Abstract: The present invention relates to an optical channel sounding transmitter apparatus, comprising an optical signal generator for generating an optical carrier signal; an optical modulator for modulating the optical carrier signal with a predetermined training sequence to obtain an modulated optical signal; a first optical transmitter for transmitting the optical carrier signal; and a second optical transmitter for transmitting the modulated optical signal. Further the present invention relates to a coherent optical channel sounding receiver apparatus, comprising a first optical receiver for receiving an optical carrier signal over a first optical channel; a second optical receiver for receiving a modulated optical signal over a second optical channel; an optical down converter for down converting the modulated optical signal using the received optical carrier signal to obtain a down converted signal; and a channel estimator for estimating a channel characteristic of the second optical channel.

Abstract: The present invention relates to an optical channel sounding transmitter apparatus, comprising an optical signal generator for generating an optical carrier signal; an optical modulator for modulating the optical carrier signal with a predetermined training sequence to obtain an modulated optical signal; a first optical transmitter for transmitting the optical carrier signal; and a second optical transmitter for transmitting the modulated optical signal. Further the present invention relates to a coherent optical channel sounding receiver apparatus, comprising a first optical receiver for receiving an optical carrier signal over a first optical channel; a second optical receiver for receiving a modulated optical signal over a second optical channel; an optical down converter for down converting the modulated optical signal using the received optical carrier signal to obtain a down converted signal; and a channel estimator for estimating a channel characteristic of the second optical channel.

Abstract: The present disclosure relates to a method for estimating chromatic dispersion of a received optical signal (Rx(f)), the method comprising: scanning the received optical signal (Rx(f)) through a number (M) of chromatic dispersion compensation filters in a chromatic dispersion filter range (Dmin . . . Dmax) between a first chromatic dispersion value (Dmin) and a second chromatic dispersion value (Dmax) with a resolution (?D) determined by the chromatic dispersion filter range (Dmin . . . Dmax) normalized by the number (M) of chromatic dispersion compensation filters to obtain filtered samples (Rx, D(f)) of the received optical signal (Rx(f)); and determining a correlation function (CD(?,B)) indicating an estimate of the chromatic dispersion by correlating the filtered samples (Rx, D(f)) of the received optical signal (Rx(f)) with respect to frequency shifts (?) over a correlation bandwidth (B), wherein the correlation bandwidth (B), the chromatic dispersion filter range (Dmin . . .

Abstract: The present disclosure relates to a method for detecting a parity error in a sequence of DQPSK symbols of a digital transmission system, comprising determining a first demodulated symbol r1; determining a second demodulated symbol r2; determining a first parity symbol p1; determining a second parity symbol p2; determining a super-parity symbol q1; and detecting a parity error in the sequence of DQPSK symbols by comparing a combination of the first parity symbol p1 and the second parity symbol p2 against the super-parity symbol q1, wherein a parity between two DQPSK symbols describes a phase difference between the two DQPSK symbols.

Abstract: The filter device includes a filter for filtering the input signal with a first set of filter coefficients, and for filtering the input signal with a second set of coefficients, a frequency domain correlator for correlating a first subset of frequency domain components of the first filtered signal to obtain a first correlation value, and for correlating a second subset of frequency domain components of the second filtered signal to obtain a second correlation value, wherein the first subset of correlated frequency domain components and the second subset of correlated frequency domain components are respectively located within a predetermined range of the correlated signals, and a processor for selecting either the first set of filter coefficients or the second set of filter coefficients upon the basis of the first correlation value and the second correlation value for filtering the input signal.

Abstract: An adaptive filter configured to filter an input signal comprises Fourier transforming unit configured to transform the input signal into a frequency domain signal upon the basis of the Fourier transform, weighting unit configured to weight at least a portion of the frequency domain signal with a filter coefficient of the dispersion filter in frequency domain to obtain a filtered signal in frequency domain, correlating unit configured to correlate the filtered signal in frequency domain to obtain a correlation value, and adaptation unit configured to adapt the filter coefficient upon the basis of the correlation value.

Abstract: The invention relates to a clock recovery apparatus being configured to recover clock information from an input signal. The clock recovery apparatus comprises Fourier transforming means (201) being configured to transform the input signal into a frequency domain signal upon the basis of a Fourier transform, correlating means (215) being configured to correlate the frequency domain signal to obtain a correlation value associated with a certain frequency, and clock recovery means (217) being configured to determine whether the certain frequency corresponds to a clock frequency in order to recover the clock information.

Abstract: A clock phase recovery apparatus includes a clock estimator for estimating a first clock signal and a second clock signal upon the basis of an input signal, the input signal comprising a first sub-signal according to a first optical polarization and a second sub-signal according to a second optical polarization, the first clock signal comprising a first clock magnitude and a first clock phase, the second clock signal comprising a second clock magnitude and a second clock phase, and a selector for selecting the first clock phase to form the estimated clock phase if the first clock magnitude is greater than the second clock magnitude, or for selecting the second clock phase to form the estimated clock phase if the second clock magnitude is greater than the first clock magnitude.

Abstract: The present disclosure relates to a method for estimating chromatic dispersion of a received optical signal (Rx(f)), the method comprising: scanning the received optical signal (Rx(f)) through a number (M) of chromatic dispersion compensation filters in a chromatic dispersion filter range (Dmin . . . Dmax) between a first chromatic dispersion value (Dmin) and a second chromatic dispersion value (Dmax) with a resolution (?D) determined by the chromatic dispersion filter range (Dmin . . . Dmax) normalized by the number (M) of chromatic dispersion compensation filters to obtain filtered samples (Rx, D(f)) of the received optical signal (Rx(f)); and determining a correlation function (CD(?,B)) indicating an estimate of the chromatic dispersion by correlating the filtered samples (Rx, D(f)) of the received optical signal (Rx(f)) with respect to frequency shifts (?) over a correlation bandwidth (B), wherein the correlation bandwidth (B), the chromatic dispersion filter range (Dmin . . .

Abstract: A clock phase recovery apparatus includes a clock estimator for estimating a first clock signal and a second clock signal upon the basis of an input signal, the input signal comprising a first sub-signal according to a first optical polarization and a second sub-signal according to a second optical polarization, the first clock signal comprising a first clock magnitude and a first clock phase, the second clock signal comprising a second clock magnitude and a second clock phase, and a selector for selecting the first clock phase to form the estimated clock phase if the first clock magnitude is greater than the second clock magnitude, or for selecting the second clock phase to form the estimated clock phase if the second clock magnitude is greater than the first clock magnitude.

Abstract: The present disclosure relates to a method for detecting a parity error in a sequence of DQPSK symbols of a digital transmission system, comprising determining a first demodulated symbol r1; determining a second demodulated symbol r2; determining a first parity symbol p1; determining a second parity symbol p2; determining a super-parity symbol q1; and detecting a parity error in the sequence of DQPSK symbols by comparing a combination of the first parity symbol p1 and the second parity symbol p2 against the super-parity symbol q1, wherein a parity between two DQPSK symbols describes a phase difference between the two DQPSK symbols.

Abstract: The filter device comprises a filter for filtering the input signal with a first set of filter coefficients, and for filtering the input signal with a second set of coefficients, a frequency domain correlator for correlating a first subset of frequency domain components of the first filtered signal to obtain a first correlation value, and for correlating a second subset of frequency domain components of the second filtered signal to obtain a second correlation value, wherein the first subset of correlated frequency domain components and the second subset of correlated frequency domain components are respectively located within a predetermined range of the correlated signals comprising the clock frequency, and a processor for selecting either the first set of filter coefficients or the second set of filter coefficients upon the basis of the first correlation value and the second correlation value for filtering the input signal.

Abstract: The invention relates to a clock recovery apparatus being configured to recover clock information from an input signal. The clock recovery apparatus comprises Fourier transforming means (201) being configured to transform the input signal into a frequency domain signal upon the basis of a Fourier transform, correlating means (215) being configured to correlate the frequency domain signal to obtain a correlation value associated with a certain frequency, and clock recovery means (217) being configured to determine whether the certain frequency corresponds to a clock frequency in order to recover the clock information.

Abstract: The invention relates to a filter device (200) for filtering an input signal (s(t)). The filter device (200) has a plurality of taps (210-216) having a respective filter coefficient (w0-w6) and a plurality of delay elements (221-226), wherein at least two delay elements (221-226) have different delays.

Abstract: A transponder is adapted to communicate with a further transponder over at least one optical channel. The transponder comprises a first receiver having a monitor and a first transmitter. The first receiver is configured to receive a first signal transmitted by a second transmitter of the further transponder over the optical channel. The monitor is configured to provide at least one channel parameter describing the optical channel in dependence on the received first signal. The first transmitter is configured to transmit the at least one channel parameter to the further transponder for adjusting a pre-equalizer of the further transponder.

Abstract: An adaptive filter configured to filter an input signal comprises Fourier transforming unit configured to transform the input signal into a frequency domain signal upon the basis of the Fourier transform, weighting unit configured to weight at least a portion of the frequency domain signal with a filter coefficient of the dispersion filter in frequency domain to obtain a filtered signal in frequency domain, correlating unit configured to correlate the filtered signal in frequency domain to obtain a correlation value, and adaptation unit configured to adapt the filter coefficient upon the basis of the correlation value.