An optical modulation apparatus comprises first, second, and third optical modulators arranged so as to collectively modulate light coupled into a first optical input in all three dimensions of the three-dimensional Stokes vector space, to produce an optical output signal. The optical modulation apparatus further comprises a modulating circuit having a digital input configured to N generate first, second, and third modulating signals for driving the first, second, and third optical modulators so as to map digital data to an M-point optical constellation in the optical output signal. The points in the M-point optical constellation are distributed in the three-dimensional Stokes vector space such that the constellation figure of merit for the M-point optical constellation equals at least half of the maximum achievable constellation figure of merit for M points in the three-dimensional Stokes vector space.

Techniques for transmitting a data signal through an optical communications system. An encoder is configured to encode the data signal to generate symbols to be modulated onto an optical carrier. Each symbol encodes multiple bits of data and includes a first portion selected from a first constellation and a second portion selected from a second constellation. The first and second constellations have respective different average amplitudes. Each of the first and second constellations have a cardinality of at least two and the cardinality of the first constellation is greater than the cardinality of the second constellation. A modulator is configured to modulate a first frame of the optical signal using the first portion and modulate a second frame of the optical signal using the second portion. A selection of one frame of the optical signal to be used as the first frame encodes at least 1 bit of data.

Techniques for transmitting a data signal through an optical communications system. An encoder is configured to encode the data signal to generate symbols to be modulated onto an optical carrier. Each symbol encodes multiple bits of data and includes a first portion selected from a first constellation and a second portion selected from a second constellation. The first and second constellations have respective different average amplitudes. Each of the first and second constellations have a cardinality of at least two and the cardinality of the first constellation is greater than the cardinality of the second constellation. A modulator is configured to modulate a first frame of the optical signal using the first portion and modulate a second frame of the optical signal using the second portion. A selection of one frame of the optical signal to be used as the first frame encodes at least 1 bit of data.

A first optical network device groups a plurality of FlexO instance frames into one group, where each of the plurality of FlexO instance frames carries one OTU signal; then, performs multiplexing on the plurality of FlexO instance frames grouped into one group, to generate one first FlexO frame; next, performing scrambling and FEC processing on the first FlexO frame to generate one second FlexO frame and send it to a second optical network device. If a rate of the FlexO instance frame is 100 Gbps and two FlexO instance frames are grouped into one group, the 200 G optical module can be used in the transmission method.

A first optical network device groups a plurality of FlexO instance frames into one group, where each of the plurality of FlexO instance frames carries one OTU signal; then, performs multiplexing on the plurality of FlexO instance frames grouped into one group, to generate one first FlexO frame; next, performing scrambling and FEC processing on the first FlexO frame to generate one second FlexO frame and send it to a second optical network device. If a rate of the FlexO instance frame is 100 Gbps and two FlexO instance frames are grouped into one group, the 200 G optical module can be used in the transmission method.

The present invention relates to a method for processing a digital signal through a linear device. The digital signal makes a transition from a first level to a second level. The method comprises pre-emphasizing the digital signal before/after processing it by the linear device. Pre-emphasizing the digital signal includes: pre-emphasizing the digital signal by applying an undershoot to the first level before the transition, when the first level is lower than the second level; and/or pre-emphasizing the digital signal by applying an overshoot to the first level before the transition, when the first level is higher than the second level. The present invention also relates to an apparatus using the above method.

A system monitors optical performance of an optical link within an optical network. The system includes an optical transmitter having an expanded-spectrum pilot-tone modulator for modulating an expanded-spectrum pilot tone onto a high-speed data signal to generate an expanded-spectrum optical signal and an optical receiver for receiving the expanded-spectrum optical signal and for detecting and decoding the expanded-spectrum pilot tone to enable monitoring of the optical performance of the optical link.

A transmitter includes: a substrate; a signal source disposed on the substrate; an electrical-to-optical (E/O) converter disposed on the substrate and that converts an electrical signal outputted from the signal source into an optical signal; an optical cable that carries the optical signal; and an optical connector disposed at an end of the optical cable. The electrical signal is inputted into the E/O converter.

A transmitter includes: a substrate; a signal source disposed on the substrate; an electrical-to-optical (E/O) converter disposed on the substrate and that converts an electrical signal outputted from the signal source into an optical signal; an optical cable that carries the optical signal; and an optical connector disposed at an end of the optical cable. The electrical signal is inputted into the E/O converter.

We disclose an optical transport system configured to reduce nonlinear signal distortions using an electronic phase rotation, the phase value of which is determined using pre-filtering, e.g., via a low-pass filter, of the digital samples representing an optical communication signal prior to applying a squaring operation to the digital samples. In some embodiments, the phase value used in the electronic phase rotation can be determined using double filtering of the digital samples that, in addition to the pre-filtering, employs post-filtering, e.g., via another low-pass filter, of the digital samples generated by the squaring operation. The electronic phase rotation can be implemented as part of a backward-propagation algorithm that, in addition to reducing the nonlinear signal distortions, provides at least partial dispersion compensation. In various embodiments, the corresponding backward-propagation module can be incorporated into the transmitter's digital signal processor (DSP) or the receiver's DSP.