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Networks-on-chip (NoCs) can improve the communication bandwidth and power efficiency of multiprocessor systems-on-chip (MPSoC). However, traditional metallic interconnects consume significant amount of power to deliver even higher communication bandwidth required in the near future. Optical NoCs are based on optical interconnects and optical routers, and have significant bandwidth and power advantages. This paper proposed a high-performance low-power low-cost optical router, Cygnus, for optical NoCs. Cygnus is non-blocking and based on silicon microresonators. We compared Cygnus with other microresonator-based routers, and analyzed their power consumption, optical power insertion loss, and the number of microresonators used in detail. The results show that Cygnus has the lowest power consumption and losses, and requires the lowest number of microresonators. For example, Cygnus has 50% less power consumption, 51% less optical power insertion loss, and 20% less microresonators than the optimized traditional optical crossbar router. Comparing to a high-performance 45nm electronic router, Cygnus consumes 96% less power. Moreover, the passive routing feature of Cygnus guarantees that, while using dimension order routing algorithm, the maximum power consumption to route a packet through a network is a small constant number, regardless of the network size. For example, the maximum power consumption is 4.80fJ/bit under current technologies. We simulated and analyzed an 8 times 8 2D mesh NoC built from Cygnus and showed the end-to-end delay and network throughput under different offered loads and packet sizes.