Abstract: A system and a method for testing a high-speed ADC in a DP-QPSK receiver are disclosed. The system includes a simulation module for outputting a data flow and performing signal recovery, an arbitrary waveform generator for receiving the data flow and outputting a high-speed analog signal and a clock signal, a high-speed ADC for converting the high-speed analog signal and the clock signal into a high-speed digital signal, a cache memory circuit for converting the high-speed digital signal into a low-speed digital signal, and a logic analyzer for sending the low-speed digital signal to the simulation module.

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 method and structure for a coherent optical receiver device. Timing recovery (TR) is implemented after channel dispersion (i.e., chromatic dispersion (CD) and polarization mode dispersion (PMD)) compensation blocks. This architecture provides both improves performance and reduces power consumption of the device. Also, a TR loop is provided, enabling computing, by an error evaluation module, a first sampling phase error (SPE) and computing, by a timing phase information (TPI) module coupled to the error evaluation module, a second SPE from a plurality of CD equalizer taps PMD equalizer taps. The first and second SPE are combined into a total phase error (TPE) in a combining module, and the resulting TPE is filtered by a timing recovery (TR) filter coupled to an interpolated timing recovery (ITR) module and the combining module. The ITR module then synchronizes an input signal of the coherent optical receiver according to the TPE.

Abstract: An optical transceiving apparatus includes an optical transmitting device performing polarization multiplexing on and transmitting as polarization multiplexed signal light, a first signal light of a predetermined polarization direction and a second signal light of a polarization direction different from the predetermined polarization direction; an optical receiving device receiving the signal light transmitted from the optical transmitting device through an optical transmission path; an acquiring unit acquiring information indicative of magnitude relation of intensity between the first signal light and the second signal light included in the signal light received by the optical receiving device; and a control unit controlling the magnitude relation of intensity between the first signal light and the second signal light included in the signal light output from the optical transmitting device, to be opposite to the magnitude relation indicated by the information acquired by the acquiring unit.

Abstract: An optical source (10) comprising: a first laser (12) arranged to generate a first optical signal (14) having a first state of polarization and a first optical frequency; a second laser (16) arranged to generate a second optical signal (18, 48, 78) having a second state of polarization, substantially orthogonal to the first state of polarization, and having a second optical frequency, different to the first optical frequency by a preselected frequency difference, ??; a polarization beam coupler (20) 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 states of polarization; and an output (22) arranged to output the composite optical signal (24).

Abstract: An optical source (10) comprising: a first laser (12) arranged to generate a first optical signal (14) having a first state of polarization and a first optical frequency; a second laser (16) arranged to generate a second optical signal (18, 48, 78) having a second state of polarization, substantially orthogonal to the first state of polarization, and having a second optical frequency, different to the first optical frequency by a preselected frequency difference, ??; a polarization beam coupler (20) 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 states of polarization; and an output (22) arranged to output the composite optical signal (24).

Abstract: An optical device may include a laser emitter to generate a first laser beam and a second laser beam with orthogonal polarization states. The optical device may include first and second photodetectors to generate respective first currents based on optical powers of the first and second laser beams. The optical device may include a polarization-based beam splitter to combine the first and second laser beams. The optical device may include a wavelength filter to filter the first and second laser beams based on respective wavelengths of the first and second laser beams. The optical device may include a third photodetector and a fourth photodetector to generate respective second currents based on optical powers of the first and second laser beams after filtration. The wavelengths of the first and second laser beams may be controlled based on the first currents and the second currents.

Abstract: The present disclosure discloses a method for eliminating nonlinear effects, a transmitter and a receiver. The method includes: setting signals to be transmitted and redundant signals, where the redundant signals are symmetrical to the signals, which are to be transmitted, about Y axis; and after the setting is completed, respectively executing dispersion pre-compensation on the signals to be transmitted and the redundant signals, and executing signal modulation after the dispersion pre-compensation is completed.

Abstract: A Raman pump laser control apparatus comprises a wavelength division multiplexer, a tap coupler, a photoelectric detector, an analog amplification processing circuit, an analog-to-digital converter, a fast Raman pump control unit, an digital-analog converter, and a Raman pump laser. The fast Raman pump control unit, after having known anticipated output light power of the Raman pump laser, based on a direct relationship between a current anticipated output light power of the Raman pump laser and input digital quantity that is needed by the digital-analog converter, uses a feedforward control mechanism so that actual output light power of the Raman pump laser fastly approximates the anticipated output light power thereof, and then synchronously combines with a feedback control mechanism so that the actual output light power of the Raman pump laser is precisely locked on the anticipated output light power, thereby achieving fast and precise control of the Raman pump laser.

Abstract: Systems and methods are disclosed for receiving data by radio frequency (RF) mixing to down-convert in-phase and quadrature parts of a photo-detected electrical RF band signal to baseband for data conversion; controlling a mixing phase of a electrical local oscillator (LO) at one or more RF mixing modules; selecting one of the RF sub-bands to be down-converted to baseband after coherent photo-detection; and performing RF sub-band de-multiplexing for ultra-wide band optical digital coherent detection.

Abstract: An optical transmitter includes: a mapper that generates an electric field information signal from transmission data; a phase rotation circuit that adds a phase rotation to the electric field information signal; a driver that generates a driving signal from the electric field information signal to which the phase rotation is added; a modulator that generates a modulated optical signal according to the driving signal; and a controller that controls a bias of the modulator according to a change in a carrier frequency of the modulated optical signal corresponding to the phase rotation that is added to the electric field information signal by the phase rotation circuit.

Abstract: An optical multiplexer and methods of making and calibrating the same are disclosed. A method of aligning components in a multichannel optical/optoelectronic transmitter includes passively fixing a plurality of light emitters in place on a substrate; adjusting positions of a first lens passing light from a first light emitter and an optical signal transmission medium receiving the light from the first light emitter until a far field spot of the light from the first light emitter is at or near an end of the transmission medium; fixing one or more optical subassemblies on the substrate; and adjusting positions of the optical subassembly(ies) to align light from the remaining light emitters with the far field spot. Some embodiments include multiple optical subassemblies, each including a lens and a filter. Other embodiments include one optical subassembly including a mirror and a beam combiner.

Abstract: A system for communication over a fiber link is disclosed. The system comprises a transmitter to transmit an information signal that comprises an information spectrum, and to transmit two spectrally inverted copies of the information spectrum over the predefined length of the fiber link, the two spectrally inverted copies corresponding to a first spectrum with a first center wavelength and to a second spectrum with a second center wavelength, the second spectrum being inverted relative to the first spectrum and the second center wavelength being different from the first center wavelength, and a receiver to receive the first spectrum and the second spectrum, and to estimate a phase rotation of the second spectrum relative to the first spectrum by comparing a first phase measured from the first spectrum with a second phase measured from the second spectrum.

Abstract: Methods and apparatus for asymmetric distribution of mixed content via a network. Current optical fiber-based access network technologies are multiplexed onto the same fiber for delivery via a common Optical Distribution Network (ODN). Various embodiments of the present disclosure are directed to combining (using optical multiplexing and power splitting) two or more optical user-technologies onto a single Passive Optical Network (PON) while maintaining an independent serving group size and operational independence for each of the combined user-technologies. The disclosed methods and apparatus allow the so-called “outside plant” architecture (i.e., the fiber optic infrastructure from the headend to the customer premises) to be independent of the user-technologies and network architecture that are provided via the outside plant.

Abstract: A method of wavelength conversion without polarization tracking is provided. A system is also provided that converts an input signal into an output signal of a different wavelength that contains all of the amplitude, phase, and polarization information of the original signal. The method includes separating, using a polarization-diversity optical mixer, an input optical signal of a first wavelength into a plurality of electrical signals containing amplitudes and phases while maintaining the polarization information of the input signal, converting each of the amplitudes and phases into individual photo-currents using a photo-diode, converting each of the output photo-currents into voltages using an amplifier, modulating the multitude of voltages to a second wavelength using a modulator, where the separated electrical signals are up-converted to generate an output optical signal that maintains the same amplitude, phase, and polarization information as was contained in the input signal.

Abstract: Provided is a frequency error estimating apparatus used for a coherent optical receiver, which determines an amplitude of a baseband digital electrical signal converted from a received light signal modulated with a phase and amplitude shift keying, determines, with respect to each determined amplitude, a modulated phase component of the baseband digital electrical signal based on phase noise estimation values and frequency error estimation values of N previous symbols (N is a positive integer), and calculates a frequency error based on an inter-symbol phase difference of a signal obtained by cancelling the modulated phase component from the baseband digital electrical signal.

Abstract: Provided is a waveguide-type polarization beam splitter in which deterioration of a polarization extinction ratio due to temperature change and wavelength change is suppressed. A groove is formed to extend across a pair of optical waveguide arms and two quarter wave plates are provided in the groove to extend respectively across the arms. Polarization axes of the quarter wave plates are orthogonal to each other. A first optical coupler which gives a phase difference of 0° or 180° between coupled or split light beams and a second optical coupler which gives a phase difference of 90° or ?90° between coupled or split light beams are used in combination.

Abstract: A polarization multiplexed receiver includes a polarization separator and optical mixing, detecting and analog-to-digital components. The polarization separator receives polarization multiplexed optical signals containing a first data stream and a second data stream, and operate upon the polarization multiplexed optical signals to separate, in an optical domain, the first data stream and the second data stream to generate a first optical output having the first data stream and a second optical output having the second data stream. The optical mixing, detecting and analog-to-digital converting components receive the first and second optical outputs from the polarization separator, extract, in a digital domain, the first data stream from the first optical output of the polarization separator, and extract, in the digital domain, the second data stream from the second optical output of the polarization separator.

Abstract: This disclosure is directed to optical-to-electrical receiver and transceiver integrated circuits that can be used to send and receive multiple optical signal data streams using at least one optical bus. In one aspect, a fan-in integrated circuit of a node includes an arbiter/multiplexer, and at least one receiver. Each receiver is electronically connected to the arbiter/multiplexer. Each receiver receives at least one optical signal over an optical broadcast bus and converts the optical signals into a data stream encoded in electronic signals. The arbiter/multiplexer selects one receiver at a time to send an electronic signal to the arbiter/multiplexer and outputs the electronic signal to the node for processing.

Abstract: Methods and systems for mitigating effects of polarization dependent loss (PDL) in an optical network transmitting a multi-carrier optical signal comprising a plurality of subcarriers may involve assigning and modifying a state of polarization to each subcarrier prior to transmission. An assigned state of polarization for each subcarrier may be modified for the subcarrier in the digital domain and/or the optical domain. Various specific assignment methods may be used, including individual subcarrier assignment, subcarrier set assignment, arbitrary subcarrier group assignment, random assignment, and/or combinations thereof. The assigned states of polarization may be selected based on a resulting minimum PDL-induced peak-to-peak power variation over a sum of the subcarriers for all orientations of a principal axis of PDL.

Abstract: An optical transmission apparatus includes an optical amplifier configured to amplify a wavelength-division multiplexed signal light using an amplifying medium doped with a rare earth ion, a first optical transmitter configured to output a wavelength of a dual-polarization-multiplexed signal to a short wavelength side of an amplification band of the optical amplifier, a second optical transmitter configured to output a wavelength of a non polarization-multiplexed signal to a long wavelength side of the amplification band of the optical amplifier, and an optical multiplexer configured to input a wavelength-division multiplexed signal to the optical amplifier, the wavelength-division multiplexed signal comprising the non polarization-multiplexed signal and the dual-polarization-multiplexed signal.

Abstract: The present invention discloses a system for signalling within optical or combined optical/electronic networks wherein a first transmission node executes polarization multiplexing on transmitted traffic, and at one or more intermediate nodes one or more of the following processes are carried out on the sent traffic: demultiplexing by polarization and/or polarization and/or SOP-alignment. Further a method for packet handling within optical packet switched networks where, at a first transmission node carries out polarization demultiplexing of transmitted traffic, and at one or a number of intermediate nodes carries out one or more of the following processes on the transmitted traffic; demultiplexing by polarization, and/or polarization and/or SOP-alignment. Said separation into states of polarization is used in separation of QoS-classes.

Abstract: A tunable dispersion compensation device includes a plurality of tunable dispersion compensators coupled in series, a controller configured to control an amount of chromatic dispersion to be set in each of the plurality of tunable dispersion compensators, and a table including a correspondence relationship between an amount of chromatic dispersion and a wavelength band, for each of the plurality of tunable dispersion compensators, wherein the controller decides an amount of chromatic dispersion to be set in each of the plurality of tunable dispersion compensators, based on a total amount of chromatic dispersion desired for the plurality of tunable dispersion compensators and the correspondence relationship included in the table so that a difference between bandwidths of a first tunable dispersion compensator having the widest wavelength band and a second tunable dispersion compensator having the narrowest wavelength band, among the plurality of tunable dispersion compensators, is within a given range.

Abstract: A WDM optical signal is transmitted through a tunable optical filter and is polarization-nulled to find optical signal to noise ratio of individual WDM channels. The polarization nulling can be performed using a heuristic multipoint extrema search method, such as Nelder-Mead method. A plurality of checkpoints can be included in the search to verify the progress and to improve the overall robustness of a real-time polarization nulling.

Abstract: A method and a device for data processing in an optical communication network are provided, wherein in an energy saving mode of a polarization multiplexing system data signals are transmitted or received via one polarization plane; and wherein components of the transmitter or receiver of the other polarization plane are at least partially operated in a reduced power mode. Furthermore, a communication system is suggested comprising said device.

Abstract: It is provided a polarization multiplexing optical transceiver including a polarization multiplexing optical transceiver, a polarization multiplexing optical receiver, a transmission side polarization state control unit and a reception side polarization state control unit. The polarization multiplexing optical receiver includes: a polarization demultiplexing unit; a plurality of information signal reconstruction units configured to receive the reconstructed polarization component on the transmission side as an input, and reconstruct and extract information signals; and an information signal coupling unit configured to one of couple and select the information signals output by the plurality of information signal reconstruction units and output the resultant under control of the reception side polarization state control unit.

Abstract: Methods and systems for decoding a signal include compensating for impairments in a received signal using at least carrier phase estimation, where residual phase error remains after compensation; calculating symbol log-likelihood ratios (LLRs) for symbols in the compensated signal using Monte Carlo integration; demapping the symbols in the compensated signal using the symbol LLRs and extrinsic information from signal decoding to produce one or more estimated codewords; and decoding each estimated codeword with a decoder that generates a decoded codeword and extrinsic information.

Abstract: An optical receiver includes: an optical brancher configured to branch polarization multiplexed light to a first polarization multiplexed light and a second polarization multiplexed light, the polarization multiplexed light in which a pilot signal is superimposed on at least one of a first polarization and a second polarization; an optical fiber configured to transmit the first polarization multiplexed light; a first polarization rotator configured to control a first polarization state of the first polarization multiplexed light output from the optical fiber; a first polarization separator configured to separate the second polarization multiplexed light into a third polarization and a fourth polarization; and a controller configured to control the first polarization rotator based on one of a first pilot signal included in the third polarization and a second pilot signal included in the fourth polarization.

Abstract: An optical receiver, includes: a signal processor to perform digital signal processing on a polarization demultiplexed signal obtained by demultiplexing a polarization multiplexed signal corresponding to a reception signal, the signal processor includes: an adaptive equalization circuit to compensate for the polarization demultiplexed signal by control of a filter coefficient; a first frequency offset estimation circuit to receive a first polarization demultiplexed signal diverged at a preceding stage and estimate a first frequency offset; a second frequency offset estimation circuit to receive a second polarization demultiplexed signal diverged at a succeeding stage and estimate a second frequency offset; and a decision circuit to decide whether the filter coefficient is correct based on a first difference between the first frequency offset and the second frequency offset and output, when deciding that the filter coefficient is incorrect, a first trigger for re-calculation of the filter coefficient.

Abstract: An apparatus comprising a processor configured to obtain one or more plant conditions regarding at least one of a plurality of customer premises equipment (CPEs) remotely coupled to the apparatus via electrical lines, and divide the plurality of coupled CPEs into a number of profile groups based on the one or more plant conditions, wherein each profile group comprises at least one CPE and supports one or more modulation orders.

Abstract: A method implemented by a middlebox comprising registering a customer premises equipment (CPE) in the middlebox, wherein the CPE is coupled to the middlebox via an electrical line, and facilitating registration of the CPE in a central office (CO) equipment coupled to the middlebox.

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: In a receiver, a reception front end receives a polarization-scrambled polarization multiplexed optical signal, polarization-separates the received polarization multiplexed optical signal, and converts each signal into quantized signals. A digital signal processor samples the quantized signals, demodulates the signals by using a polarization separation digital signal processing algorithm, and outputs demodulated signals. When phase and amplitude variations of the demodulated signals are greater than a predetermined value, a control circuit causes the digital signal processor to interrupt processing using the polarization separation digital signal processing algorithm, changes an initial value of a filter coefficient, and then causes the digital signal processor to start the processing using the polarization separation digital signal processing algorithm.

Abstract: An Optical Access Network, a Optical Network Unit (ONU) and various methods for exchanging information are provided.

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: 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: The embodiments provide an inverse channel apparatus and transmitter, receiver and system containing the apparatus; wherein the inverse channel apparatus comprises: an inverse nonlinear calculating unit configured to perform nonlinear additive calculation and nonlinear multiplicative calculation on input signals, so as to obtain signals containing nonlinear damage of the input signals on at least one polarization state; and an inverse linear calculating unit configured to calculate signals containing nonlinear damage and linear damage of the input signals on at least one polarization state according to the signals containing nonlinear damage of the input signals on at least one polarization state and a linear function of a channel.

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 transport system configured to transmit information using two or more modulated optical carriers spaced at spectral intervals that are smaller than the baud rate. An example optical receiver in the optical transport system includes a signal equalizer configured to implement frequency-diversity multiple-input/multiple-output signal processing directed at canceling the effects of inter-carrier interference caused by the spectral overlap between adjacent modulated optical carriers to enable the optical receiver to recover individual data streams encoded onto the different modulated optical carriers at the corresponding optical transmitter(s). Some embodiments of the optical transport system may advantageously be capable of achieving a higher spectral efficiency than the spectral efficiency supported by the optical orthogonal-frequency-division-multiplexing transmission format.

Abstract: A planar lightwave circuit includes a substrate in which a groove being formed, the groove dividing the substrate into a first area and a second area; a first filter, a second filter, and a third filter intruded into the groove; as are formed in the first area, a first and a second waveguides formed to guide signal light and local oscillation light; a third and a fourth waveguides formed to guide signal light and local oscillation light; a first 90-degree optical hybrid; as are formed in the second area, a fifth and sixth waveguides formed to guide signal light and local oscillation light; and a second 90-degree optical hybrid.

Abstract: An optical transport system that transmits data using relatively short FEC-encoded data frames. The corresponding modulated optical signals are decoded at an optical receiver using frame-based maximum likelihood sequence estimation that relies on data redundancy present in each FEC-encoded data frame for the determination of its source bits. In some embodiments, the modulated optical signals carrying the FEC-encoded data frames are generated using a polarization-division-multiplexed constellation. The FEC-coding rate and frame length can be adjusted without changing the constellation, which advantageously enables the optical transport system to dynamically adapt its transmission format to the changing link conditions in a manner that results in better overall receiver sensitivity than that achieved with comparable bit-rate-adaptation methods that rely on a constellation change rather than on a change of the FEC-coding rate.

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: An optical module includes a waveguide substrate having an optical waveguide and electrodes that apply electronic signals to the optical waveguide; a relay substrate disposed adjacently to the waveguide substrate; and a termination substrate disposed sandwiching the waveguide substrate with the relay substrate. The electrodes respectively have a first wiring portion connected from the relay substrate through the waveguide substrate to the termination substrate and a second wiring portion extending from the first wiring portion and branching on the termination substrate. In the second wiring portion, one branched wiring portion has a capacitor and a termination resistor, and another branched wiring portion extends through a bias resistor to a DC electrode on the relay substrate. The second wiring portion is divided into a first group extending in a first direction along the optical waveguide and a second group extending in a direction opposite to the first direction.

Abstract: A polarization multiplexed receiver includes a polarization separator and optical mixing, detecting and analog-to-digital components. The polarization separator receives polarization multiplexed optical signals containing a first data stream and a second data stream, and operate upon the polarization multiplexed optical signals to separate, in an optical domain, the first data stream and the second data stream to generate a first optical output having the first data stream and a second optical output having the second data stream. The optical mixing, detecting and analog-to-digital converting components receive the first and second optical outputs from the polarization separator, extract, in a digital domain, the first data stream from the first optical output of the polarization separator, and extract, in the digital domain, the second data stream from the second optical output of the polarization separator.

Abstract: An object of the present invention is to provide an optical 90-degree hybrid circuit which is capable of easily adjusting the optical power ratio between signal and local oscillator and suppresses an optical system of an optical receiver becoming complex and optical receivers using the same.

Abstract: A receiving-side integrated optical circuit of an optical transceiver has an optical wavelength demultiplexer to separate signal light components of the different wavelengths contained in a wavelength division multiplexed signal received from each of N links of a transmission path, a set of N optical amplifiers inserted between the transmission path and the optical wavelength demultiplexer, each optical amplifier being configured to collectively amplify the signal light components of the different wavelengths contained in the received wavelength division multiplexed signal, and a set of photo detectors arranged after the optical wavelength demultiplexer and to detect the signal light components of the different wavelengths.

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: Disclosed are universal QPSK transmitter structures and methods for generating different QPSK signals exhibiting different polarization schemes, namely PolMux, PolMod and PolSw. The bit rate of the generated signals is variable, thereby allowing the transmitter to adjust to varying network traffic conditions. Advantageously, the generated signals may be detected by analog receivers (PolSw-QPSK) and coherent receivers (PolMux-QPSK, PolMod-QPSK, and PolSw-QPSK).

Abstract: The present document relates to optical communication systems. In particular, the present document relates to high efficiency wavelength division multiplexing (WDM) optical communication systems. An optical transmitter (210) adapted to transmit an optical signal on an optical wavelength division multiplexed, referred to as WDM, transmission channel (111) to a corresponding optical receiver (230) is described.

Abstract: It becomes difficult to regenerate transmitting signals depending on modulation systems for the optical phase modulation in a polarization multiplexed optical communication system employing the optical digital coherent communication system, therefore, an optical transmitter according to an exemplary aspect of the invention includes first optical quadrature modulation means for performing a phase modulation on a first continuous light beam and outputting a first transmitting light beam; second optical quadrature modulation means for performing a phase modulation on a second continuous light beam belonging in the same frequency band as that of the first continuous light beam and outputting a second transmitting light beam; optical phase difference adding means for adding an optical phase difference varying temporally between the first transmitting light beam and the second transmitting light beam; and polarization multiplexing means for polarization-multiplexing the first transmitting light beam and the second