Glasses containing hyperpolarizable entities have a potential and scie
ntifical interest for their nonlinear optical properties. Within this
scope glasses of the Na2O-TiO2-P2O5 system have been investigated with
a high sensitivity absolute interferometric technique. The values of
the third order nonlinear susceptibilities will be discussed from the
structural point of view and by extension to glasses of the bond orbit
al theory of Lines [3].