An optical transport system configured to compensate nonlinear signal distortions using a backward-propagation algorithm in which some effects of polarization mode dispersion on the nonlinear signal distortions are accounted for by employing two or more different approximations of said effects within the bandwidth of the optical communication signal. In an example embodiment, the corresponding digital signal processor (DSP) is configured to switch between different approximations based on a comparison, with a fixed threshold value, of a difference between frequencies of various optical waves contributing to the nonlinear signal distortions, e.g., through four-wave-mixing processes. In different embodiments, the backward-propagation algorithm can be executed by the transmitter's DSP or the receiver's DSP.

An optical transport system configured to compensate nonlinear signal distortions using a backward-propagation algorithm in which some effects of polarization mode dispersion on the nonlinear signal distortions are accounted for by employing two or more different approximations of said effects within the bandwidth of the optical communication signal. In an example embodiment, the corresponding digital signal processor (DSP) is configured to switch between different approximations based on a comparison, with a fixed threshold value, of a difference between frequencies of various optical waves contributing to the nonlinear signal distortions, e.g., through four-wave-mixing processes. In different embodiments, the backward-propagation algorithm can be executed by the transmitter's DSP or the receiver's DSP.

A crosstalk estimation system includes: a light source unit that generates a polarization-multiplexed light, which is a polarized light having multiplexed polarizations, of each wavelength in a sideband of a modulated signal and emits the polarization-multiplexed light of each wavelength; a multiplexer that multiplexes the modulated signal with the polarization-multiplexed light for each core, which is associated with one of the wavelengths; a transmission line that transmits the modulated signal multiplexed with the polarization-multiplexed light of each wavelength through a different core; a separation unit that separates the polarization-multiplexed light from the modulated signal multiplexed with the polarization-multiplexed light for each core; a measurement unit that generates light intensity data on the polarization-multiplexed light of each wavelength; and an estimation unit that estimates a crosstalk between the cores based on a difference in light intensity between the polarization-multiplexed light of the wavelengths.

An optical transmitter includes an I-component optical modulation unit, a Q-component optical modulation unit, and a 2×2 optical coupler. The I-component optical modulation unit generates modulated light based on an I-component data signal. The Q-component optical modulation unit generates modulated light based on a Q-component data signal. The 2×2 optical coupler receives the modulated light generated by the I-component optical modulation unit from a first input port, receives the modulated light generated by the Q-component optical modulation unit from a second input port, generates two optical QAM signals having a phase conjugate relationship from the modulated light which has been input from the first input port and the modulated light which has been input from the second input port, outputs one of said two optical QAM signals from a first output port, and outputs the other one of said two optical QAM signals from a second output port.

The disclosure relates to a method, an optical receiver and an optical system for compensating, at an optical receiver, signal distortions induced in an optical carrier signal by a periodic copropagating optical signal, wherein the optical carrier signal and the copropagating signal copropagate at least in part of an optical system or network, by: receiving, at the optical receiver, the optical carrier signal, wherein the optical carrier signal is distorted by the copropagating signal; determining, at the optical receiver, a period of a periodic component of the distorted optical carrier signal; determining, at the optical receiver, a periodic distortion of the distorted optical carrier signal; and generating a compensation signal to correct the distorted optical carrier signal according to the determined periodic distortion.

The disclosure relates to a method, an optical receiver and an optical system for compensating, at an optical receiver, signal distortions induced in an optical carrier signal by a periodic copropagating optical signal, wherein the optical carrier signal and the copropagating signal copropagate at least in part of an optical system or network, by: receiving, at the optical receiver, the optical carrier signal, wherein the optical carrier signal is distorted by the copropagating signal; determining, at the optical receiver, a period of a periodic component of the distorted optical carrier signal; determining, at the optical receiver, a periodic distortion of the distorted optical carrier signal; and generating a compensation signal to correct the distorted optical carrier signal according to the determined periodic distortion.

An optical reception device includes a coefficient update section which optimizes a dispersion coefficient used in compensation of wavelength dispersion of a received signal obtained by receiving an optical signal according to a coherent detection method and a phase rotation amount used in compensation of a nonlinear optical effect of the received signal, and a transmission characteristic estimation section which estimates a transmission characteristic of a transmission line by using the optimized dispersion coefficient and the optimized phase rotation amount.

An optical reception device includes a coefficient update section which optimizes a dispersion coefficient used in compensation of wavelength dispersion of a received signal obtained by receiving an optical signal according to a coherent detection method and a phase rotation amount used in compensation of a nonlinear optical effect of the received signal, and a transmission characteristic estimation section which estimates a transmission characteristic of a transmission line by using the optimized dispersion coefficient and the optimized phase rotation amount.

A method for per-span optical fiber nonlinearity compensation comprises determining values of fiber parameters characterizing one or more target optical fibers in one or more respective spans of a link, and applying selected weight values to one or more photonic computing chips (PCCs), each PCC integrated in a different respective span of the link, wherein selection of the weight values is based on the values of the fiber parameters and a mapping associated with each PCC. The method further comprises transmitting an optical signal through the link, wherein each integrated PCC emulates an inverse of a nonlinear transfer function of the target optical fiber in the respective span, thereby reducing nonlinearity contributed by the one or more target optical fibers to the optical signal.

A method for per-span optical fiber nonlinearity compensation comprises determining values of fiber parameters characterizing one or more target optical fibers in one or more respective spans of a link, and applying selected weight values to one or more photonic computing chips (PCCs), each PCC integrated in a different respective span of the link, wherein selection of the weight values is based on the values of the fiber parameters and a mapping associated with each PCC. The method further comprises transmitting an optical signal through the link, wherein each integrated PCC emulates an inverse of a nonlinear transfer function of the target optical fiber in the respective span, thereby reducing nonlinearity contributed by the one or more target optical fibers to the optical signal.