dispersion compensation device includes: an optical branching unit to branch an optical signal to be received; a first dispersion compensator to perform dispersion compensation on one part of the optical signal branched by the optical branching unit with a variable compensation amount; a second dispersion compensator to perform dispersion compensation on another part of the optical signal branched by the optical branching unit; a monitoring unit to monitor the communication quality of an output optical signal of the second dispersion compensator; and a controlling unit to determine the direction of variation in chromatic dispersion of the optical signal based on the direction of variation in communication quality monitored by the monitoring unit and control the compensation amount of the first dispersion compensator based on the result of the determination.

Abstract: An OCDM communication system and a method for correcting failure of the same are provided. In the system, encoders and decoders are provided respectively for channels. Each encoder, including an SSFBG, encodes an optical signal using a code value determined according to distance between adjacent unit fiber Bragg gratings in the SFFBG. Each decoder, including an SFFBG, generates a received optical signal by decoding the encoded signal using a code value determined in the same manner. A set temperature of each encoder and decoder is calculated and a corresponding control signal is generated based on average power and error rate detection signals of each received optical signal. The temperature of each encoder or decoder is individually adjusted according to the control signal, which makes equal the code values of an encoder and decoder of a channel in which average power of a received signal has changed or error rate thereof is excessive.

Abstract: Filter implementation using Hermitian conjugates and time division multiplexing (TDM) is disclosed to more efficiently compensate for chromatic dispersion of optical signals transmitted over a fiber optic medium. Embodiments for an input, filter, and output sections of a Digital Signal Processor (DSP) are described. The disclosed methods, and corresponding apparatus and systems enables a substantial reduction in the complexity of the hardware needed to implement CD compensation in the DSP. According to another embodiment, Inverse-Fourier transform circuits receive TDM data from the filter section and assemble the TDM data format back to a non-TDM format.

Abstract: An apparatus for generating a dispersion compensation signal includes a splitting module for splitting a data signal to be transmitted into N channels of data signals; N pre-processing modules for adjusting in frequency domain the phases and amplitudes of the N channels of data signals and outputting N channels of pre-warped electrical signals; an optical carrier generating module for generating N channels of coherent optical carriers; N electro-optic modulators for modulating the N channels of coherent optical carriers based on the N channels of pre-warped electrical signals and generating N channels of pre-warped optical signals; an optical coupling module for coupling the N channels of pre-warped optical signals into a dispersion compensation optical signal. By pre-processing the data signals, the present disclosure may allow the use of existing devices to generate a dispersion compensation signal so that the bandwidth requirement set by prior art on the electrical device is reduced.

Abstract: A method of controlling communication between transceivers includes transmitting payload data from a transmitter of a first transceiver in a data channel of a physical link to a receiver of a second transceiver, the second transceiver further including an equalizer, varying equalizer settings in the equalizer, analyzing effects of varying equalizer settings to determine transmitter diagnostic settings for the first transceiver, and transmitting the transmitter diagnostic settings from a transmitter of the second transceiver in an out-of-band channel of a physical link to a receiver of the first transceiver a second transceiver in a data channel.

Abstract: A digital filter is provided for processing an electrical input signal to be conveyed through an optical communications system. The processing generates a predistorted electrical signal using a compensation function that substantially mitigates for intra-channel non-linearity imparted to the communications signal by the optical communications system. The digital filter has a memory having a limited size storing a reduced data set used for approximating an original, unreduced data set used to implement the compensation function. The reduced data set is used for the digital filter to apply the compensation function to mitigate the intra-channel non-linearity over longer transmission distances of the optical communications system than would be possible without the use of the reduced data set.

Abstract: An optical network contains dispersion compensation modules with Fiber Bragg Gratings. A photo detector behind the Fiber Bragg Grating detects the not reflected rest of the gratings input signal and therefore the dispersion compensation modules input signal. This information is used to reduce the expenditure and to avoid errors of configuration or administration of the dispersion compensating subsystem of the optical network.

Abstract: An embodiment of the invention is a technique to equalize received samples. A coefficient generator generates filter coefficients using an error vector and input samples. A filter stage generates equalized samples from input samples using the filter coefficients. The received samples are provided by a receiver front end in an optical transmission channel carrying transmitted symbols. Other embodiments are also described.

Abstract: An embodiment of the invention is a technique to equalize received samples. A coefficient generator generates filter coefficients using a rotated error vector. A filter stage generates equalized samples or slicer input vector from received samples or rotated received samples using the filter coefficients. The received samples are provided by a receiver front end in an optical transmission channel carrying transmitted symbols.

Abstract: A signal equalizer for compensating impairments of an optical signal received through a link of a high speed optical communications network. At least one set of compensation vectors are computed for compensating at least two distinct types of impairments. A frequency domain processor is coupled to receive respective raw multi-bit in-phase (I) and quadrature (Q) sample streams of each received polarization of the optical signal. The frequency domain processor operates to digitally process the multi-bit sample streams, using the compensation vectors, to generate multi-bit estimates of symbols modulated onto each transmitted polarization of the optical signal. The frequency domain processor exhibits respective different responses to each one of the at least two distinct types of impairments.

Abstract: A method and system for improving the performance of a differential-phase modulated optical communication system is disclosed. The system comprises a demodulator having a tunable element to adjust the free-spectral range (FSR) thereof, and a tunable phase shifter to adjust a frequency of a signal passing therethrough.

Abstract: An apparatus and method is disclosed for producing and filtering optical and electrical waveforms. The apparatus includes an electro-optical modulator, an optical filter capable of modulating at least two spectral regions within the bandwidth of the electrical waveform, and an optical-to-electrical converter. The optical filter includes a spatial dispersion means, a spatial modulating means having the capability to substantially independently modulate a characteristic of each of a pair of optical spatial elements.

Abstract: The invention describes an integrated-photonics arrangement, implementable in a multi-guide vertical integration (MGVI) structure composed from III-V semiconductors and grown in one epitaxial growth run, allowing for the integration of semiconductor optical amplifier (SOA) and PIN photodetector (PIN) structures within a common wavelength-designated waveguide of the plurality of the vertically integrated wavelength-designated waveguides forming the MGVI structure. The integration includes a wavelength filter integrated between the SOA and PIN to reduce noise within the PIN arising from ASE generated by the SOA. In exemplary embodiments of the invention, the wavelength filter is integrated into MGVI structure either within a common wavelength designated waveguide or within the wavelength-designated waveguide.

Abstract: A light dispersion filter is composed of three or more optically transparent layers each having a value equal to the value of the product of the refractive index and thickness of the optically transparent layer and transmitted light, and a plurality of partially reflective layers arranged alternately with the optically transparent layers and having predetermined reflectivities. Alternatively, a light dispersion filter has a plurality of etalon resonators which are arranged in series such that the value of the product of the refractive index of air and the interval of the etalon resonators is equal to the value of the product of the refractive index and thickness of the optically transparent layers.

Abstract: The present application describes methods and systems for use in a communications network. More specifically, a method of deploying an optical demodulator arrangement having at least one interferometer in a network that transmits an optical signal is provided. The optical signal may include one or more on-off-keyed signals and one or more DMPSK signals. In some embodiments, the DMPSK signal is a DQPSK signal. The network may include one or more of fiber spans carrying the signals. The interferometer may have a first optical path and a second optical path and a time delay is formed between the first and second optical paths. The method may involve determining a cross-talk penalty that results from cross-phase modulation between the channels, and determining a time delay value for the interferometer. The time delay value may be determined based at least in part on determined the cross-talk penalty.

Abstract: Methods, apparatuses, and systems are presented for performing adaptive equalization involving receiving a signal originating from a channel associated with inter-symbol interference, filtering the signal using a filter having a plurality of adjustable tap weights to produce a filtered signal, and adaptively updating each of the plurality of adjustable tap weights to a new value to reduce effects of inter-symbol interference, wherein each of the plurality of adjustable tap weights is adaptively updated to take into account a constraint relating to a measure of error in the filtered signal and a constraint relating to group delay associated with the filter. Each of the plurality of adjustable tap weights may be adaptively updated to drive group delay associated with the filter toward a target group delay.

Abstract: An optical device comprising an optical device comprising a Mach-Zehnder interferometer having a first 2×2 optical coupler, a second 2×2 optical coupler, a first optical arm, and a second optical arm. The first and second arms connecting corresponding pairs of optical ports of the first and second 2×2 optical couplers. The second optical arm has a longer optical path than the first arm. The device also comprises one or more optical resonators optically coupled to the first optical arm and an optical splitter. The optical splitter is coupled to deliver a portion of an input optical signal to one port of the first 2×2 optical coupler and to deliver a remaining portion of the input optical signal to one port of the second optical coupler.

Abstract: A channel memory length selection method for wireless communication systems is provided. The method comprises estimating an initial channel impulse response (CIR) for the wireless communication system; determining a first refined CIR with a first group of taps and a second refined CIR with a second group of taps based upon the initial CIR, number of the second group of taps being less than number of the first group of taps; and selecting either the number of the first group of taps or the number of the second group of taps as the channel memory length according to an energy concentration criterion in regard to the first refined CIR and the second refined CIR.

Abstract: A variable dispersion compensating unit compensates an optical signal, and changes the compensation amount according to a control signal that has a given frequency. After demodulation of the compensated optical signal, error conditions of the signal are monitored and an error signal is output. A band pass filter filters the error signal for a component having a frequency equal to or less than the given frequency. Based on the component and on the control signal, a synchronous detecting circuit generates a compensation amount modification signal. The compensation amount modification signal is superposed on the control signal.

Abstract: The optical transmitter and receiver of the invention includes: a variable dispersion compensator that performs wavelength dispersion compensation on an optical signal of a differential M-phase modulation format input from a transmission path; an optical amplifier that compensates an optical loss in the variable dispersion compensator; a delay interferometer that delays and interference processes the optical signal output from the optical amplifier; and a photoelectric conversion circuit that photoelectric converts the output light from the delay interferometer to generate a demodulated electric signal. The output level of the optical amplifier is decreased at the time of start up to deteriorate the OSNR of the optical signal input to the photoelectric conversion circuit, to thereby realize a state in which an error occurs more easily, and then optimization control of the variable dispersion compensator and the delay interferometer is started.

Abstract: A receiver device for optical data signals, in particular optical data signals in the Gb/s range, comprising an opto-electrical conversion unit, a frequency multiplicator unit (24) for frequency-multiplying the converted electrical data signal, and a clock recovery unit is characterized in that the frequency multiplicator unit (24) performs a frequency multiplication by a factor of n, with n being a natural number larger than 2. The receiver device has an improved tolerance on dispersion as far as generating a clock line is concerned.

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: Systems and methods for multiplexing two or more channels of a quantum key distribution (QKD) system are disclosed. A method includes putting the optical public channel signal (SP1) in return-to-zero (RZ) format in a transmitter (T) in one QKD station (Alice) and amplifying this signal (thereby forming SP1*) just prior to this signal being detected with a detector (30) in a receiver (R) at the other QKD station (Bob). The method further includes precisely gating the detector via a gating element (40) and a coincident signal (PN1?) with pulses that coincide with the expected arrival times of the pulses in the detected (electrical) public channel signal (SP2). This allows for the public channel signal to have much less power, making it more amenable for multiplexing with the other QKD signals.

Abstract: An optical device includes an interferometer for a received optical differential phase shift keying DPSK signal, and an equalizer integrated with the interferometer in a manner for reducing from optical filtering effects an interference by signal bits of the DPSK signal with signal bits of a contiguous DPSK signal. The interferometer is a Michelson delay interferometer type, but can also be a Mach-Zehnder delay interferometer type on fiber, waveguide or other optical structure. The equalizer is a Fabry-Perot type equalizer, but can be a ring resonator type or a fiber based equalizer.

Abstract: Optical transmission system (200) comprising: an optical source (210) adapted to generate a modulated optical signal having an optical spectrum and a dispersion robustness; an optical dispersion compensation filter (250) optically connected to the optical source, comprising at least two cascaded optical resonators and having a periodic transfer function that is rigidly translatable in the frequency spectrum and characterized by a free spectral range (FSR); a control system (270; 280; 260) adapted to act on the optical compensation filter in order rigidly to translate said transfer function along the frequency spectrum in a first and in a second position in such a way that: in a first position in the frequency spectrum of said transfer function, the mean chromatic dispersion weighted over said optical spectrum of the modulated signal is greater, in absolute value, than the value of dispersion robustness; in a second position in the frequency spectrum of said transfer function, the mean chromatic dispersion wei

Abstract: Certain aspects of a method and system for optimum channel equalization between a host Serializer-Deserializer (SerDes) and an optical module may compensate and reduce dispersion loss along an electrical transmit path of a transmitter and an optical transmit path coupled to the transmitter via pre-emphasis. The data degradation as a result of the dispersion loss along the electrical transmit path of the transmitter and the optical transmit path coupled to the transmitter may be recovered by equalizing signals received via an electrical receive path of a receiver communicatively coupled to the transmitter.

Abstract: An optical repeater device of the present invention comprises: a preamble compensating circuit 53, for taking out a normal data signal from burst signals propagating through a communication transmission path, and for adding a preamble signal before and/or after the data signal. Furthermore, the preamble compensating circuit 53 comprises: a detector circuit 53a, for inputting the burst signal, and for outputting only the normal data signal; a buffer circuit 53b, for storing the data signal output from the detector circuit 53a, and for outputting thereof; a preamble signal generation circuit 53d, for outputting at least one type of the preamble signal; and an data output select circuit 53e, for outputting the data signal at the time of the data signal input from the buffer circuit 53b, and for outputting the preamble signal from the preamble signal generation circuit 53d at any other time thereof.

Abstract: Systems and methods according to these exemplary embodiments provide for methods and systems improving the protocol efficiency in passive optical networks. Additionally, methods and systems for calculating and transmitting an equalization delay change message are described.

Abstract: An optical transmission system for transmitting an optical pulse in a dielectric waveguide, the system including a filter for altering a shape of the optical pulse in both amplitude and phase with respect to time so as to substantially suppress the generation of third-order nonlinearities and increase a power level of the optical pulse, the filter further providing a secure encrypted optical waveform that may be decrypted by a matching optical filter, the system allowing for energy sharing of the pulses to substantially increase system bandwidth.

Abstract: An optical communication system combines strong electrical pre-filtering of data at the transmitter and digital feedback equalization (DFE) at the receiver to enhance spectral efficiency. The system can be applied to optical networking and digital communication systems, including binary modulated systems optical network systems.

Abstract: In order to enhance dispersion control, the apparatus includes a dispersion controller; a quality index generator generating a quality index representing a quality of an optical signal output from the dispersion controller; and a searching unit searching for an amount of dispersion control applying to the dispersion controller which amount optimizes the quality index, wherein the searching unit includes a splitting-half searching unit roughly searching, in a splitting half method, a range in which dispersion is controllable by the dispersion controller for an amount of dispersion control such that the quality index generated by the quality index generator becomes preferable, and a sweep searching unit thoroughly searching, by sweeping, a limited range based on the amount of dispersion searched by the splitting-half searching unit for an amount of dispersion control that optimizes the quality index generated by the quality index generator.

Abstract: A method and apparatus for switching at least one wavelength component of an optical signal beam from a first state to a second state. The phase characterizing the optical signal component is incremented by interaction with one or more escort beams in a non-linear medium thereby switching the state of the optical signal component on the basis of its incremented phase. Multiple escort beams may also be employed to switch different wavelength components of the signal. The method may be employed to achieve high speed, and substantially transparent, switching of phase, intensity or polarization of a signal.

Abstract: A system and method for dispersion compensation of an optical signal in a hybrid network includes generating optical traffic in a first set of one or more channels, wherein the traffic in the first set of channels is modulated using a first modulation technique. Optical traffic is generated in a second set of one or more channels, wherein the traffic in the second set of channels is modulated using a second modulation technique. An optical dispersion pre-compensation is applied to the second set of channels. The first set of channels and the second set of channels are combined to form an optical signal, and the optical signal is transmitted over an optical network.

Abstract: An interference-rejection coding method for an optical wireless communication system and such an optical wireless communication system are provided. The coding method uses delay modulation, block code techniques and filtering to reduce the low frequency interference from light sources. A plurality of codewords from the block codes are reserved for performing digital data recovery. The invention removes the need of analog clock data recovery circuit, and does not require complex hardware for realization. Therefore, it can be applied to a wide range of applications, such as optical WLAN, data transmission of medical facilities, wireless communication in the aircraft, encrypted data transmission network, and low-priced transmission interfaces.

Abstract: A signal processor for compensating for optical fibre chromatic dispersion comprising encoding means (5) for encoding a source signal (2) received from a data source (6), splitting means (8) to separate the encoded signal (7) from the encoding means (5) into an in-phase component (10) and an in-quadrature component (11), a first filter means (12) adapted to receive the in-phase component (10) and a second filter means (13) adapted to receive the in-quadrature component (11), the first filter means (12) and second filter means (13) being adapted to filter the in-phase and in-quadrature components respectively. The outputs (14, 15) from the filter means form the input to the optical modulator means (3).

Abstract: A digital filter is provided for processing an electrical input signal to be conveyed through an optical communications system. The processing generates a predistorted electrical signal using a compensation function that substantially mitigates for intra-channel non-linearity imparted to the communications signal by the optical communications system. The digital filter has a memory having a limited size storing a reduced data set used for approximating an original, unreduced data set used to implement the compensation function. The reduced data set is used for the digital filter to apply the compensation function to mitigate the intra-channel non-linearity over longer transmission distances of the optical communications system than would be possible without the use of the reduced data set.

Abstract: An integrated transceiver contains a optical equalizer for a distorted O/E-converted signal, an adaptive regenerator coupled to the equalizer, and a clock recovery circuit coupled to the adaptive regenerator. The transceiver has further an embedded processing unit and an integrated programmable memory which stores software program. The processing unit is coupled to adjust threshold values of the adaptive regenerator according to a software algorithm loaded into the memory.

Abstract: A multi-level modulation receiving device for adaptively compensating for chromatic dispersion and polarization mode dispersion with high precision. Each equalizing filter has at least one variable parameter as a weight therefor and equalizes the waveform of a corresponding channel signal in accordance with an averaged variable parameter value. A signal quality monitor monitors the signal quality of the filter output signal, and a variable parameter value calculator calculates a variable parameter value to be set as the variable parameter, in accordance with the signal quality. A variable parameter averaging unit averages the variable parameter values calculated for respective channels, to generate an averaged variable parameter value, and sends the averaged variable parameter value to the equalizing filters such that the same weight is set in the equalizing filters associated with the n channels.

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: The present invention provides: (1) a compensator that compensates a wide range of amount of dispersion of light in a wide bandwidth band; and (2) a variable dispersion slope compensator applicable to the case where a transmission path suitable for a wavelength division multiplexing transmission system produces a wavelength dispersion slope.

Abstract: This device for optically regenerating pulses includes a synchronous intensity modulator to provide time synchronization for pulses passing through it and to stabilize intensity fluctuations in the pulses. In addition, it includes noise suppression circuitry in the form of a saturable absorber that is distinct from the synchronous intensity modulator and the intensity fluctuations stabilizer.

Abstract: An optical equalizer/dispersion compensator (E/CDC) comprises an input/output for receiving a multiplexed channel signal comprising a plurality of channel signals of different wavelengths. An optical amplifier may be coupled to receive, as an input/output, the multiplexed channel signals which amplifier may be a semiconductor optical amplifier (SOA) or a gain clamped-semiconductor optical amplifier (GC-SOA). A variable optical attenuator (VOA) is coupled to the optical amplifier and a chromatic dispersion compensator (CDC) is coupled to the variable optical attenuator. A mirror or Faraday rotator mirror (FRM) is coupled to the chromatic dispersion compensator to reflect the multiplexed channel signal back through these optical components The E/CDC components may be integrated in a photonic integrated circuit (PIC) chip.

Abstract: A method of receiving optical channels including providing an optical band filter configured to filter at least one optical channel from a multiple channel optical signal and provide a band filtered optical signal. A periodic filter is configured to filter and/or shape one channel from the band filtered optical signal and provide the periodic filtered, shaped signal to a receiver and other optical system. The invention also relates to corresponding systems and apparatuses.

Abstract: An all optical network for optical signal traffic has at least a first ring with at least one transmitter and one receiver. The first ring includes a plurality of network nodes. At least a first add/drop broadband coupler is coupled to the first ring. The broadband coupler includes an add port and a drop port to add and drop wavelengths to and or from the first ring, a pass-through direction and an add/drop direction. The first add/drop broadband coupler is configured to minimize a pass-through loss in the first ring and is positioned on the first ring.

Abstract: A dispersion compensator is applicable to a WDM optical transmission system and features low loss, wideband usage, and minimum ripple. The dispersion compensator is constructed so that the light emitted from a collimator will be reflected from an etalon of a 100% single-side reflectance by arranging the etalon and a mirror in parallel or with a slight angle and then enter another collimator. Elements for achieving variable dispersion compensation by changing temperature using a heater, for example, are also provided. In addition, these dispersion compensating elements are provided in multi-stage form and the angle of the mirror and the reflectance of the etalon are optimized. Thus, it becomes possible to realize a dispersion compensator applicable to a WDM optical transmission system and featuring low loss, wideband usage, and minimum ripple.

Abstract: A laser filter circuit includes an input terminal configured to receive an input laser signal and a first filter chain configured to generate a filtered signal. The first filter chain is coupled to the input terminal and has one or more filters connected in series. Each filter includes one or more adjustable capacitor networks. An adjustable capacitor controller generates one or more capacitor switch control signals based on an operating frequency of the input laser signal. The one or more control signals are for adjusting the capacitance of the one or more adjustable capacitor networks in the first filter chain. A plurality of output terminal output the filtered signal from the first filter chain.

Abstract: A light dispersion filter is composed of three or more optically transparent layers each having a value equal to the value of the product of the refractive index and thickness of the optically transparent layer and transmitted light, and a plurality of partially reflective layers arranged alternately with the optically transparent layers and having predetermined reflectivities. Alternatively, a light dispersion filter has a plurality of etalon resonators which are arranged in series such that the value of the product of the refractive index of air and the interval of the etalon resonators is equal to the value of the product of the refractive index and thickness of the optically transparent layers.

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

Abstract: In an over-sampled maximum-likelihood sequence estimation (MLSE) receiver system, the optimal sample spacing is determined for a variety of conditions. In an illustrative implementation, the system includes an optical filter for tightly filtering an incoming optical data signal with an on-off-keying (OOK) non-return-to-zero (NRZ) format, followed by an optical-to-electrical converter, an electrical filter, a sampler, and a MLSE receiver. The sampler samples the filtered electrical data signal twice each bit period with unequal sample spacings. For wide optical filtering bandwidths, the optimal sample spacing occurs at less than 50% of a bit period. For narrow bandwidths, the optimal sample instances occur closer to the maximum eye opening.