Formula for two-carrier intermodulation distortion in wavelengthconverted subcarrier multiplexed signals via cross gain modulation

We present, for the first time to our knowledge, closed expression for the computation of the harmonic and intermodulation distortions that appear on a wavelength converted two-tone subcarrier modulation (SCM) signal via cross gain modulation     

New BIST Schemes for Structural Testing of Pipelined Analog to Digital Converters

Two alternative BIST schemes are proposed for structural testing of pipelined Analog-to-Digital Converters (ADC). They are oriented to fault detection in the converter stages rather than to measure the whole ADC electrical performance parameters. The operational principle of both strategies relies on testing every ADC stage reconfigured as an A/D-D/A block and applying as input a simple DC stimuli set which is easily obtained, without strong precision requirements, by a resistive network. The main differences between both strategies relate to the way the output response is evaluated. In the BIST#1 scheme, analog and digital outputs are compared with reference levels generated with a reference D/A converter and a counter. In the BIST#2 strategy, only digital outputs are available and they are compared with fault-free values previously stored in an on-chip register. The new techniques are intended to be used in pipelined converters of an arbitrary number of conversion stages and with a digital self-correction mechanism.     

ADC Non-Linearity Low-Cost Test Through a Simplified Double-Histogram Method

This paper introduces a method to reduce the requirements of the test sources for evaluating the non-linearity characteristics of Analogue-to-Digital converters. The method is based on a non-interleaved Double-Histogram test independent of the test signal waveform. It has been validated by simulation results in a 16-bit pipeline A/D converter and by an experimental example using the AD6644 commercial converter.     

Heterogeneous photocatalytic hydrogen generation in a solar pilot plant

Few studies have been published about large scale heterogeneous photocatalysis hydrogen generation with simultaneous removal of organic pollutants. The purpose of the present work was to study the simultaneous photocatalytic hydrogen production and organic pollutant removal under direct solar irradiation at pilot-plant scale. The experiments were performed in a Compound Parabolic Collector (CPC) at the Plataforma Solar de Almería (PSA). The efficiencies of two different photocatalytic systems, one based on a nitrogen doped and platinized TiO₂, and the other using a platinized CdS–ZnS composite were evaluated. Formic acid and glycerol were used as sacrificial electron donors. Also, experiments using real municipal wastewaters were carried out showing simultaneous hydrogen generation and partial water pollutant removal. The largest amounts of hydrogen were obtained with aqueous solutions of formic acid, although the experiments with real wastewater gave moderate amounts of hydrogen, pointing towards the possible future use of such waters for photocatalytic hydrogen generation.     

Generalized Bloch wave analysis for fiber and waveguide gratings

We have developed a generalized Bloch wave approach for the analysis of aperiodic gratings. This method yields both a macroscopic (i.e., reflection or transmission coefficient) as well as a microscopic (i.e., dispersion diagram and microstructure of the propagating internal field) characterization of fiber and waveguide aperiodic gratings     

Precise measurement of semiconductor laser chirp using effect ofpropagation in dispersive fiber and application to simulation oftransmission through fiber gratings

Measurements of small-signal intensity modulation from direct-modulated distributed feedback (DFB) semiconductor lasers after propagation in dispersive fiber have previously been used to extract intrinsic laser chirp parameters such as linewidth enhancement factor and crossover frequency. Here, we demonstrate that the simple rate equations do not satisfactorily account for the frequency response of real DFB lasers and describe some experimental techniques that conveniently determiner the precise laser chirp. Implications for simulation of high-speed lightwave systems are also considered     

10 Gbit/s transmission over 50 km nonzero dispersion-shifted fibreusing 1.3 μm directly modulated uncooled transmitters

A 1.3 μm uncooled transmitter with wide-open eye diagrams at laser temperatures of 20, 50, and 85°C is presented. Using this transmitter, it is demonstrated that 10 Gbit/s transmission is possible over a 50 km nonzero dispersion-shifted Lucent TrueWave-RS fibre. This result is compared with transmission over a 55 km standard singlemode fibre     

Environmental assessment of different photo-Fenton approaches for commercial reactive dye removal

An environmental study using life cycle assessment (LCA) has been applied to three bench-scale wastewater treatments for Cibacron Red FN-R hetero-bireactive dye removal: artificial light photo-Fenton process, solar driven photo-Fenton process and artificial light photo-Fenton process coupled to a biological treatment. The study is focused on electricity and chemicals consumption, transports and atmosphere and water emissions generated by the different processes involved. Results show that the artificial light photo-Fenton process is the worst treatment in terms of environmental impact. On the other hand, both solar driven and coupled to biological photo-Fenton processes reduce significantly the environmental damage, although none can be identified as the best in all impact categories. The major environmental impact is attributed to the H2O2 consumption and to the electrical energy consumption to run the UVA lamp. An economic analysis of the different photo-Fenton processes has also been performed and the results are discussed together with those obtained from the environmental assessment.     

Removal of organic contaminants in paper pulp effluents by AOPs: an economic study

The degradation of the organic content of a bleaching Kraft mill effluent was carried out using Advanced Oxidation Processes (AOPs). The study was focused on the identification of the AOP, or combination of AOPs, that showed the highest efficiency together with the lowest cost. Direct UV photolysis (UV), TiO₂ assisted‐photocatalysis (TiO₂/UV), Fenton, Fenton‐like, and photo‐Fenton reactions (Fe(II)/H₂O/UV), UV‐assisted ozonation (O₃/UV) and addition of Fe²⁺ and/or H₂O₂ to the TiO₂/UV and the O₃/UV systems, were used for the degradation of a conventional cellulose bleaching effluent. The effluent was characterized by the general parameters TOC, COD and color, and analyzed for chlorinated low molecular weight compounds using GC–MS. The costs of the systems per unit of TOC reduction were compared. Fenton, Fenton‐like and photo‐Fenton reactions achieved better levels of TOC degradation than photocatalysis and with lower cost's than photocatalytic treatments. Ozonation is an effective but rather expensive process. The use of UVA light, however, increased the effectiveness of ozonation with a significant decrease (>25%) in the operational cost. © 2002 Society of Chemical Industry