Alcatel

Alcatel Lucent

Henning Bülow

Fred Buchali

Axel Klekamp

The invention relates to a method of generating a feedback signal for adjusting a polarization mode dispersion compensator (PMDC,) in a transmission system with alternate-polarization. A first signal () is determined by measuring a spectral component of the radio frequency modulation of an optical signal () at a particular radio frequency. Preferably, the radio frequency essentially corresponds to half the symbol rate of the optical signal (). Also a second signal () is determined by coupling the optical signal () into a delay line interferometer (DLI,) having a delay essentially corresponding to the symbol period or an odd multiple of the symbol period between its arms (). Downstream of the DLI (), the signal is optical-to-electrically converted. Downstream of the optical-to-electrical conversion, an intensity measurement is performed. The first () and second () signals are then combined to generate the feedback signal ().

Generation of a feedback signal for a polarization mode dispersion compensator in a communication system using alternate-polarization

An optical receiver has an adaptive optical compensator and/or an adaptive electrical equalizer for compensating signal distortion in a received optical signal. In order to achieve a very fast adaptation of the receiver to the actual signal distortion, which is important for example for bursts mode optical signals in a packet-switched optical transmission network, at least one predetermined trainings sequence is provided in the optical signal, which is known at the receiver and thus enables fast adaptation of the compensator and/or equalizer to the actual signal distortion.

Optical transmission method and optical receiver

A fiber optical system () for transmitting an optical signal comprises an optical fiber line () with a plurality of successively arranged polarization scramblers (to) for polarization modulation of the optical signal transmitted through the optical fiber line () and a reference frequency signal () which synchronizes scrambling frequencies of all of the polarization scramblers (to) to a common reference frequency.

Fiber optical system for PMD mitigation by polarization scrambling

A receiver () for an optical signal containing a time jitter and a time-varying distortion caused by a periodic polarization scrambled signal comprises at least one decision gate () and a clock recovery module () providing a clock signal (C) recovered from the optical signal to the at least one decision gate (). The receiver () further comprises a scrambling frequency generator () synchronized to the scrambling frequency and phase of the polarization scrambled signal, a jitter function generator () generating a clock phase control signal (&#x394;&#x3c6;) reproducing the time jitter, and at least one clock phase modulator () modulating the phase of the clock signal (C) according to the clock phase control signal (&#x394;&#x3c6;).

Receiver for PMD mitigation by polarization scrambling

A method for estimating at least one optical link parameter using a Viterbi equalizer () generating averaged values (M) of signal amplitudes of a distorted optical signal transmitted through an optical link () for a set of decided bit patterns (a, b, c, d, . . . ), the method comprising the following steps: forming a first parameter set (S) characteristic of a distorted signal sequence using the averaged values (M(a), M(b), M(d), M(g)) for a given sequence (abdg) of bit patterns (a, b, c, d, . . . ), comparing the first parameter set (S) to a plurality of reference parameter sets (R, R, . . . ) characteristic for reference signal sequences of the same sequence (abdg) of bit patterns (a, b, c, d, . . . ), each of the reference parameter sets (R, R, . . . ) having a known value of the at least one optical link parameter, and selecting the reference parameter set (R) with the closest correlation to the first parameter set (S), the known value of the at least one optical link parameter of the selected reference parameter set (R) being used as an estimate for the at least one optical link parameter. A computer program product comprising a software or a hardware implementing the method.

Performance monitoring for optical links

A polarization mode dispersion (PMD) controller device for controlling the state of polarization of an optical light wave comprising a dispersion compensation unit () and an adaptation control unit (), wherein the dispersion compensation unit () comprises a multitude of compensation stages processing the optical light wave, and wherein the adaptation control unit () controls the dispersion compensation unit () is characterized in that at least one feed-forward signal tap (--) is provided tapping the optical light wave inserted into one of the compensation stages, that the feed-forward signal(s) is(are) fed into a distortion analyzer unit () and that the distortion analyzer unit () provides the adaptation control unit () with information about the incoming optical light wave. It accelerates the adaptation speed and lowers the costs of a high-speed PMD controller device.

Polarization mode dispersion controller device and method for its operation

The present invention concerns a method for performing optical dispersion compensation of wavelength division multiplexed (WDM) optical signals. The method comprises the steps of providing a compensation stage with an optical transmission medium to be used as parallel operating cascade of polarization controllers and optical birefringent elements to compensate dispersion of the WDM optical signals when being transmitted spectrally dispersed into the different wavelength channels in parallel through the parallel cascades. The method is being characterized by determining the chromatic dispersion of the optical signals at one or few different wavelength channels possibly allowing an extrapolation of the chromatic dispersion to the other wavelength channels for defining accordingly an additional feedback signal to be used for the polarization controller setting.

Multi-wavelength CD and PMD compensator

An optical time multiplexer for generating an N Gbits/s output signal () from n data modulated input pulse streams () with a pulse frequency of N/n GHz, where n&#x3b5;IN and n&#x2267;2, with a combiner device for passively interleaving the n input pulse streams () is characterized by at least n&#x2212;1 first phase shifting elements () tuning the optical phases of at least n&#x2212;1 input pulse streams () and being connected to a controller device (), which derives at least n&#x2212;1 control signals from a comparison of the optical phases of the n input pulse streams () and controls the at least n&#x2212;1 first phase shifting elements () such that the optical phases of all n input pulse streams () are locked with respect to each other. This optical time multuplexer reduces the drifting penalty of ODTM signals due to multiplexer instability, it prohibits the broadening of RZ pulses, and it grants the possibility to easily generate carrier-suppressed RZ signals or similar modulation formats.

Actively stabilized time multiplexer

A process is proposed for recovering disturbed digital signals, wherein the electrical signals pass through a feedback equalizer and an analogue control of the setting parameters of the equalizers is performed. A pseudo-error monitor, which facilitates a high-speed adjustment of decision element thresholds, is also provided.

Process for recovering digital optical signals and a feedback decision circuit

An integrated chromatic dispersion compensator for optical signals in optical communication networks, comprising a plurality of cascaded stages of optical dispersion elements arranged in the form of a lattice filter structure, is characterized by at least one tapping device disposed between consecutive stages of the optical dispersion elements for tapping inter stage signals, feeding each tapped inter stage signal into a separate feedback loop, which in turn is feeding adaptation parameters into at least one of the stages of the optical dispersion elements preceding the corresponding tapping device of the inter stage signal. The invention presents a compact dispersion compensator that can dynamically be adapted to varying dispersion situations and that is capable of compensating the chromatic dispersion of a multitude of data channels at the same time.

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Kornwestheim, Germany

Henning Bülow