摘要:
A method of transmitting a data signal using an optical transmitter of an optical communications system. The optical transmitter is configured to modulate an optical carrier in successive signalling intervals to generate an optical signal. A modulation scheme is provided which comprises a multi-dimensional symbol constellation. The modulation scheme is designed such that an average degree of polarization of a modulated optical signal output from the optical transmitter has a first value when averaged across a first signaling interval, and has a second value when averaged across more than one and fewer than 100 signaling intervals. The second value is less than 10 percent of the first value. During run-time, an encoder of the optical transmitter encoding a data signal to be transmitted as symbols of the constellation, and a modulator of the optical transmitter modulating available dimensions of the optical carrier in accordance with the symbols.
摘要:
An optical transmitter is operable to generate an optical signal by modulating a number N of frequency divisional multiplexing (FDM) subcarriers using transformed digital signals which are determined by applying a pseudo FDM (pFDM) transformation to preliminary digital signals representative of multi-bit symbols. Rather than experiencing the effects of the number N of FDM channels, the optical signal experiences the effects of a different number M of pFDM channels, where M≠N. In some examples, the number M of pFDM channels is less than the number N of FDM channels, and frequency-dependent degradations may be averaged across different symbol streams. In other examples, the number M of pFDM channels is greater than the number N of FDM channels, and different symbol streams may experience different frequency-dependent degradations. An optical receiver is operable to apply an inverse pFDM transformation in order to recover estimates of the multi-bit symbols.
摘要:
Techniques for transmitting a data signal through an optical communications system. An encoder is configured to encode the data signal to generate symbols to be modulated onto an optical carrier. Each symbol encodes multiple bits of data and includes a first portion selected from a first constellation and a second portion selected from a second constellation. The first and second constellations have respective different average amplitudes. Each of the first and second constellations have a cardinality of at least two and the cardinality of the first constellation is greater than the cardinality of the second constellation. A modulator is configured to modulate a first frame of the optical signal using the first portion and modulate a second frame of the optical signal using the second portion. A selection of one frame of the optical signal to be used as the first frame encodes at least 1 bit of data.
摘要:
Techniques for transmitting a data signal through an optical communications system. An encoder is configured to encode the data signal to generate symbols to be modulated onto an optical carrier. Each symbol encodes multiple bits of data and includes a first portion selected from a first constellation and a second portion selected from a second constellation. The first and second constellations have respective different average amplitudes. Each of the first and second constellations have a cardinality of at least two and the cardinality of the first constellation is greater than the cardinality of the second constellation. A modulator is configured to modulate a first frame of the optical signal using the first portion and modulate a second frame of the optical signal using the second portion. A selection of one frame of the optical signal to be used as the first frame encodes at least I bit of data.
摘要:
A receiver may receive an optical signal over an optical communications channel established between the receiver and a transmitter, the received optical signal comprising a degraded version of a modulated optical signal generated at the transmitter. The receiver may determine received digital signals corresponding to a plurality of first dimensions of the received optical signal, wherein the first dimensions correspond to dimensions of an optical carrier modulated at the transmitter to represent a multi-bit symbol, and wherein the first dimensions are distributed over two or more timeslots. The receiver may determine preliminary digital drive signal estimates using an inverse dimensional transformation and the received digital signals, the preliminary digital drive signal estimates corresponding to a plurality of second dimensions. The receiver may determine an estimate of the multi-bit symbol using the preliminary digital drive signal estimates. The inverse dimensional transformation may average signal degradations in the received digital signals.
摘要:
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.
摘要:
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.
摘要:
A method of transmitting a data signal using an optical transmitter of an optical communications system. The optical transmitter is configured to modulate an optical carrier in successive signalling intervals to generate an optical signal. A modulation scheme is provided which comprises a multi-dimensional symbol constellation. The modulation scheme is designed such that an average degree of polarization of a modulated optical signal output from the optical transmitter has a first value when averaged across a first signalling interval, and has a second value when averaged across more than one and fewer than 100 signalling intervals. The second value is less than 10 percent of the first value. During run-time, an encoder of the optical transmitter encoding a data signal to be transmitted as symbols of the constellation, and a modulator of the optical transmitter modulating available dimensions of the optical carrier in accordance with the symbols.
摘要:
A system configured to perform a method for estimating external noise in a communication channel between a transmitter and a receiver is described. The method comprises obtaining a measurement of effective noise on decoded symbols at the receiver, the decoded symbols comprising noisy versions of symbols conveyed by a communication signal transmitted over the communication channel. The method further comprises storing a representation of a relationship between the effective noise, external noise in the communication channel, and one or more variable parameters. The method further comprises storing applicable values of the variable parameters, wherein each applicable value is associated with current properties of the transmitter or current properties of the receiver or both. The method further comprises calculating an estimate of the external noise in the communication channel using the effective noise, the applicable values of the variable parameters, and the representation of the relationship.
摘要:
Using pump-probe measurements on multi-span optical links may result in the determination of one or more of the following: 1) wavelength-dependent power profile and gain evolution along the optical link; 2) wavelength-dependent dispersion map; and 3) location of regions of high polarization-dependent loss (PDL) and polarization-mode dispersion (PMD). Such measurements may be a useful diagnostic for maintenance and upgrade activities on deployed cables as well as for commissioning new cables.