Fine-Tuning of Mach-Zehnder Phase Using Low-Resolution Digital-to-Analog Converters

We present a novel approach for achieving fine phase-tuning control of a Mach-Zehnder interferometer-based photonic switch. We demonstrate the concept in a fabricated silicon photonic switch containing dual thermo-optic phase tuners driven from identical monolithically integrated low-resolution digital-to-analog converters. The delivered resolution gains and additional power overheads of the demonstrated approach are assessed through experimental measurements. Using the approach, we show a resolution improvement of more than a factor of seven with only a 1.7% increase in power dissipation.