  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 $\mu$m and the amorphous/crystalline local structure around the Er3+ ion is
evidenced.
