The porous core layer deposited by modified chemical vapour deposition process has been analyzed in terms of thickness, pore size distribution, homogeneity and characteristics of the soot particles to investigate their variation with deposition temperature and input vapour composition. The compositions selected were SiO(2), SiO(2)-GeO(2) and SiO(2)-P(2)O(5). Rare earth ions were incorporated into the deposit by a solution doping technique. The analysis of deposited microstructures was found to provide a quantitative indication about the rare earth incorporation and its variation with respect to process conditions. Thus the characterization provides a method of controlling rare earth doping and ultimate preform/fiber properties.

No abstract

No abstract

The development of materials for optical signal processing represents a major issue in present technology. In this contribution we present a study on Er-doped fiber preforms where particular attention is devoted on how the addition of CaO in the glass modifies the local environment of the rare earth. The results from photoluminescence and Extended X-ray Absorption Fine Structure (EXAFS) are compared and a clear link between the width of the emission line at 1.5 µm and the amorphous/crystalline local structure around the Er3+ ion is evidenced.Keywords: Optic fibers; EXAFS; Erbium; Nanoparticles 1. Introduction Knowledge of the environment of rare earth ions in glasses is essential for the understanding of the spectral properties of these glasses and the design of new glass compositions for photonics applications. Among the rare earths, erbium is especially interesting because the 4I13/2 − 4I15/2 transition at ≈1.54 µm coincides with the lowest attenuation window of silica glass fiber; hence, erbium doped glasses can be used to amplify attenuated signals in optical fiber telecommunication systems. While Erbium-Doped Fiber Amplifier (EDFA) was developed 20 years ago, extensive studies are still carried out to improve its properties. In particular, linear dimensions should be reduced although the severe limitations imposed by the poor rare earth solubility into silica matrix. Moreover, spectral bandwidth should be increased to improve the Wavelength Division Multiplexing (WDM) applications. To solve these problems, various approaches have been proposed namely Er-Tm co-doping [1] or Er incorporation in nanoparticles (NP). However, to be compatible with optical waveguide applications, Rayleigh scattering must be kept at a minimum. For this purpose, Tick proposed that the particles size must be less than 15 nm with a narrow distribution size and high density [2]. There are reports on thin films containing semiconductor and metal nanoparticles acting as sensitizers, absorbing the incident light with a high crosssection and exciting erbium co-doped ions in the nanoparticle vicinity through energy transfer [3][4][5][6][7][8]. Here we propose for the first time to incorporate Er into oxide nanoparticles in optical fibers to improve the spectroscopic properties of erbium ions. To our knowledge only few studies on nano-structured silica fibers were dedicated to metal ions properties [9]. In our samples, oxide nano-structures are prepared by adjusting the composition of usual modifiers in the core of the fiber. A glass with an immiscibility gap is obtained and two phases are then formed with high and low silica content. The nanoparticles are preserved when the perform is drawn into a fiber. An effective method to study the incorporation of Er in a matrix is by Extended X-ray Absorption Fine Structure (EXAFS) [10] as this technique provides quantitative information on the geometry and chemical composition of the environment of the element under study. The Er site has been successfully studied by this technique in a var...

No abstract

No abstract

No abstract

No abstract