Abstract: An optical module includes a housing, a plurality of active optical components and a path changer component. The housing has an airtight chamber. The active optical components are provided in the airtight chamber. The path changer component is provided in the airtight chamber, and the path changer component is configured to change an optical path of at least one of the active optical components.

Abstract: Described herein are systems and methods that manage polarization in coherent optical receivers by using analog signal processing that eliminates the need for ultra-fast, power-hungry ADCs and DSPs and that would require digitization of the full-bandwidth signal path and result in bulky and expensive circuit designs. Various embodiments of the invention provide polarization correction by using an analog polarization correction circuit that implements the equivalent of two matrix operations. This is accomplished by using analog electronics that comprises a combination of variable and unity gain amplifiers to align polarizations of input signals to generate a polarization-corrected output signal that is further aligned with the polarization frame of reference of the receiver.

Abstract: A technology is described for a Photonic Integrated Circuit (PIC) radio frequency (RF) in-phase quadrature phase (I/O) correlator. The PIC RF Correlator can comprise two optical waveguides to receive first and second optical signals that are modulated by first and second RF signals, respectively. Two 1 to M optical splitters can split the first and second RF modulated optical signals. Optical delay lines can delay the M split first RF modulated optical signals. M optical balanced couplers can receive and combine the M first delayed RF modulated optical signals with the M split second RF modulated optical signals. Balanced photodetectors can output a differential integration on the first and second combined RF modulated optical signals for in-phase and quadrature phase signals. A processor can add the outputs of the M optical balanced photodetectors to form a frequency domain correlated signal of the first and second RF signals with real and imaginary parts.

Abstract: A technology is described for a Photonic Integrated Circuit (PIC) radio frequency (RF) correlator. The PIC RF Correlator can comprise two optical waveguides to receive first and second optical signals that are modulated by first and second RF signals, respectively. Two 1 to M optical splitters can split the first and second RF modulated optical signals. Optical delay lines can delay the M split first RF modulated optical signals. M optical balanced couplers can receive and combine the M first delayed RF modulated optical signals with the M split second RF modulated optical signals. Balanced photodetectors can output a differential integration on the first and second combined RF modulated optical signals. A processor can add the outputs of the M optical balanced photodetectors to form a frequency domain correlated signal of the first and second RF signals.

Abstract: Disclosed is a method for reconstructing an electromagnetic vector wave backscattered in all or part of an optical fiber. According to an embodiment of the method a light signal of a frequency v0 or v0+vA is injected into the optical fiber. A step of polarization-resolved heterodyne optical detection includes the generation of at least two orthogonally polarized backscattered light signals, producing a beat preferably of a frequency vA. At least one photodetector converts the orthogonally polarized backscattered light signals into initial analog signals. Electrical homodyne detection is performed by an IQ demodulator so as to generate I and Q demodulated analog signals. A processing module reconstructs the electromagnetic vector wave backscattered in all or part of the optical fiber.

Abstract: An apparatus includes an input receiving a modulated optical data signal having components of at least first and second polarizations, a first optical detector receiving the data signal, the first optical detector being first polarization-selective or first polarization-sensitive, passing components of the data signal having the second polarization, and outputting a first electrical signal, a second optical detector coupled to the first optical detector to receive the components of the data signal having the second polarization, and outputting a second electrical signal, and a processor applying a Kramers-Kronig process to the first and second electrical signals, and outputting the data signal using the Kramers-Kronig processed first and second electrical signals.

Abstract: Optical systems, receivers, devices, and methods including a free space beam combining and polarization splitting prism to receive local oscillator light and optical signals in substantially parallel input paths that are in the same plane and output two orthogonally polarized beams in substantially parallel output paths that are substantially perpendicular to the plane of the input paths. Light in one of the incoming paths is reflected toward a combining surface that combines the local oscillator light and the optical signal. The combined beam then encounters a polarization splitting surface that splits the combined beam into two orthogonally polarized beams. One of the polarized beam may be reflected 90 degrees in plane and then both orthogonally polarized beams are reflected 90 degrees of out of plane to output each orthogonally polarized beam into substantially parallel optical output paths.

Abstract: A detecting system is provided for detecting distant objects. The system includes a light source configured to emit light pulses towards a distant object, the light pulses are being polarized at a predefined polarization angle; a detector configured to detect at least a portion of the light pulses reflected from the distant objects; and at least one linear polarizer configured for polarizing light at the polarization angle and being so disposed with respect to the detector such that the light reaching the detector passes through the linear polarizer and is polarized at the polarization angle.

Abstract: Described herein are systems and methods that perform coarse chromatic dispersion (CD) compensation by applying precomputed coarse front-end equalizer (FEE) tap weights to a receiver based on an assumed propagation distance. After a waiting period, the FEE tap weights are applied, and it is determined whether the FEE tap weights cause a decision-directed tracking of channel rotations to satisfy a stability metric. In response to the stability metric not being satisfied, the assumed propagation distance is adjusted and used to obtain updated FEE tap weights. Conversely, if the stability metric is satisfied, a fine CD compensation is performed that comprises maintaining the updated FEE tap weights; performing an iterative least-mean-squared (LMS) error adaption to adjust Back-End Equalizer (BEE) tap weights and obtain updated BEE tap weights; and using the updated BEE tap weights to adjust the FEE tap weights to, ultimately, have the BEE output an equalized data bit stream.

Abstract: The present disclosure relates to a radio unit (420, 420A, 420B) adapted for cross-polar signal transfer (230), comprising an optical transmit interface (430, 430A, 430B) and an optical receive interface (440, 440A, 440B) which are arranged to transfer cross-polar signals for cross-polar interference cancellation, XPIC, to and from an external source, respectively. The optical transmit interface (430, 430A, 430B) and the optical receive interface (440, 440A, 440B) are arranged at equal distances (D) from a symmetry line (450) of the interfaces, and in a plane (451) perpendicular to the symmetry line (450). Upon rotation of the radio unit (420, 420A, 420B) about the symmetry line (450) by 180 degrees, the optical transmit interface after rotation aligns with the optical receive interface before rotation, and the optical receive interface after rotation aligns with the optical transmit interface before rotation.

Abstract: A method and structure for signal propagation in a coherent optical receiver device. Asynchronous equalization helps to reduce complexity and power dissipation, and also improves the robustness of timing recovery. However, conventional devices using inverse interpolation filters ignore adaptation algorithms. The present invention provides for forward propagation and backward propagation. In the forward case, the filter input signal is forward propagated through a filter to the adaptation engine, while, in the backward case, the error signal is backward propagated through a filter to the asynchronous domain. Using such forward and backward propagation schemes reduces implementation complexity while providing optical device performance.

Abstract: To provide a photodetector which enables reception of massively parallel optical communication, and with which a large volume of data for multi-mode transmission or multi-core transmission can be received instantaneously at once. A photodetector comprising a two-dimensional photodetector array in which a plurality of photodetectors 9 are arranged in a two-dimensional array, and which includes a wire 12 having a width of not more than 4 ?m between the plurality of photodetectors. Each of the photodetectors has a light reception area with a side measuring not more than 100 ?m. The plurality of photodetectors arranged in a two-dimensional array are spaced apart from each other by not less than 20 ?m.

Abstract: In a method, computer and magnetic resonance (MR) apparatus for normalizing MR contrast images of an examination object that has two chemically different substances (SW, SF), wherein the first substance produces a first image signal and the second substance produces a second image signal, a processor is provided with a complex-valued contrast having pixels with signal contributions from the first and second substances. A phase correction of this contrast image is performed by calculating a real-valued contrast from the amount of the image signals of each pixel of the complex-valued contrast image. A mathematically smooth correction map is determined based on a number of the pixels that have a defined real-valued contrast. The intensity of pixels of the complex-valued contrast image are homogenized with other scans based on the correction map.

Abstract: Described herein are systems and methods that manage polarization in coherent optical receivers by using analog signal processing that eliminates the need for ultra-fast, power-hungry ADCs and DSPs and that would require digitization of the full-bandwidth signal path and result in bulky and expensive circuit designs. Various embodiments of the invention provide polarization correction by using an analog polarization correction circuit that implements the equivalent of two matrix operations. This is accomplished by using analog electronics that comprises a combination of variable and unity gain amplifiers to align polarizations of input signals to generate a polarization-corrected output signal that is further aligned with the polarization frame of reference of the receiver.

Abstract: A method includes distributing payload data among a master sub-band and a plurality of slave sub-bands. The master sub-band and the plurality of slave sub-bands collectively extend over an allocated frequency spectrum; the master sub-band and the plurality of slave sub-bands are associated with different carrier frequencies; and the master sub-band has a center frequency that corresponds to a center frequency of the allocated frequency spectrum. The method includes generating modulated data for the master sub-band and the plurality of slave sub-bands based on the distributed payload data; and transmitting an optical signal to an optical medium representing the modulated data.

Abstract: A coherent optical module includes an optical power monitor configured to monitor power of a wavelength multiplexed signal, a local oscillator configured to output a local oscillation light with an optical power corresponding to the monitored power of the wavelength multiplexed signal, a coherent receiver configured to receive an optical signal from the wavelength multiplexed signal by an interference with the local oscillation light, and a converter configured to convert the received optical signal to an electrical signal.

Abstract: One or more embodiments of an apparatus, system and method of compensating image data for phase fluctuations caused by a wave deforming medium, and storage or recording mediums for use therewith, are provided herein. At least one embodiment of the method comprises capturing, by a sensor of an imaging system, first image data and second image data for each of a plurality of pixel positions of the sensor, the sensor capturing an object through a wave deforming medium causing a defocus disparity between the first image data and second image data; and determining the defocus disparity between the first image data and the second image data, the defocus disparity corresponding to a defocus wavefront deviation of the wave deforming medium. The method may further comprise compensating the image data captured by the sensor for phase fluctuations caused by the wave deforming medium using the determined defocus disparity.

Abstract: A method and structure for signal propagation in a coherent optical receiver device. Asynchronous equalization helps to reduce complexity and power dissipation, and also improves the robustness of timing recovery. However, conventional devices using inverse interpolation filters ignore adaptation algorithms. The present invention provides for forward propagation and backward propagation. In the forward case, the filter input signal is forward propagated through a filter to the adaptation engine, while, in the backward case, the error signal is backward propagated through a filter to the asynchronous domain. Using such forward and backward propagation schemes reduces implementation complexity while providing optical device performance.

Abstract: A transmission-type polarization insensitive modulator implemented as a polarization insensitive micro ring modulator (PIMRM) includes a first polarization splitter-rotator (PSR) configured to generate a first light beam and a second light beam having a common polarization from an input, a micro ring configured to modulate the first light beam with data to generate a first output signal, and modulate the second light beam with data to generate a second output signal, and a second PSR configured to combine the first output signal and the second output signal to form a modulated output signal, wherein the micro ring is disposed in between the first PSR and the second PSR.

Abstract: An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at a test modulation frequency F. COR performance parameters are determined by comparing two frequency components of the COR output. CMRR is determined based on a strength of a direct detection spectral line at the modulation frequency relative to that of spectrally-shifted lines at (F±f). GDV information is obtained by modulating one of the lights at two phase-locked frequencies, such as F and 2F, and comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two frequencies.

Abstract: A method and structure for signal propagation in a coherent optical receiver device. Asynchronous equalization helps to reduce complexity and power dissipation, and also improves the robustness of timing recovery. However, conventional devices using inverse interpolation filters ignore adaptation algorithms. The present invention provides for forward propagation and backward propagation. In the forward case, the filter input signal is forward propagated through a filter to the adaptation engine, while, in the backward case, the error signal is backward propagated through a filter to the asynchronous domain. Using such forward and backward propagation schemes reduces implementation complexity while providing optical device performance.

Abstract: The receiver 11 for self-homodyne detection comprises a coherent detection system and a direct detection system. The receiver comprises a polarization splitter 13, a first splitter 15, a 90 degree polarization rotor 17, a hybrid detector 19, a first balanced detector 21, and a processor 23.

Abstract: Provided are methods and systems for receiving and processing optical signals. A dual single side band (SSB) modulation scheme is utilized to take advantage of a given wavelengths' bandwidth. Modulation schemes are employed that modulate each SSB with their In-phase (I) and Quadrature (Q) components. The methods and systems discussed utilize an adaptive equalizer and an LMS algorithm to remove imaging components of the left and right SSBs provided by the modulators. The adaptive equalizer and the LMS algorithm also compensate for linear and nonlinear distortions. Various algorithms can be employed, including but not limited to, algorithms for updating crosstalk coefficients in the equalizer, where the cross talk coefficients are induced from the imaging from the modulation of the dual SSB signal, and for updating coefficients relating to linear and nonlinear distortion.

Abstract: The present document provides a method and device for compensating a phase deviation, which are applied to a data sequence between a first training sequence and a second training sequence which are received by a receiving end; The method includes: determining a first phase difference between a first training sequence and a standard training sequence used for reference, and a second phase difference between a second training sequence and the standard training sequence; determining a subdata sequence requiring a phase compensation in multiple subdata sequences forming the data sequence according to the first phase difference and the second phase difference; calculating a phase compensation value corresponding to the subdata sequence requiring the phase compensation by using the first phase difference and the second phase difference; and conducting the phase compensation on the subdata sequence requiring the phase compensation by using the phase compensation value corresponding to the subdata sequence.

Abstract: A digital communication receiver uses a maximum likelihood sequence estimation stage to recover symbols from digitized sample values of a received signal. A probability density function is calculated and used to improve a soft decision forward error correction calculation. The results of error decoding, which represent error corrected data bits, are further used to improve the probability density function calculation.

Abstract: An advanced split ODU architecture is provided. The advanced architecture includes an indoor communication unit including a digital modem assembly configured to modulate and demodulate digital data, and also includes a digital interface module configured to transmit and/or receive the digital data, over a digital communication pathway, between the indoor communication unit and an external outdoor communication unit. The advanced architecture further includes an outdoor communication unit having a digital interface module configured to transmit and/or receive the digital data, over the digital communication pathway, between the outdoor communication unit and an external indoor communication unit, and also includes a digital to analog converter configured to convert the digital data to analog data and an analog to digital converter configured to convert the analog data to the digital data, and further includes an RF module configured to convert the analog data between a baseband and a radio frequency.

Abstract: An optical receiver having a plurality of optical IQ modulators arranged in a butterfly configuration and configured to operate as an optical polarization de-multiplexer. The optical receiver further has (i) an opto-electric circuit configured to apply optical homodyne detection to an optical input signal received by the optical receiver and (ii) a controller configured to generate one or more control signals for driving the IQ modulators of the plurality based on one or more electrical feedback signals received from the opto-electric circuit.

Abstract: Systems and methods for data transport, comprising encoding one or more streams of input data using nonbinary low density parity check (NB-LDPC) encoders, corresponding to orthogonal polarization states. Receiving one or more streams of input data using a buffer coupled to the encoders, the data written to the buffer bR bits at a time, where R is the code rate. Generating one or more signals using a 2b-ary mapper implemented as a look-up table (LUT) to store coordinates of a corresponding signal constellation, the 2b-ary mapper configured to assign bits of one or more signals to a signal constellation and to associate the bits of the signals with signal constellation points, wherein the constellation is expanded to avoid bandwidth expansion due to coding, generating substantial net coding gains within a same bandwidth. Modulating nonbinary LDPC-coded data streams using in-phase/quadrature (I/Q) modulators and multiplexing the data streams using polarization beam combiner.

Abstract: An optical receiver having an optical IQ modulator configured to generate an optical local-oscillator (OLO) signal for optical homodyne detection of an optical input signal applied to the optical receiver. The optical receiver further has (i) a phase detector configured to generate an electrical measure of the phase difference between the OLO signal and a carrier wave of the optical input signal and (ii) a phase-lock loop configured to drive the optical IQ modulator using the electrical measure. In an embodiment, the phase detector is configured to generate the electrical measure using both I and Q components of the homodyne-detected signal and in a manner that enables the optical receiver to be compatible with the M-QAM modulation format.

Abstract: In order to allow reception in which receive sensitivity does not depend upon polarization state in reception of a multi-level phase optical signal, in this optical reception method, a multi-level phase optical signal of a single polarization is separated into a first optical signal and a second optical signal of which polarizations are mutually orthogonal, the ratio of the power of the first optical signal to the power of the second signal is calculated, and the difference between the phase of the first optical signal and the phase of second optical signal is calculated as an amount of compensation, whereupon, on the basis of the ratio and the amount of compensation, the first optical signal and the second optical signal are combined using a maximal ratio combining method, and the amount of compensation is modified on the basis of the ratio.

Abstract: An optical transmission system 1 includes an optical transmitter 10 and an optical receiver 200. The optical transmitter 10 includes, a multiplexed code sequence generation unit 90a arranged to multiplex a code included in the transmission code sequence to be time shifted, and an optical transmission unit 90b that converts a multiplexed code sequence into a light signal and transmit it. The optical receiver 200 includes, an optical reception unit 240 that receives and converts the light signal transmitted from the optical transmitter 10 into a code sequence, and a transmission code sequence regeneration unit 380 that regenerates the transmission code sequence by identifying a code based on a value of a plurality of codes each corresponding to one another included in the code sequence.

Abstract: Apparatus for analyzing, identifying, or imaging a target is configured to avoid and/or prevent nulls that may occur periodically during a terahertz sweep. Exemplary apparatus may utilize a second harmonic lock-in amplifier to generate an error signal used to adjust a DC bias of a phase modulator to maintain an in-phase relationship between beams to avoid nulls in an output signal during frequency sweeping.

Abstract: Provided is a polarization separation device which converges filter coefficients used in polarization separating process more quickly.

Abstract: An optical signal is converted into an electric signal by an O/E converter on the reception side, and converted into a digital signal by an analog/digital conversion unit. In a capture unit A at the input stage of the digital signal processing unit at the next stage, the constellation of a signal output from an analog/digital conversion unit is acquired for each polarization. According to the constellation information, the amplitude value of the electric signal input to the analog/digital conversion unit is corrected so that the value is optimum. Also, the capture unit B acquires the constellation on the signal after the demodulation by the digital signal processing. According to the constellation information, the amplitude of the I and Q signals and the skew between the I and Q signals are corrected.

Abstract: An example embodiment includes optical receiver that includes a polarization beam splitter (PBS), a polarization controller, and a forward error correction (FEC). The PBS is configured to split a received optical signal having an unknown polarization state into two orthogonal polarizations (x?-polarization and y?-polarization). The polarization controller includes no more than two couplers and no more than two phase shifters per wavelength channel of the x?-polarization and the y?-polarization. The polarization controller is configured to demultiplex the x?-polarization and the y?-polarization into a first demultiplexed signal having an first polarization on which a data signal is modulated and a second demultiplexed signal having a second, orthogonal polarization on which a pilot carrier oscillator signal is encoded. The FEC decoder module is configured to correct a burst of errors resulting from resetting one of the phase shifters based on error correction code (ECC) data encoded in the data signal.

Abstract: A local oscillation light source outputs locally-oscillated light. An light receiving unit phase-separates an input optical signal by making the optical signal interfere with the locally-oscillated light and outputs an analog electric signal corresponding to the phase-separated optical signal. An analog-to-digital converting unit converts the analog electric signal into a digital signal. A processing unit performs digital signal processing by using the digital signal. A failure detection unit determines whether or not the optical signal is being input to the light receiving unit, or detects a failure in the light receiving unit, the analog-to-digital converting unit or the processing unit based on light intensity of the optical signal, whether or not the analog electric signal can be generated in the light receiving unit, and an amplitude of the analog electric signal output from the light receiving unit.

Abstract: Current optical networks are engineered to handle amplifier noise and chromatic dispersion. Polarization mode dispersion occurs in optical networks due splitting of the light energy of a pulse propagating in a fiber into two modes. Compensating for polarization mode dispersion is a difficult and expensive task and hence only few commercial systems have been deployed to deal with this issue. A polarization mode dispersion compensation module according to an example embodiment of the present invention compensates for polarization mode dispersion by determining a performance metric related to an error rate of an optical signal in at least one polarization mode in a filtered state. Based on the performance metric, a control vector is determined to control the optical signal in the at least one polarization mode in the filtered state. The control vector is then applied to a polarization effecting device to compensate for polarization mode dispersion.

Abstract: Provided are a polarization multiplexing optical receiving device and a polarization multiplexing optical receiving method with which a mismatch of optical intensity between polarized signals accumulated in an optical transmission path of an optical receiving system can be compensated with high precision, and a high-quality polarized optical signal can be received.

Abstract: In order to appropriately demultiplex the polarization multiplexed BPSK signal without using a training sequence and decreasing the resistance to a frequency offset, an optical receiver includes a coherent optical detection unit receiving an optical signal in which BPSK modulated carrier waves are polarization-multiplexed, performing coherent detection by mixing the received optical signal with local light, and outputting first electrical signals corresponding to the carrier waves; a butterfly FIR filter receiving the first electrical signals and extracting second electrical signals corresponding to each of the carrier waves from the first electrical signals; and a coefficient control unit for calculating a sum of respective phases of the second electrical signals output from the butterfly FIR filter, adaptively controlling tap coefficients of the butterfly FIR filter so that the calculated phase sum may become equal to 0 or ?, and outputting tap coefficients after being controlled to the butterfly FIR filter

Abstract: A fiber network is monitored in order to detect physical intrusion. The state of polarization of an optical fiber is monitored. A fiber tap is determined to have occurred if the state of polarization of the fiber changes beyond a predetermined amount found to be associated with all types of fiber taps. Alternately, it may be determined that a fiber tap has occurred if the state of polarization changes beyond a second predetermined amount and in a predetermined direction. Monitoring of the state of polarization occurs before and after a time period chosen to be less than a time during which the state of polarization of the optical fiber is expected to drift. This step eliminates false positives due to natural fiber PMD drift.

Abstract: A coherent optical receiver measures a portion of a spectra of a multi-channel optical signal that includes at least one signal adjacent to a selected signal. The coherent optical receiver determines structure and bandwidth information for the measured portion of spectra, and determines one or more filter parameters for the selected signal based on the structure and bandwidth information of the at least one signal adjacent to the selected signal. The coherent optical receiver adjusts one or more active filter parameters of a carrier phase estimator in the optical coherent receiver to have values corresponding to the determined one or more filter parameters.

Abstract: An apparatus, e.g. an optical receiver, includes an optical front end and an equalizer. The front end is configured for receiving an optical signal bearing first and second symbols on respective first and second polarization channels. The equalizer is configured to 1) select a first cost function if the first symbol has greater energy than the second symbol, 2) select a second different cost function if the second symbol has a greater energy than the first symbol, and 3) based on the selected cost function, update coefficients of an adaptive filter configured to demultiplex and equalize the first and second polarization channels.

Abstract: A method for processing optical signals includes performing frequency mixing, photoelectric detection, analog/digital conversion, and dispersion compensation on received input optical signals. First-path polarization multiplexing optical signals and second-path polarization multiplexing optical signals. An initialization update process is performed on filter coefficients. Polarization compensation is performed on the first-path polarization multiplexing optical signals and the second-path polarization multiplexing optical signals by using the filter coefficients on which the initialization update is performed to obtain initialized x-path optical signals and initialized y-path optical signals. Preset x-path training sequences and y-path training sequences are synchronized by using the initialized x-path optical signals and the initialized y-path optical signals. If a synchronization result indicates that polarization cross occurs, the polarization cross is rectified.

Abstract: A transmitter in an optical communications system includes a digital signal processor for processing a data signal to generate a sample stream encoding successive symbols in accordance with a constrained phase modulation scheme having a constellation of at least two symbols and a modulation phase constrained to a phase range spanning less than 4?. A digital-to-analog converter converts the sample stream into a corresponding analog drive signal. A finite range phase modulator modulates a phase of a continuous wavelength channel light in accordance with the analog drive signal, to generate a modulated channel light for transmission through the optical communications system. A receiver in the optical communications system includes an optical stage for detecting phase and amplitude of the modulated channel light and for generating a corresponding sample stream, and a digital signal processor for processing the sample stream to estimate each successive symbol of the modulated channel light.

Abstract: An apparatus including a polarization controller is described. The polarizer controller is communicatively coupled via a feedback loop to an evaluation module located near an optical receiver. The evaluation module is configured to measure polarization dependent loss (PDL) of an optical signal received at the optical receiver. The polarization controller is configured to receive feedback control data regarding the PDL from the evaluation module. Additionally, the polarization controller is configured to modify a state of polarization of the optical signal at an optical transmitter, which is communicatively coupled to the optical receiver, based on the feedback control data.

Abstract: This disclosure describes the Fast Chromatic Dispersion Estimation (FCDE) techniques which corrects for chromatic dispersion in high data rate optical communications systems such as some coherent optical communications systems. FCDE may utilize transform such as fast-Fourier transforms to estimate the chromatic dispersion. From an estimation of the chromatic dispersion, the techniques may determine filter tap coefficients for compensating the chromatic dispersion.

Abstract: An optical transmission/reception system includes a modulator for modulating light based on data to output signal light; a transmission-side signal processor performing transmission-side digital signal processing which imparts a polarization change to the signal light by the optical modulation with respect to an input signal; an optical transmitter in which the modulator performs the optical modulation based on the input signal subjected to the transmission-side digital signal processing in the transmission-side signal processor; and an optical receiver including a converter converting the signal light inputted from the optical transmitter via a transmission path to a digital electric signal for each polarization component, and a reception-side signal processor performing reception-side digital signal processing which imparts a polarization change having a property substantially inverse to a property of the polarization change in the transmission-side signal processor with respect to the digital electric sign

Abstract: An optical digital coherent receiver includes: a polarization separation circuit configured to perform polarization separation on a received signal and output polarized signals; and a determination circuit configured to trigger a start of digital signal processing in a stage subsequent to the polarization separation circuit when it is determined that a distribution of a peak of an amplitude of one of the polarized signals has a characteristic corresponding to a modulation method used on a transmitting side.

Abstract: Methods and systems of data symbol recovery in a coherent optical receiver of an optical communications system. A respective probabilistic phase error is calculated for each of a plurality of data symbol estimates. A phase rotation is calculated based on the probabilistic phase error estimates, using a filter function, and the phase rotation applied to at least one data symbol estimate to generate a corresponding rotated symbol estimate. Each rotated symbol estimate is processed to generate corresponding decision values of each data symbol.

Abstract: A system and method for blind equalization of a QAM signal. Equalization is achieved using an algorithm characterized by cost function that is a function the Euclidian distance, e.g. the minimum Euclidian distance, between points of the constellation associated with the QAM signal, i.e. the distance between symbols.