Abstract: A received optical signal is coherently demodulated and converted into orthogonal x-polarization samples, and y-polarization samples. These samples are converted into signal x-samples and signal y-samples by an FIR butterfly filter. Correction values are calculated in an error calculating circuit of a control unit and added to filter transfer functions derived by a standard algorithm to determine corrected filter coefficients. Degenerate convergences calculating the transfer functions are avoided.

Abstract: A transmitter with two optical sources generates two optical carrier signals having different frequencies. The optical carrier signals are combined and divided in a first coupler and fed to carrier signal inputs of two modulators. The mixed carrier signals are separately modulated by two modulation signals (a(t)) and (b(t)) and the modulated signals are combined in a first combiner and emitted as transmission signal. Only one demodulator is necessary to regain the modulation signals (a(t) and b(t)).

Abstract: An apparatus for optical communication and optical communication method are provided, the method comprising the steps of generating an optical signal for transmitting the sequence of information data, transmitting the sequence of information data as a sequence of transmit matrices, S(k) being the k-th transmit matrix and k being a positive integer, and wherein the sequence of transmit matrices is transmitted through an optical channel characterized by a unitary channel matrix H, receiving a sequence of receive matrices, the k-th receive matrix R(k) being expressed as: R(k)=H·S(k)+N(k) wherein k is a positive integer and N(k) is a complex matrix of noise samples and providing a sequence of decision matrices, the k-th decision matrix D(k) being expressed as: D(k)=RH(k?1)R(k).

Abstract: The arrangement includes a transmitter (1-6) with two optical sources (1, 2) generating two optical carrier signals (L1, L2) having different frequencies. The optical carrier signals (L1, L2) are combined and divided in a first coupler (2) and fed to carrier signal inputs of two modulators (4, 5). The mixed carrier signals (L1+jL2, jL1+L2) are separately modulated by two modulation signals (a(t)) and (b(t)) and the modulated signals ((A1+jA2), (jB1+B2)) are combined in a first combiner and emitted as transmission signal (X(t)). Only on demodulator is necessary to regain the modulation signals (a(t), b(t)).

Abstract: From an real valued OFDM signal (S0(t)) is a baseband signal (SB(t)) derived and converted into a complex single sideband modulation signal (n(t)). This is modulated onto an optical carrier (fOC) to generate a SSB transmission signal (SOT) having a small bandwidth an carrying the information in the envelope or in the power of the envelope. According to the modulation direct detection is possible. Only a small bandwidth is necessary for the transmission.

Abstract: A method and a device for processing a signal determine a timing phase over an observation interval of an input signal. A frequency estimation is determined based on the timing phase. A phase correction is determined for the observation interval based on the timing phase and the frequency offset. Then the phase correction is used to adjust the timing of the input signal. Also, a communication system with at least one such device is described.

Abstract: The invention describes a method and an arrangement for transmitting an optical transmission signal with reduced polarisation-dependent loss. A first transmission signal component and a second orthogonal transmission signal component of the optical transmission signal are transmitted with a time difference between said transmission signal components.

Abstract: A signal processing method and a signal processing arrangement for coherent receivers are provided. The method includes the steps of receiving a coherent complex signal, extracting orthogonal in-phase and quadrature signal components from the coherent complex signal, quantizing the orthogonal signal components independently, combining the quantized orthogonal signal components as real and imaginary part of a complex number resulting in a first signal, and soft differential decoding the first signal resulting in a second signal.

Abstract: Component signal values are derived from component signals and fed to at least one fixed equalizer which generates equalizer output signals. The signals are fed to phase error detectors generating phase error signals. The phase error signals are combined with further phase error signals derived by further error detectors receiving signal values from further equalizers and/or the component signal values directly from sample units.

Abstract: A method for processing data in an optical network element. A multi-carrier signal is linear pre-coded and the linear pre-coded signal is modulated. A corresponding optical network element is also described.

Abstract: A received optical signal (SH, Sv) is coherently demodulated and converted into orthogonal x-polarisation samples (rx(n)), and y-polarisation samples (ry(n)). These samples are converted into signal x-samples zx(n) and signal y-samples zy(n) by an FIR butterfly filter (8). Correction values are calculated in an error calculating circuit (12) of a control unit (11) and added to filter transfer functions derived by a standard algorithm to determine corrected filter coefficients. Degenerate convergences calculating the transfer functions are avoided.

Abstract: A received optical signal is coherently demodulated and converted into electrical complex samples, which are dispersion compensated in a compensation filter. A control circuit calculates comparison values from corrected samples and an estimated error value. A plurality of compensation functions is applied according to a predetermined dispersion range and after a second iteration, the compensation filter is set to an optimum compensation function.

Abstract: The arrangement includes a transmitter (1-6) with two optical sources (1, 2) generating two optical carrier signals (L1, L2) having different frequencies. The optical carrier signals (L1, L2) are combined and divided in a first coupler (2) and fed to carrier signal inputs of two modulators (4, 5). The mixed carrier signals (L1+jL2, jL1+L2) are separately modulated by two modulation signals (a(t)) and (b(t)) and the modulated signals ((A1+jA2), (jB1+B2)) are combined in a first combiner and emitted as transmission signal (X(t)). Only on demodulator is necessary to regain the modulation signals (a(t), b(t)).

Abstract: A method and a device are provided for phase recovery of at least two channels comprising the steps of (i) a phase is estimated for each channel; (ii) the phase estimated of each channel is superimposed by a coupling factor with at least one other phase estimated. Further, a communication system is suggested comprising such a device.

Abstract: A method and a device are provided for data processing. The data contains symbols and a control parameter is determined based on a correlation property of the symbols of the data. In this manner signal recovery is achieved that is robust against any kind of distortion and is fast enough to track time varying clocking disturbances. Further, a communication system is provided containing such a device.

Abstract: Binary signals are converted at the transmission end into two optical signals which are combined into a polarization multiplex signal and are then transmitted. The transmitted polarization multiplex signal is divided at the receiving end into two polarized signal parts which are converted in a linear manner into orthogonal electrical components and are supplied to a multidimensional filter. Said multidimensional filter replaces a polarization controller, restores the signal values that correspond to the signals at the transmission end, and compensates signal distortions.

Abstract: From an real valued OFDM signal (S0(t)) is a baseband signal (SB(t)) derived and converted into a complex single sideband modulation signal (n(t)). This is modulated onto an optical carrier (fOC) to generate a SSB transmission signal (SOT) having a small bandwidth an carrying the information in the envelope or in the power of the envelope. According to the modulation direct detection is possible. Only a small bandwidth is necessary for the transmission.

Abstract: The performance of concatenated codes are improved by generating check bits from information bits, which are represented by an information matrix, by an outer code. The information bits and the check bits are cyclically shifted to obtain an interleaved code matrix. Then, the bits of the interleaved code matrix are coded by an inner code, where at least the outer code, or the inner code, is a product code.

Abstract: Demodulation of CPM-modulated information symbols which are demodulated after being transmitted through an AWGN channel, using only partial whitened matched filtering, whereby finite pulses are produced which, however, are still accompanied by interferences in the form of remaining colored noise which can be approximately converted into white noise by a successive additional whitening filter so that the noise power will be minimized. For correcting the accompanying symbol interferences, a sequence estimation with reduced number of states follows.