Coherent Driver Modulator With Flexible Printed Circuit RF Interface for 128-Gbaud Operations

We developed a flexible printed circuit (FPC) RF interface InP-based high-bandwidth coherent driver modulator (CDM) for 128-Gbaud class operations. To increase the bandwidth of the CDM, an FPC RF interface was introduced to the CDM package, which significantly improved the roll-off frequency by about 40 GHz compared with a conventional package with a surface-mount-type RF interface. The FPC package has a 3-dB bandwidth of about 75 GHz and roll-off frequency above 110 GHz. These are the best characteristics among the CDM packages reported so far. By integrating a modulator with an electro-optic (EO) 3-dB bandwidth of >67 GHz and a driver IC with an electrical 3-dB bandwidth of >75 GHz in this package, the CDM had an EO 3-dB bandwidth of >72 GHz. This EO 3-dB bandwidth is sufficient for 128 Gbaud-class operations. Furthermore, we performed 128-Gbaud dual polarization 16QAM modulations and confirmed good back-to-back bit-error-rate characteristics.