DAC-less PAM-4 generation in the O-band using a silicon Mach-Zehnder modulator

International audienceWe demonstrate 20-Gb/s 4-level pulse amplitude modulation (PAM-4) signal generation using a silicon Mach-Zehnder modulator (MZM) in the O-band. The modulator is driven by two independent binary streams, and the PAM-4 signal is thus generated directly on the chip, avoiding the use of power-hungry digital-to-analog converters (DACs). With optimized amplitude levels of the binary signals applied to the two arms of the MZM, a pre-forward error correction (FEC) bit-error rate (BER) as low as 7.6 × 10 −7 is obtained. In comparison with a commercially available LiNbO 3 modulator, the penalty is only 2 dB at the KP4 FEC threshold of 2.2 × 10 −4

Generation of electro-optic frequency combs with optimized flatness in a silicon ring resonator modulator

The flatness of electro-optic frequency combs (EOFCs) generated in a single silicon ring resonator modulator (RRM) is optimized by employing harmonic superposition of the radio-frequency driving signal. A differential evolution algorithm is employed in conjunction with a simplified model of the RRM for offline optimization of the amplitudes and phases of harmonic driving signals and the operating point of the RRM. The optimized driving signals are then applied to a silicon RRM. EOFCs containing 7 and 9 lines are synthesized with a power imbalance between the lines of 2.9 dB and 5.4 dB, respectively, compared to 9.4 dB for an optimized 5-line comb generated from a single sinusoidal driving signal.Comment: 4 pages, 5 figures, submitted to Optics Letter

A pan-European epidemiological study reveals honey bee colony survival depends on beekeeper education and disease control

Reports of honey bee population decline has spurred many national efforts to understand the extent of the problem and to identify causative or associated factors. However, our collective understanding of the factors has been hampered by a lack of joined up trans-national effort. Moreover, the impacts of beekeeper knowledge and beekeeping management practices have often been overlooked, despite honey bees being a managed pollinator. Here, we established a standardised active monitoring network for 5 798 apiaries over two consecutive years to quantify honey bee colony mortality across 17 European countries. Our data demonstrate that overwinter losses ranged between 2% and 32%, and that high summer losses were likely to follow high winter losses. Multivariate Poisson regression models revealed that hobbyist beekeepers with small apiaries and little experience in beekeeping had double the winter mortality rate when compared to professional beekeepers. Furthermore, honey bees kept by professional beekeepers never showed signs of disease, unlike apiaries from hobbyist beekeepers that had symptoms of bacterial infection and heavy Varroa infestation. Our data highlight beekeeper background and apicultural practices as major drivers of honey bee colony losses. The benefits of conducting trans-national monitoring schemes and improving beekeeper training are discussed

Cases of mistaken identity: The Asian Hornet

With the threat of the invasive Asian hornet (Vespa velutina; AH) arriving in the UK from continental Europe, the National Bee Unit (NBU) has been working with colleagues in the Non-Native Species Secretariat (NNSS), the Centre for Ecology & Hydrology (CEH) and Bee Health Policy (BHP) to raise awareness of this potentially damaging predator of honey bees and other pollinating insects (https://secure.fera.defra.gov.uk/beebase/ index.cfm?pageid=208)

Novel compact transmitters for short-reach optical communication

International audienceIn this talk, we will review our recent work on the demonstration of novel compact transmitter structures employing Si or III-V integration for short reach optical communications. A special focus will be given on means to address the limitations induced by group-velocity dispersion for such systems. Customized modulators operating in the O-band, or employing single-sideband modulation in conjunction with single- (PAM2 and PAM4) or multi-carrier (OFDM) modulation in the C-band will be presented

Comprehensive frequency chirp characterization of silicon ring resonator modulators

International audienceThe frequency chirping properties of a silicon ring resonator modulator are experimentally investigated and compared to a numerical model. The influence of the wavelength detuning and the modulation frequency are highlighted for the first time

Frequency Chirp Characterization of Silicon Ring Resonator Modulators

International audienceThe frequency chirping properties of silicon ring resonator modulators (RRMs) are experimentally investigated under sinusoidal modulation. The modulated electric field at the output of an RRM is measured in the time domain thanks to a coherent detection system. The power and phase waveforms are then analyzed in terms of their temporal phase and amplitude for different wavelength detunings between the optical source and the resonance and for different modulation frequencies. The evolution of the frequency chirp, described through a peak-to-peak chirp parameter, is quantified as a function of wavelength detuning and modulation frequency for the first time

Novel compact transmitters for short-reach optical communication

International audienceIn this talk, we will review our recent work on the demonstration of novel compact transmitter structures employing Si or III-V integration for short reach optical communications. A special focus will be given on means to address the limitations induced by group-velocity dispersion for such systems. Customized modulators operating in the O-band, or employing single-sideband modulation in conjunction with single- (PAM2 and PAM4) or multi-carrier (OFDM) modulation in the C-band will be presented

Declines of managed honey bees and beekeepers in Europe

Growing evidence indicates that European managed honey bees are in decline, but information for Europe remains patchy and localized. Here we compile data from 18 European countries to assess trends in the number of honey bee colonies and beekeepers between 1965 and 2005. We found consistent declines in colony numbers in central European countries and some increases in Mediterranean countries. Beekeeper numbers have declined in all of the European countries examined. Our data support the view that honey bees are in decline at least in some regions, which is probably closely linked to the decreasing number of beekeepers. Our data on colony numbers and beekeepers must, however, be interpreted with caution due to different approaches and socioeconomic factors in the various countries, thereby limiting their comparability. We therefore make specific recommendations for standardized methodologies to be adopted at the national and global level to assist in the future monitoring of honey bees

O-band DAC-less PAM-4 generation with a silicon dual-drive Mach-Zehnder Modulator

International audience4-level pulse amplitude modulation (PAM-4) is the chosen modulation format for next generation optical short-reach data communications such as intra-datacenter communications. On-chip generation of PAM-4 signals is possible using a single dual-drive Mach-Zehnder modulator (MZM). By driving the modulator with two voltage-unbalanced binary signals it is possible to avoid any power hungry electrical digital-to-analog converter (DAC). PAM-4 signal generation at 20 Gbit/s is demonstrated using a silicon dual-drive MZM in the O-band. A bit error rate (BER) of 3.8.10-3 is measured at-6 dBm input power