Modulation-aware multipath routing and spectrum allocation in elastic optical networks

Elastic Optical Network (EON) or Flex-Grid network enables flexible assignment of spectral resources. With Orthogonal Frequency-Division Multiplexing (OFDM) technologies, the spectral resources for an end-to-end optical path can be allocated based on the modulation format and the optical reach in EON. The routing and spectrum allocation (RSA) algorithm in EON allocates enough sub-carriers along the spectrum path (SP) to satisfy the connection request. Due to the spectrum-continuity and sub-carrier consecutiveness constraints, an RSA algorithm may not have sufficient contiguous sub-carriers available along a single SP. Instead of using a single SP, in this paper, we propose a multipath RSA algorithm in EON called Modulation-aware Multipath Routing and Spectrum Allocation (MMRSA) algorithm in which the connection demands are satisfied using a minimum number of paths with distance adaptive modulation techniques. Simulation results demonstrate that the proposed MMRSA algorithm results in a lower blocking probability as compared to other existing multipath and single path RSA algorithms. Our study also shows that a combined usage of multipath routing and flexible distance-adaptive modulation techniques can reduce the blocking probability while consuming the number of sub-carriers similar to that of a single path routing algorithms.