Crosstalk and BER performance of closely-spaced silicon-on-insulator waveguide arrays

The high interest for on-chip communications is driven by the possibility to exchange massive amounts of data between different resources (CPUs, GPUs, memories) directly on a system-on-chip. Optical on-chip transmission techniques promise to enhance bandwidth density and transmission reach compared to current electronic solutions. In this context, mode division multiplexing in integrated optical waveguides has been investigated, but it still suffers from crosstalk and scalability issues. To overcome these problems, super-modes in arrays of closely-spaced waveguides can be exploited, supporting many parallel channels with low crosstalk. In this paper we consider non-uniform arrays of closely-spaced waveguides in silicon photonics, and experimentally assess the spectral and BER performance of several array designs. Results demonstrate parallel data transmissions at 10 Gb/s over different waveguides with crosstalk <-16 dB and a power penalty <1 dB at BER =1e-9, paving the way for ultra-dense and low-crosstalk on-chip communications.