RingO: an experimental WDM optical packet network for metro applications

This paper presents Ring Optical Network (RingO), a wavelength-division-multiplexing (WDM), ring-based, optical packet network suitable for a high-capacity metro environment. We present three alternative architectural designs and elaborate on the effectiveness of optic with respect to electronic technologies, trying to identify an optimal mix. We present the design and prototyping of a simple but efficient access control protocol, based upon the equivalence of the proposed network architecture with input-buffering packet switches. We discuss the problem of node allocation to WDM channels, which can be viewed as a particular optical network design problem. We, finally, briefly illustrate the fault protection properties of the RingO architecture. The main contribution of this paper is the identification and experimental validation of an innovative optical network architecture, which is feasible and cost effective with technologies available today, and can be a valid alternative to more consolidated solutions in metro applications.     

Analytical expressions of the guided mode field distribution:analysis and comparison

Methods for determining the parameters of the three different approximate solutions for the fundamental mode field distribution of Ti:LiNbO₃ optical waveguides by using the variational technique are presented. This analysis gives closer approximation not only to the field distribution, but also to the propagation constant. Comparison with the exact results for the exponential index distribution in depth shows that these trial functions are closer to the real solution. It is also shown that these solutions are as accurate as the effective index method for Ti:LiNbO₃ strip waveguides. The analysis provides an approach for comparing and assessing these solutions     

The random coded modulation: performance and euclidean distance spectrum evaluation

We apply the random coding argument to coded modulation. The well-known union bound on the error probability of general signaling schemes is revisited. The random coded modulation idea is introduced and a simple bound on the average performance of coded constellations is presented. A relationship between the union bound and the cut-off rate is exhibited by introducing the concept of N-dimensional partial cut-off rate. We define finite theta series for bounded finite-dimensional constellations and their related transfer functions. Bounds on the block and symbol error probability based on the transfer function are derived. The discussion is then focused on the squared Euclidean distance distribution. The evaluation of such parameters as its first two moments (average squared distance and squared distance variance) is considered by either finite theta series or transfer function of the bounded signal set. The Euclidean distance spectra of a few multidimensional coded modulation schemes based on square/cross constituent two-dimensional constellations are presented. Their respective partial cut-off rates are computed. We discuss the asymptotic behaviour and we show that almost all very long coded constellations are good (actually, they tend to become quasi-identical in a certain sense). Finally, we examine how to extend the initial union bound to Gallager-type bounds.     

Single‐Step Deposition of Au‐ and Pt‐Nanoparticle‐Functionalized Tungsten Oxide Nanoneedles Synthesized Via Aerosol‐Assisted CVD,and Used for Fabrication of Selective Gas Microsensor Arrays

Tungsten oxide nanostructures functionalized with gold or platinum NPs are synthesized and integrated, using a single‐step method via aerosol‐assisted chemical vapour deposition, onto micro‐electromechanical system (MEMS)‐based gas‐sensor platforms. This co‐deposition method is demonstrated to be an effective route to incorporate metal nanoparticles (NP) or combinations of metal NPs into nanostructured materials, resulting in an attractive way of tuning functionality in metal oxides (MOX). The results show variations in electronic and sensing properties of tungsten oxide according to the metal NPs introduced, which are used to discriminate effectively analytes (C₂H₅OH, H₂, and CO) that are present in proton‐exchange fuel cells. Improved sensing characteristics, in particular to H₂, are observed at 250 °C with Pt‐functionalized tungsten oxide films, whereas non‐functionalized tungsten oxide films show responses to low concentrations of CO at low temperatures. Differences in the sensing characteristics of these films are attributed to the different reactivities of metal NPs (Au and Pt), and to the degree of electronic interaction at the MOX/metal NP interface. The method presented in this work has advantages over other methods of integrating nanomaterials and devices, of having fewer processing steps, relatively low processing temperature, and no requirement for substrate pre‐treatment.     

Synthesis of heating patterns by interference of microwaves

Synthesis of heating patterns by interference of microwaves and time averaging of the resulting intensity fields is proposed as a novel approach to microwave heating. In the process multiple incident signals which are phase shifted relative to each other are fed into an applicator inside which they result in interference patterns. The position of the field patterns' peaks and troughs is changed via the relative phase difference between the incident signals. An overall mean pattern is the result of time averaging individually weighted patterns. Carbon composite blocks located inside a slotted waveguide are exposed to signals from two coherent magnetron based sources to demonstrate the idea. Their results clearly show that individual heating patterns are a function of relative phase difference between sources as predicted by theory and that only a small number of instantaneous patterns is necessary to realize the desired and predetermined mean distribution pattern. Although the topology is not applicator specific it is limited by the requirement of interference. This can be inhibited by excessive material losses.     

A novel gate geometry for the IGBT: the trench planar insulatedgate bipolar transistor (TPIGBT)

This letter demonstrates a simple way to improve the performance of a planar, fine lithography insulated gate bipolar transistor (IGBT), by incorporating a trench gate between the cathode cells. The results of this new trench-planar IGBT (TPIGBT) clearly demonstrate a significant reduction in the voltage drop without degrading the breakdown voltage. The switching analysis indicates that the TPIGBT represents a good trade-off between planar and trench structures. By separating the trench gate requirements away from the cathode cells, the technology development cycle and costs can be reduced. Furthermore, the reduced cell-width and the shallow trench presents TPIGBT as a cost-effective structure for high-voltage applications     

Epitaxial liftoff microcavities for 1.55-μm quantum-well spatiallight modulators

Microcavities operating at 1.55 μm have been realized according to the epitaxial liftoff (ELO) technique. The process is described and characterized. No significant variation of the optical properties of the grafted devices has been found. The technique is then applied to a spatial light modulator made by inserting a 3-μm multiple-quantum-well device in a short asymmetric Fabry-Perot microcavity. An enhancement by a factor 1000 of the performances of the switching component is obtained. The input diffraction efficiency reaches 2% in a degenerated four wave mixing configuration with a pulse energy of 1 μJ/cm² and without any applied electric field     

High-voltage CdSe-Ge TFT driver circuits for passive AC-TFELdisplays

Since an electroluminescent display (ELD) is a capacitive display driven at high voltage, it is necessary to fabricate high-voltage, large-current drivers. It is shown that a 20-μm complementary CdSe-Ge thin-film transistor technology can be used to integrate the high-voltage section of the drive circuits on the substrate of an ELD. The realized column driver levels a 15 V CMOS signal up to a modulation voltage of 50 V. A novel tristate row driver circuit, which is based on the symmetric character of the thin-film transistor, handles row selecting voltages of about 200 V together with current pulses of approximately 100 mA. In this paper, the design, simulation, and measurement of these circuits are described. Technology problems due to high voltages were solved