S-RMCSA: A Security-Aware Routing and Spectrum Assignment Framework with QKD and Physical-Layer Encryption in SDM-EONs

We present S-RMCSA, a new security-aware routing and spectrum assignment framework for space-division multiplexing elastic optical networks (SDM-EONs). Unlike traditional approaches that focus only on blocking and crosstalk, S-RMCSA integrates quantum key distribution (QKD) and physical-layer encryption directly into network resource allocation. Each traffic demand is assigned a security profile that decides whether a dedicated QKD lane is placed on an isolated fiber core and whether chaos masking or constellation twisting is applied for added protection. A multi-objective cost function balances crosstalk, fragmentation, encryption overhead, and survivability. Simulation results on the NSFNET with 7-core MCF links show that S-RMCSA lowers blocking probability by up to 29%, improves crosstalk margin by over 5 dB, and maintains QKD key rates above 10 kbps over 500 km. Importantly, it secures more than 97% of critical demands with minimal spectral overhead, enabling confidential and resilient next-generation optical networks.