Abstract: Device and methods for real-time polarization-dependent loss monitoring at coherent transceivers. In one embodiment, there is provided a method of monitoring a polarization dependent loss (PDL) of a signal during transmission through an optical communication link, the method comprising: receiving the signal by a coherent receiver, the received signal being subjected to one or more impairments in Amplifier Gain Control (AGC) mode, the one or more impairments including PDL; estimating an AGC gain effect of the AGC mode; compensating for the AGC gain effect in the received signal; determining the PDL from the compensated signal; and reporting the PDL.

Abstract: A polar encoder comprises an input, an output and a processor operatively connected to the input and to the output. The input either receives first, second and third codewords, or receives information bits used by the processor for generating first, second and third probabilistic constellation shaping codewords. The processor combines the first and second codewords, to produce a first modulation symbol bit, combines the first and third codewords to produce a second modulation symbol bit, and combines the first, second and third codewords to produce a third modulation symbol bit. The output forwards the modulation symbol bits to a bit to symbol mapper. The polar encoder may be included in a transmitter that further comprises the bit to symbol mapper receiving the modulation symbol bits and generating modulation symbols, and a modulator modulating a carrier using the modulation symbols.

Abstract: Methods and encoders for encoding information bits to generate codewords for transmission across a communication channel are described. The method includes receiving input data comprising bits of information bits and frozen bits. Each bit has a value. Further, the method identifies at least one special arrangement in a subset of input data depending on locations of the information bits and the frozen bits. This subset of input data is of length L. The subset of input data has at least one special arrangement that enables direct computations instead of a series of computations to determine a preliminary output. The method generates a codeword for the input data from the preliminary output.

Abstract: The disclosed systems and methods for compensating the polarization dependent loss (PDL) in communication networks comprising: i) filtering, by a first feed-forward filter, a current set of symbols in an equalized X-Pol signal; ii) filtering, by a second feed-forward filter, a current set of symbols in an equalized Y-Pol signal; iii) filtering, by a first feed-backward filter, a previously decided set of symbols associated with the equalized X-Pol signal; iv) filtering, by a second feed-backward filter a previously decided set of symbols associated with the equalized Y-Pol signal; v) adding, by a first adder, the outputs from the first feed-forward filter and the second feed-forward filter; and vi) subtracting, by the first adder, the outputs from the first feed-backward filter and the second feed-backward filter from the addition of outputs from the first feed-forward filter and the second feed-forward filter to determine the symbols in the equalized X-Pol signal.

Abstract: A polar encoder comprises an input, an output and a processor operatively connected to the input and to the output. The input either receives first, second and third codewords, or receives information bits used by the processor for generating first, second and third probabilistic constellation shaping codewords. The processor combines the first and second codewords, to produce a first modulation symbol bit, combines the first and third codewords to produce a second modulation symbol bit, and combines the first, second and third codewords to produce a third modulation symbol bit. The output forwards the modulation symbol bits to a bit to symbol mapper. The polar encoder may be included in a transmitter that further comprises the bit to symbol mapper receiving the modulation symbol bits and generating modulation symbols, and a modulator modulating a carrier using the modulation symbols.

Abstract: Methods and encoders for encoding information bits to generate codewords for transmission across a communication channel are described. The method includes receiving input data comprising bits of information bits and frozen bits. Each bit has a value. Further, the method identifies at least one special arrangement in a subset of input data depending on locations of the information bits and the frozen bits. This subset of input data is of length L. The subset of input data has at least one special arrangement that enables direct computations instead of a series of computations to determine a preliminary output. The method generates a codeword for the input data from the preliminary output.

Abstract: The disclosed systems, structures, and methods are directed to encoding and decoding information for transmission across a communication channel. The encoding method includes: distributing the information bits between m parallel polar codes such that each of the m parallel polar codes includes a subset of the information bits; splitting the subset of information bits in each of the m parallel polar codes into a protected information section and a full rate information section; protecting information bits in the protected information section of each of the m parallel polar codes; arranging a plurality of frozen bits in each of the m parallel polar codes; and generating a polar encoded codeword for each of the m parallel polar codes.

Abstract: The disclosed systems and methods for encoding, by a polar encoder, K message bits into an encoded message bits sequence C(M) using polar codes, where K and M are integer values and M is greater than or equal to K; rearranging, by an interleaver, the encoded message bits sequence C(M) to rearranged encoded message bits sequence C?(M) such that a C(i)th bit and a C ? ( M 2 + i ) th bit of the encoded message bits sequence C(M) are arranged together, where i is an integer value that varies between 1 to M 2 ; mapping, by a bits-to-symbol mapper, the rearranged encoded message bits sequence C(M) to N non-binary symbols, where N is an integer value; and processing, by a transmitter symbol processor, the N non-binary symbols to transmit the processed non-binary symbols towards a receiver.

Abstract: The disclosed systems, structures, and methods are directed to encoding and decoding information for transmission across a communication channel. The encoding method includes: distributing the information bits between m parallel polar codes such that each of the m parallel polar codes includes a subset of the information bits; splitting the subset of information bits in each of the m parallel polar codes into a protected information section and a full rate information section; protecting information bits in the protected information section of each of the m parallel polar codes; arranging a plurality of frozen bits in each of the m parallel polar codes; and generating a polar encoded codeword for each of the m parallel polar codes.

Abstract: Methods and devices for IQ time skew and conjugation compensation and calibration of a coherent transmitter or transceiver are described. A pilot tone is combined with a digital data signal such that relative powers of the pilot tone in each of two frequency bands of the transmitted data signal may be detected by a pilot tone detector and used to calculate the time skew between I and Q modulation channels of the transmitter. A transmitter DSP applies IQ time skew bias to the data signal to compensate for any calculated IQ time skew. The pilot tone detector also provides the transmitter DSP with the information necessary to detect phase conjugation of the optical signal, which can be corrected by inverting the polarity of the data signal or changing the phase bias point of the optical modulator.

Abstract: The disclosed systems, structures, and methods are directed to encoding and decoding information for transmission across a communication channel. The encoding method includes: distributing the information bits between m parallel polar codes such that each of the m parallel polar codes includes a subset of the information bits; splitting the subset of information bits in each of the m parallel polar codes into a protected information section and a full rate information section; protecting information bits in the protected information section of each of the m parallel polar codes; arranging a plurality of frozen bits in each of the m parallel polar codes; and generating a polar encoded codeword for each of the m parallel polar codes.

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 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: Methods and apparatuses for IQ time skew calibration in a coherent transceiver are described. A four-channel signal is received. A set of inputs is constructed for a 4×8 MIMO equalizer by converting the four-channel signal into four complex inputs that each have a phase shift corresponding to an estimated carrier frequency offset. The set of inputs further includes conjugate replicas of the four complex inputs. Using output from the 4×8 MIMO equalizer, equalizer coefficients are calculated by minimizing error between the MIMO output and a reference signal. Receiver and transmitter IQ skew are estimated using the equalizer coefficients, by converting the equalizer coefficients form the time domain to the frequency domain to determine receiver and transmitter IQ differential phase responses, which are indicative of respective receiver and transmitter IQ skew in the time domain. Skew compensation is then performed.

Abstract: A receiver architecture is described for phase noise compensation in the presence of inter-channel interference (ICI) and inter-symbol interference (ISI), particularly for time-frequency packing (TFP) transmissions. The receiver includes a coarse phase noise (PN) estimator, a PN compensation module, an ICI cancellation module, an ISI compensation module, a FEC decoder, and an iterative PN estimator. The iterative PN estimator receives log likelihood ratio (LLR) information from the decoder and provides an iterative PN estimation to the PN compensation module. The decoder also provides LLR to the ISI compensation module, and to at least one other receiver for another subchannel that is immediately adjacent in frequency. The ICI cancellation module receives decoder output from at least one adjacent subchannel, which the ICI cancellation module uses to provide a ICI-cancelled signal.

Abstract: The disclosed systems, structures, and methods are directed to encoding and decoding information for transmission across a communication channel. The method includes dividing the information between m parallel polar codes such that each of the m parallel polar codes includes a plurality of information bits, and splitting the information bits in each of the m parallel polar codes into a private part and a public part. The public part includes an information section and a repetition section, wherein the information bits of the public part are arranged in the information section. Bits in the information section of the public part of each of the m parallel polar codes are repeated in the repetition section of the public part of at least a second one of the m parallel polar codes.

Abstract: A receiver architecture is described for phase noise compensation in the presence of inter-channel interference (ICI) and inter-symbol interference (ISI), particularly for time-frequency packing (TFP) transmissions. The receiver includes a coarse phase noise (PN) estimator, a PN compensation module, an ICI cancellation module, an ISI compensation module, a FEC decoder, and an iterative PN estimator. The iterative PN estimator receives log likelihood ratio (LLR) information from the decoder and provides an iterative PN estimation to the PN compensation module. The decoder also provides LLR to the ISI compensation module, and to at least one other receiver for another subchannel that is immediately adjacent in frequency. The ICI cancellation module receives decoder output from at least one adjacent subchannel, which the ICI cancellation module uses to provide a ICI-cancelled signal.

Abstract: Methods and devices for power imbalance compensation and calibration of a coherent transmitter or transceiver are described. A pilot tone is combined with a digital data signal such that relative amplitudes of the pilot tone in each of four transmitted optical data channels may be detected by a pilot tone detector and used to calculate any power imbalances between I/Q phase channels and/or X/Y polarized channels of the transmitter. The pilot tone detector applies gain to the data signal of the transmitter to compensate for any calculated power imbalances. Because the pilot tone is combined with the digital data signal, its amplitude in each received channel is proportional to the data signal power of that channel.

Abstract: The disclosed systems and methods are directed to transmitting and receiving symbols. In particular, splitting, a symbol dataset into symbol subsets, modulating, the symbol subsets using different sub-carriers, roll off factors and time acceleration factors, performing frequency shifting and combining the frequency shifted and modulated symbol subsets to generate a digital multiband (DMB) signal, transmitting and receiving the DMB signal, down converting the received DMB signal into a plurality of baseband signals, segregating the plurality of baseband signals in accordance with a manner by which the symbol subsets have been processed before transmission, forwarding a first portion of the plurality of baseband signals to a minimum mean square error (MMSE) based receiver, forwarding a second portion of the plurality of baseband signals to a matched filter-based receiver, and combining the output of the MMSE based receiver and matched filter-based receiver to generate an equivalent symbol dataset.

Abstract: Methods and apparatuses for IQ time skew calibration in a coherent transceiver are described. A four-channel signal is received. A set of inputs is constructed for a 4×8 MIMO equalizer by converting the four-channel signal into four complex inputs that each have a phase shift corresponding to an estimated carrier frequency offset. The set of inputs further includes conjugate replicas of the four complex inputs. Using output from the 4×8 MIMO equalizer, equalizer coefficients are calculated by minimizing error between the MIMO output and a reference signal. Receiver and transmitter IQ skew are estimated using the equalizer coefficients, by converting the equalizer coefficients form the time domain to the frequency domain to determine receiver and transmitter IQ differential phase responses, which are indicative of respective receiver and transmitter IQ skew in the time domain. Skew compensation is then performed.