Obstacle evasion in free-space optical communications utilizing Airy beams

A high speed free-space optical communication system capable of self-bending signal transmission around line-of-sight obstacles is proposed and demonstrated. Airy beams are generated and controlled to achieve different propagating trajectories, and the signal transmission characteristics of these beams around the obstacle are investigated. Our results confirm that, by optimising their ballistic trajectories, Airy beams are able to bypass obstacles with more signal energy and thus improve the communication performance compared with normal Gaussian beams.Comment: 8 pages, 4 figure

The influence of preincubation time of prepared sperm before IVF on fertilization, embryo developmental competence and the reproductive outcomes

Objectives: It has been provided that if incubation time of prepared sperm can affect sperm motility and DNA fragment, but little is known about the influence of sperm preincubation time (SI) on the sperm’s fertilizing ability, subsequent embryonic development and pregnancy outcomes in in vitro fertilization (IVF). The aim of this study was to explore the association of SI with fertilization rate, embryo development and clinical outcomes in IVF, further, to find an optimal preincubation time for prepared sperm before insemination in IVF. Material and methods: This retrospective cohort study included a total of 1453 infertile couples undergoing IVF in our center performed from January 2016 to January 2019. Sperm were preincubated at 37℃ 6% CO2 for different times before insemination. Preincubation time associated with fertilization rate (FR), 2PN rate, D3 good quality embryo rate, fresh embryo implantation rate (IR), blastocyst formation rate, cumulative pregnancy rate (CPR), cumulative ongoing pregnancy rate (COPR), cumulative live birth rate (CLBR), newborn health and gender ratio were analyzed by chi-square analysis. Results: FR and 2PN rate of SI more than four hours SI groups (> 4 h SI group) decreased significantly compared with other SI groups (p < 0.01). There were no significant differences of the D3 high quality embryo rate among five SI groups. The blastocyst formation rate of  > 4 h SI group was significantly lower than that of 2–3 h SI group (45.5% vs 56.1%, p < 0.05); and 1–2 h SI group also had significant difference with 2–3 h and 3–4 h SI group (48.9% vs 56.1% and 54.6%, p < 0.05). There were a significant decrease of fresh IR and CPR in ≤1 h SI group compared with 1–2 h SI group (19.6% vs. 38.0%, p < 0.05; 62.7% vs 73.7%, p < 0.05); ≤ 1 h SI group also have the lowest CLBR (45.6%), it had statistic differences with 1–2 SI group and 3–4 SI group (45.6% vs 63.2%, p < 0.01; 45.6% vs 61.2%, p < 0.05). Conclusions: The sperm preincubated time at 37℃ 6% CO2 before insemination could influence sperm fertilizing ability, blastocyst formation, embryo implantation and CLBR in IVF cycles. The best time for prepared sperm preincubation at 37℃ is one to four hours before insemination in IVF

Orbital-angular-momentum mode-group multiplexed transmission over a graded-index ring-core fiber based on receive diversity and maximal ratio combining

An orbital-angular-momentum (OAM) mode-group multiplexing (MGM) scheme using high-order mode groups (MGs) in a graded-index ring-core fiber (GIRCF) is proposed, in which a receive-diversity architecture is designed for each MG to suppress the mode partition noise resulting from random intra-group mode crosstalk. The signal-to-noise ratio (SNR) of the received signals is further improved by a simple maximal ratio combining (MRC) technique on the receiver side to efficiently take advantage of the diversity gain of the receiver. Intensity-modulated direct-detection (IM-DD) systems transmitting three OAM mode groups with total 100-Gb/s discrete multi-tone (DMT) signals over a 1-km GIRCF and two OAM mode groups with total 40-Gb/s DMT signals over an 18.4-km GIRCF are experimentally demonstrated, respectively, to confirm the feasibility of our proposed OAM-MGM scheme

Scalable mode division multiplexed transmission over a 10-km ring-core fiber using high-order orbital angular momentum modes

We propose and demonstrate a scalable mode division multiplexing scheme based on orbital angular momentum modes in ring core fibers. In this scheme, the high-order mode groups of a ring core fiber are sufficiently de-coupled by the large differential effective refractive index so that multiple-input multiple-output (MIMO) equalization is only used for crosstalk equalization within each mode group. We design and fabricate a graded-index ring core fiber that supports 5 mode groups with low inter-mode-group coupling, small intra-mode-group differential group delay, and small group velocity dispersion slope over the C-band for the high-order mode groups. We implement a two-dimensional wavelength- and mode-division multiplexed transmission experiment involving 10 wavelengths and 2 mode groups each with 4 OAM modes, transmitting 32 GBaud Nyquist QPSK signals over all 80 channels. An aggregate capacity of 5.12 Tb/s and an overall spectral efficiency of 9 bit/s/Hz over 10 km are realized, only using modular 4x4 MIMO processing with 15 taps to recover signals from the intra-mode-group mode coupling. Given the fixed number of modes in each mode group and the low inter-mode-group coupling in ring core fibres, our scheme strikes a balance in the trade-off between system capacity and digital signal processing complexity, and therefore has good potential for capacity upscaling at an expense of only modularly increasing the number of mode-groups with fixed-size (4x4) MIMO blocks

Mode division multiplexing based on ring core optical fibers

The unique modal characteristics of ring core fibers (RCFs) potentially enable the implementation of mode-division multiplexing (MDM) schemes that can increase optical data transmission capacity with either low-complexity modular multi-input multi-output (MIMO) equalization or no MIMO equalization. This paper attempts to present a comprehensive review of recent research on the key aspects of RCF-based MDM transmission. Starting from fundamental fiber modal structures, a theoretical comparison between RCFs and conventional step-index and graded-index multi-mode fibers in terms of their MDM capacity and the associated MIMO complexity is given first as the underlining rationale behind RCF-MDM. This is followed by a discussion of RCF design considerations for achieving high-mode channel count and low crosstalk performances in either MIMO-free or modular MIMO transmission schemes. The principles and implementations of RCF mode (de-)multiplexing devices are discussed in detail, followed by RCF-based optical amplifiers culminating in MIMO-free or modular-MIMO RCF-MDM data transmission schemes. A discussion on further research directions is also given

Abundance of palynomorphs and dinoflagellate stratigraphy of ODP Hole 184-1148A, South China Sea

Dinoflagellate stratigraphy is described for the section from 364.75 to 843.85 meters below seafloor (mbsf) at Site 1148 (Sections 184-1148A-40X-1 through 76X-6 and 184-1148B-39X-CC through 56X-1) in the South China Sea. Two assemblage zones and two subzones are defined, based on characteristics of the assemblages and lowest/highest occurrences of some key species. These are the Cleistosphaeridium diversispinosum Assemblage Zone (Zone A; Oligocene), with the Enneadocysta pectiniformis Subzone (Subzone A-1) and the Cordosphaeridium gracile Subzone (Subzone A-2), and the Polysphaeridium zoharyi Assemblage Zone (Zone B; early Miocene). The highest concurrent occurrence of Enneadocysta arcuata, Eneadocysta multicornuta, Homotryblium plectilum, and Homotryblium tenuispinosum delineates the upper boundary of Zone A, which appears to mark a hiatus. Subzone A-1 is of early Oligocene age, as evidenced by the highest occurrences of E. pectiniformis and Phthanoperidinium amoenum at the upper boundary of the subzone. Subzone A-2 is of late Oligocene age based on the highest occurrences of C. gracile and Wetzeliella gochtii close to the upper boundary of the subzone and the occurrence of Distatodinium ellipticum and Membranophoridium aspinatum within the subzone. Zone B is dated as early Miocene based on the lowest occurrences of Cerebrocysta satchelliae, Hystrichosphaeropsis obscura, Melitasphaeridium choanophorum, Membranilarnacia? picena, and Tuberculodinium vancampoae within the zone. The present assemblage zones/subzones are correlative to various degrees with coeval zones/assemblages from areas of high to low latitudes in terms of common key species. We have compared the species content of the assemblage Zones A and B, and the subzones A-1 and A-2, with coeval assemblage(s)/zone(s) described from many, often widely distant, high- and low-latitude regions of the world. These comparisons show that, to various degrees and aside from a number of key species, the coordinated presence of certain important species may also help to assign an age to a given assemblage

Online Rapid Detection Method of Fertilizer Solution Information Based on Characteristic Frequency Response Features

Online rapid detection of a fertilizer solution’s type and concentration is crucial for intelligent water and fertilizer machines to realize intellectual precision variable fertilization. In this paper, a cylindrical capacitance sensor was designed based on the dielectric properties of the fertilizer solution, and an online rapid detection method of fertilizer type and concentration was proposed based on the characteristic frequency response mode. Three fertilizer solutions, potassium chloride, calcium superphosphate, and urea, were used as test objects. Ten concentrations of each fertilizer solution in the 10~100 g/L range were taken as the test fertilizer solution. Then, under the action of a series of sine wave excitation signals from 1 kHz to 10 MHz, the sensor’s amplitude-frequency/phase-frequency response data were obtained. The detection strategy of ‘first type, then concentration’ was adopted to realize rapid online detection of fertilizer type and concentration. Experimental results indicated that the maximum relative error of the sensor stability test was 0.72%, and the maximum error of concentration detection was 7.26%. Thus, the intelligent water and fertilizer machine can give feedback on the information of a fertilizer solution in real-time during the process of precise variable fertilization, thus improving the intelligence of water and fertilizer machines