A double frequency overtone of the fundamental NH bond related vibration was found to dominate the optical loss in the 1.5–1.6 μm range in high index GeSiON-based planar waveguides deposited by plasma-enhanced chemical vapor deposition using hydrogen-based precursors. The fundamental NH bond-related absorption and its double frequency overtone were measured to be ∼560 cm-1 and 1.8 cm-1, respectively, resulting in their ratio of 310±10. The optical loss, extracted from analysis of the NH-related absorption is consistent with the directly measured optical loss in the waveguide structures. It was shown that using the deuterated precursors results in incorporation of ND bonds in the GeSiON films. The NH bond absorption band was eliminated in the deuterated films, leading to low optical losses in the communication band. © 2002 American Institute of Physics.