iTRAN explores new concepts for multi-wavelength optical sources and integration of wavelength division multiplexing (WDM) transmitters for optical interconnects. This represents a completely different scenario from long-haul and metro fiber links because in optical interconnects, a higher level of photonic integration is required to keep power consumption, size and cost down. Both short-reach (up to ~10 m) and long-reach (up to ~ 2 km) coexist in the datacenter, and are subjects of research in iTRAN.
iTRAN explores multi-wavelength vertical-cavity surface-emitting laser (VCSEL) arrays with silicon photonics (SiPh) passive technology for short-reach interconnects. For long-reach interconnects, where aggregate capacities are at least an order-of-magnitude higher than in short-reach, iTRAN investigates the generation of optical frequency combs on chip that can simultaneously generate hundreds of precisely frequency-locked WDM channels. iTRAN also explores 3D integration of comb chips with SiPh active technology for advanced modulation and data encoding. In addition to including the wavelength dimension, iTRAN develops new higher-order-modulation formats (HOMs) and digital signal processing (DSP) techniques optimized for the target distances.