Damp Heat test on LiNbO optical modulators

A recent study [1] showed corrosion phenomena in LiNbO-based optical modula tors, used for external laser modulation in 10 Gbit systems, when tested (B ellcore 468) at 40 degreesC 95%RH under 10 V, 3 V and 0 V bias. Environment al conditions, typical of storage tests, were not too different from their operating level, while 10 V bias was roughly 3 times its standard value. Th e most straightforward interpretation of some residual contaminant introduc ed by a final polymeric passivation step was then evaluated by testing iden tical, nonpassivated devices. The occurrence of similar degradation even in that case moved the focus on Anodic Gold Corrosion as an intrinsic mechani sm of the technology under test, recalling similar phenomena occurred on Si devices some 20 years ago. On the other hand, the evidence for different r obustness vs. that mechanism for quite comparable devices from another supp ly points out the incomplete knowledge of the many factors that may switch or enhance the phenomenon. (C) 2001 Published by Elsevier Science Ltd.