Defragmentation of flexible dense wavelength division multiplexing (FDWDM) networks using wavelength tunability criterion

Flexible spectrum ROADMs facilitate networks to support channels operating at heterogeneous line rates by allocating spectral resources in a dynamic and flexible manner leading to better Spectral Efficiency. In a realistic network, traffic scenario is very dynamic in nature leading to continuous tear down of existing demands and set up of new demands. This dynamic tear down and set up process leads to fragmentation of the network, in terms of spectral resources, called “Spectral fragmentation” resulting in the blocking of new demands. Therefore, an optimization mechanism handling spectrum fragmentation, called “Spectrum Defragmentation”, is of vital importance in flexgrid optical networks. Defragmentation of the spectral resources can be obtained by either changing wavelength of the demand or route of the demand or both. This paper discusses a novel defragmentation algorithm considering only the wavelength tunability criterion and performs defragmentation by moving as minimal existing traffic demands as possible in order to support the new demand.