**2. The roadmap toward elastic optical networks**

A number of different industry surveys indicate the global IP traffic is increasing at a startling rate i.e. more than 30% per year [17] and estimates that by 2025 the Internet will burn 7% of the 2010 global electricity supply [18]. This heralds the start of a huge wave of data driven mainly by broadcasting or multicasting, streaming of IPTV, high-quality videos using ultrahigh-definition (4 k \_ 8 k pixels) videos and rich media files that clients migrating to an all smart phones and tablets, enabling video to be consumed more conveniently stored in cloud architecture such as Microsoft Azure or Apple's iCloud via network connections anywhere, anytime.

To cope with this expected growth in traffic volume technological advances to date have allowed an increase in DWDM data rates to higher than 100 Gb/s per optical carrier, but these technologies will soon be close their practical or theoretical limits. To offset this growing trend and the consequences of unbridled demand,

research efforts are focused on the ways to improve the efficiency of these networks, often by leveraging photonic alternatives to provide improved performance [19]. The evolution of optical nodes and networks has been characterized by continuous enhancements in the parameters listed in **Figure 1**. These parameters are inter-dependent and their relative temporal evolution, combined with the related network economics, will dictate the exact network evolution, assuming maturity of the available technology. For an optical network to accommodate all the above requirements, it must transparently transmit, switch channels (e.g. wavelengths,

## **Figure 1.**

*Vision for a transparent reconfigurable optical network: it is the relative development of the each of five parameters with respect to time and that will dictate the network evolution.*

**Figure 2.** *Evolution in optical transmission technology [22].*
