Migration steps toward flexi-grid networks

It is widely acknowledged by operators and market analysts from all parts of the telecommunications industry that bandwidth demand is increasing dramatically, year by year. This traffic growth highly impacts on all network segments and pushes network operators to consider new networking solutions. Flexi-grid technologies enable more flexible use of the spectral resources, increasing the overall network spectral efficiency. However, the currently deployed fixed-grid dense wavelength division multiplexing (DWDM) optical infrastructure might be replaced with new components to enable this technology. This paper first identifies a realistic expectation of modulation formats for the next 10 years and quantifies the possible capacity gains. Second, we study when the capacity will be exhausted using current fixed-grid optical channel assignment, and compare this with a pack of novel evolution strategies toward flexi-grid. Results show that the capacity will be exhausted by 2019 in the Spanish core network, and that by applying the flexi-grid evolutionary model, the network life can be extended up to five years. A shorter-term rationale to migrate to flexi-grid is the availability of cost-effective 400 Gbps and 1 Tbps transmission.