We present a linear and nonlinear digital pre-distortion (DPD) tailored to the components of an optical transmitter. The DPD concept uses nonlinear models of the transmitter devices, which are ...obtained from direct component measurements. While the digital-to-analog converter and driver amplifier are modeled jointly by a Volterra series, the modulator is modeled independently as a Wiener system. This allows for a block-wise compensation of the modulator by a Hammerstein system and a pre-distortion of the electrical components by a second Volterra series. In simulations and extensive experiments, the performance of our approach for nonlinear DPD is compared to an equivalent linear solution as well as to a configuration without any DPD. The experiments were performed using M-ary quadrature-amplitude modulation (M-QAM) formats ranging from 16- to 128-QAM at a symbol rate of 32 GBd. It is shown that the DPD improves the required optical signal-to-noise ratio at a bit error ratio of 2·10 -2 by at least 1.2 dB. Nonlinear DPD outperforms linear DPD by an additional 0.9 and 2.7 dB for higher-order modulation formats such as 64-QAM and 128-QAM, respectively.
In this invited contribution, we discuss technology options for bandwidth-variable transceivers which are key components for the realization of flexible software-defined optical networking. ...Bandwidth-variable transceivers enable the software-controlled adaptation of physical layer parameters such as transmitted bit rate, spectral efficiency and transparent reach according to the traffic demands at hand. In particular, we focus on recent advances in four-dimensional modulation formats and in modulation format transparent data-aided digital signal processing. It is argued that four-dimensional modulation formats present an attractive complement to conventional polarization-multiplexed formats in the context of bandwidth-variable transceivers, where they enable a smooth transition with respect to spectral efficiency while requiring marginal additional hardware effort. Results of numerical simulations and experiments supporting this statement are presented. For the cost-efficient hardware implementation of bandwidth-variable transceivers supporting several polarization-multiplexed and four-dimensional modulation formats, digital signal processing algorithms are required which operate format transparent and consume little hardware resources. We discuss data-aided signal processing as one possible option, in particular with respect to carrier frequency recovery and channel estimation in combination with frequency domain equalization.
We study the mental maps of spectators using psychological network models during a large naturally occurring extreme ritual. Our aim was to identify the psychometric network structure of ...psychological reactions to an extreme ritual, and to investigate the core features of ritual cognition among its spectators. Participants who observed the Nine Emperor God (or Vegetarian) Festival (N = 1041 Taoist-Buddhists) completed measures of social, affective, behavioral and uncertainty cognitions. Applying undirected psychometric network models, we found that: 1) cognitions clustered in a small set of communities, and were 2) organized along two major dimensions (positive . negative valence, uncertainty beliefs 'vs.' uncertainty management). We argue that our study is an important step in theory building efforts, and that our findings offer insights for integrating theories of ritual. Thus, our study points towards new directions for theories of ritual by mapping the interdependence of psychological reactions and identifying the core cognition of a ritual.
We present a digital signal processing (DSP) scheme that performs hyperparameter tuning (HT) via Bayesian optimization (BO) to autonomously optimize memory tap distribution of Volterra series and ...adapt parameters used in the synthetization of a digital pre-distortion (DPD) filter for optical transmitters. Besides providing a time-efficient technique, this work demonstrates that the self-adaptation of DPD hyperparameters to correct the component-induced nonlinear distortions as different driver amplifier (DA) gains, symbol rates and modulation formats are used, leads to an improvement in transmitter performance. The scheme has been validated in back-to-back (b2b) experiments using dual-polarization (DP) 64 and 256 quadrature amplitude modulation (QAM) formats, and symbol rates of 64 and 80 GBd. For DP-64QAM at 64 GBd, it is shown that the DPD scheme reduces the required optical signal-to-noise ratio (OSNR) at a bit error ratio of 10 -2 by 0.9 dB and 0.6 dB with respect to linear DPD and a heuristic nonlinear DPD approach, respectively. Moreover, we show that the proposed approach also reduces filter complexity by 75% in conjunction with the use of memory polynomials (MP), while achieving a similar performance to Volterra pre-distortion filters.
Guest EditorialUltra Wideband WDM Systems Napoli, Antonio; Fischer, Johannes Karl; Namiki, Shu ...
Journal of lightwave technology,
2020-March1,-1, 2020-3-1, Letnik:
38, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The papers in this special section focuses on ultrawideband wavelength division multiplexing (WDM) systems. Applications such as video streaming and cloud computing became part of our daily life. ...With others, they are considerably contributing to generate the enormous amount of data that is nowadays transmitted over the global optical backbone. The topics range from network operators perspective to components design and numerical analysis. The first two manuscripts discusses the optimization and challenges of systems where C and L-band are employed for transmission.
Ancient philosophy proposed a wide range of possible approaches to life which may enhance well-being. Stoic philosophy has influenced various therapeutic traditions. Individuals today may adopt an ...approach to life representing a naive Stoic Ideology, which nevertheless reflects a misinterpretation of stoic philosophy. How do these interpretations affect well-being and meaning in life? We examine the differential effects of Stoic Ideology on eudaimonic versus hedonic well-being across three cultural contexts. In this pre-registered study, across samples in New Zealand (
N
= 636), Norway (
N
= 290), and the US (
N
= 381) we found that a) Stoic Ideology can be measured across all three contexts and b) Converging evidence that Stoic Ideology was negatively related to both hedonic well-being and eudaimonic well-being. Focusing on specific relationships, we found especially pronounced effects for Taciturnity (the desire to not express emotions) and Serenity (the desire to feel less emotions). Despite being a misinterpretation of stoic philosophy, these findings highlight the important role of individuals’ orientations to emotional processing for well-being.
We present an experimental investigation of different Kerr nonlinearity mitigation schemes in a 2-span dispersion-compensated link of 160-km length for 4 × 28-GBd single-polarization 16-QAM signal ...transmission. We consider optical phase conjugation (OPC) based on mid-link spectral inversion, digital backpropagation (DBP), and transmission of phase-conjugated twin-waves with either digital coherent superposition (DCS) or all-optical coherent superposition employing phase-sensitive amplification (PSA). The experiments are performed in a single-channel and a wavelength-division multiplexing (WDM) scenario. For single-channel operation, phase-conjugated twin waves with DCS provided superior performance compared to all the other mitigation schemes with a maximum Q 2 -factor improvement of 1.7 dB compared to signal transmission without any nonlinearity mitigation. The DBP, however, showed a higher nonlinear threshold than all the other schemes in our experiments. In the WDM scenario, DBP showed worse performance than the other mitigation schemes whereas the DCS again provided a higher Q 2 -factor improvement than the other techniques with a maximum Q 2 -factor improvement of 1.9 dB. The PSA and the mid-link OPC showed similar nonlinearity mitigation performance both in single-channel and WDM scenarios.
Digital pre-compensation techniques are among the enablers for cost-efficient high-capacity transponders. In this paper we describe various methods to mitigate the impairments introduced by ...state-of-the-art components within modern optical transceivers. Numerical and experimental results validate their performance and benefits.
•Tutorial on digital, linear and nonlinear, pre-compensation techniques.•Different easy-to-be-used formulae.•Comprehensive series of results ranging from back-to-back to transmission.•Real-time realization of DPC methods in a FPGA.
We experimentally investigate four-dimensional (4-D) Trellis coded modulation (TCM) based on polarization-division multiplexed (PDM) 16-ary quadrature amplitude modulation (QAM), PDM-32QAM, and ...PDM-64QAM formats. A multirate optical transponder is enabled by only a single-encoder/decoder structure. The scheme is resilient to cycle-slip events due to its 90° phase rotation invariant property. In addition, the performance of 4-D turbo TCM (TTCM) is investigated. The superior performance of TTCM over TCM is experimentally validated. Furthermore, the performance of 4-D TCM/TTCM is compared with standard PDM-mQAM formats combined with the soft-decision (SD) forward error correction (FEC) codes. It is shown that 4-D TCM concatenated with a low-complexity hard-decision FEC could be an interesting candidate for complexity-performance tradeoff with SD-FEC.
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