Optical Networks
Optical networks provide fundamental support in today’s ICT sector as they carry the majority of global Internet traffic and other data communication services. Optical networks offer a number of benefits, such as huge bandwidth, low signal attenuation, and the most important very low energy consumption.
Low energy consumption characteristic is particularly useful in data centers, where network capacity demand increases rapidly and energy consumption needs to be controlled. As a result, over the last years, several optical network architectures dedicated to data centers were proposed. The majority of them use optical switches or other active optical devices. The recently proposed ones use passive optical elements (signal splitters, combiners, filters, de-multiplexers, or array waveguide gratings) to provide required connectivity, with no need of expensive optical switching and/or energy-demanding optical-electrical-optical signal conversion. Although the passive approaches provide several benefits (e.g. low infrastructure cost, extremely low energy consumption, and low latency), the number of interconnected nodes is restricted due to the limited number of spectrum resources (wavelengths). The challenge is how to optimally use the limited spectrum resources in order to increase the number of connected nodes. One approach is to group the nodes into multiple broadcast domains such that the spectrum resources are less wasted, or even can be reused within other domains.