Abstract: This disclosure describes techniques to sample electrical data streams in coherent receivers. For instance, an analog-to-digital converter (ADC) samples the received electrical data stream at a sampling rate that is nominally twice or greater than twice the symbol rate of the electrical data stream that the ADC receives. A digital filter receives the digital data stream from the ADC, and digitally filters the digital data streams to output a filtered digital electrical data stream at an effective sampling rate that is less than the sampling rate and less than twice the symbol rate, and greater than or equal to the symbol rate.

Abstract: A receiver for fiber optic communications.

Abstract: There is presented an optical apparatus comprising first and second photon pair sources configured to convert at least one pump light photon into a first and second correlated signal and idler photon pairs. In one example, the apparatus is configured to use one of the signal and idler photons from the first correlated photon pair for controlling the conversion of the pump light photon in the second photon pair source. The apparatus may configured such that, at least one of the signal and idler photons from the first correlated photon pair is output from the first photon pair source onto an optical path wherein at least one of the signal and idler photons from the second correlated photon pair is output from the second photon pair source onto the optical path. A method is also provided for outputting one or more photons using the optical apparatus.

Abstract: An optical transmission apparatus includes: a coherent detector configured to receive light including different polarization components from an optical transmission path, and perform coherent detection of received light including the different polarization components; an adaptive equalizer configured to adaptively equalize, by a digital filter, a complex electric signal for each of the polarization components obtained by the coherent detection, a gain value for controlling an amplitude of the complex electric signal being applied to the complex electric signal; and a polarization dependent loss monitor configured to determine a polarization dependent loss of the optical transmission path, based on a correction filter parameter obtained by correcting a filter parameter of the digital filter according to the gain value, the filter parameter being adaptively updated by an adaptive equalization of the adaptive equalizer.

Abstract: A receiver for fiber optic communications.

Abstract: The present invention relates to a transmitter and a receiver including multiple first and second transceiving units. Each of the first and the second transceiving units includes a first and a second radiation slices and a first and a second transceiving circuits disposed thereon. In the transmitter, the first and the second transceiving units receive first and second internal transmission signals at first and second polarization from the first and the second radiation slices, and transmit first and second external transmission signals generated from transformation through the first and the second radiation slices. In the receiver, the first and the second transceiving units receive first and second external reception signals at first and second polarization through the first and the second radiation slices, and transmit first and second internal reception signals at first and second polarization generated from transformation through the first and the second radiation slices.

Abstract: According to one embodiment, a display device includes a plurality of display elements arranged in a matrix, a plurality of scanning lines, a plurality of signal lines, and a controller configured to control display by sequentially supplying an image signal and a control signal to the plurality of signal lines and the plurality of scanning lines, respectively, wherein the controller repeats a display period in which the display is controlled and a display blanking period in which the display is paused to display a frame image, and at least two types of display periods with different lengths are used when a frame image is displayed.

Abstract: A novel digital signal processing scheme (DSP) for quadrature duobinary (QDB) spectrum shaped polarization multiplexed quadrature phase shift keying (PM-QPSK) based on multi-modulus blind equalizations (MMBE) is proposed and demonstrated with both simulation and experimental results. The key algorithms for this novel digital signal processing scheme include the cascaded multi-modulus algorithm (CMMA) for blind polarization de-multiplexing, multi-modulus QPSK partitioning frequency offset estimation (FOE) and two stage carrier phase recovery (CPR) with maximum likelihood phase estimation. The final signal is detected by maximum-likelihood sequence detection (MLSD) for data BER measurement. The feasibility of the proposed digital signal processing scheme is demonstrated by the experiment of 112 Gb/s QDB spectrum shaped PM-QPSK signal with a 25 GHz bandwidth waveshaper for Nyquist WDM channels.

Abstract: A light transmitter to transmit multiple light packets, each formatted to include a same message comprising a series of bits, each bit represented as light that is intensity modulated over a bit period at a frequency indicative of the bit. The light packets are transmitted at different start-times to establish different phases, one for each of the light packets, to permit a light receiver to sample each message at a different phase of a fixed sample timeline that is asynchronous to the bit period and the frequency. The light receiver samples the multiple light packets based on the sample timeline, to sample each received message at one of the different sample phases, then constructs a best series of bits based on the multiple demodulated messages.

Abstract: A wavelength division multiplexing optical transmission apparatus includes a plurality of polarization multiplexing optical modulation means, polarization-maintaining optical multiplexing means, and delay adjustment means. The polarization multiplexing optical modulation means generate a plurality of polarization multiplexed optical modulation signals having different wavelengths. The polarization-maintaining optical multiplexing means multiplexes the wavelengths of the polarization multiplexed optical modulation signals to generate a wavelength multiplexed optical signal (WDM). The delay adjustment means adjusts a delay such that light intensities of polarization multiplexed optical modulation signals having adjacent wavelengths in the wavelength multiplexed optical signal (WDM) vary inversely with respect to each other.

Abstract: An optical transceiver in an optical communications network, comprising a receiver configured to receive an optical signal comprising an X-polarization component that comprises a first frame and a Y-polarization component that comprises a second frame. The optical transceiver also comprises a processor coupled to the receiver and configured to determine, in a time domain, a phase estimate according to the first frame and the second frame, determine, in a frequency domain, a channel estimate for the optical signal according to a relationship between the first frame, the second frame, and the phase estimate, and determine a compensated optical signal according to the channel estimate. The optical transceiver further comprises a transmitter coupled to the processor and configured to transmit the compensated optical signal to a downstream component in the optical communications network.

Abstract: A coherent optical receiver includes: an attenuator that adjusts a power of an input optical signal; a mixer that mixes an optical signal output from the attenuator and local oscillator light; a photo detector that converts an optical signal output from the mixer into an electric signal; an amplifier that amplifies an output signal of the photo detector; a gain controller that controls a gain of the amplifier; a memory that stores dependence information that indicates a relation between an input optical power of an optical signal of a specified wavelength and a gain of the amplifier; and a controller that calculates an input optical power of the target wavelength based on a gain of the amplifier and the dependence information, and controls an attenuation amount of the attenuator based on the calculated input optical power, when a WDM optical signal is input into the coherent optical receiver.

Abstract: A receiver that may include a receiver front end arranged to receive (a) a received signal, (b) a reference signal generated by a local oscillator laser, and to output a first intermediate signal; a carrier phase estimator that is arranged to receive the first intermediate signal and to generate a phase estimation signal that represents a phase difference between the received signal and the reference signal; wherein the carrier phase estimator comprises a multi-symbol-differential-detection module and a carrier phase demodulator; and an output circuit arranged to receive the phase estimation signal and to apply a slicing operation to provide an output signal of the carrier phase estimator.

Abstract: Methods and systems for a polarization immune wavelength division multiplexing demultiplexer are disclosed and may include, in an optoelectronic transceiver having an input coupler, a demultiplexer, and an amplitude scrambler: receiving input optical signals of different polarization via the input coupler, communicating the input optical signals to the amplitude scrambler via waveguides, configuring the average optical power in each of the waveguides utilizing the amplitude scrambler, and demultiplexing the optical signals utilizing the demultiplexer. The amplitude scrambler may include phase modulators and a coupling section. The phase modulators may include sections of P-N junctions in the two waveguides. The demultiplexer may include a Mach-Zehnder Interferometer. The demultiplexed signals may be received utilizing photodetectors. The input coupler may include a polarization splitting grating coupler.

Abstract: An apparatus to measure the position of a mark, the apparatus including an illumination arrangement to direct radiation across a pupil of the apparatus, the illumination arrangement including an illumination source to provide multiple-wavelength radiation of substantially equal polarization and a wave plate to alter the polarization of the radiation in dependency of the wavelength, such that radiation of different polarization is supplied; an objective to direct radiation on the mark using the radiation supplied by the illumination arrangement while scanning the radiation across the mark in a scanning direction; a radiation processing element to process radiation that is diffracted by the mark and received by the objective; and a detection arrangement to detect variation in an intensity of radiation output by the radiation processing element during the scanning and to calculate from the detected variation a position of the mark in at least a first direction of measurement.

Abstract: A digital coherent receiver that receives a first optical signal in a WDM optical signal includes: a front-end circuit configured to generate a digital signal indicating the first optical signal; a waveform distortion corrector configured to generate a correction result signal indicating a first optical signal whose waveform distortion has been corrected by performing a digital arithmetic operation on the digital signal using at least one dispersion compensators and at least one nonlinear compensators; and a controller configured to adjust operation states of specified dispersion compensators among the plurality of dispersion compensators and specified nonlinear compensators among the plurality of nonlinear compensators. The number of the specified dispersion compensators and the number of the specified nonlinear compensators are determined based on the number of spans of an optical transmission line through which the first optical signal is transmitted.

Abstract: The present disclosure provides a method and system for fine estimation of a local oscillator frequency offset of a received signal at a coherent receiver, by evaluating the probability mass function (PMF) of the signal phase of output symbols at different frequencies. At frequencies other than the actual frequency offset, the signal phase is uniformly distributed in [??,?] such that the summation of a function of PMF values where the function is convex or concave between 0 and 1 can be utilized to determine an a frequency offset to be used by the coherent receiver.

Abstract: Techniques are described herein for filtering and/or otherwise isolating or extracting components of multi-component signals. More specifically, embodiments of the present disclosure describe techniques for filtering and/or otherwise extracting a continuous wave component (or wireless power component) and a modulated data component from a multi-component signal. In some embodiments, the techniques describe systems, apparatuses and methods for filtering and/or otherwise isolating or extracting a frequency (e.g., modulated data component) from a continuous wave (e.g., wireless power component) without affecting the levels of other frequencies. The individual components or signals can be transmitted by one or more sources and received at one or more existing antennas of an electronic device simultaneously.

Abstract: The embodiments of the invention provide methods to deal with problems of cycle slips, angular skew, and residual phase noise for high-speed optical communications employing any arbitrary high-order multi-dimensional modulation formats. The embodiments use a slip process analyzer, a skew angle estimator, and a phase noise variance estimator to provide feedforward soft-decision information of a carrier phase recovery (CPE) for more accurate likelihood calculation based on a high-order hidden Markov model (HMM). The log-likelihood calculation can be done jointly in dual polarization with joint Markov state transition. Some embodiments use a kernel filter or a particle filter for log-likelihood calculation.

Abstract: A digital coherent receiving apparatus includes a first oscillator for outputting a local light signal of a fixed frequency, a hybrid unit mixing the local light signal with a light signal received by a receiver, a second oscillator for outputting a sampling signal of a sampling frequency, a converter for converting the mixed light signal into digital signal synchronizing with the sampling signal, a waveform adjuster for adjusting a waveform distortion of the converted digital signal, a phase adjustor for adjusting a phase of the digital signal adjusted by the waveform adjustor, a demodulator for demodulating the digital signal adjusted by the phase adjuster, and a phase detector for detecting a phase of the digital signal adjusted by the phase adjuster, and a control signal output unit for outputting a frequency control signal on the basis of the detected phase signal to the second oscillator.

Abstract: We disclose communication methods using which a cluster of network nodes is interconnected via an optical interconnect and an electrical switch engine. A communication method executed at a master optical transceiver coupled to one side of the optical interconnect enables that transceiver to establish an optical communication link with any one of a plurality of slave optical transceivers coupled to the other side of the optical interconnect. A communication method executed at a slave optical transceiver enables that transceiver to communicate with the master optical transceivers without having its own light source and, instead, modulating data onto previously un-modulated signaling dimensions of the incoming optical waveforms, which are then turned around and broadcast back to the master optical transceivers.

Abstract: A method of optical communication comprising encoding four modulated symbols to generate four encoded symbols in two orthogonal polarizations and transmitting the four encoded symbols in two successive time slots. An optical communication apparatus comprising a processor configured to receive two sequences of digital symbols in a plurality of time slots, wherein the two sequences correspond to two components of two orthogonal polarizations, wherein one digital symbol per polarization is received in each of the plurality of time slots, divide each of the two sequences into a plurality of groups using a modulo operation of time, wherein each group comprises two digital symbols received in two consecutive time slots, and adaptively equalize the four digital symbols of the two consecutive time slots using a 4×4 matrix to generate four modulated symbols, wherein the 4×4 matrix comprises 16 tap-vectors.

Abstract: System and method for equalizing a high bit rate optical communication channel in a symbol spaced adaptive Multiple-In-Multiple-Out (MIMO) system, where the optical communication channel carries a signal that is sampled at a symbol rate. Accordingly, Anti Aliasing Filtering (which introduces distortions in the form of Deterministic Inter Symbol Interference D-ISI) is applied in a MIMO channel, in order to reduce the aliasing effect associated with symbol rate sampling. The Polarization Mode Dispersions introduced in the optical communication channel are solely compensated by a MIMO Equalizer, which ignores the Deterministic ISI (D-ISI) distortion. Then the Deterministic ISI (D-ISI) distortion is solely compensated by an independent Deterministic Equalizer (DE).

Abstract: A receiver for fiber optic communications.

Abstract: In some examples, a transmit assembly is described that may include a first optical transmitter, a second optical transmitter, and a polarizing beam combiner. The first optical transmitter may be configured to emit a first optical data signal centered at a first frequency. The second optical transmitter may be configured to emit a second optical data signal centered at a second frequency offset from the first frequency by a nominal offset n. The polarizing beam combiner may be configured to generate a dual carrier optical data signal by polarization interleaving the first optical data signal with the second optical data signal. An output of the polarizing beam combiner may be configured to be communicatively coupled via an optical transmission medium to a polarization-insensitive receive assembly.

Abstract: A light pulse source (100), being adapted for generating repetitive optical pulses, comprises a continuous wave (cw) laser (10) being arranged for providing cw laser light, an optical microresonator (20) being made of a resonator material, which has a third order (Kerr) nonlinearity and an anomalous resonator dispersion, wherein the cw laser (10) is arranged for coupling the cw laser light into the optical microresonator (20), which, at a predetermined relative detuning of the cw laser (10) and the optical microresonator (20), is capable of including a light field in a soliton state, wherein soliton shaped pulses can be coupled out of the optical microresonator (20) for providing the repetitive optical pulses, and a tuning device (30) being arranged for creating and maintaining the predetermined relative detuning of the cw laser (10) and the optical microresonator (20) based on a tuning time profile being selected in dependency on a thermal time constant of the optical microresonator (20) such that the solito

Abstract: A received optical signal is coherently demodulated and converted into electrical complex samples (p(n); (px(n), py(n)), which are dispersion compensated in a compensation filter (11). A control circuit (12, 13, 14, 15) calculates comparison values (R1, R2) from corrected samples q(n) and an estimated error value (?MIN). A plurality of compensation function (T(M)) is applied according to a predetermined dispersion (CD) range and after a second iteration is the compensation filter (11) set to an optimum compensation function (T(M)).

Abstract: Embodiments of the disclosure include a method and apparatus for detecting and removing cycle slip. A phase-modulated signal having a plurality of phase-modulated symbols is received at an optical receiver, and, for each phase-modulated symbol, a phase-error estimate of a phase error of the phase-modulated symbol is generated. The presence of a cycle slip is then detected based on the phase-error estimates, and, a phase of each of one or more of the received phase-modulated symbols is adjusted to remove the detected cycle slip without adjusting a local oscillator.

Abstract: A SWIR hyperspectral imaging filter has serial stages along an optical signal path with angularly distributed birefringent retarders and polarizers. The retarders can include active retarders such as tunable liquid crystal birefringent elements, passive retarders such as fixed retarders, and/or combinations thereof. Distinctly different periodic transmission spectra are provided by different filter stages, each having multiple retarders, in particular with some stages having broad bandpass peaks at wide spectral spacing and other stages have very narrow closely spaced peaks. The respective spectra include at least one tunably selectable band at which the transmission spectra of the filter stages coincide, whereby the salutary narrow bandpass and wide spectral spacing ranges of different stages apply together, resulting in a high finesse wavelength filter suitable for spectral imaging.

Abstract: An optical signal (116) is modulated with a transmitted electrical signal comprising an information-bearing component (122) and a pilot tone (120) having a predetermined frequency. Transmission of the signal results in distortion, including nonlinear optical transmission impairments. A method of receiving the signal includes detecting the optical signal to produce a received electrical signal (X) comprising a distorted variant of the transmitted electrical signal. The pilot tone is extracted from the received electrical signal using a filtering operation (308) having a predetermined characteristic, and a compensation signal determined based upon the extracted pilot tone. The compensation signal is applied to the received electrical signal (X) to produce a compensated signal (Y) having reduced distortion.

Abstract: A method of optical communication comprising encoding four modulated symbols to generate four encoded symbols in two orthogonal polarizations and transmitting the four encoded symbols in two successive time slots. An optical communication apparatus comprising a processor configured to receive two sequences of digital symbols in a plurality of time slots, wherein the two sequences correspond to two components of two orthogonal polarizations, wherein one digital symbol per polarization is received in each of the plurality of time slots, divide each of the two sequences into a plurality of groups using a modulo operation of time, wherein each group comprises two digital symbols received in two consecutive time slots, and adaptively equalize the four digital symbols of the two consecutive time slots using a 4×4 matrix to generate four modulated symbols, wherein the 4×4 matrix comprises 16 tap-vectors.

Abstract: Proposed is a method of demodulating a phase modulated optical signal received from an optical channel. A time-discrete electrical signal is derived from the phase modulated optical signal, using a local optical signal, which has a frequency that is essentially equal to a carrier frequency of the phase modulated optical signal. A phase error between the local optical signal and the phase modulated optical signal is compensated, by deriving from the local optical signal a phase offset and modifying the derived time-discrete electrical signal by this phase offset. A chromatic dispersion caused by the optical channel is compensated, by filtering the modified time-discrete electrical signal using a digital filter.

Abstract: To that end, it is an object of the invention to provide a method for converting a high-speed digital signal in the form of optical pulses intended to be transmitted within optical guides, within which the signal is converted into a series of optical pulses in three possible phase states (?/6, 5?/6, ??/2) separated from one another two-by-two by an angle greater than ?/2.

Abstract: A receiver and a multi-symbol-differential-detection (MSDD) module, the MSDD may include an input node for receiving an input signal having a noisy phase; a summation and rotation unit; and an output unit; wherein the output unit is arranged to output an output signal and a normalized output signal; wherein the output signal represents the input signal but has a reconstructed phase; wherein the summation and rotation unit is arranged to receive the input signal and the output signal and to provide a reference signal that reflects a weighted sum of phase rotated and delayed previously received input signals; wherein the output unit comprises a phase difference calculator, a slicer, a delay unit and a normalizer; wherein the phase difference calculator is arranged to generate a difference signal indicative of a phase difference between the reference signal and the input signal; wherein the slicer and the delay unit are arranged to generate the output signal by slicing the difference signal to provide a sliced s

Abstract: A transmitter and a receiver for an optical telecommunication system of the WDM type are disclosed. In one aspect, the transmitter uses a chromato-temporal encoder which, with each block of symbols to be transmitted, associates a code matrix, where each element of the matrix corresponds to a wavelength and a use of the channel. The transmitter includes multiple modulators, where each modulator modulates a laser beam at a wavelength during a use of the channel by an element corresponding to the code matrix. The beams modulated in this manner are multiplexed in an optical fiber. Another embodiment using both a wavelength and a polarization encoding is also proposed.

Abstract: Methods, systems, and devices are described for equalizing data from an optical signal. Samples are filtered with at least one filter to compensate for polarization mode dispersion in an optical path. The filtered samples may be used to determine errors based on a difference between a radius of a recovered symbol and a target radius. A parameter may be assigned to one or more of the errors and properties of the at least one filter may be updated based on the assigned parameters. The parameter may be assigned from a small set of parameters based on at least one threshold value. Outputs generated from the filtered samples may also be assigned a parameter from a different set of parameters. The parameter assigned to the output may be used to update the particular set of taps of the at least one filter from which the output was generated.

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: Disclosed are a forward discrete/inverse-discrete Fourier transform device and method for optical orthogonal frequency division multiplexing (OFDM) communication and a transmitting and receiving apparatus. The forward inverse-discrete Fourier transform device includes N 1:N splitters for splitting subcarrier signals received from N inputs corresponding to the number of optical frequencies of subcarriers, a phase shift delay array module for shifting phases of the split signals from the 1:N splitters, N N:1 power couplers for coupling signals output from the phase shift delay array module, a time delay array module for performing time delay on optical OFDM symbols from the N:1 power couplers, and an N:1 power coupler for coupling signals output from the time delay array module.

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 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: An optical communication system has a receiver that includes a plurality of photon counting sensors that each receive photons and generate pulses based on the received photons, and an electronic circuit that aggregates the number of pulses from the plurality of photon counting sensors into a merged pulse count. A demodulator samples the merged pulse count at predetermined time intervals to determine a number of photons received by the plurality of photon counting sensors during different sampling time intervals.

Abstract: A method and system for transferring data comprising: an entangled photon source for producing first and second entangled photons associated with a receiver and a sender, respectively; a Bell state measurement device for performing a joint Bell state measurement on the second entangled photon and the at least one qubit; the Bell state measurement device outputting two bits of data to be used at the receiver; a transmission channel for transmitting two bits from the outcome of the Bell state measurement device to the receiver; a unitary transformation device for performing a unitary transformation operation on the first entangled photon based upon the value of the two bits of data; at least one detector for detecting encoded information from the first entangled photon; at least one processor operating to determine whether or not to transmit portions of data from a sequential successive qubit based upon the preceding qubit.

Abstract: A method and apparatus for simultaneous processing of signals impressed on a horizontal polarization of a light wave and on a vertical polarization of the light wave is provided. In one embodiment, a horizontal polarization pilot tone is impressed on a data signal carried by the horizontal polarization and a vertical polarization pilot tone is impressed on a data signal carried by the vertical polarization. A receiver processes the dual-polarized light wave and converts it to an X channel signal and a Y channel signal. The X and Y channel signals are processed in separate channels to recover a phase and frequency offset between them and a local oscillator. The phase and frequency recovered and frequency de-multiplexed signals are further processed to polarization de-multiplex the data signal carried by the horizontal polarization and the data signal carried by the vertical polarization.

Abstract: A network element has at least one input, to which an optical signal can be fed, and at least one output, which is equipped to emit an optical signal; a first coupler having an input linked to the network element input and a first and a second output; an optical receiver having at least one input coupled to the second output of the first coupler and at least one output; an optical sender having at least one input of which is linked to the output of the optical receiver; a signal processing device being arranged in the signal path; a second coupler having a first input linked to the first output of the first coupler, a second input linked to the output of the optical sender, and an output which is linked to the first output of the network element.

Abstract: In accordance with the present disclosure, disadvantages and problems associated with polarization dependent effects of a polarization multiplexed optical signal may be reduced through polarization scrambling. In accordance with an embodiment of the present disclosure a method for detecting polarization scrambling of a polarization multiplexed optical signal comprises receiving a polarization multiplexed optical signal associated with an optical network. The polarization multiplexed optical signal including a scrambled polarization orientation, the polarization orientation scrambled according to a scrambling frequency. The method further comprising receiving a polarization signal indicating the polarization scrambling of the received optical signal. The method additionally comprises descrambling the optical signal according to the polarization scrambling as indicated by the polarization signal.

Abstract: In some examples, a transmit assembly is described that may include a first optical transmitter, a second optical transmitter, and a polarizing beam combiner. The first optical transmitter may be configured to emit a first optical data signal centered at a first frequency. The second optical transmitter may be configured to emit a second optical data signal centered at a second frequency offset from the first frequency by a nominal offset n. The polarizing beam combiner may be configured to generate a dual carrier optical data signal by polarization interleaving the first optical data signal with the second optical data signal. An output of the polarizing beam combiner may be configured to be communicatively coupled via an optical transmission medium to a polarization-insensitive receive assembly.

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: A polarization state of a transmission signal can be changed at a high speed based on a symbol-rate By switching a first switch, a second switch, and a third switch with time, one of an X-polarized wave_I-signal as a Y-polarized wave_I-signal, a signal caused by performing logical inversion for an X-polarized wave_I-signal, an X-polarized wave_Q-signal and a signal caused by logical inversion for an X-polarized wave_Q-signal is input to a second modulator. Further, by switching the first switch, the second switch and the third switch with time, the second modulator is input one of the X-polarized wave_I-signal as the Y-polarized wave_Q-signal, the X-polarized wave_I-signal, the signal caused by performing logical inversion for the X-polarized wave_I-signal, the X-polarized wave_Q-signal and the signal caused by performing logical inversion for the X-polarized wave_Q-signal. Thereby, a polarization state of a transmission signal can be changed at high speed based on a symbol-rate speed.

Abstract: Techniques for timing synchronization in an optical orthogonal frequency division multiplexing (OOFDM) system includes providing a time-domain training symbol having a symmetric distribution and producing the training symbol by transmitting a real-valued PN sequence on each subcarrier under the OOFDM. The training sequence includes an initial value, followed by an odd length palindromic sequence of values.

Abstract: One embodiment is a Poisson-based communication system. The system includes a receiver that comprises a photodetector that receives photons and generates pulses based on the received photons, a sampling event counter that counts the number of generated pulses by the photodetector and a demodulator. The demodulator samples the sampling event counter at predetermined time intervals to determine an occurrence of a first state when light pulse energy has been transmitted by a transmitter and received by the photodetector and an occurrence of a second state when light pulse energy has not been transmitted by the transmitter and received by the photodetector.