At present, modern society is facing a serious challenge in supporting the ever-increasing global energy consumption. Moreover, it is expected that the energy sustainability problem will be further complicated by rapidly growing energy demands in emerging economies, which currently represent about one half of the world''s population. Information and Communication Technology (ICT), which is empowered by high-speed networking and cloud computing, is thus extremely important in providing a key social infrastructure for universal energy efficiency. Network traffic is continuously growing at a rate of 40% per year, a growth rate which may become even higher due to emerging traffic demands, such as those required by machine-to-machine (M2M) communication. In order to accommodate the future traffic explosion, higher network capacity is needed, yet such a transmission capacity increase could also increase power consumption of key network equipment, such as high capacity routers. Consequently, in order to address energy challenges and realize a sustainable society that is friendly to humans and the earth, we have to resolve the urgent issue of network power consumption and achieve “Green of ICT”. Advanced photonics technology is considered to be highly promising for enabling energy efficient high-speed digital transmission over wide area networks, and various research works have been reported in this area. In this talk, key contributions of photonics technologies toward realizing green ICT are addressed. Power savings enabled by advanced photonics is categorized in three levels: (1) network level power savings, (2) equipment level power savings, and (3) device level power savings. At the network level, drastic power reduction is expected by optimizing a combination of electrical and optical switching in order to maximize IP off-loading at switching nodes. To maximize the number of optical cut-through paths that are by-passed from router traffic, flexibility - n optical path assignment is a key milestone, which was realized by colorless, directionless and contentionless (CDC) switching capability and advanced optical node functionality. Digital coherent is another key technology for flexible optical path assignment which enables highly adaptive and long distance transmission. Equipment level power savings can be realized by utilizing three technologies. The advance in CMOS LSI technology enables a significant power consumption reduction in large-scale digital signal processing inside optical modules. A network virtualization technology such as OpenFlow provides intensive use of hardware thus powered equipment can be minimized. Highly efficient equipment heat radiation technology is also important that will reduce power for cooling facility. For device level power savings, we present silicon photonics optical device technologies that enable an order of magnitude device size reduction for high capacity optical switches. Innovation using these photonics technologies is expected to take on a primal role in achieving an energy efficient system infrastructure which is indispensable for sustainable society that is friendly to humans and the earth.
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