1. University of Bologna,DEI "Guglielmo Marconi",Bologna,Italy
2. University of Ferrara,Department of Engineering,Ferrara,Italy
3. University of Milano-Bicocca,Department of Physics,Milano,Italy
4. IEIIT-CNR,Torino,Italy
5. ICON Photonics,Champs-Sur-Marne,France
6. Le CNAM-ESYCOM-CNRS,Paris,France