Abstract

The large modulation bandwidth, low switching voltage, low insertion loss, and well controlled chirp and linearity characteristics of lithium niobate electrooptic modulators make them the option of choice for many lightwave system applications. To optimize their performance, automatic biasing circuits are commonly used to account for slowly varying changes of the required bias voltage setpoint. Through continued improvements, the rate of bias drift has been significantly reduced so that today LiNbO₃ devices can operate continuously for thousands of hours and longer without requiring reset of the tracking circuit. Some applications, such as long-haul, high-speed, digital telecommunications, however, require reset-free durations 10 to 100 times longer. A demonstration that this stringent level of bias voltage stability is attainable has recently been reported [1]. Here, to facilitate further progress on the understanding and engineering of bias stability, we extend previous resistor-capacitor (RC) models of the device structure and use it to analyze bias stability data. We find compelling evidence that interfaces between materials play a significant role in determining the long term behavior.

© 1994 Optical Society of America