I. Introduction
The explosive growth of Internet data traffic has been driving an accentuated ever increasing bandwidth demand of the communications systems backbones [1]. According to research conducted by Cisco Systems [2], the global Internet traffic will reach 1.6 zettabytes by 2018 with a growth of 21 percent from 2013 to 2018. This increase is due to applications such as online video, VoIP, online game, Digital TV, Mobile Email and social networking, which have distinct bandwidth demands. Recently, several studies [1], [3]–[7] have pointed out that it is possible to allocate spectrum resources in accordance with the required traffic demand. This new optical network architecture is commonly referred to as Elastic Optical Network (EON), SLICE network, Flexible-Grid Optical Network or Gridless Network.