SDN-enabled flexible CV-QKD for coexistence with programmable transceivers

Optical transport networks are evolving toward unprecedented capacity, sustainability, and security requirements. We present an SDN-enabled architecture for integrating continuous variable quantum key distribution (CV-QKD) into programmable optical networks, adopting sliceable bandwidth/bitrate variable transceivers (S-BVTs) and/or pluggable modules. The proposed solution combines a TeraFlowSDN-based SD-QKD network controller with a reconfigurable CV-QKD system through interfaces compliant with ETSI GS QKD 015. Experimental validation demonstrates real-time monitoring and dynamic wavelength (re)configuration, facilitating coexistence. Alternative dense wavelength-division multiplexing (DWDM) co-propagation scenarios are presented, and flexible channel allocation strategies are analyzed and discussed. Simulation results further evaluate evolutionary scenarios involving coexistence with 400G pluggable modules at 0 dBm launch power. The analysis identifies the maximum number of supported classical channels (up to 20 over a 20 km fiber link) and suitable spectral allocation in accordance with the experimental results. Furthermore, we compare the coexistence performance of CV-QKD adopting discrete components and an early version of a photonic integrated circuit (PIC) receiver, supporting half the number of 400G channels. Performance enhancement can be envisioned with further PIC design improvement and optimization. The obtained results confirm the viability of SDN-controlled CV-QKD as an enabler for quantum secure operation in future optical transport networks and a promising evolutionary path toward the adoption of this technology.