Energy-efficient optical networks [Series Editorial]

The emerging trends of 2014 have continued to dominate the developments in the first half of 2015: 1. The packet optical transport system (P-OTS) concept supports the service provider goal to build a common network infrastructure by integrating Ethernet, IP/MPLS, and DWDM 2. There has been intensifying focus and attention on network functions virtualization (NFV) and software-defined networking (SDN) to provide service providers with the tools for more effective operation and management of communications networks in general, and optical communications networks in particular.