Abstract: In the apparatus and the associated method, N-ary phase shift keyed received signals R12 are temporally demultiplexed in a 1:M demultiplexer DEMUX. In each of the sub-units DU1 . . . DUM the carrier signal C12 of the received signal R12 is recovered. The carrier phase angle angC12 is always chosen in the range ??/N . . . ?/N. Occurring phase jumps PHJ of the carrier phase angle angC12 from one sub-unit DU(i?1) to the next, DUi, of size ±2?/N are detected and are taken into account in a differential decoding of the synchronously demoudlated received signals R12. For this purpose, signals of the same or other sub-units must be temporarily stored in the sub-unit DUi until they are needed. In this way one obtains a high tolerance with respect to phase noise of the received signal R12.

Abstract: According to the system and method of the present invention, the frequency of an optical data signal is modulated on the transmitter side, and group transit time changes of the optical signal are detected on the receiver side. These group transit time changes are preferably determined via synchronous demodulation of a control signal of a voltage-controlled oscillator for timing recovery and are a measurement for any chromatic dispersion, which can be compensated via a chromatic dispersion compensator. The parasitic amplitude modulation generated with the frequency modulation can be used to obtain a reference signal for the synchronous demodulation.

Abstract: Device for detecting polarization mode dispersion of an optical data signal, which has at least one EXOR gate together with an averaging device for measuring at least one value of the autocorrelation function of a baseband signal distorted by polarization mode dispersion.

Abstract: A polarization scrambler and associated method for polarization scrambling are provided, wherein light is passed through a retarder whose eigen modes and delay vary with time and which is driven with alternating signals at two harmonic frequencies. One exemplary embodiment with an electrooptical wave plate operates with a horizontal or vertical input polarization and supplies output polarizations which vary with time and have uncorrelated normalized Stokes parameters. The polarization scrambler which is produced can be used in devices for detection of polarization mode dispersion.

Abstract: A polarization scrambler, and associated method for polarization scrambling, is provided wherein light is passed through a time-variant retarder. At least after upstream connection or downstream connection of a time-invariant retarder, this time-variant retarder may be represented as a retarder with eigen modes which are uniformly distributed on the Poincaré sphere and with a delay of 5?/6. An exemplary embodiment contains only two electro-optical wave plates, which are actuated by alternating signals containing harmonics. The polarization scrambler which is produced is independent of the input polarization of the light and can be used in devices for detection of polarization mode dispersion.

Abstract: A device is provided for detecting polarization mode dispersion of an optical data signal, wherein the device includes at least two filters, each of which is respectively followed by a power detector. A better compensation can ensue due to the combination of a large monotony range and great steepness in the employment of a number of filters.

Abstract: A polarization transformer/PMD compensator chip contains a differential TE-TM phase modulator at its input. The modulator generates a TE-TM phase modulation. The mode converter voltages are driven with driving signals that are free of DC components. DC drift is thereby safely avoided.

Abstract: In the apparatus and the associated method, N-ary phase shift keyed received signals R12 are temporally demultiplexed in a 1:M demultiplexer DEMUX. In each of the sub-units DU1 . . . DUM the carrier signal C12 of the received signal R12 is recovered. The carrier phase angle angC12 is always chosen in the range ??/N . . . ?/N. Occurring phase jumps PHJ of the carrier phase angle angC12 from one sub-unit DU(i?1) to the next, DUi, of size ±2?/N are detected and are taken into account in a differential decoding of the synchronously demoudlated received signals R12. For this purpose, signals of the same or other sub-units must be temporarily stored in the sub-unit DUi until they are needed. In this way one obtains a high tolerance with respect to phase noise of the received signal R12.

Abstract: An optical signal alternately traverses a total of n couplers and n−1 DGD units, arranged therebetween, with a differential group delay between two signal modes. The power division between the two signal modes is measured in each DGD unit in a power division controller, and a signal that is proportional to the difference between the powers in the two signal modes is obtained. The signal is led to an integrating controller whose control signal is led to a differential phase shifter that is accommodated in the DGD unit present upstream in the beam path. The difference between the powers of the two signal modes is thereby brought to zero at least approximately. This has the consequence that it is essentially only the chromatic dispersion that is generated or equalized, but no other disturbing distortions of the optical signal are produced.

Abstract: A polarization transformer/PMD compensator chip contains a differential TE−TM phase modulator at its input. The modulator generates a TE−TM phase modulation. The mode converter voltages are driven with driving signals that are free of DC components. DC drift is thereby safely avoided.

Abstract: An intradyne receiver provides a received intradyne signal X which comprises at least two, mutually phase-shifted, and N-ary phase shift keyed intradyne part signals Xk. Here N=2 for binary and N=4 for quaternary PSK. For carrier recovery purposes their frequency is multiplied by a factor of N in an intradyne frequency multiplier FM. After passing a lowpass filter TPY the filtered, frequency-multiplied intradyne signal is passed through an intradyne frequency divider IDF1, IDF2 with carrier intradyne signals C1, C2 as output signals that allow to demodulate the received intradyne signal X. The intradyne frequency divider undertakes more than one state change while changing the phase of the carrier intradyne signal by 2&pgr;/N. It can be formed as a regenerative intradyne frequency divider. When used for coherent optical data transmission this allows to tolerate comparatively large laser line widths.

Abstract: A method and apparatus for determining polarization dispersion of optical signals by measuring respective deviations between output signals that correspond to spectral power densities of the optical signal, and the output signals in undistorted conditions. The present method and apparatus uses output voltages from a plurality of filters in determining the polarization dispersion.

Abstract: According to the system and method of the present invention, the frequency of an optical data signal is modulated on the transmitter side, and group transit time changes of the optical signal are detected on the receiver side. These group transit time changes are preferably determined via synchronous demodulation of a control signal of a voltage-controlled oscillator for timing recovery and are a measurement for any chromatic dispersion, which can be compensated via a chromatic dispersion compensator. The parasitic amplitude modulation generated with the frequency modulation can be used to obtain a reference signal for the synchronous demodulation.

Abstract: A polarization transformer/PMD compensator chip contains a differential TE-TM phase modulator at its input. The modulator generates a TE-TM phase modulation. The mode converter voltages are driven with driving signals that are free of DC components. DC drift is thereby safely avoided.

Abstract: The invention specifies a method and apparatus for optical polarization control which enable non-ideal component behavior to be corrected by means of a calibration table. This ensures shorter constructional length, lower operating voltages or higher level functions (ER instead of GSBA).

Abstract: For characterizing polarization transformers or PMD compensators, a polarization transformer to be characterized is operated as a mode converter with full mode conversion and variable orientation. A polarization control sees to it that a further polarization transformer assures the desired, overall polarization transformation. Conclusions about the precision with which the polarization transformer to be characterized works can be drawn from the nature and strength or, too, from the absence of changes of control signals of this further polarization transformer, and this can be improved. The method is particularly suited for the automatic follow-up of DC drift in polarization transformers or PMD compensators with lithium niobate components.

Abstract: For the purpose of optical transmission, narrow pulses are generated with the aid of at least two modulators (M1, M2), in which use is made of drive signals (TS1, TS2) of the same frequency with different amplitudes, the modulators having different working points.

Abstract: A polarization of at least one modulated optical signal is varied at the transmitter side. Upon receiving the signals, propagation time variations of at least one optical signal are detected at the receiver side. These propagation time variations are determined preferably by evaluating the variations of the integral of the control signal of a voltage-controlled oscillator in the clock recovery and are a measure for existing polarization mode dispersion, which may be compensated by means of a polarization mode dispersion compensator.

Abstract: A polarization scrambler and associated method for polarization scrambling are provided, wherein light is passed through a retarder whose eigen modes and delay vary with time and which is driven with alternating signals at two harmonic frequencies. One exemplary embodiment with an electrooptical wave plate operates with a horizontal or vertical input polarization and supplies output polarizations which vary with time and have uncorrelated normalized Stokes parameters. The polarization scrambler which is produced can be used in devices for detection of polarization mode dispersion.

Abstract: A polarization mode dispersion compensator including a number of polarization mode converters. At least three mode converters, or at least three groups of mode converters, are individually actuated by at least three control voltages to compensate for PMD.