A transmitter of a communications system includes a first encoder configured to apply a shaping operation to a data signal to generate a shaped data signal, a second encoder configured to encode the shaped data signal according to a forward error correction (FEC) scheme to generate an encoded signal, and a constellation mapper configured to modulate the encoded signal to symbol values according to a modulation scheme to generate a corresponding symbol stream for transmission through the communications system. The shaping operation reduces average constellation energy for constellations of the modulation scheme.

In some embodiments, an apparatus includes an optical transmitter module that can be electrically coupled to an electrical serializer/deserializer and a controller. The optical transmitter module can include an electrical detector that can receive an in-band signal. The electrical detector can send to the controller a first power error signal and a second power error signal based on the in-band signal. The controller can send a correction control signal to the electrical serializer/deserializer based on the first power error signal and the second power error signal such that the electrical serializer/deserializer sends a pre-emphasized signal to the optical transmitter module based on the correction control signal. In such embodiments, the first power error signal, the second power signal and the correction control signal are out-of-band signals.

The disclosure relates to a multi-modulation-format compatible high-speed laser signal generation system and method. The disclosure can greatly improve modulation format compatibility of a laser communication system and saves system upgrading costs and resource costs. The system mainly includes a control instruction unit, a serial-parallel changeover switch unit, a precoding switch unit, a power control unit, an IQ modulator, a narrow line width laser, and a bias point control unit, wherein the control instruction unit is respectively connected to the serial-parallel changeover switch unit, the precoding switch unit, the power control unit, and the bias point control unit; the serial-parallel changeover switch unit, the precoding switch unit, the power control unit, and the IQ modulator are electrically connected in sequence; the narrow line width laser is connected to an optical input end of the IQ modulator; and the bias point control unit is connected to the IQ modulator.

Methods and systems for a distributed optical transmitter with local domain splitting are disclosed and may include, in an optical modulator integrated in a silicon photonics chip: receiving electrical signals, communicating the electrical signals to domain splitters along a length of waveguides of the optical modulator via one or more delay lines, and generating electrical signals in voltage domains utilizing the domain splitters for modulating the optical signals in the waveguides of the optical modulator by driving diodes with the electrical signals generated in the voltage domains. The delay lines may comprise one delay element per domain splitter, or may comprise a delay element per domain splitter for a first subset of the domain splitters and more than one delay element per domain splitter for a second subset of the domain splitters.

Provided are a laser diode driver for a multilevel optical signal and a multilevel optical signal transmission device including the same, wherein the laser diode driver includes: a clock generator configured to generate and output a clock signal; a first latch configured to delay output of data corresponding to a first timing of the clock signal from among data sequentially input at each data input period; a second latch configured to delay output of data corresponding to a second timing of the clock signal from among data sequentially input at each data input period; a first synchronization processor configured to output a signal corresponding to the data input by the first latch according to the clock signal; and a second synchronization processor configured to output a signal corresponding to the data input by the second latch according to the clock signal.

Methods and systems for a distributed optical transmitter with local domain splitting are disclosed and may include, in an optical modulator integrated in a silicon photonics chip: receiving electrical signals, communicating the electrical signals to domain splitters along a length of waveguides of the optical modulator via one or more delay lines, and generating electrical signals in voltage domains utilizing the domain splitters for modulating the optical signals in the waveguides of the optical modulator by driving diodes with the electrical signals generated in the voltage domains. The delay lines may comprise one delay element per domain splitter, or may comprise a delay element per domain splitter for a first subset of the domain splitters and more than one delay element per domain splitter for a second subset of the domain splitters.

Methods and systems for a distributed optical transmitter with local domain splitting is disclosed and may include, in an optical modulator integrated in a silicon photonics chip: receiving electrical signals, communicating the electrical signals to domain splitters along a length of waveguides of the optical modulator utilizing one or more delay lines, and generating electrical signals in voltage domains utilizing the domain splitters for modulating the optical signals in the waveguides of the optical modulator by driving diodes with the electrical signals generated in the voltage domains. The delay lines may comprise one delay element per domain splitter, or may comprise a delay element per domain splitter for a first subset of the domain splitters and more than one delay element per domain splitter for a second subset of the domain splitters.

A transmitter of a communications system includes a first encoder configured to apply a shaping operation to a data signal to generate a shaped data signal, a second encoder configured to encode the shaped data signal according to a forward error correction (FEC) scheme to generate an encoded signal, and a constellation mapper configured to modulate the encoded signal to symbol values according to a modulation scheme to generate a corresponding symbol stream for transmission through the communications system. The shaping operation reduces average constellation energy for constellations of the modulation scheme.

A system and method for a high-speed transmitter comprising a precoder configured to receive a sequence of input symbols and to generate for each received symbol a respective recoded symbol is disclosed. The transmitter includes a recoding unit configured for recoding each current received PAM-M based on the recoded symbol immediately preceding the current recoded symbol at the recoding unit, a shift unit configured for determining a shift value for each current received symbol from the recoding unit based on the symbol received from the recoding unit and immediately preceding the current symbol at the shift unit; and Feed-Forward Equalizer unit for applying the shift values to the respective symbols received from the recoding unit to generate a corresponding sequence of output symbols to be transmitted in an output stream.

A signal processing method is provided. Under the method, a first digital signal can be obtained by an optical transmitter. The first digital signal is a one-dimensional bipolar digital signal. A spectral compression and filtering can be performed by the optical transmitter on the first digital signal to generate a second digital signal. A frequency shift can be performed by the optical transmitter on the second digital signal such that a center location of a spectrum of the frequency-shifted second digital signal is at a frequency of 0.