Network-on-Chip or Network-on-a-Chip (NoC or NOC) is an approach to designing the communication subsystem between Semiconductor intellectual property core|IP cores in a System-on-a-Chip (SoC). NoCs can span synchronous and asynchronous clock domains or use unclocked asynchronous circuit|asynchronous logic. NoC applies Computer network|networking theory and methods to on-chip communication and brings notable improvements over conventional Computer bus|bus and Crossbar switch|crossbar interconnections. NoC improves the scalability of SoCs, and the power efficiency of complex SoCs compared to other designs. Research has been done on integrated optical waveguides and devices comprising an Optical Network-on-Chip (ONoC).