Abstract: A communication system is configured to generate a perturbed signal by perturbing an amplitude of a spectrum of an original signal in one or more spectral regions, and to propagate the perturbed signal through components of the communication system. The communication system is further configured to obtain a measurement of the perturbed signal in a first spectral region of the one or more spectral regions following the propagation of the perturbed signal, and to calculate an estimate of an impairment associated with the communication system based on the measurement.

Abstract: A transmitter maps an N-bit sequence to a point selected from a four-dimensional (4D) constellation consisting of 2N points which form a subset of a Cartesian product of first and second two-dimensional (2D) constellations, the first constellation consisting of M1 points divided into first, second, and third points, and the second constellation consisting of M2 points divided into fourth, fifth, and sixth points, wherein M1, M2?5, and wherein log2(M1×M2)>N. The subset includes any 4D point that is generated by combining any one of the M1 points and any one of the fourth points; includes any 4D point that is generated by combining any one of the first points and any one of M2 points; and excludes any 4D point that is generated by combining any third point and any sixth point. An optical signal representing the selected point is transmitted to a receiver.

Abstract: A transmitter maps an N-bit sequence to a point selected from a four-dimensional (4D) constellation consisting of 2N points which form a subset of a Cartesian product of first and second two-dimensional (2D) constellations, the first constellation consisting of M1 points divided into first, second, and third points, and the second constellation consisting of M2 points divided into fourth, fifth, and sixth points, wherein M1, M2?5, and wherein log2(M1×M2)>N. The subset includes any 4D point that is generated by combining any one of the M1 points and any one of the fourth points; includes any 4D point that is generated by combining any one of the first points and any one of M2 points; and excludes any 4D point that is generated by combining any third point and any sixth point. An optical signal representing the selected point is transmitted to a receiver.

Abstract: A communication system is configured to generate a perturbed signal by perturbing an amplitude of a spectrum of an original signal in one or more spectral regions, and to propagate the perturbed signal through components of the communication system. The communication system is further configured to obtain a measurement of the perturbed signal in a first spectral region of the one or more spectral regions following the propagation of the perturbed signal, and to calculate an estimate of an impairment associated with the communication system based on the measurement.

Abstract: 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.

Abstract: 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.

Abstract: A transmitter (102,200) applies a dimensional transformation to preliminary digital drive signals representing symbols, thereby generating transformed digital drive signals (704) designed to represent each symbol using a plurality of first dimensions of an optical carrier (242), the first dimensions distributed over two or more timeslots. The preliminary digital drive signals are designed to represent each symbol using a plurality of second dimensions of the carrier, which differ from the first dimensions. Using the transformed signals, the transmitter generates (706) an optical signal (260). A receiver (102,300) receives (802) an optical signal (360) and determines received digital signals (804) corresponding to the first dimensions. The receiver applies an inverse dimensional transformation to the received digital signals to generate preliminary digital drive signal estimates (806) corresponding to the second dimensions, thereby permitting estimation of the symbols (808).

Abstract: An optical transmitter device includes a digital signal processor (DSP) having digital hardware. The DSP is operative to generate shaped bits from a first set of information bits, and to apply a systematic forward error correction (FEC) scheme to encode the shaped bits and a second set of information bits, where the first set of information bits and the second set of information bits are disjoint sets. Unshaped bits and the shaped bits are mapped to selected symbols or are used to select symbols from one or more constellations. The selected symbols are mapped to physical dimensions. Each unshaped bit is either one of the second set of information bits or one of multiple parity bits resulting from the FEC encoding. In this manner, a target spectral efficiency is achieved.

Abstract: An optical transmitter (102,200) is operable to generate an optical signal (260) 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 (102,300) is operable to apply an inverse pFDM transformation to recover estimates of the multi-bit symbols.

Abstract: Systems and method include a detector communicatively coupled to a fiber span; and processing circuitry connected to the detector and configured to digitally sample and process an output of the detector, detect phase changes in the output, and identify an electrostrictive response of the fiber span based on the detected phase changes and based on a dependence of the detected phase changes with frequency. A property of the fiber span can be determined on the electrostrictive response. The property of the optical fiber can include one or more of optical fiber material type, optical fiber material property, optical fiber area, optical fiber geometry, optical fiber condition, optical fiber stress and strain, optical fiber temperature. and optical fiber radiation exposure.

Abstract: An optical transmitter (102,200) is operable to generate an optical signal (260) 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 (102,300) is operable to apply an inverse pFDM transformation to recover estimates of the multi-bit symbols.

Abstract: A transmitter (102,200) applies a dimensional transformation to preliminary digital drive signals representing symbols, thereby generating transformed digital drive signals (704) designed to represent each symbol using a plurality of first dimensions of an optical carrier (242), the first dimensions distributed over two or more timeslots. The preliminary digital drive signals are designed to represent each symbol using a plurality of second dimensions of the carrier, which differ from the first dimensions. Using the transformed signals, the transmitter generates (706) an optical signal (260). A receiver (102,300) receives (802) an optical signal (360) and determines received digital signals (804) corresponding to the first dimensions. The receiver applies an inverse dimensional transformation to the received digital signals to generate preliminary digital drive signal estimates (806) corresponding to the second dimensions, thereby permitting estimation of the symbols (808).

Abstract: An optical transmitter device includes a digital signal processor (DSP) having digital hardware. The DSP is operative to generate shaped bits from a first set of information bits, and to apply a systematic forward error correction (FEC) scheme to encode the shaped bits and a second set of information bits, where the first set of information bits and the second set of information bits are disjoint sets. Unshaped bits and the shaped bits are mapped to selected symbols or are used to select symbols from one or more constellations. The selected symbols are mapped to physical dimensions. Each unshaped bit is either one of the second set of information bits or one of multiple parity bits resulting from the FEC encoding. In this manner, a target spectral efficiency is achieved.

Abstract: An optical transmitter is operative to generate, from a plurality of encoded client bits, a set of symbols exhibiting non-uniform visitation probabilities in at least one dimension, to encode the set of symbols across a plurality of frequency division multiplexing (FDM) subcarriers, and to transmit an optical signal comprising the plurality of FDM subcarriers across which the set of symbols is encoded. An optical receiver is operative to decode a set of symbol estimates from a plurality of FDM subcarriers, the symbol estimates comprising estimates of symbols exhibiting non-uniform visitation probabilities in at least one dimension, and to recover client bits from the set of symbol estimates.

Abstract: Systems and methods for estimating a transmit symbol sequence implemented in a coherent receiver include receiving a nominally error-free information bit sequence subsequent to Forward Error Correction (FEC) decoding; determining a nominally error-free estimate of the transmitted bit sequence based on the nominally error-free information bit sequence; and determining a nominally error-free estimate of the transmit symbol sequence by mapping the transmit bit sequence to transmit symbols. The system and methods can further include comparing a transmit optical field based on the transmit symbols to a received optical field for one or more measurements.

Abstract: Systems and method include a detector communicatively coupled to a fiber span; and processing circuitry connected to the detector and configured to digitally sample and process an output of the detector, detect phase changes in the output, and identify an electrostrictive response of the fiber span based on the detected phase changes and based on a dependence of the detected phase changes with frequency. A property of the fiber span can be determined on the electrostrictive response. The property of the optical fiber can include one or more of optical fiber material type, optical fiber material property, optical fiber area, optical fiber geometry, optical fiber condition, optical fiber stress and strain, optical fiber temperature. and optical fiber radiation exposure.

Abstract: Methods and assemblies for determining a property or environment of an optical fiber, including: measuring a frequency dependent electrostrictive response of an optical fiber; and based on the measured frequency dependent electrostrictive response, determining a property of the optical fiber. The property or environment of the optical fiber includes one or more of optical fiber type, optical fiber material type, optical fiber material property, optical fiber area, optical fiber geometry, optical fiber condition, optical fiber stress and strain, optical fiber environment, optical fiber temperature, optical fiber routing, optical fiber spooling, and optical fiber radiation exposure.

Abstract: Multiple receivers are comprised in a flexible coherent transceiver of a multi-span optical fiber network. Each of the multiple receivers is operative to handle communications on a respective channel. The multiple receivers measure optical characteristics. For each of the multiple receivers, the optical characteristics include optical nonlinear interactions on the respective channel, the optical nonlinear interactions being at least partially dependent from one span to another span. An optical power of a signal on each of the multiple channels is adjusted as a function of the optical characteristics.

Abstract: 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.

Abstract: 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.