Estudi sobre equalització electrònica per a sistemes de comunicació per fibra òptica

Estudi realitzat a partir d’una estada a Bell Labs (Lucent Technologies), New Jersey (Estats Units), entre el 15 de setembre de 2005 i el 15 de gener de 2006. Els sistemes de transmissió per fibra òptica fonamenten les principals xarxes de comunicacions. A mesura que la demanda d’ample de banda per usuari creixi, seran necessaris nous sistemes que siguin capaços de cobrir les necessitats a curt i llarg termini. La tecnologia dels sistemes òptics limita fortament la complexitat dels sistemes de transmissió / recepció en comparació, per exemple, als sistemes d’ones de ràdio. La tendència és la de dissenyar sistemes avançats amb detecció directa i mirar d’aplicar tècniques bàsiques de processat del senyal. Una d’aquestes tècniques és l’equalització electrònica, és a dir, fer ús de les tècniques de processament del senyal per tal de compensar la distorsió introduïda pel canal, deguda per una o diverses degradacions típiques: dispersió cromàtica, efectes no lineals, dispersió del mode de polarització (PMD) ... Dins d’un entorn comercial d’empresa, s’ha avaluat el funcionament dels sistemes d’equalització FFE-DFE aixi com MLSE en presència de dispersió cromàtica i/o dispersió del mode de polarització (PMD) en transmissions NRZ/RZ.

Anàlisi de Requeriments per un Model de Xarxa de Telecomunicacions amb aplicació des d'un Sistema d'Informació Geogràfica

La idea principal és crear un model d'una xarxa de telecomunicacions gestionable des d'un programari d'informació geogràfica (GIS). Es tracta de dissenyar una xarxa simple de fibra òptica similar a les que es fan per a la connexió directa de clients amb aquesta tecnologia.

A monolithic glass chip for active single-cell sorting based on mechanical phenotyping

The mechanical properties of biological cells have long been considered as inherent markers of biological function and disease. However, the screening and active sorting of heterogeneous populations based on serial single-cell mechanical measurements has not been demonstrated. Here we present a novel monolithic glass chip for combined fluorescence detection and mechanical phenotyping using an optical stretcher. A new design and manufacturing process, involving the bonding of two asymmetrically etched glass plates, combines exact optical fiber alignment, low laser damage threshold and high imaging quality with the possibility of several microfluidic inlet and outlet channels. We show the utility of such a custombuilt optical stretcher glass chip by measuring and sorting single cells in a heterogeneous population based on their different mechanical properties and verify sorting accuracy by simultaneous fluorescence detection. This offers new possibilities of exact characterization and sorting of small populations based on rheological properties for biological and biomedical applications.

Optical analysis of textured plastic substrates to be used in thin silicon solar cells

Light confinement strategies in thin-film silicon solar cells play a crucial role in the performance of the devices. In this work, the possible use of Ag-coated stamped polymers as reflectors to be used in n-i-p solar cells is studied. Different random roughnesses (nanometer and micrometer size) have been transferred on poly(methylmethacrylate) (PMMA) by hot embossing. Morphological and optical analyses of masters, stamped polymers and reflectors have been carried out evidencing a positive surface transference on the polymer and the viability of a further application in solar cells.

Avalanche dynamics of fiber bundle models

We present a detailed analytical and numerical study of the avalanche distributions of the continuous damage fiber bundle model CDFBM . Linearly elastic fibers undergo a series of partial failure events which give rise to a gradual degradation of their stiffness. We show that the model reproduces a wide range of mechanical behaviors. We find that macroscopic hardening and plastic responses are characterized by avalanche distributions, which exhibit an algebraic decay with exponents between 5/2 and 2 different from those observed in mean-field fiber bundle models. We also derive analytically the phase diagram of a family of CDFBM which covers a large variety of potential avalanche size distributions. Our results provide a unified view of the statistics of breaking avalanches in fiber bundle models

Design of surface forces apparatus for tribology studies combined with nonlinear optical spectroscopy

We describe the design, calibration, and performance of surface forces apparatus with the capability of illumination of the contact interface for spectroscopic investigation using optical techniques. The apparatus can be placed in the path of a Nd-YAG laser for studies of the linear response or the second harmonic and sum-frequency generation from a material confined between the two surfaces. In addition to the standard fringes of equal chromatic order technique, which we have digitized for accurate and fast analysis, the distance of separation can be measured with a fiber-optic interferometer during spectroscopic measurements (2 Å resolution and 10 ms response time). The sample approach is accomplished through application of a motor drive, piezoelectric actuator, or electromagnetic lever deflection for variable degrees of range, sensitivity, and response time. To demonstrate the operation of the instrument, the stepwise expulsion of discrete layers of octamethylcyclotetrasiloxane from the contact is shown. Lateral forces may also be studied by using piezoelectric bimorphs to induce and direct the motion of one surface.