A Compact Low-Power 320-Gb/s WDM Transmitter Based on Silicon Microrings

We demonstrate a compact and low-power wavelength-division multiplexing transmitter near a 1550-nm wavelength using silicon microrings. The transmitter is implemented on a silicon-on-insulator photonics platform with a compact footprint of 0.5
$\hbox{mm}^{2}$
. The transmitter incorporates 8 wavelength channels with 200-GHz spacing. Each channel achieved error-free operation at 40 Gb/s, resulting in an aggregated data transmission capability of 320 Gb/s. To our knowledge, this is the highest aggregated data rate demonstrated in silicon wavelength-division multiplexing transmitters. Owing to the small device capacitance and the efficient pn-junction modulator design, the transmitter achieves low energy-per-bit values of 36 fJ/bit under 2.4
${\rm V}_{\rm pp}$
drive and 144 fJ/bit under 4.8
${\rm V}_{\rm pp}$
drive. Comparisons are made to a commercial lithium niobate modulator in terms of bit-error-rate versus optical signal-to-noise ratio.