Crosstalk Reduction in Hybrid Quantum-Classical Networks

In this paper, we propose and investigate several crosstalk reduction techniques for hybrid quantum-classical dense-wavelength-division-multiplexing systems. The transmission of intense classical signals alongside weak quantum ones on the same fiber introduces some crosstalk noise, mainly due to Raman scattering and nonideal channel isolation, that may severely affect the performance of quantum key distribution systems. We examine the conventional methods of suppressing this crosstalk noise, and enhance them by proposing an appropriate channel allocation method that reduces the background crosstalk effectively. Another approach proposed in this paper is the usage of orthogonal frequency division multiplexing, which offers efficient spectral and temporal filtering features.