56 Gb/s NRZ O-band Hybrid BiCMOS-Silicon Photonics Receiver using Ge/Si Avalanche Photodiode

We report on hybrid BiCMOS-Silicon photonics receivers with waveguide coupled Ge/Si avalanche photodiodes, designed in a lateral separate charge absorption multiplication configuration. We demonstrate optical modulation amplitude sensitivities of −14.4 dBm for error-free operation at 50 Gb/s and −18.6 dBm under the KP4-FEC limit at 56 Gb/s using NRZ-OOK modulation. An in-depth analysis of the receiver sensitivity is carried out to understand the impact of dark current, and to identify pathways for further improvements. The demonstration of such highly sensitive receivers, supported with a receiver model, paves the way to improve optical link margins at 50 Gb/s and beyond.