Instead of piling on more laser wavelengths, the University of Washington uses microring modulators for coherent QAM, pushing a single wavelength to 320Gb/s at just 0.69pJ/b. RAMZI sidesteps MRM amplitude-phase coupling and time-multiplexed thermal tuning cuts the cost of thermal stability, delivering coherent, low-power and compact on low-cost 45nm silicon photonics.