Aktuelle Publikationen

Externally modulated DFB lasers (EML) and vertically illuminated photodetectors are presented. Because of their excellent high-speed behavior and operation wavelength of 1310 nm, the devices are of interest for intra-data center communication. Since the EML and the photodetector chips are compatible with current systems, these devices are candidates for upgrading existing transceivers to higher baud rates. Therefore, a proof of concept for 100 GBaud data transmission with the presented components is demonstrated. Even without predistor! tion, the experiments show clearly open eye diagrams.

In this paper we present an example-based approach for visual speech synthesis. We combine the advantages of deep generative models and classical animation approaches to create a real-time capable facial animation framework based on volumetric captures.

Second harmonic generation is an efficient way to create coherent radiation at wavelengths that are not accessible with standard laser sources. In this work we demonstrate second harmonic generation from 1550 nm to 775 nm in a polymer photonic integrated circuit via the hybrid integration of a periodically poled lithium niobate crystal. The bulk crystal is inserted in an on-chip free-space section between two waveguide couple! d GRIN lenses. Fiber to fiber conversion efficiencies were 0.03 %/W for a continuous wave laser source and 100 %/W for a femtosecond laser source. Furthermore, third and fourth harmonic light at 517 nm and 388 nm was observed.

Using the concept of a “THz-Wireless Fiber Extender” it is possible to combine the flexibility of wireless networks with the high capacity of fiber-optical networks. In this article, we report on a real-time short-range demonstration of a 100 Gb/s fiber extender and discuss the potential of long-range data transmission at 300 GHz using a 500-meter-long wireless link in Berlin, Germany.

To address the capacity crunch in optical metropolitan networks caused by the roll out of innovations in the context of 5G and beyond innovative approaches are required to increase the achievable throughput. Multi band systems are an interesting solution to address this issue. In this contribution, we investigate the capacity limits of such networks.

Using a coherent laboratory setup with up to 768 Gb/s data rate (64-GBd DP-64QAM), we experimentally show that multilevel coding (MLC) provides superior physical layer security (i.e. smaller security gaps) as compared to conventional bit-interleaved coded modulation (BICM) . MLC offers a flexible trade-off between security and net secure data rate.

Besides the biological and epidemiological factors, a multitude of social and economic criteria also govern the extent of the coronavirus disease spread within a population. Consequently, there is an active debate regarding the critical socio-economic determinants that contribute to the impact of the resulting pandemic. Here, we leverage Bayesian model averaging techniques and country level data to investigate the potential of 31 determinants, describing a diverse set of socio-economic characteristics, in explaining the outcome of the first wave of the coronavirus pandemic. We show that the true empirical model behind the coronavirus outcome is constituted only of few determinants. To understand the relationship between the potential determinants in the specification of the true model, we develop the coronavirus determinants Jointness space. The extent to which each determinant is able to provide a credible explanation varies between countries due to their heterogeneous socio-economic characteristics. In this aspect, the obtained Jointness map acts as a bridge between theoretical investigations and empirical observations and offers an alternate view for the joint importance of the socio-economic determinants when used for developing policies aimed at preventing future epidemic crises.

We demonstrate a fully packaged photodetector module based on surface-illuminated modified uni-traveling-carrier (MUTC) photodiode (PD) and investigate its DC and RF characteristics. It has a very a low dark current below 2 nA at the operational reverse bias of 4 V and a responsivity of 0.49 A/W at 1550 nm. The module shows a high f3dB bandwidth of 38 GHz for low optical input powers and excellent linearity with RF output power levels of 11.7 dBm at 40 GHz. The power conversion efficiency ? PCE was 6.7% at 40 GHz making it suitable for RF signal generation.

We propose two algorithms that use both models and datasets to estimate angular power spectra from channel covariance matrices in massive MIMO systems. The first algorithm is an iterative fixed-point method that solves a hierarchical problem. It uses model knowledge to narrow down candidate angular power spectra to a set that is consistent with a measured covariance matrix. Then, from this set, the algorithm selects the angular power spectrum with minimum distance to its expected value with respect to a Hilbertian metric learned from data. The second algorithm solves an alternative optimization problem with a single application of a solver for nonnegative least squares programs. By fusing information obtained from datasets and models, both algorithms can outperform existing approaches based on models, and they are also robust against environmental changes and small datasets.

Digital contact tracing approaches based on Bluetooth low energy (BLE) have the potential to efficiently contain and delay outbreaks of infectious diseases such as the ongoing SARS-CoV- 2 pandemic. In this work we propose an approach to reliably detect subjects that have spent enough time in close proximity to be at risk of being infected. Our study is an important proof of concept that will aid the battery of epidemiological policies.