Bidirectional tuning of microring-based silicon photonic transceivers for optimal energy efficiency

Abstract

Microring-based silicon photonic transceivers are promising to resolve the communication bottleneck of future high-performance computing systems. To rectify process variations in microring resonance wavelengths, thermal tuning is usually preferred over electrical tuning due to its preservation of extinction ratios and quality factors. However, the low energy efficiency of resistive thermal tuners results in nontrivial tuning cost and overall energy consumption of the transceiver. In this study, we propose a hybrid tuning strategy which involves both thermal and electrical tuning. Our strategy determines the tuning direction of each resonance wavelength with the goal of optimizing the transceiver energy efficiency without compromising signal integrity. Formulated as an integer programming problem and solved by a genetic algorithm, our tuning strategy yields 32%~53% savings of overall energy per bit for measured data of 5-channel transceivers at 5~10 Gb/s per channel, and up to 24% saving for synthetic data of 30-channel transceivers, generated based on the process variation models built upon measured data. We further investigated a polynomial-time approximation method which achieves over 100x speedup in tuning scheme computation, while still maintaining considerable energy-per-bit savings.