# Wavelength Assignment in Hybrid Quantum-Classical Networks. (arXiv:1701.08270v2 [quant-ph] UPDATED)

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.