Investigating Raman backscattering decay and the perspective of time-multiplexed quantum communications

We have studied the temporal dynamics of Raman scattering caused by classical power in optical fiber and its impact on counter-propagating quantum signals. We investigated, on the entire telecom bands, the duration during which the quantum channel cannot be used in a time-division multiplexing context. Thereby, we estimated performance in terms of secure key rates within the framework of time-division multiplexing. By applying our model to the discrete variable quantum key distribution (DV-QKD) protocol BB84 in different optical communication contexts, we demonstrate the feasibility of counter-propagating time-multiplexing classical and quantum communications. Our results highlight a better preservation of the maximum communication distance for quantum channels compared to other multiplexing schemes.