Norbert Hanik

Bio: Norbert Hanik is an academic researcher from Technische Universität München. The author has contributed to research in topics: Transmission (telecommunications) & Wavelength-division multiplexing. The author has an hindex of 28, co-authored 145 publications receiving 2699 citations. Previous affiliations of Norbert Hanik include Deutsche Telekom & Ludwig Maximilian University of Munich.

Performance of Stereo Multiplexing in systems using direct detection with optimum dispersion maps

Abstract: We present Stereo Multiplexing, a novel technique that permits simultaneous direct detection of two modulated optical carriers. This is accomplished by modulating the optical carriers with the difference and the sum of two signals. The linear performance of Stereo-multiplexed DQPSK signals is compared to single-carrier DQPSK and dual-carrier DQPSK. Subsequently, by means of simulations, the robustness of each format is compared after DWDM transmission of 55.5 Gb/s through 1040 km of SMF. This is done by searching the optimum dispersion map and input powers for each format and looking at the stability of the performance around the optimum. We show that the best performance and robustness is obtained by sharing the information between two carriers, and that Stereo is only 1 dB below dual-carrier NRZ-DQPSK. This small penalty can be tolerated if cost and complexity at the receiver side must be kept low.

Eigenvalue Trajectories in Multispan Soliton Transmission Systems under Lumped and Distributed Amplification

Abstract: The trajectories of discrete eigenvalues of solitonic pulses are studied numerically for different amplification schemes. For the case of eigenvalue ‘collision‘ and ‘absorption‘ into the real axis detailed simulation results of the critical propagation sections are given and discussed in regards to their influence on pulse stability.

On the Effect of Polarisation-Mode Dispersion on the Channel Capacity of Coherent Fibre-optic Communication Systems

Abstract: Although the value itself is difficult to determine, it is well-known that the channel capacity of fibre-optic communication systems is limited by optical and electrical noise and non-linear effects such as the Kerr effect or the square-law characteristics of the photodiode at the receiver. We investigate the impact of another capacity- degrading fibre-effect, Polarisation-Mode Dispersion (PMD), in single-channel single-span systems with optical amplification and coherent detection. Results for the capacity of PMD-limited channels are derived for first- order and higher-order PMD. As PMD may be considered a slowly-varying effect (in time), the capacity distribution is also discussed.

On Probabilistic Shaping of Quadrature Amplitude Modulation for the Nonlinear Fiber Channel

Abstract: Different aspects of probabilistic shaping for a multi-span optical communication system are studied. First, a numerical analysis of the additive white Gaussian noise (AWGN) channel investigates the effect of using a small number of input probability mass functions (PMFs) for a range of signal-to-noise ratios (SNRs), instead of optimizing the constellation shaping for each SNR. It is shown that if a small penalty of at most 0.1 dB SNR to the full shaping gain is acceptable, just two shaped PMFs are required per quadrature amplitude modulation (QAM) over a large SNR range. For a multi-span wavelength division multiplexing (WDM) optical fiber system with 64QAM input, it is shown that just one PMF is required to achieve large gains over uniform input for distances from 1,400 km to 3,000 km. Using recently developed theoretical models that extend the Gaussian noise (GN) model and full-field split-step simulations, we illustrate the ramifications of probabilistic shaping on the effective SNR after fiber propagation. Our results show that, for a fixed average optical launch power, a shaping gain is obtained for the noise contributions from fiber amplifiers and modulation-independent nonlinear interference (NLI), whereas shaping simultaneously causes a penalty as it leads to an increased NLI. However, this nonlinear shaping loss is found to have a relatively minor impact, and optimizing the shaped PMF with a modulation-dependent GN model confirms that the PMF found for AWGN is also a good choice for a multi-span fiber system.

Space-division multiplexing in optical fibres

Abstract: This Review summarizes the simultaneous transmission of several independent spatial channels of light along optical fibres to expand the data-carrying capacity of optical communications. Recent results achieved in both multicore and multimode optical fibres are documented.

OFDM for Optical Communications

Abstract: Orthogonal frequency division multiplexing (OFDM) is a modulation technique which is now used in most new and emerging broadband wired and wireless communication systems because it is an effective solution to intersymbol interference caused by a dispersive channel. Very recently a number of researchers have shown that OFDM is also a promising technology for optical communications. This paper gives a tutorial overview of OFDM highlighting the aspects that are likely to be important in optical applications. To achieve good performance in optical systems OFDM must be adapted in various ways. The constraints imposed by single mode optical fiber, multimode optical fiber and optical wireless are discussed and the new forms of optical OFDM which have been developed are outlined. The main drawbacks of OFDM are its high peak to average power ratio and its sensitivity to phase noise and frequency offset. The impairments that these cause are described and their implications for optical systems discussed.

Optical phase-shift-keyed transmission

Abstract: Differential-phase-shift keying (DPSK) has recently been used to reach record distances in long-haul lightwave communication systems. This paper will review theoretical, as well as implementation, aspects of DPSK, and discuss experimental results.

Comparison of Asymmetrically Clipped Optical OFDM and DC-Biased Optical OFDM in AWGN

Abstract: We present theoretical and simulation results for the performance of asymmetrically-clipped optical OFDM (ACO-OFDM) and DC-biased optical OFDM (DCO-OFDM) in AWGN for intensity-modulated direct-detection systems. Constellations from 4 QAM to 1024 QAM are considered. For DCO-OFDM, the optimum bias depends on the constellation size which limits its performance in adaptive systems. ACO-OFDM requires less optical power for a given data rate than DCO-OFDM for all but the largest constellations and is better suited to adaptive systems as the same structure is optimum for all constellations.

Space-division multiplexing: the next frontier in optical communication

Abstract: Space-division multiplexing (SDM) uses multiplicity of space channels to increase capacity for optical communication. It is applicable for optical communication in both free space and guided waves. This paper focuses on SDM for fiber-optic communication using few-mode fibers or multimode fibers, in particular on the critical challenge of mode crosstalk. Multiple-input–multiple-output (MIMO) equalization methods developed for wireless communication can be applied as an electronic method to equalize mode crosstalk. Optical approaches, including differential modal group delay management, strong mode coupling, and multicore fibers, are necessary to bring the computational complexity for MIMO mode crosstalk equalization to practical levels. Progress in passive devices, such as (de)multiplexers, and active devices, such as amplifiers and switches, which are considered straightforward challenges in comparison with mode crosstalk, are reviewed. Finally, we present the prospects for SDM in optical transmission and networking.