Abstract: Wireless communications systems and methods related to information associated with a reconfigurable intelligent surface (RIS) in a wireless communication network are provided. For example, a method of wireless communication performed by a wireless communications device may include transmitting, to a reconfigurable intelligent surface (RIS), a request for information associated with the RIS and receiving, from the RIS, the information. Other features are also claimed and described.

Abstract: A transmitter for an optical communication network includes a primary laser source input substantially confined to a single longitudinal mode, an input data stream, and a modulator including at least one secondary laser having a resonator frequency of the single longitudinal mode of the primary laser source. The modulator is configured to receive the primary laser source input and the input data stream, and output a laser modulated data stream.

Abstract: A clock synchronization apparatus, an optical transmitter, an optical receiver, and a clock synchronization method are provided. In the clock synchronization apparatus, a digital interpolator adjusts a sampling clock frequency of a digital signal under sampling clock control of a clock control circuit.

Abstract: An access network includes a first local network node configured to serve one or more first client devices according to a first network protocol, a second local network node configured to serve one or more second client devices according to a second network protocol different than the first network protocol, and a hub in operable communication with the first and second local network nodes over respective transport media. The hub contains a centralized network node configured to generate a first digitized radio frequency (RF) stream to the first local network node and a second digitized RF stream to the second local network node. The first digitized RF stream corresponds to the first network protocol and the second digitized RF stream corresponds to the second network protocol.

Abstract: Provided is a transmission method that improves data reception quality in radio transmission using a single-carrier scheme and/or a multi-carrier scheme. The transmission method includes: generating a plurality of first modulated signals and a plurality of second modulated signals from transmission data, the plurality of first modulated signals being signals generated using a 16QAM modulation scheme, and the plurality of second modulated signals being signals generated using uniform constellation 64QAM modulation; generating, from the plurality of first modulated signals and the plurality of second modulated signals, a plurality of first signal-processed signals and a plurality of second signal-processed signals which satisfy a predetermined equation; and changing the predetermined equation when a 64QAM modulation used to generate the plurality of second modulated signals is switched from the uniform constellation 64QAM modulation to a non-uniform constellation 64QAM modulation.

Abstract: Among the various aspects of the present disclosure is the provision of systems or methods for polarization division multiplexed (PDM) optical transmission. For example, the PDM optical transmission system can comprise a chip with one or more aluminum nanowire filters attached to the surface of the chip, such as division of focal Plane (DoFP) polarimeter filter array bonded on the receiver IC.

Abstract: Probabilistic constellation shaping (PCS) is applied to a desired probability distribution over the 2-D constellation points. Constellation points are partitioned into multiple disjoint sets in which all the constellation points within a subset have the same energy level (i.e., amplitude) or distance from the origin on the complex plane. Each of the sets may be further subdivided into smaller disjoint sets of constellation points to facilitate labeling of the constellation points. The sets may be indexed from 0 to the total number of disjoint sets to form an index set. The desired distribution may then be applied over the index set either using a distribution matcher (DM) or using a lookup table. The desired distribution may be generated before forward error correction (FEC) encoding that preserves the generated amplitude distribution through FEC encoding of data bits.

Abstract: A large number of degrees for relays of optical signals transmitted via optical paths in the degrees is secured. A wavelength cross-connect device 20A performs a relay by splitting optical signals from respective degrees indicated by reference numerals 40l, 40h, 40m, 40q, each of the degrees being provided by optical fibers, via respective optical couplers and outputting the split optical signals to output sides of the plurality of degrees via respective WSSs 23a to 23d. As the optical couplers, variable couplers 27a to 27d whose respective splitting ratios, each of which is a ratio of optical signal power losses in splitting an optical signal, are variable are used. The wavelength cross-connect device 20A includes a control unit 26 that performs control to change the splitting ratios in such a manner as to eliminate an imbalance among OSNR margins of the output sides of the degrees in which a plurality of optical paths transmitting the split optical signals extend.

Abstract: The invention presents an equalizing device, a corresponding method and an optical signal with a frame structure for enabling the method. The equalizing device includes a first 2×2 MIMO equalizer configured to perform a first equalization on the digital signal, supported by a 2×2 MIMO channel estimation of the channel based on the digital signal. Further, the device includes a second 2×2 MIMO equalizer, arranged after the first equalizer and configured to perform a second equalization on the digital signal, supported by a State of Polarization (SOP) estimation of the optical signal based on the digital signal.

Abstract: A spatial optical transmitter modulates an optical signal of a single wavelength in accordance with a signal to be transmitted, divides the modulated optical signal into two, rotates polarizations of the two divided optical signals, and transmits the two optical signals as optical signals of two orthogonal polarizations to space.

Abstract: Provided is an optoelectronic light source that includes a plurality of semiconductor lasers each configured to emit a laser beam and arranged on a mounting platform, and a redirecting optical element configured to redirect the laser beams. The redirecting optical element includes for each one of the plurality of semiconductor lasers a separate reflection zone, the reflection zones are shaped differently from one another, and after passing the redirecting optical element, the laser beams run in a common plane.

Abstract: The disclosed systems, structures, and methods are directed to a single-stage frequency-domain equalization (FDEQ) structure implemented on a processor, comprising a data preprocessing unit configured to concatenate received data samples in time-domain digital signals, transform the concatenated data samples in the time-domain digital signals to frequency-domain digital signals, and an adaptive equalizer comprising 2×2 multiple-input multiple output (MIMO) configured to compensate for non-time-varying fixed impairments and time-varying adaptive impairments in the frequency-domain digital signals.

Abstract: An apparatus and method to monitor a polarization change by inserting pilot signals in a transmission signal and converting the pilot signals in the receiving signal from a Jones space into a Stokes space. A velocity of a polarization change of the optical link is estimated by using the Stokes vectors of the pilot signals, thereby directly and accurately estimating the polarization change of the optical link. Moreover, estimation of the velocity of the polarization may be applicable where rotation of state of polarization and polarization-dependent loss coexist in an optical link.

Abstract: A method and structure for tap centering in a coherent optical receiver device. The center of gravity (CG) of the filter coefficients can be used to evaluate a proper convergence of a time-domain adaptive equalizer. However, the computation of CG in a dual-polarization optical coherent receiver is difficult when a frequency domain (FD) adaptive equalizer is adopted. In this case, the implementation of several inverse fast-Fourier transform (IFFT) stages is required to back time domain impulse response. Here, examples of the present invention estimate CG directly from the FD equalizer taps and compensate for an error of convergence based off of the estimated CG. This estimation method and associated device architecture is able to achieve an excellent tradeoff between accuracy and complexity.

Abstract: A device for coherently detecting data in an optical signal, called a useful signal, received over a first single-mode optical fibre. The device includes: a second single-mode optical fibre that receives an oscillation optical signal; a polarization-managing device that receives as input either, in a first case, the oscillation optical signal, or, in a second case, the useful signal, and that delivers as output two separate signals, over two single-mode optical guides. The coherently detecting device is configured so that a set of the three signals, which consists of the two separate signals and of either, in the first case, the useful signal, or, in the second case, the oscillation signal, is presented to a single photodiode.

Abstract: Methods and apparatus for coherent transmitter calibration are provided that employ direct detection (DD) using one single photodetector (PD). The provided method and apparatus do not require hardware for coherent reception, or additional ADCs for quality control. An additional optical tone is added to a QAM optical signal that is outside the band of the QAM optical signal. The result of this is that after direct detection, there is a correlation between the real and imaginary parts, and the imaginary part can be recovered with a Hilbert transform. The estimated QAM optical signal obtained by direct detection is used to perform a transmitter factory calibration method to calibrate for one or more transmitter impairments and/or to perform in-line self-calibration.

Abstract: A state of polarization tracking recovery method and apparatus. The apparatus at least includes a processor configured to fit Stokes vectors to which predetermined symbols correspond of two states of polarization in a received dual-polarization multiplexing optical signal on a Poincare sphere to obtain a fitted plane. The processor calculates a compensation matrix for polarization-dependent loss (PDL) in a Jones space by moving a center of the fitted plane to the origin of the Poincare sphere, and calculates a demultiplexing matrix used for polarization demultiplexing in a Jones space by rotating the fitted plane with the center being moved to the origin until a normal vector of the fitted plane is parallel with a first axis of the Stokes space and rotating the fitted plane with the center being moved to the origin to a plane constituted by a second axis and a third axis of the Stokes space.

Abstract: A method for reconfigurable optical signal processing. The method includes generating a first pump pulse by propagating a first input pump through a first dispersive medium, generating a first modulated signal by applying a parametric nonlinear wave mixing process on an input optical signal and the first pump pulse, generating a first transformed signal of the input optical signal by propagating the first modulated signal through a second dispersive medium, generating a multiplied signal by multiplying the first transformed signal by a Green's function, generating a second pump pulse by propagating a second input pump through a third dispersive medium, generating a second modulated signal by applying the parametric nonlinear wave mixing process on the multiplied signal utilizing the second pump pulse, and generating a second transformed signal of the multiplied signal by propagating the second modulated signal through a fourth dispersive medium.

Abstract: A digital coherent receiver includes: an adaptive equalizer configured to execute, using a first tap coefficient, adaptive equalization processing on a digital signal that corresponds to a signal; a first coefficient updating unit configured to update the first tap coefficient based on the digital signal on which the adaptive equalization processing has not been executed, the digital signal on which the adaptive equalization processing has been executed, and a first step size; a second coefficient updating unit configured to update a second tap coefficient based on the digital signal on which the adaptive equalization processing has not been executed, the digital signal on which the adaptive equalization processing has been executed, and a second step size; and a control unit configured to detect a fluctuation speed of a state of polarization of the digital signal based on the second tap coefficient, and change the first tap coefficient to the updated second tap coefficient if it is determined that the fluctu

Abstract: An optical transmission system includes an optical transmitter and an optical receiver. The optical transmitter includes a low speed signal generation unit configured to generate, based on an input signal of a transmission data sequence and a signal obtained by cyclically shifting a spectrum of the input signal, a plurality of low speed signals, a high speed signal generation unit configured to digital-to-analog convert and synthesize the plurality of low speed signals to generate a high speed signal, and an optical modulation unit configured to transmit an optical signal obtained by modulation of the high speed signal to a transmission path.

Abstract: An apparatus for signal modulation in a point-to-multipoint optical network is configured to modulate a single-wavelength carrier wave before distribution towards optical receivers of a first type adapted for intensity detection and a second type adapted for optical field detection. The apparatus includes a first module configured to modulate the carrier wave by varying the intensity of the carrier wave to represent data intended for the first type of receivers, and by controlling the phase and/or polarization of the carrier wave during selected periods. The apparatus includes a second module configured to modulate the carrier wave by varying the phase and/or polarization of the carrier wave to represent data intended for the second type of receivers, and by varying the intensity of the carrier wave during selected periods.

Abstract: A polarization controller is configured to control polarization of an optical signal. The polarization controller includes a first polarization rotator and a second polarization rotator controllable by control settings. The polarization controller includes a monitor unit configured to generate a monitoring value indicating a performance of the polarization controller. The polarization controller is configured to determine from the monitoring value if the polarization controller is operating in a selected one of a plurality of optimal performance states. If operation is not in an optimal performance state, the polarization controller is further configured to select different control settings to select an alternate one of the plurality of optimal performance states for the polarization controller.

Abstract: The various embodiments provide an optical transmission system comprising an optical transmitter configured to transmit data over an optical fiber transmission channel comprising a multi-core fiber, the data being carried by optical signals, the optical signals propagating along the multi-core fiber according to two or more cores, the multi-core fiber being associated with fiber parameters and misalignment losses values, at least one scrambling device being arranged in the optical fiber transmission channel for scrambling the two or more cores according to a scrambling function, wherein the optical fiber transmission channel comprises a system configuration device configured to determine a core dependent loss value depending on the fiber parameters, at least one misalignment loss, a number of the at least one scrambling device, and the scrambling function.

Abstract: Embodiments provide an optical transmission system comprising an optical transmitter configured to transmit data over an optical fiber transmission channel comprising a multi-core fiber, the data being carried by one or more optical signals propagating along the multi-core fiber according to a plurality of cores, each core among the plurality of cores being associated with one or more core parameters, wherein the optical transmission system comprises a core selection device configured to select a set of transmit cores among the plurality of cores according to a transmit core selection criterion, the transmit core selection criterion being related to the one or more core parameters, the optical transmitter being configured to transmit the data over the set of transmit cores.

Abstract: A liquid crystal-based non-mechanical beam steering device that permits steering in the mid-wave infrared and has a chalcogenide waveguide. The waveguide core, the subcladding, or both comprise a chalcogenide glass. The liquid crystal-based non-mechanical beam steering device has a tapered subcladding and a liquid crystal layer.

Abstract: Provided is an optical transmission/reception device (1) for transmitting or receiving an optical signal via a communication path (2) in which a phase change of the optical signal is suppressed. The optical transmission/reception device (1) includes: a transmission device (10) including a framer generation unit (11), a symbol mapping unit (12), and an optical modulation unit (13); and a reception device (20) including an optical reception front end unit (21), an A/D conversion unit (22), a polarization separation unit (23), and a phase estimating unit (24) for estimating a phase of at least one of a plurality of polarizations from a plurality of polarization signals separated by the polarization separation unit (23) and estimating a phase of a remaining polarization on the basis of the estimated phase.

Abstract: A method and structure for tap centering in a coherent optical receiver device. The center of gravity (CG) of the filter coefficients can be used to evaluate a proper convergence of a time-domain adaptive equalizer. However, the computation of CG in a dual-polarization optical coherent receiver is difficult when a frequency domain (FD) adaptive equalizer is adopted. In this case, the implementation of several inverse fast-Fourier transform (IFFT) stages is required to back time domain impulse response. Here, examples of the present invention estimate CG directly from the FD equalizer taps and compensate for an error of convergence based off of the estimated CG. This estimation method and associated device architecture is able to achieve an excellent tradeoff between accuracy and complexity.

Abstract: Provided is a transmission method that improves data reception quality in radio transmission using a single-carrier scheme and/or a multi-carrier scheme. The transmission method includes: generating a plurality of first modulated signals and a plurality of second modulated signals from transmission data, the plurality of first modulated signals being signals generated using a 16 QAM modulation scheme, and the plurality of second modulated signals being signals generated using uniform constellation 64 QAM modulation; generating, from the plurality of first modulated signals and the plurality of second modulated signals, a plurality of first signal-processed signals and a plurality of second signal-processed signals which satisfy a predetermined equation; and changing the predetermined equation when a 64 QAM modulation used to generate the plurality of second modulated signals is switched from the uniform constellation 64 QAM modulation to a non-uniform constellation 64 QAM modulation.

Abstract: A full duplex communication network includes a first coherent optics transceiver having (i) a first receiver, and (ii) a first transmitter configured to transmit a first dual polarized signal. The network further includes a second coherent optics transceiver having (i) a second receiver configured to receive the first dual polarized signal, and (ii) a second transmitter configured to transmit a second dual polarized signal. The network further includes an optical transport medium operably coupling the first coherent optics transceiver to the second coherent optics transceiver, and a first compensation module configured to filter (i) crosstalk between orthogonal components of the first dual polarized signal, and (ii) reflections between the first dual polarized signal and the second dual polarized signal.

Abstract: Systems and methods described herein are provided for radiation pattern and modulation (RPM) based on channel-state information (CSI). The method may comprise receiving a set of bits; dividing the set of bits into at least three groups, wherein at least one group is size limited by a diversity order and selection factor applied by a CSI controller; mapping the groups to distinct control signals; generating a modulated RF signal and selecting at least one configurable antenna and a configuration of said at least one antenna based on the control signals; and transmitting the modulated RF signal through the at least one configured antenna.

Abstract: A light source device includes first and second light source units, a first polarization beam splitter, and a polarization conversion element. The first light source unit emits first linear polarization light in a first direction. The second light source unit is disposed facing the first light source unit, and emits the first linear polarization light in a second direction opposite to the first direction. The first linear polarization light emitted from the first light source unit is reflected by the first polarization beam splitter in a third direction perpendicular to the first and second directions. The first linear polarization light emitted from the second light source unit is reflected by the first polarization beam splitter in a fourth direction opposite to the third direction, is converted into the second linear polarization light by the polarization conversion element, and is reflected in the third direction.

Abstract: A small and inexpensive optical modulator having suppressed temperature drift and high reliability and an optical transmission device using the same are provided. The optical modulator includes an optical waveguide substrate where an optical waveguide is formed; a control electrode that is provided on the optical waveguide substrate and applies an electric field to the optical waveguide; and a relay substrate that is disposed in the vicinity of the optical waveguide substrate and includes electrical wirings that relay electrical signals from the outside to the control electrode. The control electrode includes a signal electrode. The optical modulator comprises terminating units that include terminal resistors that terminate the signal electrode. At least a part of the terminating units are provided on the relay substrate.

Abstract: In order to enable flexible and efficient operations according to various electric power circumstances, a digital optical communication system 1 is provided with multiple optical transfer apparatuses 2, 3 and a communication control unit 4. The optical transfer apparatuses 2, 3 respectively house optical transmission/reception devices 10, 20 each including a reception-side waveform equalization processing unit 12 and a transmission-side waveform equalization processing unit 11 that perform, respectively on the reception side and on the transmission side, equalization processing for compensating waveform distortion that occurs on transfer paths 5, 6.

Abstract: When a frequency deviation compensation amount is compensated for by use of frequency shift, a phase offset occurs between adjacent input blocks included in a plurality of input blocks as divided, with the result that an error occurs in a reconstructed bit sequence. A frequency deviation compensation system of the invention is characterized by comprising: a frequency deviation compensation means for compensating for a frequency deviation occurring in a signal by use of frequency shift; and a phase offset compensation means for compensating for a phase offset occurring, in the signal, due to the frequency shift.

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 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: A method for transmitting a digital frame by an optical network unit in a digital communications network includes steps of arranging received data into a series of symbols, installing a primary cyclic prefix immediately preceding the series of symbols in time, and inserting individual ones of a plurality of secondary cyclic prefixes between each adjacent pair of symbols in the series of symbols. A length of each secondary cyclic prefix corresponds to a first duration shorter than an amount of time needed to turn on a laser of the optical network unit. The method further includes a step of providing to the optical network unit the digital frame. The digital frame includes the primary cyclic prefix, the plurality of secondary cyclic prefixes, and the series of symbols. The method further includes a step of modulating the provided digital frame by a laser of the optical network unit.

Abstract: Systems and methods for constellation shaping of QAM modulation formats in an optical transport network may include selecting a target information rate for an optical transmission path, determining a measure of fiber nonlinearity for transmission media on the path, and selecting, dependent on the measure of fiber nonlinearity, one of multiple supported shaping parameter pairs, each specifying a respective shaping strength level and a respective error correction strength level. A network management system may configure optical transponders to apply probabilistic shaping to a QAM modulation format in accordance with the selected shaping parameter pair. A shaping parameter pair specifying a high shaping strength level and a low error correction strength level may be selected when the measure of fiber nonlinearity is high. A shaping parameter pair specifying a low shaping strength level and a high error correction strength level may be selected when the measure of fiber nonlinearity is low.

Abstract: A method (10) of bi-directional optical communication, the method comprising: generating (12) a first optical communication signal for transmission in one direction through an optical fibre, generating the first optical communication signal comprising: receiving information for transmission and generating (14) a baseband signal comprising a representation of the information; performing digital upconversion (16) of the baseband signal to form an upconverted baseband signal; performing optical modulation (18) of an optical carrier signal with the upconverted baseband signal; and restricting an optical spectrum of the first optical communication signal to a first portion of an optical channel frequency slot by performing one of digital filtering (16) in addition to digital upconversion and optical filtering (36) after optical modulation; and receiving (20) a second optical communication signal transmitted in an opposite direction through the optical fibre, the second optical communication signal having an optica

Abstract: Systems and methods for polarization converters are disclosed. An example wireless communication system includes a first transceiver module of a wireless communication system configured to form one or more linearly polarized communication links with a second transceiver module of the wireless communication system, and a polarization converter positioned between the first and second transceiver modules and configured to convert the one or more linearly polarized communication links to circularly polarized communication links. The polarization converter includes first and second frequency selective surfaces (FSSs) formed from respective first and second metalized layers of a printed circuit board (PCB), each FSS includes an array of capacitive patches and inductive traces forming an array of unit cells, and each unit cell of the second FSS is aligned with each unit cell of the first FSS.

Abstract: Systems and methods for optical data transport, including controlling data transport across an optical transmission medium by generating two-dimensional (2D) distribution matchers (DMs) based on probabilistic fold shaping (PFS) and arbitrary probabilistic shaping (APS). The 2D PFS-based DM is can encode any N-fold rotationally symmetrical Quadrature Amplitude Modulation (QAM) format by applying the 2D PFS-based DM only to symbols in one quadrant based on a target entropy. A fold index yield uniform distribution is determined, and is utilized to carry generated uniform distributed parity check bits across the optical transmission medium. The 2D APS-based DM can encode any arbitrary modulation formats by encoding uniform binary data to generate non-uniform target symbols, and generating a probability distribution for the target symbols by indirectly applying the 2D APS-based DM based on a target probability distribution and a detected code rate of generated FEC code.

Abstract: Provided is a transmission method that improves data reception quality in radio transmission using a single-carrier scheme and/or a multi-carrier scheme. The transmission method includes: generating a plurality of first modulated signals and a plurality of second modulated signals from transmission data, the plurality of first modulated signals being signals generated using a 16 QAM modulation scheme, and the plurality of second modulated signals being signals generated using uniform constellation 64 QAM modulation; generating, from the plurality of first modulated signals and the plurality of second modulated signals, a plurality of first signal-processed signals and a plurality of second signal-processed signals which satisfy a predetermined equation; and changing the predetermined equation when a 64 QAM modulation used to generate the plurality of second modulated signals is switched from the uniform constellation 64 QAM modulation to a non-uniform constellation 64 QAM modulation.

Abstract: An optical source comprises a first laser arranged to generate a first optical signal having a first state of polarization (SOP) and a first optical frequency; a second laser arranged to generate a second optical signal having a second SOP, substantially orthogonal to the first SOP, and having a second optical frequency, different from the first optical frequency by a preselected frequency difference; a polarisation beam coupler arranged to combine the first optical signal and the second optical signal into a composite optical signal comprising both the first optical signal and the second optical signal having said substantially orthogonal SOPs; and an output arranged to output the composite optical signal.

Abstract: An optical module includes a light emitter array in which a plurality of light emitters are arranged, and a lens group which converges light beams output from the light emitter array, wherein in a stage where the light beams reach the lens group, planes of polarization of the light beams are different between adjacent light emitters.

Abstract: Systems and methods for constellation shaping of M-QAM modulation formats in optical transport networks may receive binary data to be transmitted as an optical signal and partition symbols of an M-QAM constellation in the complex plane into two non-overlapping subsets of symbols, The systems and methods may include assigning respective probabilities to each symbol in the first subset of symbols dependent on a target probability distribution for the first subset, mapping at least a portion of the received binary data to the symbols in the first subset, including generating a respective codeword for each symbol in the first subset, in a first symbol period, providing data representing the respective codewords mapped to the symbols in the first subset to an optical modulator for transmission, and refraining from providing any data representing codewords mapped to the symbols in the second subset to the optical modulator until a second symbol period.

Abstract: A device (100) for processing a signal, the device comprising a polarization module (102) configured to receive a multi-wavelength optical input signal (Si) comprising a plurality of wavelengths, and for each wavelength. The polarization module is configured to convert a component of each wavelength having a first polarization mode into a converted component having a second, different, polarization mode. The device further comprises a processing module (104,106,114,128) configured to combine the converted component of each wavelength with a direct component of each wavelength received with said second polarization mode. The processing module is configured to generate a multi-wavelength optical output signal (So) solely having said second polarization mode.

Abstract: In the optical transmission system to transmit optical signals using a plurality of adjacent paths, it is difficult to detect a delay difference between a plurality of paths and chromatic dispersion with a high degree of accuracy due to a crosstalk; therefore, a method for detecting optical signal information according to an exemplary aspect of the present invention includes generating a plurality of data signal sequences corresponding to a plurality of paths multiplexed spatially, each of the plurality of data signal sequences obtained by inserting periodically a training signal with a plurality of frequency components in a data signal, in the plurality of data signal sequences, the training signals respectively included in the data signal sequences to be propagated through adjacent paths at least having different frequency components from each other at the same timing, each of a plurality of the training signals included in one of the data signal sequences having the plurality of frequency components whose

Abstract: An optical module includes a light source; a demultiplexer configured to demultiplex a light into a transmission light and a local light; an optical modulator; an excitation light source; an optical waveguide substrate that includes: a polarization beam splitter configured to split a reception light into an X-polarized component and a Y-polarized component, a beam splitter, a pair of optical hybrid circuits configured to cause the X-polarized component and the Y-polarized component to interfere with the local light split by the beam splitter, a pair of local light waveguides configured to couple the beam splitter and the pair of optical hybrid circuits, a pair of reception light waveguides configured to couple the polarization beam splitter and the pair of optical hybrid circuits, wherein the pair of local light waveguides and the transmission light waveguide are doped with a rare-earth ion that amplifies a light when the excitation light is introduced.

Abstract: Various embodiments relate to a method including: coupling one or more optical spatial pilot signals into a first end of optical fiber, wherein the optical fiber is a multimode optical fiber; Reflecting and modifying each mode of the optical pilot signals at a second end of the optical fiber; receiving a reflected portion of the one or more optical spatial pilot signals at the first end of the of the optical fiber in response to the reflected portion having propagated through the optical fiber in both directions; processing the reflected spatial pilot to determine components of one of a round-trip transfer matrix of the optical fiber and a single-direction transfer matrix of the optical fiber.

Abstract: A phase estimation method and apparatus for a polarization multiplexing system, where the method includes performing, by a receive end, state of polarization (SOP) rotation on a received first SOP signal and second SOP signal according to an angle of previous SOP rotation, extracting a pilot using adaptive filtering, and performing carrier phase estimation according to the extracted pilot. This prevents a noise signal from being extracted and can make a carrier phase estimation result more accurate.

Abstract: A signal processing device processes an electric field information signal indicating a polarization multiplexed optical signal in which different modulation formats are used. A first optical signal transmitted in a first polarization component and a second optical signal transmitted in a second polarization component are multiplexed in the polarization multiplexed optical signal. The signal processing device includes a generator and a compensation circuit. The generator selects the first polarization component or the second polarization component based on modulation formats of the first and second optical signals, and generates a compensation value for compensating for an electric field information signal of a selected polarization component based on the electric field information signal of the selected polarization component. The compensation circuit compensates for electric field information signals of the first and second polarization components using the compensation value generated by the generator.