Network expansion strategy for elastic optical networks that considers channel capacity upgrades

We propose introducing aligned frequency assignment to each bandwidth channel, i.e., the semi-flexible grid, with the goal of minimizing frequency slot fragmentation under dynamic flexible-grid network expansion considering the expected need for channel capacity upgrades. In semi-flexible grid networks, for each set of channels having the same frequency bandwidth, a regular grid is defined where its spacing is the same as the required bandwidth and channels are aligned to their corresponding grids. A network expansion algorithm is developed that maximizes the efficiency of semi-flexible grid assignment to achieve efficient channel bandwidth upgrading. Numerical experiments prove that the number of fibers necessary and the degree of fragmentation in the frequency domain are reduced by 15% and 80%, respectively, compared to conventional flexible grid networks accommodating the same traffic.