Site degenerate electronic defect states in oxide materials generally are stabilized against tunneling by electron-phonon coupling, forming small polarons. Their properties, especially optical absorption, are exemplified with a two-state system (SiO2 : E'1). Generalizations to more complicated systems are given (MgO : V-, SiO2 : [Al]°, etc.). The impact on applicational aspects, including radiation induced optical attenuation of glass fibers, is emphasized