Abstract: In an optical transmission system, a first modulated signal is generated at the transmitting end by modulating a first carrier signal with a first data signal and a second modulated signal is generated by modulating a second carrier signal, which differs from the first carrier signal by a differential frequency, with a second data signal. The first and second modulated signals are polarized orthogonally with respect to one another and combined to form an optical multiplex signal and are transmitted. At the receiving end, the optical multiplex signal is conducted via a polarization control element to a polarization splitter which splits the optical multiplex signal into the first and second modulated signals.

Abstract: In an optical transmission system, a first modulated signal with a first transmission bit rate is generated at the transmitting end by modulating a first carrier signal with the first data signal, using a nonreturn to zero coding, and a second modulated signal with a second transmission bit rate is generated by modulating a second carrier signal with the second data signal, using a return to zero coding. The first and second modulated signal are polarized orthogonally with respect to one another and combined to form an optical multiplex signal and transmitted. At the receiving end, the optical multiplex signal is conducted via a polarization control element to a polarization splitter which splits the optical multiplex signal into the first and second modulated signal.

Abstract: The invention relates to a measuring method that allows to measure non-linearities of an optical fiber (OF) unilaterally, that is at the beginning or at the end of the optical fiber (OF). To this end, an optical test signal (ots) is launched into the optical fiber (OF), the test signal power (Ps) of which is modified. A first entry threshold (SBS1) of the stimulated Brillouin scattering is detected on the basis of the modified power (Pros) of the reflected optical signal (ros). In a second step, at least one modulated optical pump signal (ops) is launched into the optical fiber (OF) in addition to the optical test signal (ots). A second entry threshold (SBS2) of the stimulated Brillouin scattering is detected on the basis of the modified power (Ps) of the optical test signal (ots). The non-linearity coefficient (&ggr;) of the optical fiber (OF) is determined by evaluating the at least first and second entry thresholds (SBS1, SBS2), the test and pump signal parameters and the fiber parameters.

Abstract: The invention relates to a modular optical network node, which divides the optical input signals into optical subbands, processed by a central element or by several central elements and which then recombines the optical subbands once again to form an optical output signal. Various functionalities, such as add-drop functionality, a drop and continue functionality, a multicast functionality, a broadcast functionality, a ring interconnect functionality, and a cross connect functionality, can be assigned to the central element or to the central elements of the modular optical network node. According to the assignment of a functionality, the modular optical network node can be used in networks having a different structure.

Abstract: A compensation system for adaptive equalization of an optical signal, wherein an optical filter, whose complex coefficients are adjustable, is used for signal equalization. The quality of the optical signal is used, after conversion to an electrical data signal, as a control criterion. The compensation device can largely compensate for distortion produced by dispersion, polarization mode dispersion or self phase modulation. An optical compensation filter with a wide free spectral range is used to compensate for the wavelength-dependent dispersion in a wavelength-division multiplexed system. The setting of the filter may be fixed, or may be adjusted adaptively in a closed control loop.

Abstract: In an optical transmission system, a first modulated signal is generated at the transmitting end by modulating a first carrier signal with a first data signal and a second modulated signal is generated by modulating a second carrier signal, which differs from the first carrier signal by a differential frequency, with a second data signal. The first and second modulated signals are polarized orthogonally with respect to one another and combined to form an optical multiplex signal and are transmitted. At the receiving end, the optical multiplex signal is conducted via a polarization control element to a polarization splitter which splits the optical multiplex signal into the first and second modulated signals.

Abstract: An apparatus is provided for compensating for polarization mode dispersion which is caused during transmission of a light wave via an optical waveguide, to an optical communication network having such an apparatus, and a method for compensating for polarization mode dispersion which is caused during transmission of a light wave via an optical waveguide is also provided.

Abstract: A system for compensating for distortions in optical signals, wherein the series connection of a controllable polarization-dependent delay element and of a controllable filter allows good signal distortion correction; for example, due to group delay dispersion or polarization mode dispersion. The series circuit also may contain further devices for signal improvement.

Abstract: The invention relates to a method and to a system for amplitude modulation of an optical signal (os) with a binary data signal (ds). To this end, the optical signal (os) is divided up into a first and a second adjustable optical signal (os1, os2). The first optical signal (os1) is supplied to a modulator (MZM) that outputs an optical transmission signal (ts) after amplitude modulation with a binary data signal (ds). A counter-phase second optical signal (gps) is produced from the second adjustable optical signal (os2) and the optical transmission signal (ts) and the counter-phase second optical signal (gps) are combined to a carrier-reduced optical transmission signal (rts).

Abstract: The stimulated Brillouin backscatter is reduced by non-linear effects, such as self-phase modulation or cross-phase modulation. Due to the cross-phase modulation, a bandwidth spread and, as result thereof, a reduction of the stimulated Brillouin backscatter is also achieved by supplying at least one amplitude-modulated pump signal.

Abstract: A method for determining signal quality in optical transmission systems, wherein the effective signal-to-noise ratio is determined by measuring amplitude histograms of a signal and by calculating characteristic histogram moments and additional interference is ascertained by comparing the characteristic histogram moments with the optical signal-to-noise ratio.

Abstract: In order to synchronize the phases of two RZ data signals (RZS1, RZS2) combined to form a time multiplex signal (MS1), the power of half the fundamental made of the multiplex signal (MS1) is measured and the phase difference is controlled such that its power assumes a minimum.

Abstract: Method for phase-synchronous supply of an optical pulsed signal or an optical NRZ transmission signal and an electrical data signal, wherein an optical pulsed signal and an electrical data signal which are synchronized with respect to an electrical clock signal are supplied to an electrooptical modulator in order to produce an optical RZ transmission signal. In order to control the phase-synchronous supply, a portion of the optical RZ transmission signal is output, and the output portion is converted to an electrical signal. The power, the current or the voltage of the electrical signal is then determined in a narrow frequency band around the frequency which corresponds to half the data rate, and the determined power, current or voltage values are used to control the phase-synchronous supply of the optical pulsed signal and/or of the electrical data signal.

Abstract: A method and apparatus for improving the signal quality of a modulated optical transmission signal wherein at least one optical signal whose frequency is reduced from the carrier signal frequency by the Brillouin frequency shift is produced in a signal production unit and this signal is injected at the end of the optical transmission fiber in the opposite direction to the transmission signal direction, so that the carrier signal component of the modulated optical transmission signal is reduced.

Abstract: A method and drive unit for controlling a modulator (128) in which the working point of the modulator (128) is regulated using a regulating circuit (124) in such a way that the working point is stable in relation to the transmission characteristic curve of the modulator (128) for a long time and under different operating conditions.