An optical coupler includes at least one input waveguide and a plurality of output waveguides. The optical coupler spatially disperses optical signals carried on the input waveguide according to wavelength to the output waveguides. The input waveguides and the output waveguides are arranged to provide crosstalk between optical signals carried on the output waveguides.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
 This invention was made with government support under contract DE-AR0000274 awarded by ARPA-E (Advanced Research Projects Agency-Energy). The government has certain rights in the invention.