Alcatel Lucent

Sebastian A Randel

Peter Johannes Winzer

Roland Ryf

Noriaki Kaneda

Jeffrey H Sinsky

Rene-Jean Essiambre

Fabian N Hauske

Alberto Sierra Noguera

Dario Pilori

Disclosed herein is an optical transport system configured to transport an amplitude-modulated optical signal generated at the transmitter using single-sideband modulation of an optical carrier and detected at the receiver using direct optical detection. The receiver is configured to estimate the level of signal-signal beat interference (SSBI) in the electrical signal generated upon direct detection of the received optical signal by first converting this electrical signal into a modified baseband signal configured for single-sideband modulation and then squaring and appropriately scaling this modified baseband signal. The receiver is further configured to subtract the estimated level of SSBI from the electrical signal generated by the direct optical detector and to process the resulting corrected electrical signal to recover the data encoded in the amplitude-modulated optical signal. Example analog and digital circuits for estimating the level of SSBI at the receiver are disclosed.

Reduction of effects of signal-signal beat interference in optical transport systems

An optical receiver having an electronic dispersion-compensation module with two parallel signal-processing branches configured to provide a greater range of dispersion compensation than that provided by a prior-art device of comparable implementation complexity. In an example embodiment, each of the signal-processing branches includes a respective bank of finite-impulse-response filters that are configured in accordance with a different respective approximation of the group delay that needs to be compensated. The two group-delay approximations used by the filter banks rely on different respective step functions, each having a respective plurality of quantized steps, with the transitions between adjacent steps in one step function being spectrally aligned with the flat portions of the corresponding steps in the other step function. The filter banks may be further configured to apply different respective frequency-dependent phase-shift and/or amplitude-scaling profiles designed to reduce signal distortions associated with the transitions between adjacent steps in the step functions.

Optical receiver having a chromatic-dispersion compensation module with a multibranch filter-bank structure

In a representative embodiment, a disclosed receiver of an optical multicarrier offset-quadrature-amplitude-modulated (MC-OQAM) signal is configured to track and compensate for the phase error in the local-oscillator (LO) signal with respect to a carrier wave of a modulated subcarrier of the optical MC-OQAM signal by tracking a minimum of a cost function that is sensitive to crosstalk between in-phase and quadrature components of the modulated subcarrier and/or crosstalk between the modulated subcarrier and at least one other modulated subcarrier of the optical MC-OQAM signal. The receiver can operate based on pure feed-forward processing and compensate the phase error in real time and without relying on pilot symbols or a PLL circuit coupled to the LO source.

Correction of a local-oscillator phase error in a coherent optical receiver

An optical receiver comprising an optical-to-electrical converter and a digital processor having one or more equalizer stages. The optical-to-electrical converter is configured to mix an optical input signal and an optical local-oscillator signal to generate a plurality of electrical digital measures of the optical input signal. The digital processor is configured to process the electrical digital measures to recover the data carried by the optical input signal. At least one of the equalizer stages is configured to perform signal-equalization processing in which the electrical digital measures and/or digital signals derived from the electrical digital measures are being treated as linear combinations of arbitrarily coupled signals, rather than one or more pairs of 90-degree phase-locked I and Q signals. The latter feature enables the digital processor to more-effectively mitigate the receiver-, link-, and/or transmitter-induced signal impairments because various orthogonality-degrading effects can be mitigated in a relatively straightforward manner.

Optical receiver having a MIMO equalizer

Disclosed herein are various embodiments of a time-domain reflectometer having a transmitter configured to apply, to a system under test (SUT), an intensity-modulated probe signal generated based on a periodic pseudo-random bit sequence. The reflectometer further has a receiver configured to receive, back from the SUT, a reflected signal corresponding to the probe signal. The receiver converts the received reflected signal into a binary bit sequence using a relatively simple slicer circuit, and without the use of complex analog circuits and/or multi-bit analog-to-digital converters. The binary bit sequence is then compared with the original pseudo-random bit sequence to obtain a measure of the impulse response of the SUT. In some embodiments, the reflectometer has a controllable noise generator that can be used, e.g., to optimize the obtained measure for the detection of multiple SUT defects having significantly differing reflection characteristics.

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Aberdeen, NJ, United States of America

Sebastian A Randel