Abstract: A receiver is provided for processing an input signal from a communication network. The receiver includes a processor and a memory configured to store computer executable instructions, which, when executed by the processor, cause the processor to (i) receive an input data signal including digital bit information, (ii) code the input data signal into a plurality of multi-level symbols, (iii) map the plurality of multi-level symbols into a plurality of constellation points in the phase domain, (iv) execute a first phase recovery subprocess on the plurality of constellation points to recover a first carrier phase of the input signal, (v) implement a Gaussian mixture model (GMM) on the recovered first carrier phase to generate an enhanced recovered carrier phase, and (vi) process the enhanced recovered carrier phase with a second phase recovery subprocess to reduce distortion from the input signal.

Abstract: Provided is a light modulator including a substrate, and a resonator configured to modulate a phase of incident light by modulating a refractive index based on an external stimulus, the resonator comprising a first reflective structure provided on the substrate, a cavity layer provided on the first reflective structure, and a second reflective structure provided on the cavity layer, wherein at least one of the first reflective structure or the second reflective structure comprises first material layers, second material layers that are alternately stacked with the first material layers, and a third material layer, and wherein each of the first material layers has a first refractive index, each of the second material layers has a second refractive index that is different from the first refractive index, and the third material layer has a third refractive index that is different from the first refractive index.

Abstract: Provided is a chromatic dispersion compensation method including: dividing a reception signal obtained by receiving an optical signal using a coherent detection scheme into a plurality of frequency bands; adjusting a timing on a time axis of the reception signal for each of the divided frequency bands; performing combination processing for combining the reception signals included in the plurality of frequency bands; performing chromatic dispersion compensation on the reception signal at any timing before or after the combination processing; selecting, before the combination processing, sections in which overlapping parts determined based on lengths of overlap parts are generated; outputting the reception signal for each of the selected sections as a division processing block; and removing the overlap parts from both ends of a processing block generated by combination of the division processing blocks in the combination processing so as to be continuous on a frequency axis.

Abstract: A method of controlling an optical transmitter includes steps of amplifying, by an EDFA, a main signal output from an optical modulator, attenuating and outputting, by a VOA, the main signal amplified and output by the EDFA, and maintaining an output power of the main signal output from the VOA at a predetermined value, suspending the phase modulation in the optical modulator to output continuous wave light from the optical modulator, disabling feedback control of the VOA that is performed by the VOA controller and maintaining a constant control signal of the VOA, disabling feedback control of a pump laser that is performed by a pump laser controller, and controlling the pump laser to modulate an intensity of the excitation light and generate an auxiliary signal having a cycle longer than a cycle of the main signal.

Abstract: Certain aspects of the present disclosure generally relate to wireless communications and more specifically to transmission resource management for ordered physical random access channel (PRACH) signals. An example method performed by a base station generally includes providing an indication of a set of transmission resources, within a narrowband region of a wider system bandwidth, for transmitting scheduled physical random access channel (PRACH) signals by a first user equipment (UE) and transmitting a command to the first UE to transmit a scheduled PRACH.

Abstract: A method and system for managing interference between transmission sources in an Optical Camera Communication (OCC) network is disclosed. The method includes receiving interference information associated with a set of transmission sources. Each of the set of transmission sources include a set of light sources configured to display one of a plurality of colors. The method further includes assigning a unique guard band to each of the set of transmission sources. The method includes sharing details of the unique guard band assigned to a first transmission source within the set of transmission sources with the camera. The camera is configured as the receiver of the first transmission source. The method further includes instructing the camera to accept data transmitted by the first transmission source based on the assigned unique guard band and drop data transmitted by the remaining set of transmission sources.

Abstract: Systems and methods for controlling optical powers of optical channels in an optical communications network comprising a plurality of nodes is described herein. The method comprises obtaining a reference optical power. The method also includes determining an optical power of an optical channel generated by an optical transmitter of a node. The method further includes applying an attenuation to the optical channel to reduce the optical power of the optical channel to the reference optical power. In some implementations, the method is performed by a network controller operating in the optical communications network.

Abstract: A skew compensation system for a coherent optical communication network includes a transmitter modulator having a first driver input for receiving a first signal from a first channel, a second driver input for receiving a second signal from a second channel, a source input for receiving a continuous wave source signal, and a modulation output in communication with an optical transport medium of the network. The system further includes a tunable delay line disposed between the second channel and the second driver input for inserting a pre-determined training sequence onto the second signal prior to the second driver input, and a processor for determining a skew amount between the second signal at the second driver input and the first signal at the first driver input, calculating a pre-compensation value corresponding to the skew amount, and reducing the skew amount at the modulation output according to the pre-compensation value.

Abstract: Provided is a wavelength path communication node device with no collision of wavelengths and routes, capable of outputting arbitrary wavelengths, and capable of outputting them to arbitrary routes. An add/drop multiplexer (11) includes a communication unit (101) that communicates an optical signal with at least one client device and at least one network and a control unit (102) that indicates a transfer destination of the optical signal according to an attribute of the received optical signal to the communication unit (101). The control unit (102) indicates an attenuation amount of the optical signal to the communication unit (101) for each connected device. When a connected device is changed, the control unit (102) instructs the communication unit (101) to change the attenuation amount. The communication unit (101) attenuates the optical signal with the attenuation amount indicated by the control unit (102) and transfers the attenuated optical signal to a transfer destination.

Abstract: A method and system for using a wavelength tunable semiconductor laser as an excitation source of a fiber optics sensing system (FOSS) based on a thermoelectric control of a laser sweep. A device can include an optical fiber; a set of fiber Bragg gratings disposed within the optical fiber; a single-frequency laser (SFL) operatively connected to the optical fiber; a thermoelectric cooler operatively connected to the SFL; a controller comprising a processor in communication with the thermoelectric cooler; and a nontransitory, computer-readable storage medium in communication with the processor. The nontransitory, computer-readable storage medium can store instructions that, when executed by the processor, cause the processor to perform operations including determining a strain value at a first fiber Bragg grating of the set of fiber Bragg gratings based on a second laser signal received at the device that is reflected from an interaction of a first laser signal with the first fiber Bragg grating.

Abstract: A system comprises quantum control interconnect circuitry configured to receive a plurality of fixed-frequency signals, a variable-frequency signal, a quantum control pulse, a quantum element readout pulse, and a quantum element return pulse. The circuitry is operable to upconvert the quantum control pulse using the fixed-frequency signals. The circuitry is operable to upconvert the readout pulse using the variable-frequency signal. The circuitry is operable to downconvert the return pulse using the variable-frequency signal.

Abstract: Optical receivers and methods for tuning an operating point of an optical resonator, such as a Fabry-Perot etalon are disclosed. A free-space optical signal is received at an optical receiver and directed towards at least one beam splitter. After passing through the beam splitter, the optical signal is reflected off a surface of the optical resonator. The reflected signal is detected and utilized to tune the operating point of the optical resonator.

Abstract: An optical signal monitor, including: a storage that holds a threshold value set for each of determination areas having a bandwidth set in accordance with an average grid of dummy light; a measurement section that sequentially measures an optical intensity of an inputted wavelength-multiplexed optical signal with respect to each of measurement areas obtained by dividing the determination area into areas with a bandwidth sufficiently smaller than a grid width of a monitoring-target optical signal composing the wavelength-multiplexed optical signal, and output measured values; and a section that determines that dummy light corresponding to the determination area needs introducing if each of measured values in the determination area is smaller than a threshold value, and, determines that dummy light corresponding to the determination area does not need introducing if at least one of the measured values in the determination area is equal to or larger than the threshold value.

Abstract: In some embodiments, an apparatus includes an optical transceiver configured to be operatively coupled to a network. The optical transceiver includes a photo diode and a processor configured to be operatively coupled to the photo diode. The photo diode is configured to measure a receiver optical power (ROP) value and send the ROP value to the processor. The processor is configured to measure a bit error rate (BER) value of a digital modulated signal at an input port of the optical transceiver. The processor is also configured to determine an estimated optical signal noise ratio (OSNR) value at the input port of the optical transceiver based on the ROP value and the BER value. The processor is configured to send a signal indicating the estimated OSNR value such that a planned route is selected for sending data signals through within the optical transceiver based on the estimated OSNR value.

Abstract: A transmission device includes a memory, and a processor coupled to the memory and configured to acquire a polarization mode dispersion value of each of wavelengths of a polarization-multiplexed optical signal having a wavelength, multiply a mean value of the polarization mode dispersion values of the wavelengths by a prescribed ratio, to thereby calculate a maximum value of the polarization mode dispersion value that is temporally varied, and select a multi-level modulation scheme of the polarization-multiplexed optical signal based on an index value of transmission quality of the polarization-multiplexed optical signal depending on the maximum value.

Abstract: In some embodiments, an apparatus includes a memory and a processor operatively coupled to the memory. The processor is configured to be operatively coupled to a first optical transponder and a second optical transponder. The processor is configured to receive, from the second optical transponder, a signal representing a skew value of an optical signal and a signal representing a bit-error-rate (BER) value of the optical signal. The skew value is associated with a skew between an in-phase component of the optical signal and a quadrature component of the optical signal. The processor is configured to determine, based on at least one of the skew value or the BER value, if a performance degradation of the first optical transponder satisfies a threshold. The processor is configured to send a control signal to the first optical transponder to adjust a pulse shaping or a data baud rate of the first optical transponder.

Abstract: It is possible to suppress carrier light with a simple configuration when modulating the carrier light to generate optical sideband components. An optical carrier-suppressed signal generator includes first splitting means used to split input carrier light into two light beams, an optical modulator which modulates one split carrier light beam and outputs light including optical sideband components, a phase modulator which phase-modulates another split carrier light beam, and second or third splitting means used to split the output light of the optical modulator into two light beams. The output light split by the second or third splitting means and the output light of the phase modulator are multiplexed to obtain the amplitude of the signal waveform of optical power, and the optical modulator is controlled such that the obtained value is minimized.

Abstract: An example device includes splitter logic to split an input sample having a predetermined number of bits into a first segment of most significant bits and a second segment of least significant bits. Pulse logic generates a pattern of pulses that correlate to the values of the most significant bits. Edge mover logic determines edge adjustment data based on the values of the least significant bits, the edge adjustment data representing an adjustment to at least one edge in the pattern of pulses. Combiner logic generates an enhanced pulse stream by adjusting at least one edge in the pattern of pulses based on the edge adjustment data.

Abstract: A system for analyzing an optical transport network is provided. The system can generate a linear OSNR and an output power profile for each optical link element of an optical link based on an input power profile, amplifier characteristics, transport fiber characteristics, and a set of operating parameters. The system can generate a nonlinear OSNR for each optical link element based on the input power profile and transport fiber characteristics of each optical link element. The system can determine an expected performance metric for the optical link based on the linear OSNR, the non-linear OSNR, and a transmitter output OSNR. The system can designate the optical link as valid for use in the optical transport network if the expected performance metric is greater than or equal to a performance metric threshold.

Abstract: An optical signal monitor, including: a storage that holds a threshold value set for each of determination areas having a bandwidth set in accordance with an average grid of dummy light; a measurement section that sequentially measures an optical intensity of an inputted wavelength-multiplexed optical signal with respect to each of measurement areas obtained by dividing the determination area into areas with a bandwidth sufficiently smaller than a grid width of a monitoring-target optical signal composing the wavelength-multiplexed optical signal, and output measured values; and a section that determines that dummy light corresponding to the determination area needs introducing if each of measured values in the determination area is smaller than a threshold value, and, determines that dummy light corresponding to the determination area does not need introducing if at least one of the measured values in the determination area is equal to or larger than the threshold value.

Abstract: An optical signal monitor, including: a storage that holds a threshold value set for each of determination areas having a bandwidth set in accordance with an average grid of dummy light; a measurement section that sequentially measures an optical intensity of an inputted wavelength-multiplexed optical signal with respect to each of measurement areas obtained by dividing the determination area into areas with a bandwidth sufficiently smaller than a grid width of a monitoring-target optical signal composing the wavelength-multiplexed optical signal, and output measured values; and a section that determines that dummy light corresponding to the determination area needs introducing if each of measured values in the determination area is smaller than a threshold value, and, determines that dummy light corresponding to the determination area does not need introducing if at least one of the measured values in the determination area is equal to or larger than the threshold value.

Abstract: A segment-based approach for fast fourier transforms of input signals is provided for the generation of baseband signals. A FFT is performed individually for each of the segments from the input signal and the FFT result from each segment is accumulated to provide a final FFT for an input signal symbol. After the samples are received for one segment, a FFT can be performed to generate an intermediate FFT result while samples for the additional segment(s) are received. The system accumulates the intermediate result from the segments into a final FFT result that can be used to generate the baseband signal. Segment-based processing of an input signal can provide faster and more efficient processing to generate a baseband signal. Segment-based processing can also decrease the required size of the input buffers for antennas.

Abstract: An optical spectral analyzer for measuring an optical multi-channel signal by separating the multi-channel signal and measuring a plurality of single-channel signals simultaneously. The spectral analyzer can include a demultiplexer configured to receive the multi-channel signal. The multi-channel signal can be a multi-channel wavelength range. The demultiplexer can separate the multi-channel signal into the plurality of single-channel signals including a first single-channel signal and a second single-channel signal. The spectral analyzer can include a plurality of optical paths. The plurality of optical paths can include a plurality of respective detectors for measuring an optical power of the respective single-channel signals. The detectors can convert the optical power of the respective single-channel signals to corresponding electrical signals.

Abstract: A transceiver (100) is disclosed for a communication node adapted to transmit a first signal to an other communication node and to receive a second signal from the other communication node. The transceiver comprises at least one antenna (110), at least one transmitter module (120), at least one receiver module (130), and a mode alternator (160). The at least one antenna is adapted to simultaneously transmit the first signal and receive the second signal, wherein the first and second signals have equal carrier frequencies and different polarizations. The second signal is for determining a channel characterization of a communication channel over which the second signal is received, and the channel characterization is for determination of one or more transmission parameters for the first signal. The mode alternator is adapted to alternate a mode of operation of the transceiver between at least a first and a second mode of operation.

Abstract: Wavelength multiplexed optical communication systems include a channeled chromatic dispersion compensator coupled to receive modulated optical beams associated with a plurality of optical channels at respective communication wavelengths. The channeled chromatic dispersion compensator applies independently selected dispersion compensations to each of the optical channels by identifying a dispersion compensation associated with a preferred bit error rate, inter-symbol interference, or other signal quality metric, or determined using optical fiber properties such as dispersion slope and zero dispersion wavelength. Chromatic dispersion compensation can be coupled with channel power equalization, and can be performed at a receiver or a transmitter or in the middle of a fiber span.

Abstract: A measuring instrument for measuring electrical characteristics of a device under test (DUT) includes a signal generator for generating a synchronization signal transmittable to a receiver and a phase shifter. The measuring instrument is configured to receive a retransmission of the synchronization signal from the receiver. The phase shifter configured to receive the synchronization signal from the signal generator and the retransmission of the synchronization signal from the receiver and shift a phase of the synchronization signal so that pulse edges of the synchronization signal are aligned at the measuring instrument and the receiver.

Abstract: The present disclosure describes a reconfigurable optical add-drop multiplexer including a wavelength selective switch configured to filter wavelengths of an optical signal; and an optical equalizer, coupled to the wavelength selective switch, configured to equalize the optical signal to mitigate optical filtering effects caused by the wavelength selective switch.

Abstract: In some embodiments, an apparatus includes a memory, a processor operatively coupled to the memory and a sensor. The sensor is configured to intercept a wireless signal associated with a vehicle. The processor configured to identify from the wireless signal (1) a bit rate of the wireless signal, (2) an encoding type associated with the wireless signal, and (3) data associated with the wireless signal. The processor configured to generate an identifier associated with the vehicle based on the bit rate, the encoding type and the data. The processor configured to correlate within the memory the identifier with additional data associated with a user of the vehicle.

Abstract: This disclosure provides systems, methods, and apparatus for mitigating the effects of interference signals on optical signals received at a direct-detection optical receivers. The optical receivers are capable of attenuating interference noise signals resulting from the interference between a transmitted optical signal transmitted from a transmitter to the optical receiver and one or more additional signals received at the optical receiver. The interference can be due to multi-path interference or due to in-band interference. The receivers include a tunable filter for filtering the received optical signal to remove the interference. A frequency offset module processes the received optical signal to determine a frequency offset indicative of the difference between the carrier frequencies of a modulated optical signal and an interference optical signal.

Abstract: Apparatuses, systems, and methods of communication using visible light communications (VLC) are provided. A system can include a VLC transmitter and a VLC receiver suitable for implementing a diversity combining technique. The diversity combining technique can include equal gain combining, selective best combining, and maximal ratio combining. The VLC transmitter can be a multi-element diversity transmitter and can provide illumination as well as data transfer.

Abstract: A method of transmitting communications traffic in an optical communication network comprising a plurality of nodes, the method comprising, at a source node: receiving communications traffic to be transmitted across the optical communication network to a target node; obtaining a path sequence defining an order in which a plurality of optical paths from the source node to the target node across the optical communication network are to be used, at least part of each optical path being spatially separate from each other optical path; and transmitting the communications traffic as a series of traffic portions, each traffic portion being transmitted for a respective preselected transmission period on a respective optical path according to the path sequence.

Abstract: Techniques are described for indicating a wavelength at which a network interface device is configured to operate. A first controller circuit may determine a wavelength at which the network interface device is operating. The wavelength at which the network interface device is operating includes at least one of an optical wavelength at which a laser of the network interface device is transmitting optical data or an optical wavelength at which a photodiode of the network interface device is receiving optical data. A second controller circuit may cause the network interface device to output a sensory output that indicates the wavelength at which the network interface device is operating.

Abstract: Methods, systems, and apparatus, for an external cavity FP laser. In one aspect, an apparatus is provided that includes a FP laser diode; a Faraday rotator (FR) coupled to receive an optical output of the FP laser diode and that rotates a polarization of the optical output; an optical fiber coupled at a first end to receive the output of the FR; a WDM filter coupled to a second end of the optical fiber to receive the optical signal from the optical fiber; and a FRM coupled directly or indirectly to an output of the WDM filter, wherein an optical output of the WDM filter is partially reflected by the FRM such that the polarization of a reflected beam is rotated, and wherein the reflected optical signal then passes through the FR with its polarization being rotated by the FR before it is injected back into the FP laser diode.

Abstract: If a configuration is employed in which modulation schemes used for an optical communication system can be switched depending on transmission conditions, it is difficult to make effective utilization of frequency resources without the power consumption increasing and the control becoming complex; therefore, an optical transmitter according to an exemplary aspect of the present invention includes an interface means for converting a digital signal to be transmitted under a predetermined transmission condition over an optical carrier wave into a parallel signal with a predetermined bit number at a predetermined transmission rate, and outputting the parallel signal; an encoding means for encoding the parallel signal using one coding system from among a plurality of convolutional coding systems with different degrees of redundancy; a mapping means for mapping an output bit signal output from the encoding means to a modulation symbol; an optical modulation means for modulating the optical carrier wave based on a sy

Abstract: Synchronizing SBS suppressing optical phase/frequency modulation of each of a plurality of optical transmitters can be achieved with a plurality of optical transmitters conveying a plurality of optical carriers; and a synchronizer coupled to each of the plurality of optical transmitters to synchronize the SBS suppressing optical phase/frequency modulation of each of the plurality of optical carriers.

Abstract: A probe generator includes: a first demultiplexer configured to branch a first optical signal having a first wavelength into at least two first polarized optical signals; a first adjustor configured to adjust the first polarized optical signals such that the first polarized optical signals have the same polarization direction and to combine the adjusted first polarized optical signals into a second optical signal; a first modulator configured to branch the second optical signal into at least two first split optical signals and to intensity-modulate each of the first split optical signals with first pilot signals; a second adjustor configured to adjust the first split optical signals intensity-modulated by the first modulator such that the intensity-modulated first split optical signals have different polarization directions; and an output unit configured to combine the first split optical signals adjusted by the second adjustor to generate a probe optical signal to be output.

Abstract: An optical transmission system includes a first optical transmission apparatus that adds a plurality of error correction codes to a main signal, retrieves, from a first error correction code that is added to the main signal and that corresponds to a first sub-carrier among the plurality of sub-carriers, a first code portion in excess of a predetermined redundancy level, distributes the first code portion to a second sub-carrier among the plurality of sub-carriers, concatenates a second code portion into the first error correction code, and transmits an optical signal including the main signal multiplexed with the first error correction code that has been concatenated with the second code portion.

Abstract: An optical receiver including: a phase modulation unit that generates local oscillation light and modulates a phase of the local oscillation light; a coherent detection unit that causes a received optical signal and the local oscillation light phase-modulated by the phase modulation unit to interfere and converts the optical signal to an electrical signal; a polarization separation/adaptive equalization unit that performs polarization separation and adaptive equalization on the electrical signal after coherent detection; and decoding units that decode the polarization-separated electrical signals outputted from the polarization separation/adaptive equalization unit.

Abstract: An optical transmitter for transmitting a multilevel amplitude-shift-keying modulated signal includes an optical modulator for modulating an optical signal with a multilevel amplitude-shift-keying modulation, and a spectral filter adapted to increase a high-frequency component of the modulated optical signal relatively to a central frequency component. The multilevel ASK modulation is quaternary ASK and the symbol rate of the optical modulator is above 40 Gbaud. An optical link connects the optical transmitter to a quadratic direct detection optical receiver.

Abstract: Disclosed are an apparatus and method configured to process video data signals operating on a passive optical network (PON). One example method of operation may include receiving a data signal at an optical distribution network node (ODN) and identifying signal interference in the data signal. The method may also include modifying a shape of the data signal in the electrical domain and transmitting the modified data signal to at least one optical termination unit (ONT).

Abstract: A system and method including a transmitter including digital signal processor for providing a shaped data output in response to an input data stream. The shaped data output is coupled to a modulator that modulates an optical signal in response to the shaped data output to provide a non-rectangular shaped output having channel spacing greater than Nyquist channel spacing. Providing a shaped output consistent the present disclosure mitigates the effects of non-linear impairments in an optical transmission system.

Abstract: Disclosed is an optical line monitoring system and method which detects an optical line where a disorder occurs, by using an OTDR (Optical Time Domain Reflectometer) pulse pattern with matching information. The optical line monitoring system generates and stores a reference OTDR pulse pattern matched with identification information of an optical channel service unit, and compares the matched reference OTDR pulse pattern with the OTDR pulse pattern collected at an inspection time to verify an optical line region where a disorder occurs.

Abstract: An apparatus comprises a receiver configured to receive first messages, a processor coupled to the receiver and configured to process the first messages, determine transmission powers associated with the first messages, and generate a transmission scheme based on the transmission powers, and a transmitter coupled to the processor and configured to transmit a second message comprising the transmission scheme. An apparatus comprises a transmitter configured to transmit a first message indicating a transmission power of the apparatus, a receiver configured to receive a second message, wherein the second message assigns to the apparatus a wavelength based on the transmission power, and a processor coupled to the transmitter and the receiver and configured to process the second message, and instruct the transmitter to transmit a third message at the wavelength.

Abstract: A communication device includes a signal correcting unit that performs signal correction on an electric signal indicating information to be transmitted to reduce signal deterioration occurring in transmission of the electric signal; a conversion unit that converts the electric signal subjected to the signal correction into a digital signal on which information indicating the signal correction performed by the signal correcting unit is superimposed; and a light-emitting element that emits light in accordance with the digital signal converted by the conversion unit.

Abstract: A spectral content of a baseband waveform is varied and a measure of the baseband waveform whose spectral content has been varied is used by a transmitter in order to convey information. According to embodiments of inventive concepts, a set of frequencies that is used to provide spectral content to the baseband waveform is varied. In some embodiments, the spectral content comprises non-contiguous first and second frequency intervals wherein a third frequency interval that is between the first and second frequency intervals remains substantially devoid of providing spectral content in order to reduce or avoid interference. In other embodiments, the spectral content that is varied comprises a bandwidth that is varied. The inventive concepts are relevant to 4G LTE carrier aggregation systems/methods and/or other aspects of 4G LTE. Various transmitter/receiver embodiments are disclosed including direct synthesis transmitter/receiver embodiments.

Abstract: A system for delivering optical power over optical conduits includes at least one optical power source delivering multiple optical power forms over an optical conduit with a counter propagating optical control signal.

Abstract: Aspects of the present invention provide techniques for compensating nonlinear impairments of a signal traversing an optical communications system. A parallel array of linear convolutional filters are configured to process a selected set of samples of the signal to generate an estimate of a nonlinear interference field. The predetermined set of samples comprises a first sample and a plurality of second samples. A processor applies the estimated nonlinear interference field to the first sample to least partially compensate the nonlinear impairment.

Abstract: An example apparatus comprises an optical transmitter which includes a first processor and at least two optical modulators. The first processor is configured to generate a first electronic representation for each of at least two optical signals for carrying payload data modulated according to a one-dimensional (1-D) modulation format, and to induce on respective ones of the first electronic representations an amount of dispersion that depends on a power-weighted accumulated dispersion (ADPW) of a transmission link through which the at least two optical signals are to be transmitted thereby generating complex-valued electronic representations of pre-dispersion-compensated optical signals. Each of the at least two optical modulators modulate a respective analog version corresponding to a respective one of the complex-valued electronic representations onto a polarization of an optical carrier.

Abstract: The present document relates to an optical communication system. In particular, the present document relates to the alignment of the laser frequency at a transmitter of the optical communication system and the local oscillator frequency at a coherent receiver of the optical communication system. A coherent optical receiver (222) is described. The receiver (222) comprises a reception unit adapted to convert a received optical signal at a carrier frequency into a digital signal using a local oscillator, referred to as LO, having an LO frequency; a spectral analysis unit adapted to estimate a degree of asymmetry of a spectrum of the received optical signal, based on the digital signal; and a transmission unit adapted to transmit an indication of the degree of asymmetry to a near-end transponder (210) comprising a transmitter (211) of the received optical signal.

Abstract: An improved method and apparatus for reducing performance degradation in optical fiber transmission system due to polarization mode dispersion and nonlinear polarization coupling. Digital polarization scrambling with transmit and receive digital signal processing is used to reduce these effects. By performing digital polarization scrambling on all possible states of polarization with respect to the two principle axes of an optical fiber, the SOP dependent penalty is averaged out. The invention also provides a method and apparatus for performing digital polarization scrambling on the transmit side and blinded polarization tracking or synchronized polarization descrambling at the receive side. Using a configurable scrambling speed, the invention works as a polarization scanner low speed SOP rotation or as a scrambler at fast SOP rotation speeds.