Single Carrier 168-Gb/s Line-Rate PAM Direct Detection Transmission Using High-Speed Selector Power DAC for Optical Interconnects

We demonstrate the generation and detection of single-polarization 56-GBd PAM-8 and PAM-4 signals using intensity modulation and direct detection leveraging a novel high-speed high-output swing selector power DAC fabricated in an InP DHBT which does not require an external driver. Considering 7% overhead hard-decision forward error control, we validate our design by transmitting the 150 Gb/s net data rate signal based on PAM-8 over 2 km and 100 Gb/s signal based on PAM-4 over 4 km of standard single mode fiber without optical amplification. We complement the results by taking advantage of the high bandwidth of the selector power DAC to increase the PAM-4 symbol rate to 64 GBd and we compare it with the results at 56 GBd at constant information rate. We use the concept of mutual information to assess which Baud rate can achieve best sensitivity as a function of transmission distance.