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.

Investigation of future optical metro ring networks based on 100-Gigabit Metro Ethernet (100 GbME)

Abstract: This paper reports results of a performance comparison for four optical ring network architectures envisaged for future metropolitan area networks (MANs), with particular emphasis on the design of and compatibility to possible 100-Gigabit-Metro-Ethernet (100 GbME) standards. Both analytical and numerical modelling techniques were applied to quantify and compare network performance for all architectures in terms of achievable throughput, delay and the number of required wavelengths. Non-uniform traffic required additional resources and dynamic adaptation of the slotted ring architecture. The study also considered aspects of the physical transmission and interfaces (PHY)for consideration in 100 GbME standards.

Achievable Rates for Short-Reach Fiber-Optic Channels with Direct Detection.

Abstract: Spectrally efficient communication is studied for short-reach fiber-optic links with chromatic dispersion (CD) and receivers that employ direction-detection and oversampling. Achievable rates and symbol error probabilities are computed by using auxiliary channels that account for memory in the sampled symbol strings. Real-alphabet bipolar and complex-alphabet symmetric modulations are shown to achieve significant energy gains over classic intensity modulation. Moreover, frequency-domain raised-cosine (FD-RC) pulses outperform time-domain RC (TD-RC) pulses in terms of spectral efficiency for two scenarios. First, if one shares the spectrum with other users then inter-channel interference significantly reduces the TD-RC rates. Second, if there is a transmit filter to avoid interference then the detection complexity of FD-RC and TD-RC pulses is similar but FD-RC achieves higher rates.

A digital subcarrier multiplexing technique for increased spectral efficiency in optical systems using direct detection

Abstract: We propose a novel technique that allows direct detection of multicarrier signals without using DSP at the receiver. Performance at 55.5 Gb/s, back-to-back and after 1040 km of dispersion uncompensated link is assessed by simulations.

Adaptive Transmitter Pre-Distortion Using Feedback From the Far-End Receiver

Abstract: In recent years, digital pre-distortion has emerged as a powerful approach to compensate linear and non-linear imperfections of the transmitter. Previous solutions are either based on factory calibration or use a local auxiliary receiver. Here, we present a digital pre-distortion architecture to compensate transmitter frequency response and I/Q skew, which relies upon a feedback from the far-end receiver and uses the signal propagated over the optical link. The effectiveness of the proposed solution is validated over different transmission systems for dual-polarization 64 QAM net 400 Gb/s and 16 QAM net 200 Gb/s signals.

Equalizer complexity of mode-division multiplexed coherent receivers

Abstract: One of the possible solutions is to use space division multiplexing in order to overcome the capacity crunch. Few mode fibers (FMF) have attracted a lot of attention in the recent years, however still a lot of research is required to enable transmission over FMF. One of the problems with the realization of FMF transmission is that these fibers have a modal dispersion which results in high number of equalization taps which might make the FMFs impractical. The complexities of common equalizer schemes are analyzed in this paper in terms of complex multiplications per bit. It is found that training symbol based equalizers have significantly lower complexity compared to blind approaches for long-haul transmission. Among the training symbol based schemes, OFDM requires the lowest complexity for crosstalk compensation in a mode-division multiplexed receiver. The main challenge for training symbol based approaches is the increased data rate due to extra overhead required for cyclic prefix and training symbols. In order to achieve 2000 km transmission, the modal dispersion must be below 6 ps/km when the OFDM specific overhead is limited to 10%. This shows that for few mode transmission systems the reduction of modal delay is essential to enable long-haul performance.

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.