Abstract: An apparatus comprises an optical data receiver to receive first and second data-modulated optical carriers in different wavelength bands via a free space optical link and to generate an output digital data stream from demodulated segments of the first and second data-modulated optical carriers. The optical data receiver is configured to make selections between temporally corresponding portions of the first and second data-modulated optical carriers for generating successive portions of the output digital data stream. The optical data receiver is configured to make one of the selections between two of the temporally corresponding portions of the first and second data-modulated optical carriers based on at least one value of a quality indicator obtained for at least one of two temporally corresponding portions.

Abstract: A method and device for optical data transmission are disclosed. Data bits are transmitted in the form of data symbols, by modulating an optical signal in dependence on the data bits and in accordance with two or more constellation schemes. The data bits are transmitted, by generating first data symbols, which represent respective sets of data bits containing an even number of data bits. The first data symbols are generated, by modulating the optical signal in accordance with a first constellation scheme. Furthermore, the data bits are transmitted, by generating second data symbols, which represent respective sets of data bits having an odd number of data bits. The second data symbols are generated, by modulating the optical signal in accordance with a second constellation scheme. The first and the second data symbols are generated at a predefined symbol rate, such that the first and the second data symbols are interleaved in time.

Abstract: An amplification device includes an element for splitting an input optical signal into first and second optical signals having first and second polarization modes, first and second amplification stages each including polarized SOAs for amplifying the first and second optical signals depending on driving currents, an intermediate processing stage for compensating optical characteristics of the optical gain bandwidth of the first amplification stage depending on driving currents, an element for combining the first and second optical signals outputted by the second amplification stage to produce an output optical signal, and a control means producing the driving currents depending on information representative of powers of the first and second optical signals before the polarized SOAs of each amplification stage and on a targeted power of the output optical signal.

Abstract: An amplification device includes an element for splitting an input optical signal into first and second optical signals having first and second polarization modes, first and second amplification stages each including polarized SOAs for amplifying the first and second optical signals depending on driving currents, an intermediate processing stage for compensating optical characteristics of the optical gain bandwidth of the first amplification stage depending on driving currents, an element for combining the first and second optical signals outputted by the second amplification stage to produce an output optical signal, and a control means producing the driving currents depending on information representative of powers of the first and second optical signals before the polarized SOAs of each amplification stage and on a targeted power of the output optical signal.

Abstract: Proposed is a method of equalizing an optical signal that has an overall bandwidth formed on a number of adjacent spectral slots, wherein the signal comprises a set of non-overlapping subcarrier signals. A distribution of the subcarrier signals onto the slots is such, that at least one slot is occupied by more than one subcarrier signal. The signal is received and amplified. Respective power levels are measured for the subcarrier signals. Distribution data is provided, which indicates the distribution of the subcarrier signals onto the spectral slots. Power level data is provided, which indicates for the spectral slots respective desired power levels. For the spectral slots respective attenuation values are derived, using the measured power levels, the distribution data and the power level data. Finally, the optical transmission signal is attenuated within the spectral slots individually, using the derived attenuation values.

Abstract: Proposed is a method of equalizing an optical signal that has an overall bandwidth formed on a number of adjacent spectral slots, wherein the signal comprises a set of non-overlapping subcarrier signals. A distribution of the subcarrier signals onto the slots is such, that at least one slot is occupied by more than one subcarrier signal. The signal is received and amplified. Respective power levels are measured for the subcarrier signals. Distribution data is provided, which indicates the distribution of the subcarrier signals onto the spectral slots. Power level data is provided, which indicates for the spectral slots respective desired power levels. For the spectral slots respective attenuation values are derived, using the measured power levels, the distribution data and the power level data. Finally, the optical transmission signal is attenuated within the spectral slots individually, using the derived attenuation values.

Abstract: An optical transmitter for transmitting a multilevel amplitude-shift-keying modulated signal includes an optical modulator for modulating an optical signal with a multilevel amplitude-shift-keying modulation, and a spectral filter adapted to increase a high-frequency component of the modulated optical signal relatively to a central frequency component. The multilevel ASK modulation is quaternary ASK and the symbol rate of the optical modulator is above 40 Gbaud. An optical link connects the optical transmitter to a quadratic direct detection optical receiver.

Abstract: Proposed is a method of optical data transmission. The method comprises different steps. At least one stream of data bits is received. Sets of data bits are mapped onto successive logical states. The logical states correspond to respective sets of two initial QPSK symbols chosen according to a QPSK mapping and according to a set partitioning rule. The logical states are differentially encoded according to a differential encoding rule. For the differentially encoded logical states respective sets of two resulting QPSK symbols are derived according to the QPSK mapping and according to the set partitioning rule. The encoded sets of two QPSK symbols are transmitted using polarization division multiplexing. The differential encoding rule results in a differential encoding of one of the initial QPSK symbols but not the other of the initial QPSK symbols.

Abstract: An exemplary method and apparatus are provided for high efficiency wavelength division multiplexing (WDM) optical communication systems. An optical transmitter adapted to transmit an optical signal on an optical WDM transmission channel to a corresponding optical receiver is described. The optical transmitter comprises a symbol generation unit adapted to convert input data into a sequence of data symbols at a symbol rate B; with B being a real number greater zero; an amplitude modulation unit adapted to modulate an amplitude of every Nth data symbol in a sequence derived from the sequence of data symbols, thereby creating a modulated sequence of data symbols; wherein N is an integer; wherein N>2; and a digital-to-optical converter adapted to convert a sequence derived from the modulated sequence of data symbols into an optical signal to be transmitted to the optical receiver.

Abstract: The present document relates to optical communication systems. In particular, the present document relates to high efficiency wavelength division multiplexing (WDM) optical communication systems. An optical transmitter (210) adapted to transmit an optical signal on an optical wavelength division multiplexed, referred to as WDM, transmission channel (111) to a corresponding optical receiver (230) is described.

Abstract: Proposed is a method of optical data transmission. The method comprises different steps. At least one stream of data bits is received. Sets of data bits are mapped onto successive logical states. The logical states correspond to respective sets of two initial QPSK symbols chosen according to a QPSK mapping and according to a set partitioning rule. The logical states are differentially encoded according to a differential encoding rule. For the differentially encoded logical states respective sets of two resulting QPSK symbols are derived according to the QPSK mapping and according to the set partitioning rule. The encoded sets of two QPSK symbols are transmitted using polarization division multiplexing. The differential encoding rule results in a differential encoding of one of the initial QPSK symbols but not the other of the initial QPSK symbols.

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 method and device for optical data transmission are disclosed. Data bits are transmitted in the form of data symbols, by modulating an optical signal in dependence on the data bits and in accordance with two or more constellation schemes. The data bits are transmitted, by generating first data symbols, which represent respective sets of data bits containing an even number of data bits. The first data symbols are generated, by modulating the optical signal in accordance with a first constellation scheme. Furthermore, the data bits are transmitted, by generating second data symbols, which represent respective sets of data bits having an odd number of data bits. The second data symbols are generated, by modulating the optical signal in accordance with a second constellation scheme. The first and the second data symbols are generated at a predefined symbol rate, such that the first and the second data symbols are interleaved in time.

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: To that end, it is an object of the invention to provide a method for converting a high-speed digital signal in the form of optical pulses intended to be transmitted within optical guides, within which the signal is converted into a series of optical pulses in three possible phase states (?/6, 5?/6, ??/2) separated from one another two-by-two by an angle greater than ?/2.

Abstract: An optical transmitter for transmitting a multilevel amplitude-shift-keying modulated signal includes an optical modulator for modulating an optical signal with a multilevel amplitude-shift-keying modulation, and a spectral filter adapted to increase a high-frequency component of the modulated optical signal relatively to a central frequency component. The multilevel ASK modulation is quaternary ASK and the symbol rate of the optical modulator is above 40 Gbaud. An optical link connects the optical transmitter to a quadratic direct detection optical receiver.

Abstract: An exemplary method and apparatus are provided for high efficiency wavelength division multiplexing (WDM) optical communication systems. An optical transmitter adapted to transmit an optical signal on an optical WDM transmission channel to a corresponding optical receiver is described. The optical transmitter comprises a symbol generation unit adapted to convert input data into a sequence of data symbols at a symbol rate B; with B being a real number greater zero; an amplitude modulation unit adapted to modulate an amplitude of every Nth data symbol in a sequence derived from the sequence of data symbols, thereby creating a modulated sequence of data symbols; wherein N is an integer; wherein N>2; and a digital-to-optical converter adapted to convert a sequence derived from the modulated sequence of data symbols into an optical signal to be transmitted to the optical receiver.

Abstract: The present document relates to optical communication systems. In particular, the present document relates to high efficiency wavelength division multiplexing (WDM) optical communication systems. An optical transmitter (210) adapted to transmit an optical signal on an optical wavelength division multiplexed, referred to as WDM, transmission channel (111) to a corresponding optical receiver (230) is described.

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: To that end, it is an object of the invention to provide a method for converting a high-speed digital signal in the form of optical pulses intended to be transmitted within optical guides, within which the signal is converted into a series of optical pulses in three possible phase states (?/6, 5?/6, ??/2) separated from one another two-by-two by an angle greater than ?/2.