A detailed theoretical and experimental study of buried ion-exchanged waveguides is reported. The model of the ion
concentration distribution in Ag<sup>+</sup>-Na<sup>+</sup> ion exchanged glass, which is analyzed by numerical calculations, agrees well with
our experiments showing that after the first ion-exchange, a half oval-shaped ion concentration distribution can be
obtained in the substrate; and after the second ion-exchange, the radio-shaped ion concentration distribution presents.
These results may be used to establish the necessary correlation between the ion-exchange process parameters and the