Alcatel Lucent

Oriol Bertran-Pardo

Jeremie Renaudier

Francesco Vacondio

Gabriel Charlet

Massimiliano Salsi

Christian Dorize

Jérémie Renaudier

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.

Method of optical data transmission using polarization division multiplexing and QPSK

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 () adapted to transmit an optical signal on an optical wavelength division multiplexed, referred to as WDM, transmission channel () to a corresponding optical receiver () is described. The optical transmitter () comprises a profiling unit () adapted to receive information regarding an equalization filter () adapted at the corresponding optical receiver (), based on a first optical signal received from the optical transmitter (); a pulse shaping filter unit () adapted to filter a sequence of data symbols () using a pulse shaping filter, thereby yielding a filtered sequence of data symbols (); wherein a frequency response () of the pulse shaping filter depends on the information regarding the equalization filter (); and a digital-to-optical converter () adapted to convert the filtered sequence of data symbols () into a second optical signal to be transmitted to the optical receiver ().

Flexible optimization of the signal-to-noise ratio for ultra dense coherent WDM systems

The present document relates to an optical communication system. In particular, the present document relates to the alignment of the laser frequency at a transmitter of the optical communication system and the local oscillator frequency at a coherent receiver of the optical communication system. A coherent optical receiver () is described. The receiver () comprises a reception unit adapted to convert a received optical signal at a carrier frequency into a digital signal using a local oscillator, referred to as LO, having an LO frequency; a spectral analysis unit adapted to estimate a degree of asymmetry of a spectrum of the received optical signal, based on the digital signal; and a transmission unit adapted to transmit an indication of the degree of asymmetry to a near-end transponder () comprising a transmitter () of the received optical signal.

Coherent transponder with enhanced frequency locking

Proposed is a method of demodulating a phase modulated optical signal received from an optical channel. A time-discrete electrical signal is derived from the phase modulated optical signal, using a local optical signal, which has a frequency that is essentially equal to a carrier frequency of the phase modulated optical signal. A phase error between the local optical signal and the phase modulated optical signal is compensated, by deriving from the local optical signal a phase offset and modifying the derived time-discrete electrical signal by this phase offset. A chromatic dispersion caused by the optical channel is compensated, by filtering the modified time-discrete electrical signal using a digital filter.

Method of demodulating a phase modulated optical signal

The embodiments of the present invention describe a method for optimizing the capacity of an optical communication network that uses wavelength division multiplexing, wherein the spectral distribution of the signals intended to be transmitted over a plurality of channels is done dynamically through the use of a variable spectrum grid whose spectral spacings between two successive channels are determined based on the spectral width of said signals and in which dynamic filtering of said signals is carried out before their transmission in order to adjust their spectral width based on the available spectral space, and thereby reduce crosstalk between adjacent channels when the signals are transmitted.

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Nozay, France

Oriol Bertran-Pardo