Norbert Hanik

Technische Universität München, München, Bavaria, Germany

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Publications (116)51.58 Total impact

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    ABSTRACT: In this paper, the wavelength division multiplexed (WDM) fiber optic channel is considered. It is shown that for ideal distributed Raman amplification (IDRA), the Wiener process model is suitable for the non-linear phase noise due to cross phase modulation from neighboring channels. Based on this model, a phase noise tracking algorithm is presented. We approximate the distribution of the phase noise at each time instant by a mixture of Tikhonov distributions, and derive a closed form expression for the posterior probabilities of the input symbols. This reduces the complexity dramatically compared to previous trellis-based approaches, which require numerical integration. Further, the proposed method performs very well in low-to-moderate signal-to-noise ratio (SNR), where standard decision directed (DD) methods, especially for high-order modulation, fail. The proposed algorithm does not rely on averaging, and therefore does not experience high error floors at high SNR in severe phase noise scenarios. The laser linewidth (LLW) tolerance is thereby increased for the entire SNR region compared to previous DD methods. In IDRA WDM links, the algorithm is shown to effectively combat the combined effect of both laser phase noise and non-linear phase noise, which cannot be neglected in such scenarios. In a more practical lumped amplification scheme, we show near-optimal performance for 16 QAM, 64 QAM, and 256 QAM with LLW up to 100 kHz, and reasonable performance for LLW of 1 MHz for 16 QAM and 64 QAM, at the moderate received SNR region. The performance in these cases is close to the information rate achieved by the above mentioned trellis processing.
    Full-text · Article · Dec 2015 · Journal of Lightwave Technology
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    ABSTRACT: We experimentally investigate mutual information and generalized mutual information for coherent optical transmission systems. The impact of the assumed channel distribution on the achievable rate is investigated for distributions in up to four dimensions. Single channel and wavelength division multiplexing (WDM) transmission over transmission links with and without inline dispersion compensation are studied. We show that for conventional WDM systems without inline dispersion compensation, circularly symmetric complex Gaussian distribution is a good approximation of the channel. For other channels, such as with inline dispersion compensation, this is no longer true and gains in the achievable information rate are obtained by considering more sophisticated four-dimensional (4D) distributions. We also show that for nonlinear channels, gains in the achievable information rate can also be achieved by estimating the mean values of the received constellation in four dimensions. The highest gain for such channels is seen for a 4D correlated Gaussian distribution.
    No preview · Article · Nov 2015 · Journal of Lightwave Technology
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    ABSTRACT: Probabilistic shaping of quadrature amplitude modulation (QAM) is used to enhance the sensitivity of an optical communication system. Sensitivity gains of 0.43 dB and 0.8 dB are demonstrated in back-to-back experiments by shaping of 16QAM and 64QAM, respectively. Further, numerical simulations are used to prove the robustness of probabilistic shaping to a mismatch between the constellation used and the signal-to-noise ratio (SNR) of the channel. It is found that, accepting a 0.1 dB SNR penalty, only four shaping distributions are required to support these gains for 64QAM.
    No preview · Article · Oct 2015 · IEEE Photonics Technology Letters
  • T. Fehenberger · N. Hanik
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    ABSTRACT: We study lower bounds on mutual information that are achievable rates for optimal and sub-optimal hard-decision (HD) and soft-decision (SD) decoding. These rates represent the maximum amount of information we can convey over a memoryless channel with a fixed input if ideal forward error correction (FEC) is employed. We find that the gain of complex SD decoding over HD decoding can be very small, depending on the modulation format and the system parameters. We further study the gap of a practical FEC scheme to its asymptotic limit.
    No preview · Article · Aug 2015
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    ABSTRACT: We demonstrate a record 38.4Tb/s 64QAM C-band transmission over 762km of field deployed SSMF fiber, connecting Lyon and Marseille, France, employing hybrid EDFA-Raman amplification and achieve a spectral efficiency of 8b/s/Hz. Furthermore, we demonstrate, for the first time to our knowledge, flexi-rate transmission over the same commercial link, using quad-carrier 1Tb/s 16QAM (24.0 Tb/s), 1Tb/s 32QAM (32.0 Tb/s) and 1.2Tb/s 64QAM (38.4 Tb/s).
    Full-text · Conference Paper · Jul 2015
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    ABSTRACT: Signal transmission with capacity of 41.6 Tbit/s (net data rate 16.8 Tbit/s) over 12 spatial and polarization modes is demonstrated. Dense optical orthogonal frequency division multiplexing signals with a channel spacing of 16.7 GHz across the full C band is generated. The resulting 12 tributaries are (de-)multiplexed using a novel fully packaged photonic lantern based 3-D-waveguide spatial-multiplexer. The spatially multiplexed signals are transmitted over 74.17-km weakly coupled six-mode few mode fiber enabling inline differential mode delay compensation. All 12 tributaries are detected using three oscilloscopes via coherent heterodyne receiver. The bit error rate of the 255 channel in each mode is evaluated to be below the forward error correction limit 2.4 $\,\times\,$ 10 ${\bf ^{-2}}$ assuming 20% overhead.
    No preview · Article · Apr 2015 · Journal of Lightwave Technology
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    ABSTRACT: An LDPC coded modulation scheme with probabilistic shaping, optimized interleavers and noniterative demapping is proposed. Full-field simulations show an increase in transmission distance by 8% compared to uniformly distributed input.
    Full-text · Conference Paper · Mar 2015
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    ABSTRACT: We present a digital algorithm for joint pre-compensation of the low-pass frequency response and I/Q skew in transmitters. Experimental results for DP-16QAM to DP-256QAM at 37.41 GBaud are presented.
    No preview · Article · Mar 2015
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    ABSTRACT: Lower bounds on mutual information (MI) of long-haul optical fiber systems for hard-decision and soft-decision decoding are studied. Ready-to-use expressions to calculate the MI are presented. Extensive numerical simulations are used to quantify how changes in the optical transmitter, receiver, and channel affect the achievable transmission rates of the system. Special emphasis is put to the use of different quadrature amplitude modulation formats, channel spacings, digital back-propagation schemes and probabilistic shaping. The advantages of using MI over the prevailing $Q$-factor as a figure of merit of coded optical systems are also highlighted.
    Preview · Article · Jan 2015 · Optics Express

  • No preview · Article · Jan 2015 · IEEE Photonics Technology Letters
  • T. Fehenberger · N. Hanik
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    ABSTRACT: The impact of back-propagating an entire superchannel and sub-channels thereof is quantified by evaluating mutual information. We report a 50 Gb/s per channel increase in data rate. Additionally, the Gaussian Noise model is adapted to take into account back-propagation.
    No preview · Article · Nov 2014
  • Elisabeth Oberleithner · Norbert Hanik
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    ABSTRACT: Automotive Power Line Communication (PLC) is a promising technology that enables data transmission without the need of dedicated, heavy data communication lines. This way, it allows for reducing the weight and wiring complexity of a vehicle. This paper addresses the modelling of an in-vehicle PLC channel and gives a additional understanding of the impact single system components have on the specific automotive PLC transmission characteristic. It is shown that an automotive PLC channel is mainly characterized by the car battery, number of branch (tap) lines and the loads introduced by the various electrical control units. The heoretical results are compared with measurement data in order to validate the simulation model.
    No preview · Conference Paper · Sep 2014
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    ABSTRACT: OFDM is an interesting candidate to meet the requirements of high flexibility and speed for the next generation optical access networks. We show an OFDM system utilizing a timing advance tracking algorithm to realize a synchronized upstream transmission. Therefore, a dynamic bandwidth allocation can be used in the upstream and an interleaved assignment is made possible. We then demonstrate the feasibility in a field trial with four individual ONUs using a 37.5 km field deployed feeder fiber of the Deutsche Telekom AG. Power loading and the trellis coded modulation was used to achieve a power budget supporting 32 ONUs for up- as well as downstream transmission.
    No preview · Conference Paper · Jul 2014
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    ABSTRACT: Power-budget improvement to support more Optical Network Units (ONU) is the most significant issue for passive optical access networks. Investigation on Trellis coded modulation for multi-user phase noise channel is conducted to improve the power budget for CO-OFDMA uplink transmission. The power budget is doubled enabling 37.4-km CO-OFDMA upstream transmission supporting 32 ONUs. To our best knowledge, this is the first field trial of optical access network using coherent optical - OFDM technique.
    No preview · Conference Paper · Jul 2014
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    ABSTRACT: For advanced FEC schemes with soft-decision decoding, the mutual information (MI) between sent and received symbols is the natural figure of merit at the decoder input. In this work, the transmission of signals modulated with rectangular quadrature amplitude modulation (QAM) of order 16, 64, and 256 is simulated over three different fiber links that are typical representatives of metro-area networks used by Deutsche Telekom. At the receiver, the MI between sent and received symbols is estimated using histograms for which the correct bin number is determined in a reliable way. As MI is the constrained capacity, the channel capacity of an optical communication system including all components at transmitter and receiver is found. From the capacity we can derive the maximum spectral efficiency and the maximum data rate over the entire available spectrum for a fixed transmitter, link, and receiver design. For an average metro-area network link, more than 26 Tbit/s at a 50 GHz spacing are possible over the entire C-band. By decreasing the spacing to be close to the Nyquist rate, a dual-polarization spectral efficiency of 10.8 bit/s/Hz is possible, which increases the maximum total data rate per fiber to an astonishing 43.2 Tbit/s.
    No preview · Conference Paper · May 2014
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    Tobias Fehenberger · Norbert Hanik
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    ABSTRACT: Advanced channel decoders rely on soft-decision decoder inputs for which mutual information (MI) is the natural figure of merit. In this paper, we analyze an optical fiber system by evaluating MI as the maximum achievable rate of transmission of such a system. MI is estimated by means of histograms for which the correct bin number is determined in a blind way. The MI estimate obtained this way shows excellent accuracy in comparison with the true MI of 16-state quadrature amplitude modulation (QAM) over an additive white Gaussian noise channel with additional phase noise, which is a simplified model of a nonlinear optical fiber channel. We thereby justify to use the MI estimation method to accurately estimate the MI of an optical fiber system. In the second part of this work, a transoceanic fiber system with 6000 km of standard single-mode fiber is simulated and its MI determined. Among rectangular QAMs, 16-QAM is found to be the optimal modulation scheme for this link as to performance in terms of MI and requirements on components and digital signal processing. For the reported MI of 3.1 bits/symbol, a minimum coding overhead of 29% is required when the channel memory is not taken into account. By employing ideal single-channel digital back-propagation, an increase in MI by 0.25 bits/symbol and 0.28 bits/symbol is reported for 16-QAM and 64-QAM, respectively, lowering the required overhead to 19% and 16%. When the channel spacing is decreased to be close to the Nyquist rate, the dual-polarization spectral efficiency is 5.7 bits/s/Hz, an increase of more than 2 bits/symbol compared to a 50 GHz spacing.
    Preview · Article · Apr 2014
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    ABSTRACT: Next-generation optical communication systems will continue to push the ( bandwidth $cdot$ distance) product towards its physical limit. To address this enormous demand, the usage of digital signal processing together with advanced modulation formats and coherent detection has been proposed to enable data-rates as high as 400 Gb/s per channel over distances in the order of 1000 km. These technological breakthroughs have been made possible by full compensation of linear fiber impairments using digital equalization algorithms. While linear equalization techniques have already matured over the last decade, the next logical focus is to explore solutions enabling the mitigation of the Kerr effect induced nonlinear channel impairments. One of the most promising methods to compensate for fiber nonlinearities is digital back-propagation (DBP), which has recently been acknowledged as a universal compensator for fiber propagation impairments, albeit with high computational requirements. In this paper, we discuss two proposals to reduce the hardware complexity required by DBP. The first confirms and extends published results for non-dispersion managed link, while the second introduces a novel method applicable to dispersion managed links, showing complexity reductions in the order of 50% and up to 85%, respectively. The proposed techniques are validated by comparing results obtained through post-processing of simulated and experimental data, employing single channel and WDM configurations, with advanced modulation formats, such as quadrature phase shift keying (QPSK) and 16-ary quadrature amplitude modulation (16-QAM). The considered net symbol rate for all cases is 25 GSymbol/s. Our post-processing results show that we can significantly reduce the hardware complexity without affecting the system performance. Finally, a detailed analysis of the obtained reduction is presented for the ca- e of dispersion managed link in terms of number of required complex multiplications per transmitted bit.
    Full-text · Article · Apr 2014 · Journal of Lightwave Technology
  • Tobias Fehenberger · Norbert Hanik
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    ABSTRACT: Advanced channel decoders rely on soft-decision decoder inputs for which mutual information (MI) is the natural figure of merit. In this paper, we analyze an optical fiber system by evaluating MI as the maximum achievable rate of transmission of such a system. MI is estimated by means of histograms for which the correct bin number is determined in a blind way. The MI estimate obtained this way shows excellent accuracy in comparison with the true MI of 16-state quadrature amplitude modulation (QAM) over an additive white Gaussian noise channel with additional phase noise, which is a simplified model of a nonlinear optical fiber channel. We thereby justify to use the MI estimation method to accurately estimate the MI of an optical fiber system. In the second part of this work, a transoceanic fiber system with 6000 km of standard single-mode fiber is simulated and its MI determined. Among rectangular QAMs, 16-QAM is found to be the optimal modulation scheme for this link as to performance in terms of MI and requirements on components and digital signal processing. For the reported MI of 3.1 bits/symbol, a minimum coding overhead of 29% is required when the channel memory is not taken into account. By employing ideal single-channel digital back-propagation, an increase in MI by 0.25 bits/symbol and 0.28 bits/symbol is reported for 16-QAM and 64-QAM, respectively, lowering the required overhead to 19% and 16%. When the channel spacing is decreased to be close to the Nyquist rate, the dual-polarization spectral efficiency is 5.7 bits/s/Hz, an increase of more than 2 bits/symbol compared to a 50 GHz spacing.
    No preview · Article · Mar 2014
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    ABSTRACT: The orthogonal frequency division multiple access (OFDMA)-based passive optical network (PON) is a potential candidate to meet the flexibility requirements for next-generation optical access networks. We propose an OFDMA-based PON with a transmission employing intensity modulation/direct detection in the downstream and a remodulation of a remotely seeded carrier provided by the optical line terminal with coherent detection in the upstream, which enables cost-effective colorless optical network units (ONUs). Furthermore, an OFDMA-PON field trial using the proposed scheme over 37.5 km feeder fiber is demonstrated. A power budget supporting 32 ONUs with dynamic bandwidth allocation and trellis coded modulation (TCM) is reported.
    No preview · Conference Paper · Mar 2014
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    ABSTRACT: A synchronization algorithm for coherent OFDMA-PON upstream is proposed. The feasibility of the tracking functionality is experimentally investigated. A differential delay of up to 37.6 ns was tracked and could be compensated at the ONU.
    No preview · Conference Paper · Nov 2013

Publication Stats

777 Citations
51.58 Total Impact Points

Institutions

  • 2004-2014
    • Technische Universität München
      • Institute for Communications Engineering
      München, Bavaria, Germany
  • 2002-2012
    • Christian-Albrechts-Universität zu Kiel
      • Chair for Communications
      Kiel, Schleswig-Holstein, Germany
    • Technical University of Denmark
      Lyngby, Capital Region, Denmark
    • T-Systems International GmbH
      Frankfurt, Hesse, Germany
  • 1999-2000
    • Deutsche Telekom
      Hamburg, Hamburg, Germany