Rearrangement: From wavelength routed to sliced-spectrum optical networks

Instead of the rigid frequency grid, optical networks are evolving toward a flexible and efficient use of the optical spectrum by slicing the spectrum in a series of frequency slots. The spectrum rearrangement consists in changing the spectral order of wavebands (group of frequency slots that must remain contiguous) while keeping the same distribution plan as specified by routing and spectrum assignment. The goal of spectrum rearrangement is to reduce spectral fragmentation and to maximize the bandwidth freedom to provision new lightpaths by privileging the contiguity of unused frequency slots, i.e. filling spectrum voids. Rearrangement in the described concept was first introduced by the authors for a wavelength-routed network to enhance the performance of a hierarchical structure of waveband granularities. In this paper, wavelength rearrangement is revisited all along with the newly introduced spectrum rearrangement in order to highlight on the benefit of approaching the problem from a global network view.