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Impairment Aware Routing, Bit Loading, and Spectrum Allocation in Elastic Optical Networks

The exponential growth of Internet traffic due to bandwidth hungry applications has led to the design of spectrum efficient, flexible, and scalable elastic optical networks. The scope of high spectral-efficient modulation formats and optical orthogonal frequency-division multiplexing (OFDM) in coherent optical communication systems appears to be significant in catering to the heterogeneous bandwidth demands. Furthermore, OFDM enables each subcarrier to be modulated independently to enhance the spectrum efficiency known as bit loading in OFDM. On the other hand, spectral efficiency and the optical reach of a signal are limited by the transmission impairments such as shot noise, amplified spontaneous emission noise, beat noises due to coherent detection, crosstalk in cross-connect, nonlinear and filter narrowing effects, etc. In this paper, we propose a novel impairment-aware routing, bit loading, and spectrum allocation scheme through a mixed-integer linear programming optimization framework. Within our optimization framework, we ensure that a minimum end-to-end bit error rate for each demand is provisioned in the presence of impairments. We also propose a novel heuristic for realistic networks and compare the performance with existing schemes. Through simulation, we demonstrate the benefits of our approach in terms of achieving lower blocking probability and the spectral fragmentation compared to other existing studies.