Performance Analysis on Co-Existence of COW-QKD and Classical DWDM Channels Transmission in UK National Quantum Networks

To analyse and evaluate the physical layer performance of a U.K. national quantum network (UKQNtel) utilising COW-QKD, in O band, integrated with 500 Gb/s encrypted data, in C band, over 121 km between BT Labs and the University of Cambridge, a theoretical model encompassing COW-QKD and Raman scattering noise is developed and fitted with real-world experimental data. Different physical mechanisms underpinning the link performance are identified and discussed. The model developed in this work also provides a preliminary technical guidance for future UKQNtel upgrade and expansion, as well as potentially useful insights for quantum-secured networks design prior to practical deployment.