Photonic technology is an important solution to achieve power-saving routers/switches for green networks. As networking is a worldwide matter, and as the power consumed by routers and switches is rapidly increasing, power-efficient green networks have become a subject of great interest. The main issue of green networking is relieving the increasing power consumption, and photonic technologies will be effective for such issue. Photonic technologies are low-power external input/output (I/O) port and internal interconnection subsystem, which contributes to reduce power consumption of routers and switches. For the external I/O port, 100-Gb Ethernet technologies, which use high-speed and low-power optical and electrical CMOS devices, will be described. Also, we describe the power-saving photonic technologies for interconnection subsystems for network equipments. This optical interconnection (optical backplane) technology also requires optical and electrical devices, which are compact in size, high speed, and operate at low power. This interconnection realizes a highly energy efficient router/switch with advanced network functions.