Operation of a commercial fiber-based phase-encoding QKD system over multimode fiber links

Abstract We demonstrate the experimental feasibility of a commercially available fiber-based phase-encoding quantum key distribution system ViPNet QTS, operating over a communication link incorporating a multi-mode fiber (MMF) segment of up to 20 km. Since ViPNet QTS is designed for deployment in single-mode fiber (SMF) communication links, all experiments were conducted in an SMF-MMF-SMF configuration. We report systematic measurements of transmission losses, as well as secret key generation performance for different MMF link lengths. As a result, stable secret key generation was achieved at a rate of 1.75 kbit min −1 over MMF links of up to 20 km.