Wavelength locking of silicon photonics multiplexer for DML-based WDM transmitter

We present a wavelength locking platform enabling the feedback control of silicon (Si) microring resonators (MRRs) for the realization of a 4 × 10 Gb/s wavelength-division-multiplexing (WDM) transmitter. Four thermally tunable Si MRRs are employed to multiplex the signals generated by four directly modulated lasers (DMLs) operating in the L-band, as well as to improve the quality of the DMLs signals. Feedback control is achieved through a field-programmable gate array controller by monitoring the working point of each MRR through a transparent detector integrated inside the resonator. The feedback system provides an MRR wavelength stability of about 4 pm (0.5 GHz) with a time response of 60 ms. Bit error rate (BER) measurements confirm the effectiveness and the robustness of the locking system to counteract sensitivity degradations due to thermal drifts, even under uncooled operation conditions for the Si chip

The Genomes of Oryza sativa: A History of Duplications

We report improved whole-genome shotgun sequences for the genomes of indica and japonica rice, both with multimegabase contiguity, or almost 1,000-fold improvement over the drafts of 2002. Tested against a nonredundant collection of 19,079 full-length cDNAs, 97.7% of the genes are aligned, without fragmentation, to the mapped super-scaffolds of one or the other genome. We introduce a gene identification procedure for plants that does not rely on similarity to known genes to remove erroneous predictions resulting from transposable elements. Using the available EST data to adjust for residual errors in the predictions, the estimated gene count is at least 38,000–40,000. Only 2%–3% of the genes are unique to any one subspecies, comparable to the amount of sequence that might still be missing. Despite this lack of variation in gene content, there is enormous variation in the intergenic regions. At least a quarter of the two sequences could not be aligned, and where they could be aligned, single nucleotide polymorphism (SNP) rates varied from as little as 3.0 SNP/kb in the coding regions to 27.6 SNP/kb in the transposable elements. A more inclusive new approach for analyzing duplication history is introduced here. It reveals an ancient whole-genome duplication, a recent segmental duplication on Chromosomes 11 and 12, and massive ongoing individual gene duplications. We find 18 distinct pairs of duplicated segments that cover 65.7% of the genome; 17 of these pairs date back to a common time before the divergence of the grasses. More important, ongoing individual gene duplications provide a never-ending source of raw material for gene genesis and are major contributors to the differences between members of the grass family

Interannual impact of the Victoria mode on the winter-spring surface air temperature over Eurasia and North America

Abstract Variations of the Victoria mode (VM) have received considerable attention due to their profound impacts on the climate systems in the pan-North Pacific. However, works about its impact on surface air temperature (SAT) variability over Eurasia and North America, which may be responsible for extreme weather and climate events, are limited. Here we show a significant positive and negative relationship between the VM and the winter-spring SAT anomalies over mid-to-high-latitude east-central Eurasia (MEE) and eastern North America (ENA), respectively. A local energy budget analysis shows that the contribution of the surface heat fluxes associated with the VM to the SAT anomalies is confined mainly to MEE and may not explain the formation of SAT anomalies over ENA. Furthermore, VM-induced anomalous atmospheric circulations play a crucial role in the formation of notable SAT anomalies. The positive (negative) VM is linked to negative (positive) precipitation and upper-tropospheric wind convergence (divergence) anomalies over the western North Pacific, which contribute to positive (negative) Rossby wave source (RWS) anomalies near the East Asian westerly jet core. These RWS anomalies act as disturbances that propagate eastward, exciting a wave train-like pattern. The high-level positive and negative geopotential height anomalies of the Rossby wave dominate MEE and ENA, respectively, leading to the variation in SAT anomalies. These results could advance our understanding of the relationship between the VM and SAT over the Northern Hemisphere and inspire us to pay more attention to the VM climate impacts

Five-Port Optical Router Based on Microring Switches for Photonic Networks-on-Chip

We demonstrate a five-port optical router that is suitable for large-scale photonic networks-on-chip. The optical router is designed to passively route the optical signal travelling in one direction and actively route the optical signal making a turn. In the case that an XY dimension-order routing is used, the passive routing feature guarantees that the maximum power consumption to route the data through the network is a constant that is independent of the network size. The fabricated device has an efficient footprint of similar to 460 x 1000 mu m(2). The routing functionality of the device is verified by using a 12.5-Gbit/s optical signal. The capability of multiwavlength routing for the optical router is also explored and discussed

Low power and compact eight-channel reconfigurable optical add-drop multiplexers based on cascaded microring resonators

We report an eight-channel reconfigurable optical add-drop multiplexers(ROADMs) based on cascaded microring resonators with low tuning power and compact footprint. Microheaters are fabricated on the top of microring resonators, which can modulate microring resonators by the thermo-optic effect to achieve the reconfigurable functionality of the device. We demonstrate the reconfigurable add-drop multiplexing functionality for channel spacings of100GHz and50GHz, with the channel centre wavelengths aligned to International Telecommunication Unit(ITU) grid specifications. The crosstalk values for channel spacings of100GHz and50GHz are less than-22.5dB and-15.5dB, respectively. The average tuning power is about4.854 mw/nm and the response speed is about13.0 kHz.?2011 SPIE-OSA-IEEE