Co-propagation of CV-QKD and classical signals over DWDM-based 5G fronthaul optical networks

This study investigate the integration of discrete modulated coherent state (DMCS) continuous variable quantum key distribution (CV-QKD) with wavelength division multiplexing (WDM) in 5G fronthaul optical networks. Firstly, an architecture of quantum-classical co-propagation in C-band DWDM-based 5G fornthaul network is constructed and the wavelength assignment scheme for classical/quantum channels is designed. By assigning the quantum channels in band of low Raman scattering coefficient and setting the quantum-classical channel space to be 200 GHz, the proposed scheme can effectively reduce the spontaneous Raman scattering (SpRS) and four-wave-mixing (FWM) noise. Then, the secret key rate (SKR) of DMCS protocol and the excess noise induced by SpRS are analyzed theoretically to furtherly character the co-propagation architecture. Lastly, numerical simulation is carried out to evaluate the impact of SpRS noise on the CV-QKD performance. The simulation results show that by employing the proposed wavelength assignment scheme, the co-propagation system can support positive SKR at a maximum distance of approximately 41 km for 8 classical channels use and 30 km for 16 classical channels use, respectively. Our work can provide a reference for practical deployment of quantum secured 5G fronthaul optical networks.