Oscillation Suppression of EO Response in Coherent Driver Modulator for Over 160 Gbaud Operation

We have developed a high-bandwidth coherent driver modulator (HB-CDM) with no oscillation in the electro-optic (EO) response and a 3-dB EO bandwidth exceeding 90-GHz. This can operate at over 160 Gbaud, making it the highest-bandwidth CDM ever reported. To achieve the smooth EO response of the HB-CDM, we adjusted the vertical spatial distance between the driver and the lid inside the package, which determines the cavity resonance frequency. We successfully suppressed EO oscillations by increasing the lid thickness and varying this distance, ensuring that the resonance frequency is above 100-GHz. At this frequency, the normalized EO response is below −20-dB, and the driver's \mu -factor is above 1. In addition, we demonstrated up to 168-Gbaud dual-polarization 16-QAM modulations by using the HB-CDM without EO oscillation.