8-λ × 50 Gbps/λ Heterogeneously Integrated Si-Ph DWDM Transmitter

We demonstrate a 3-D heterogeneously integrated dense wavelength-division multiplexing (DWDM) silicon-photonic transmitter simultaneously modulating eight 200-GHz spaced wavelengths at 50 Gbps/ $\lambda $ each, to deliver an aggregate per-fiber bandwidth of 400 Gbps. All necessary $O$ -band optical components are fully integrated on the photonic integrated circuit (PIC), including an eight-wavelength laser array, a broadband semiconductor optical amplifier (SOA), and eight microring modulators (MRMs). Eight 50-Gbps non-return-to-zero (NRZ) modulator drivers, capable of delivering 2- $\text{V}_{\mathrm {pp}}$ modulation voltage, are integrated in a 28-nm CMOS electronic IC (EIC). The EIC also includes a thermal control unit (TCU) to align the eight MRMs to the eight laser wavelengths by appropriately tuning integrated MRM heaters. The measured energy efficiency at 50 Gb/s of the high-speed electronics, including serializer overhead, is 1.17 pJ/bit.