Investigation of Nonlinear Effects on a Quantum Key Distribution System in DWDM Scenarios

Integrating quantum communication technologies, such as Quantum Key Distribution (QKD) into existing optical infrastructures is critical to improve their scalability, being a cornerstone of their practical implementations. Since installing optical fibers dedicated for QKD proves to be a costly solution, wavelength division multiplexing (WDM) appears to be a viable alternative. This paper investigates viable wavelength selections for the quantum channel in WDM systems. In this research, disturbances from nonlinear effects arising from conventional optical communications are introduced. Four-Wave Mixing (FWM) and Spontaneous Raman Scattering (SpRS) is modeled in various communication scenarios using OptiSystem and VPIphotonics modeling environments. Results from these simulations are evaluated, based on which guidelines are given for optical system design with QKD integration. Techniques for suppressing the noise components from the abovementioned nonlinear effects are proposed. In addition, the noise tolerance of a self-developed plug-and-play QKD architecture - implementing the BB84 protocol - was experimentally investigated to support the modeling.