Alternative routing and zone-based spectrum assignment algorithm for flexgrid optical networks

In optical flexgrid networks, the optical spectrum can be allocated at a much finer granularity than it can be in fixed-grid WDM networks and variable spectrum widths can be assigned to the lightpaths according to the transmission rates, leading to more efficient spectrum usage. However, the dynamic establishment and tear down of lightpaths yields to the fragmentation of the spectrum with increase in blocking of connections, mainly connections demanding large spectrum widths. This paper proposes a novel algorithm that introduces a zone-based assignment policy together with an alternative path routing mechanism based on the maximum capacity available. Results derived via simulation using different topologies and considering connections requests from 40Gbps to 1000Gbps, show that the proposed algorithm leads to blocking ratio consistently lower than those given by traditional approaches. It also reduces the blocking ratio of high rates connections, in some cases, by a factor of six.