Extensive Comparisons of Optical Fast-OFDM and Conventional Optical OFDM for Local and Access Networks

A performance comparison between a recently proposed novel technique known as fast orthogonal frequency-division multiplexing (FOFDM) and conventional orthogonal frequency-division multiplexing (OFDM) is undertaken over unamplified, intensity-modulated, and direct-detected directly modulated laser-based optical signals. Key transceiver parameters, such as the maximum achievable transmission capacity and the digital-to-analog/analog-to-digital converter (DAC/ADC) effects are explored thoroughly. It is shown that, similarly to conventional OFDM, the least complex and bandwidth efficient FOFDM can support up to similar to 20 Gb/s over 500 m worst-case multimode fiber (MMF) links having 3 dB effective bandwidths of similar to 200 MHz X km. For compensation of the DAC/ADC roll-off, a power-loading (PL) algorithm is adopted, leading to an FOFDM system improvement of similar to 4 dB. FOFDM and conventional OFDM give similar optimum DAC/ADC parameters over 500 m worst-case MMF, while over 50 km single-mode fiber a maximum deviation of only similar to 1 dB in clipping ratio is observed due to the imperfect chromatic dispersion compensation caused by one-tap equalizers.

Nonlinear effects generation in suspended core chalcogenide fibre

In this work we report our achievements in the elaboration and optical characterizations of low-losses suspended core optical fibers elaborated from As2S3 glass. For preforms elaboration, alternatively to other processes like the stack and draw or extrusion, we use a process based on mechanical drilling. The drawing of these drilled performs into fibers allows reaching a suspended core geometry, in which a 2 μm diameter core is linked to the fiber clad region by three supporting struts. The different fibers that have been drawn show losses close to 0.9 dB/m at 1.55 μm. The suspended core waveguide geometry has also an efficient influence on the chromatic dispersion and allows its management. Indeed, the zero dispersion wavelength, which is around 5 μm in the bulk glass, is calculated to be shifted towards around 2μm in our suspended core fibers. In order to qualify their nonlinearity we have pumped them at 1.995 μm with the help of a fibered ns source. We have observed a strong non linear response with evidence of spontaneous Raman scattering and strong spectral broadening. © 2011 SPIE.

Analysis of the four wave mixing effect (FWM) in a dispersion decreasing fiber (DDF) for a WDM system

We did a numerical investigation of the propagation of short light pulses in the region of 1.55 mu m and the conversion efficiency (CE) for the four wave mixing generation (FWM) of ordinary and dispersion decreasing fibers for use in wavelength division multiplexing (WDM) systems, Our simulations studies three different profiles, linear, hyperbolic. and constant, One conclude that for all the profiles there is decrease of the conversion efficiency with the increase in the channel separation. The hyperbolic profile present a higher efficiency of around 1000 above in magnitude compared with the others profiles at 0.2 nm of channel separation. We calculate the conversion efficiency versus the fiber length for the three profiles. The conversion efficiency for the hyperbolic profile is higher when compared to the constant and linear profiles. The other interesting point of the hyperbolic profile is that the increase of the CE in the beginning of the fiber does not show my oscillation in the CE value (log eta), which was observed for the constant and linear profiles. For all the profiles there is an increase of the conversion efficiency with the increase of the pump power. The compression factor C-i for the generated FWM signal at omega(3) was measured along the DDF's and the constant profile fibers. One can conclude that with the use of decreasing dispersion profile (DDF) fibers one can have a control of the (CE) conversion efficiency and the compression factor of the four wave mixing (FWM) generation in WDM systems. (c) 2005 Elsevier B.V. All rights reserved.

Rheological Properties of a Sodium Bentonite and Lactose Aqueous Dispersion

Aim of this paper is show the viscosity measure of a sodium bentonite-water-lactose mixture and your rheological behaviour. This analysis showed the formation of tridimensional structure type and formation of stratified silicate/lactose, this occurred due to different concentrations of organic products into mixture and due to a difference of rotation during viscosity measument. Formation of networks is a consequence of the attraction between the silicate layers in water-lactose mixture. In the present work aqueous solutions of lactose with concentration of 7%, 5%, 3%, 1% and 0% (wt %) were used.

Dynamics and Heterogeneity of Pb(II) Binding by SiO2 Nanoparticles in an Aqueous Dispersion

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dispersion of Seeds of Tree Species by the Leaf-Cutting Ant Acromyrmex subterraneus molestans (Hymenoptera: Formicidae) in Vicosa, Minas Gerais State, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Selection of surfactant compounds to enhance the dispersion of Beauveria bassiana

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dispersion capacity of Triatoma sherlocki, Triatoma juazeirensis and laboratory-bred hybrids

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of carbon nanotube fillers dispersion on mechanical behavior of phenolic/carbon nanotube nanocomposite

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Numeric simulation of pollutant dispersion by a control-volume based on finite element method

The dispersion of pollutants in the environment is an issue of great interest as it directly affects air quality, mainly in large cities. Experimental and numerical tools have been used to predict the behavior of pollutant species dispersion in the atmosphere. A software has been developed based on the control-volume based on the finite element method in order to obtain two-dimensional simulations of Navier-Stokes equations and heat or mass transportation in regions with obstacles, varying position of the pollutant source. Numeric results of some applications were obtained and, whenever possible, compared with literature results showing satisfactory accordance. Copyright (C) 2010 John Wiley & Sons, Ltd.

The structure and optical dispersion of the refractive index of tellurite glass

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Chromatic stability of acrylic resins of artificial eyes submitted to accelerated aging and polishing

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Tissue Reaction to Silver Nanoparticles Dispersion as an Alternative Irrigating Solution

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Variance dispersion graphs for comparing blocked response surface designs

In this paper, we extend the use of the variance dispersion graph (VDG) to experiments in which the response surface (RS) design must be blocked. Through several examples we evaluate the prediction performances of RS designs in non-orthogonal block designs compared with the equivalent unblocked designs and orthogonally blocked designs. These examples illustrate that good prediction performance of designs in small blocks can be expected in practice. Most importantly, we show that the allocation of the treatment set to blocks can seriously affect the prediction properties of designs; thus, much care is needed in performing this allocation.

Cytogenetic characterization of Eurysternus caribaeus (Coleoptera: Scarabaeidae): evidence of sex-autosome fusion and diploid number reduction prior to species dispersion

Mitotic and meiotic chromosomes of several populations of Eurysternus caribaeus (Coleoptera: Scarabaeidae) were analysed through conventional staining, C-banding, base-specific fluorochromes, silver nitrate staining and fluorescent in situ hybridization (FISH). All specimens showed 2n = 8 in their karyotypes, with a neo-XY sex system (Y is a submetacentric and X a metacentric) and three pairs of submetacentric autosomes. The analysis of constitutive heterochromatin (CH) revealed small blocks located in the centromeric region of all chromosomes which do not present positive staining under the fluorochromes CMA3 and DAPI. Silver nitrate staining revealed that the nucleolar organizer region (NORs) is associated with the sex chromosomes. The FISH technique revealed that rDNA sites in the X and Y are different in size. Data from different populations indicate that the diploid number reduction (2n = 8) observed in E. caribaeus is established and presumably has preceded the dispersion of this species. Moreover, this reduction occasioned the translocation of rDNA sites to the sex chromosomes, X and Y, an uncommon pattern in Scarabaeidae that was observed for the first time by the FISH in this work.