Reliability of LiNbO3 based integrated optical waveguide devices for fiber communication systems

Increasing demands for LiNbO3 (LN) optical waveguide devices installed into submarine and terrestrial fiber communication systems necessitate that high quality and long-term reliability (over 20 years) be established. In addition to general requirements for reliability in electrooptical devices, the LN devices need to assure of the de-drift phenomena in the optical output signal. The de-drift is caused by the complex electrical nature of constituent device materials; ie. LN substrates and SiO2 buffer layers on LN. Results of theoretical and experimental investigations of the suppression of de-drift are applied to the design of practical LN devices, and the devices have been in service for 4 years, as of this moment, without any failure. Here, problems on the de-drift are discussed from the viewpoints of device reliability and actual fabrication processes.