Impact of Four-Wave-Mixing Noise from Dense Wavelength-Division-Multiplexing Systems on Entangled-State Continuous-Variable Quantum key Distribution
Shanna Du, Yan Tian, Yongmin Li
Abstract
Integrating quantum key distribution (QKD) on the existing optical fiber network through dense wavelength-division multiplexing (DWDM) can greatly reduce the costs of quantum channels and improve the scalability and flexibility of the quantum communication network. In the scenarios of an access network or local area network with a large number of users, the connected optical fibers are relatively short and the quantum signal can be adjacent to the classical channels. In this case, the four-wave-mixing noise generated by the classical lights will have a severe impact on the performance of the QKD. We establish a theoretical model to characterize the excess noise in continuous-variable QKD induced by the four-wave mixing, and experimentally demonstrate the validity of the theoretical predictions. In addition, the influence of cross-phase-modulation noise between the carrier of the quantum signal and classical data channels on the QKD is investigated. To suppress the effect of the four-wave-mixing noise, an unequal channel spacing technique is employed. We realize coexistence of entangled state-based continuous-variable QKD and five adjacent DWDM classical channels with 10 dBm launch power and nonreturn-to-zero on-off-keying modulation at 2.5 Gb/s (10 Gb/s).