A compensation function mitigates a substantial portion of the chromatic dispersion imparted to a communications signal by an optical communications system. A digital input signal is digitally processed using the compensation function to generate a predistorted signal. An amplitude and a phase of an optical signal are modulated using a pair of orthogonal signal components to generate a predistorted optical signal for transmission. In one implementation, the pair of orthogonal signal components are components of the predistorted signal. In another implementation, the predistorted signal is processed using a non-linear compensator to generate a further distorted signal and the pair of orthogonal signal components are components of the further distorted signal. In that implementation, the non-linear compensator is configured to substantially compensate for nonlinearities in one or both of an optical modulator of a transmitter of the system and an optical-to-electrical converter of a receiver of the system.

An apparatus comprising a digital signal processor (DSP) unit configured to perform fiber dispersion pre-compensation on a digital signal sequence based on a dispersion value to produce a pre-compensated signal, wherein the dispersion value is associated with a remote optical receiver, a plurality of digital-to-analog converters (DACs) coupled to the DSP unit and configured to convert the pre-compensated signal into analog electrical signals, and a frontend coupled to the DACs and configured to convert the analog electrical signals into a first optical signal, adding a constant optical electric (E)-field to the first optical signal to produce a second optical signal, and transmit the second optical signal to the remote optical receiver.

A transmission device includes a first optical modulator configured to modulate, based on a packet signal for each of packets, input light into an optical packet signal and to output an optical packet signal for each of the packets; a generation circuit configured to generate an adjustment signal that adjusts slopes of a rise and a fall of a waveform of the optical packet signal; and a second optical modulator configured to modulate the optical packet signal from the first optical modulator and adjust, based on the adjustment signal, the slopes of the rise and the fall of the waveform of the optical packet signal.

A calibration apparatus trains a first machine learning-based model with a first training dataset to determine configuration parameters of an intermediate pre-distortion compensator in an optical communication system that includes a transmitter, a receiver, and an optical communication channel. The transmitter includes a pre-distortion compensator, the intermediate pre-distortion compensator, and an MZM compensator. The calibration apparatus trains a second machine learning-based model with a second training dataset to determine configuration parameters of the post-distortion compensator in the receiver. The calibration apparatus trains a third machine learning-based model with a third training dataset to determine configuration parameters of the pre-distortion compensator. When generating the second training data, the intermediate pre-distortion compensator is configured with the configuration parameters generated using the first machine learning-based model. When generating the third training data, the post-distortion compensator is configured with the configuration parameters generated using the second machine learning-based model.

In a multi-pulse light source, a dispersion compensation unit includes a spectroscopic element configured to spectrally separate a plurality of wavelength components, a separation optical element that guides a first optical pulse group including one or more wavelength components among a plurality of wavelength components, and a second optical pulse group including one or more wavelength components different from the one or more wavelength components included in the first optical pulse group among the plurality of wavelength components to optical paths different from each other, a first spatial light modulator on which the first optical pulse group is incident and which compensates dispersion for each wavelength component with respect to the first optical pulse group, and a second spatial light modulator on which the second optical pulse group is incident and which compensates dispersion for each wavelength component with respect to the second optical pulse group.

An apparatus comprising a digital signal processor (DSP) unit configured to perform fiber dispersion pre-compensation on a digital signal sequence based on a dispersion value to produce a pre-compensated signal, wherein the dispersion value is associated with a remote optical receiver, a plurality of digital-to-analog converters (DACs) coupled to the DSP unit and configured to convert the pre-compensated signal into analog electrical signals, and a frontend coupled to the DACs and configured to convert the analog electrical signals into a first optical signal, adding a constant optical electric (E)-field to the first optical signal to produce a second optical signal, and transmit the second optical signal to the remote optical receiver.

Chromatic dispersion is pre-compensated in a direct-detected orthogonal frequency-division multiplexed optical transmitter through digital signal processing methods, to generate signals that can be transmitted over an optical fiber. The dispersion pre-compensation digital signal processing may include multiplying subcarriers by a respective factor. The dispersion pre-compensation digital signal processing may instead include application of a finite impulse response filter to signals. The dispersion pre-compensation digital signal processing may instead include fast Fourier transformations of signals, application of a frequency domain filter to signals generated by the fast Fourier transformations, and inverse fast Fourier transformations of the signals produced by application of the frequency domain filter.

A system may include an optical transmitter and an optical receiver. The optical transmitter may generate optical signals associated with sub-carriers, and may provide the optical signals via an optical link. The optical receiver may receive the optical signals via the optical link, and may generate samples based on the optical signals. The samples may be associated with the sub-carriers. The optical receiver may combine the samples to form a time domain sample vector having a particular size, and may generate a frequency domain sample vector, having the particular size, based on the time domain sample vector. The optical receiver may demultiplex the frequency domain sample vector to generate domain sample vectors corresponding to the sub-carriers. The optical receiver may process the frequency domain sample vectors to generate equalized frequency domain sample vectors, and may output the equalized frequency domain sample vectors.

System and method embodiments are provided for improving reception of direct detection optical signals. In an embodiment, a method for optical transmission includes bit loading and power loading, with a digital signal processor (DSP), transmission bits of an orthogonal frequency-division multiplexing (OFDM) signal; calculating, with the DSP, a signal-signal beat interference (SSBI) component of the bit and power loaded OFDM signal by modulating each subcarrier with a symbol; and subtracting, with the DSP, the calculated SSBI component from the bit and power loaded OFDM signal.

Systems and methods for using a dispersion compensation circuit to directly modulate a laser. Techniques include calibrating a varactor bias point in a dispersion compensation circuit during manufacturing, but positioning the dispersion compensation circuit between a first attenuator and a second attenuator. Each attenuator, capable of reducing power of an input signal, may be adjustable so that the attenuation provided by each attenuator may be adjusted. The ratio of attenuation between attenuators may be adjusted based on either chirp of a laser or fiber length, and a varactor bias point may be adjusted by the other one of the chirp of the laser or fiber length. Thus, both chirp and fiber length may serve as a basis for adjusting attenuation between attenuators having a dispersion compensation circuit positioned between them.