Abstract: The invention relates to a modulation scheme for optical communication, in particular for fiber optics communication. According to invention, an optical signal is generated, both phase and polarization of which modulated in dependency of the data to be transmitted. Preferably, the generated optical signal comprises a sequence of symbols (22a-22k) and each symbol (22a-22k) has one of two different phase states and one of two different orthogonal polarization states. Bits of the data stream to be transmitted are encoded both in the phase state of a symbol (or in the phase state difference between subsequent symbols) and in the polarization state of the symbol (or in the polarization state difference between the subsequent symbols).

Abstract: The present document relates to a method and apparatus in optical transmission systems for the estimation of the carrier phase and the degree of non-linear distortions incurred in an optical transmission channel. A plurality of signal samples are provided at succeeding time instances such that the plurality of signal samples: is associated with a modulation scheme and a carrier phase; has been transmitted over the optical transmission channel; comprises a plurality of signal phases, respectively; comprises a plurality of data phases and a plurality of residual phases, respectively; and the plurality of residual phases is associated with the carrier phase. The method comprises further canceling the plurality of data phases from the plurality of signal phases by taking into account the modulation scheme; thereby yielding the plurality of residual phases; and determining a set of autocorrelation values of the plurality of residual phases for a set of lag values, respectively.

Abstract: A modulator with polarization marking comprising two input ports for receiving two optical signals at one wavelength, and exhibiting essentially perpendicular optical polarization states, capable of phase-modulating those signals with data signals and of combining them with polarization, characterized in that it comprises a source of phase overmodulation for overmodulating the phase of one of said two optical signals, said phase overmodulation exhibiting a modulation frequency substantially lower than the modulation frequency of said data signals. A method and a coherent receiver are also disclosed.

Abstract: A data transmitter (A, B, C, D) wherein, in a first operating mode, the first and second carrier signals are mutually phase-shifted, and the data module generates said first and second data signals based on different data, so as to produce, at the transmitter's output, a modulated signal exhibiting a first constellation of states (A, B, C, D) in a complex plane, and, in a second operating mode of the transmitter, the data module generates said first and second data signals correlated with one another based on common data, so as to produce, at the transmitter's output, a modulated signal exhibiting a second constellation of states (A, D; E, F) in the complex plane that is more reduced and more dispersed then said first constellation of states.

Abstract: The invention relates to a self-referenced device (1) for measuring the spectral phase of a periodic signal having a frequency fp, the periodic signal being carried by an optical signal, comprising: a phase shifting means (4); a transmission means (3) for transmitting at least three optical modes of said periodic signal to the phase shifting means, said optical modes defining beats at the fp frequency; the phase shifting means (4) being capable of modifying the phase difference between the beats at the fp frequency; characterised in that the measuring means (6, 7, 8) include: photoelectric conversion means (6) for detecting the variable term at the fp frequency of the optical signal received power in order to generate an electric signal (14) corresponding to the superimposition of the optical beats at the fp frequency; electric measuring means (7, 8) for measuring the amplitude of the electric signal in order to determine the amplitude of the beats at the fp frequency.

Abstract: The invention relates to a modulation scheme for optical communication, in particular for fiber optics communication. According to invention, an optical signal is generated, both phase and polarization of which modulated in dependency of the data to be transmitted. Preferably, the generated optical signal comprises a sequence of symbols (22a-22k) and each symbol (22a-22k) has one of two different phase states and one of two different orthogonal polarization states.