Elastic optical networks (EO-Net) represent a solution that allows multi-level elasticity in the deployment of optical resources. EO-Net considers the variation of the different parameters of an optical connection, such as symbol rate, modulation format, forward error correction (FEC) codes and spectrum assignment. Based on the flexibility of the optical connection parameters, the network can scale or lower resources according to the properties of the demands and allows the operators to deploy a more efficient network. Given the EO-Net architecture, the network does not need to be planned for peak traffic conditions, but ideally it can track the average traffic demands.
To allow elasticity characteristics, one of the first challenges is to provide flexibility in the management of spectrum resources. At present, the Wavelength Switched Optical Networks (WSON) architecture follows the standard ITU-T network specification that defines 50 GHz constant channel spacing. In order to allow flexibility in spectrum allocation, ITU-T also Defines an extended granularity in channel spacing up to 6.25 GHz. This represents the key point of so-called Flex network networks that are associated with the new Spectrum Switched Optical Networks (SSON) architecture. However, by increasing the granularity of the spectrum network, the operating complexity of such a network is also increased and this further determines requirements for the control plane running the SSON network. Proposed control plans that support flexible network networks are both expanding the currently implemented GMPLS and employing OpenFlow-based SDN solutions.
Optical networks are experiencing significant changes, driven by the exponential growth of traffic due to multimedia services and the greater uncertainty in predicting the sources of this traffic due to the ever-changing models of content providers over the Internet. The change has already begun: simple modulation of signals, which was suitable for bit rates up to 10 Gb / s, has resulted in much more sophisticated modulation schemes for 100 Gb / s and beyond. The next bottleneck is the 10-year division of the optical spectrum into a fixed "wavelength" grid, which will no longer function for 400 Gb / s and higher, announcing the need for a more flexible grid. Once the transceivers and switches become flexible, a new paradigm of elastic optical networks is born.