Benefits for Mixed-Line-Rate (MLR) and Elastic Networks Using Flexible Frequency Grids

Benefits of different channel grid configurations (ITU 50 GHz grid, 12.5 GHz grid, gridless) in a US network are analyzed for MLR/elastic networks, transparent network/network with high spectral efficiency, and for 2010/2020 traffic load scenarios. We show that elastic and MLR networks can achieve comparable performance levels using a 12.5 GHz grid. Introduction The continuously increasing capacity demand requires a highly efficient use of the available optical bandwidth of the fiber. Thus, alternatives to the ITU 50 GHz frequency grid for transmission of DWDM channels in an optical network are of great interest for increasing the transmitted information spectral efficiency (SE) and for reducing the cost per transmitted bit. Several concepts have been proposed: (1) use 1 of no fixed wavelength grid (gridless) and (2) 2,3 use of 12.5 GHz frequency slots (flex-grid) . The former one uses transmission of so called "superchannels" with highly variable sized 4 bandwidth allocation and the latter one allocates a variable number of contiguous frequency slots depending on the bit-rate for the requested traffic demand. In this paper, we analyze a 66-node USA core network equipped with bit-rate/reach adaptive (elastic) or fixed mixed-line-rate (MLR) transponders using different frequency grids in the limits of highest transparency and of highest spectral efficiency (SE) of the network. The paper is organized as follows: First we define the network model. Then we present and discuss the simulation results.