Predictive Modeling of Quasi-Static Electromagnetic Interference Effects on Electro-Optic Modulators

Electro-optic modulators (EOMs) are an interface between electrical and optical components, making them susceptible to external electromagnetic interference (EMI). In this article, we investigate the effects of low-frequency (similar to 15 MHz) EMI on lithium niobate (LiNbO3) EOMs. A predictive model for low-frequency EMI injection into a commercially available EOM is developed and validated experimentally. Specifically, analytical expressions for eye height and Q-factor are derived that predict the changes in the receiver end eye diagram, when the EOM modulation process is interrupted by the RF injection. The eye diagram gradually closes down as the RF injection power increases, owing to the signal degradation in the receiver end. A simple expression for calculating the maximum peak RF injected voltage that the EOM can tolerate prior to the system experiencing significant bit error rate is also presented. This model can be utilized to assess the survivability of EOMs under EMI.