Embodiments of the present invention provide data transmission and receiving methods based on an orthogonal frequency division multiplexing technology, and an apparatus. According to the present invention, grouping and differential encoding are performed on multiple subcarriers, and further, carrier location adjustment is performed, so as to effectively improve non-linear tolerance of a multi-subcarrier system.

A host device uses an intermediate frequency determined based on frequencies of a second-order nonlinear intermodulation distortion component and a harmonic component which are generated in an analog optical link connected to the host device, for example, an analog optical link of a distributed antenna system (DAS), and precompensates for the second-order nonlinear intermodulation distortion component and the harmonic component generated in the analog optical link.

An optical transmitter apparatus is disclosed. The apparatus includes a processor, a memory coupled to the processor, and one or more programs configured to be executed by the processor. The programs include instructions for nonlinearity estimation that characterizes nonlinearity in an optical communication and estimates an amount of symbol distortion caused by the nonlinearity, instructions for selecting and mapping symbols to provide, for the nonlinearity estimation, only symbols that meet predetermined nonlinearity criteria, and instructions for storing, in the memory, the amount of symbol distortion to be used for a nonlinearity pre-compensation.

An optical phase-shifting component is used for shifting the phase and modifying the intensity of the light beam injected into the fiber (MMF2). The component is inserted upstream or downstream of, or at an intermediate position in, the fiber. The component uses two mirrors and multiple beam paths between the mirrors. An optical phase-shifting structure (e.g., a reflective phase mask with a structured surface, which can be a mirror is effective at each reflection of the beam and gradually splits the beam into faster and slower propagation modes. The faster modes are subjected to one or more reflections more than the slower modes and are thereby decelerated. The fast and slow modes are combined again and are then transmitted in a multimode fiber in which the modes have different propagation speeds. The difference in the propagation speeds is thus at least partly compensated.

An optical phase-shifting component is used for shifting the phase and modifying the intensity of the light beam injected into the fiber (MMF2). The component is inserted upstream or downstream of, or at an intermediate position in, the fiber. The component uses two mirrors and multiple beam paths between the mirrors. An optical phase-shifting structure (e.g., a reflective phase mask with a structured surface, which can be a mirror is effective at each reflection of the beam and gradually splits the beam into faster and slower propagation modes. The faster modes are subjected to one or more reflections more than the slower modes and are thereby decelerated. The fast and slow modes are combined again and are then transmitted in a multimode fiber in which the modes have different propagation speeds. The difference in the propagation speeds is thus at least partly compensated.

An optical communication system includes a first terminal device configured to receive first data, wherein the first terminal device is configured to generate an optical waveform based on the received first data. The optical system further includes an optical communication path configured to receive the optical waveform from the first terminal device. The optical system further includes a second terminal device configured to receive the optical waveform from the optical communication path, wherein the second terminal device is configured to output second data based on the optical waveform. At least one of the first terminal device or the second terminal device includes a nonlinear waveform distortion compensation device. The nonlinear waveform compensation device is configured to correct nonlinear waveform distortion resulting from the optical waveform propagating along the optical communication path, and the nonlinear waveform compensation device includes at least one recursive intermediate layer.

A system for transmission of an optical signal, the system including an optical coupler for splitting said signal into a first copy and a second copy. The optical coupler has an input for receiving the optical signal, a first output for the first copy and a second output for the second copy. The system also includes a first optical guide connected to the first output, a second optical guide connected to the second output and a superposition module for coherently superimposing the first copy and the second copy of the signal.

A system for transmission of an optical signal, the system including an optical coupler for splitting said signal into a first copy and a second copy. The optical coupler has an input for receiving the optical signal, a first output for the first copy and a second output for the second copy. The system also includes a first optical guide connected to the first output, a second optical guide connected to the second output and a superposition module for coherently superimposing the first copy and the second copy of the signal.

An optical transmission device includes: a memory; and a processor coupled to the memory; the processor: generate a first symbol by mapping a transmission data series to a first signal point which belongs to a first group within a signal space defined with regard to characteristics of an optical carrier wave of the transmission data series; generate a second symbol by mapping the transmission data series to a second signal point belonging to a second group; calculate a perturbation quantity of a signal electric field for each of the first and second symbols based on signal electric field vector information of a symbol which is generated before the first symbol and the second symbol; and determine, as a transmission signal, a symbol having a smaller perturbation quantity between the first symbol and the second symbol.

An optical transmission device includes: a memory; and a processor coupled to the memory; the processor: generate a first symbol by mapping a transmission data series to a first signal point which belongs to a first group within a signal space defined with regard to characteristics of an optical carrier wave of the transmission data series; generate a second symbol by mapping the transmission data series to a second signal point belonging to a second group; calculate a perturbation quantity of a signal electric field for each of the first and second symbols based on signal electric field vector information of a symbol which is generated before the first symbol and the second symbol; and determine, as a transmission signal, a symbol having a smaller perturbation quantity between the first symbol and the second symbol.