Scalability of Silicon Photonic WDM Receivers for Low-Power Optical I/O

Optical input/output (I/O) must be carefully designed to scale up bandwidth of intra-data center electrical switches, while reducing energy consumption and cost. Innovative receiver architectures are key to achieving these goals. Both cascaded microring resonators (MRRs) and arrayed waveguide gratings (AWGs) can handle multiple wavelengths. For a fixed number of channels, wavelength de-interleavers can lower loss and crosstalk, and also yield more compact solutions. We present a comprehensive model to analyze six receiver architectures; we consider MRR vs. AWG, 1-stage or 2-stage de-interleaver vs. no de-interleaver. We target a 6.4 Tbps per-fiber bit rate and optimize receiver energy efficiency. We sweep combinations of data rate, channel count, and channel spacing. For each receiver under test simulation, we quantify energy consumption per bit and bandwidth density (compactness). Assuming non-return-to-zero (NRZ) modulation, we find that MRR-based receivers can achieve the 6.4 Tbps per fiber target with energy consumption at (or close to) sub-pJ/bit, while AWG-based receivers can only achieve up to 3.2 Tbps per fiber. The MRR-based receivers are generally more energy efficient and have a higher bandwidth density. Area bandwidth density up to 2.9 Tbps/$\text{mm}^{2}$ can be achieved by AWGs, and shoreline bandwidth density up to 21 Tbps/mm can be realized by MRRs. Finally, we review promising ways to further enhance the per-fiber bit rate and lower the energy consumption per bit.