Four-channel 100-Gb/s per channel discrete multitone modulation using silicon photonic integrated circuits

The emerging applications for inter and intradata center communications demand low-cost and small-from-factor optical transceivers with 100G/400G capacity. Various techniques, such as wavelength-division multiplexing (WDM), multilevel pulse-amplitude modulation, and discrete multitone (DMT), are heavily investigated in this field. Among these techniques, DMT can offer 100G capacity with 10-20G optical devices using direct detection, which provides a very promising low-cost 100G/400G solution. In this paper, we report silicon photonic four-channel DMT integrated circuits, which demonstrate net channel rates of 70 and 100 Gb/s detected by integrated germanium receivers and commercial receivers, respectively. The silicon photonic chip integrates four silicon Mach-Zehnder modulators and WDM multiplexers using thermally tuned second-order microring filters. Besides the wavelength multiplexing functionality, we also demonstrate that these microrings can serve as vestigial sideband filters to enhance the transmission performance in 20-40 km ranges. These demonstrations indicate the promise of using low-cost and high-integrated silicon photonic circuits in high capacity 100G/400G applications.