Coherent modulation up to 100 GBd 16QAM using silicon-organic hybrid (SOH) devices

We demonstrate the generation of higher-order modulation formats using silicon-based inphase/quadrature (IQ) modulators at symbol rates of up to 100 GBd. Our devices exploit the advantages of silicon-organic hybrid (SOH) integration, which combines silicon-on-insulator waveguides with highly efficient organic electro-optic (EO) cladding materials to enable small drive voltages and sub-millimeter device lengths. In our experiments, we use an SOH IQ modulator with a {\pi}-voltage of 1.6 V to generate 100 GBd 16QAM signals. This is the first time that the 100 GBd mark is reached with an IQ modulator realized on a semiconductor substrate, leading to a single-polarization line rate of 400 Gbit/s. The peak-to-peak drive voltages amount to 1.5 Vpp, corresponding to an electrical energy dissipation in the modulator of only 25 fJ/bit

Electrically packaged silicon-organic hybrid (SOH) I/Q-modulator for 64 GBd operation

Silicon-organic hybrid (SOH) electro-optic (EO) modulators combine small footprint with low operating voltage and hence low power dissipation, thus lending themselves to on-chip integration of large-scale device arrays. Here we demonstrate an electrical packaging concept that enables high-density radio-frequency (RF) interfaces between on-chip SOH devices and external circuits. The concept combines high-resolution $\mathrm{Al_2O_3}$ printed-circuit boards with technically simple metal wire bonds and is amenable to packaging of device arrays with small on-chip bond pad pitches. In a set of experiments, we characterize the performance of the underlying RF building blocks and we demonstrate the viability of the overall concept by generation of high-speed optical communication signals. Achieving line rates (symbols rates) of 128 Gbit/s (64 GBd) using quadrature-phase-shiftkeying (QPSK) modulation and of 160 Gbit/s (40 GBd) using 16-state quadrature-amplitudemodulation (16QAM), we believe that our demonstration represents an important step in bringing SOH modulators from proof-of-concept experiments to deployment in commercial environments

A verified equivalent-circuit model for slotwaveguide modulators

We formulate and experimentally validate an equivalent-circuit model based on distributed elements to describe the electric and electro-optic (EO) properties of travellingwave silicon-organic hybrid (SOH) slot-waveguide modulators. The model allows to reliably predict the small-signal EO frequency response of the modulators exploiting purely electrical measurements of the frequency-dependent RF transmission characteristics. We experimentally verify the validity of our model, and we formulate design guidelines for an optimum trade-off between optical loss due to free-carrier absorption (FCA), electro-optic bandwidth, and {\pi}-voltage of SOH slot-waveguide modulators

Comb-based WDM transmission at 10 Tbit/s using a DC-driven quantum-dash mode-locked laser diode

Chip-scale frequency comb generators have the potential to become key building blocks of compact wavelength-division multiplexing (WDM) transceivers in future metropolitan or campus-area networks. Among the various comb generator concepts, quantum-dash (QD) mode-locked laser diodes (MLLD) stand out as a particularly promising option, combining small footprint with simple operation by a DC current and offering flat broadband comb spectra. However, the data transmission performance achieved with QD-MLLD was so far limited by strong phase noise of the individual comb tones, restricting experiments to rather simple modulation formats such as quadrature phase shift keying (QPSK) or requiring hard-ware-based compensation schemes. Here we demonstrate that these limitations can be over-come by digital symbol-wise phase tracking algorithms, avoiding any hardware-based phase-noise compensation. We demonstrate 16QAM dual-polarization WDM transmission on 38 channels at an aggregate net data rate of 10.68 Tbit/s over 75 km of standard single-mode fiber. To the best of our knowledge, this corresponds to the highest data rate achieved through a DC-driven chip-scale comb generator without any hardware-based phase-noise reduction schemes

Mitgliedschaft in Gewerkschaften: Inklusions- und Exklusionstendenzen in der Organisation von Arbeitnehmerinteressen in Europa

"Die Gewerkschaften stehen heute in vielen europäischen Ländern vor beträchtlichen Mitgliederproblemen. Jedoch variiert der gewerkschaftliche Organisationsgrad zwischen einem eher niedrigen Niveau in Süd- und Osteuropa und einem höheren Niveau in Nordeuropa. Außerdem zeigen sich im internationalen Vergleich erhebliche Unterschiede zwischen sozialen Gruppen. Zu welchem Grad gelingt es den Gewerkschaften noch, ihre Klientel einzubinden und zumindest als Mitglieder zu mobilisieren? Dieser Frage wird mit Hilfe von deskriptiven Analysen des European Social Surveys von 2002/03 für West- und Ost-Deutschland sowie weiteren 18 europäischen Ländern nachgegangen. Es werden zentrale Muster der Inklusion bzw. Exklusion von Arbeitnehmerinteressen aufgezeigt und mögliche Erklärungen der (Nicht-)Mitgliedschaft in Gewerkschaften erörtert. Neben den sozialstrukturellen Ursachen für geringere Organisationsgrade von Frauen, Arbeitslosen und atypisch Beschäftigten, werden zentrale institutionelle Faktoren herausgearbeitet, die selektive Anreize für eine Gewerkschaftsmitgliedschaft schaffen und den betrieblichen Zugang für Gewerkschaften erleichtern. Die theoretische Fruchtbarkeit eines In-/ Exklusionsansatzes zeigt sich besonders in der mangelnden Repräsentation der Interessen von atypisch Beschäftigten und Arbeitslosen sowie solchen in peripheren (unorganisierten) Arbeitsplätzen." (Autorenreferat)"In many European countries trade unions face considerable membership problems. Union density varies between a mostly low level in Southern and Eastern European societies and high levels in Nordic countries. Moreover, there are considerable cross-national differences between social groups. To what degree do trade unions integrate their clientele and are they capable of mobilizing members? We study this question by using descriptive statistics from the European Social Survey of 2002/03 for (Western and Eastern) Germany and for 18 other European countries. We discuss crucial patterns of inclusion and exclusion in the organization of labour interests and possible explanatory factors for (non-)membership. In addition to social structural causes for low union density of women, the unemployed and atypical employed, we review several institutional factors that provide selective incentives for membership and foster union access to workplaces. The inclusion/exclusion perspective proves particularly valuable for the analysis of low representation of the unemployed and atypical employed as well for those working in peripheral (unorganized) workplaces." (author's abstract

Non-sliced Optical Arbitrary Waveform Measurement (OAWM) Using a Silicon Photonic Receiver Chip

Comb-based optical arbitrary waveform measurement (OAWM) techniques can overcome the bandwidth limitations of conventional coherent detection schemes and may have disruptive impact on a wide range of scientific and industrial applications. Over the previous years, different OAWM schemes have been demonstrated, showing the performance and the application potential of the concept in laboratory experiments. However, these demonstrations still relied on discrete fiber-optic components or on combinations of discrete coherent receivers with integrated optical slicing filters that require complex tuning procedures to achieve the desired performance. In this paper, we demonstrate the first wavelength-agnostic OAWM front-end that is integrated on a compact silicon photonic chip and that neither requires slicing filters nor active controls. Our OAWM system comprises four IQ receivers, which are accurately calibrated using a femtosecond mode-locked laser and which offer a total acquisition bandwidth of 170 GHz. Using sinusoidal test signals, we measure a signal-to-noise-and-distortion ratio (SINAD) of 30 dB for the reconstructed signal, which corresponds to an effective number of bits (ENOB) of 4.7 bit, where the underlying electronic analog-to-digital converters (ADC) turn out to be the main limitation. The performance of the OAWM system is further demonstrated by receiving 64QAM data signals at symbol rates of up to 100 GBd, achieving constellation signal-to-noise ratios (CSNR) that are on par with those obtained for conventional coherent receivers. In a theoretical scalability analysis, we show that increasing the channel count of non-sliced OAWM systems can improve both the acquisition bandwidth and the signal quality. We believe that our work represents a key step towards out-of-lab use of highly compact OAWM systems that rely on chip-scale integrated optical front-ends

Efficient free-space read-out of WGM lasers using circular micromirrors

Lasing from whispering-gallery mode (WGM) resonators occurs omnidirectional in azimuthal plane. Most applications of WGM resonators require spectral analysis with off-chip detectors, where in-plane emission and beam divergence hinder efficient detection. We demonstrate redirecting WGM laser emission from all azimuthal angles using a circular micromirror placed around the cavity. By collecting reflections off the micromirror via free-space optics, read-out intensity improved by one order of magnitude. Blocking vertically emitted spontaneous emission and recording reflections off the micromirror only, signal-to-noise ratio improved from 4.6 dB to 15 dB. Our read-out concept may be applied to arbitrary WGM cavity geometries without deteriorating the cavity`s quality factor