Electrical Engineering Department, Sharif University of Technology, Tehran, Iran
School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
In this paper, we propose and investigate several crosstalk reduction techniques for hybrid quantum-classical densewavelength- 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 aect 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 eectively. Another approach proposed in this paper is the usage of orthogonal frequency division multiplexing, which oers ecient spectral and temporal filtering features.