Energy-efficient wavelength-division-multiplexing systems for the next generation optical transceivers

The rapid growth of data traffic in data centers and artificial intelligence (AI) applications require optical interconnect solutions that offer scalability, high bandwidth, and energy efficiency. Recent advancements in integrated silicon photonics, particularly electro-optic modulators and wavelength-selective components, have facilitated the integration of wavelength-division multiplexing (WDM) in optical transceivers. This approach significantly enhances data rates, energy efficiency, bandwidth density, scalability, and reach, essential for the expansion of parallel computing. This dissertation presents the design and experimental validation of monolithically integrated photonic-electronic systems used in WDM transceivers. These systems employ multi-wavelength optical carriers, ultra-low-power wavelength demultiplexers, and CMOS-compatible photonic receivers, enabling next-generation terabit-per-second (Tb/s) optical links. In the first part, a multi-wavelength, multi-port optical source is demonstrated by utilizing a high-efficiency soliton microcomb with a monolithically integrated demultiplexer using capacitive phase shifters that consume zero static power. This architecture achieves autonomous comb line tracking with an ultra-low energy consumption of 2.5–10 fJ/bit, significantly outperforming thermally tuned counterparts. The second part introduces a single-chip WDM optical receiver for PAM-4 modulation format. It integrates a 32-channel autonomous demultiplexer with 32 concurrent detectors, realizing energy efficiency (<0.38 pJ/bit) and 1.024 Tb/s aggregate data rate with sub-100 ps end-to-end latency, all without the need for equalization or DSP. Fabricated in the GlobalFoundries 45SPCLO CMOS-photonic process, this receiver achieves over an order-of-magnitude improvement in bandwidth density-energy efficiency product. The third part presents a monolithically integrated 1.024 Tb/s optical receiver for NRZ modulation format implemented on 45nm CMOS SOI, combining hybrid MZI-ring demultiplexers with capacitive phase shifters and on-chip tracking circuits. This system achieves 71 fJ/bit energy efficiency with BER < 10⁻¹², further advancing the scalability and efficiency of single-chip photonic-electronic interconnects. Finally, a summary highlights the innovations and their contributions to advancing optical interconnect technology. Future directions involve investigating new component technologies, enhancing scalability, integrating sources on-chip, and boosting reliability to enable more compact, energy-efficient, and higher-performing optical communication systems.