Wavelength Assignment in Hybrid Quantum-Classical Networks

TLDR

In DWDM systems integrating quantum and classical channels, weak QKD signals are often masked by background noise from intense classical signals. The study investigates optimal wavelength assignment in such DWDM systems to mitigate this masking and proposes near‑optimal methods that maximize the total secret key rate. The authors evaluate various DWDM configurations and crosstalk sources, proposing near‑optimal wavelength assignment strategies to maximize QKD secret key rates. Numerical simulations demonstrate that interspersed quantum and classical bands yield higher secret key rates, and the proposed assignment methods significantly outperform conventional schemes while also enabling more QKD users under key‑rate constraints.

Abstract

Optimal wavelength assignment in dense-wavelength-division-multiplexing (DWDM) systems that integrate both quantum and classical channels is studied. In such systems, weak quantum key distribution (QKD) signals travel alongside intense classical signals on the same fiber, where the former can be masked by the background noise induced by the latter. Here, we investigate how optimal wavelength assignment can mitigate this problem. We consider different DWDM structures and various sources of crosstalk and propose several near-optimal wavelength assignment methods that maximize the total secret key rate of the QKD channels. Our numerical results show that the optimum wavelength assignment pattern is commonly consisted of several interspersed quantum and classical bands. Using our proposed techniques, the total secret key rate of quantum channels can substantially be improved, as compared to conventional assignment methods, in the noise dominated regimes. Alternatively, we can maximize the number of QKD users supported under certain key rate constraints.