Performance estimation of QKD-FSO system employing BB84 protocol

Quantum key distribution (QKD) has attracted significant attention in recent years due to its ability to provide unconditional security for conventional communication systems. In the present work, QKD over free space optical system (QKD-FSO) model has been analyzed considering BB84 protocol. The performance of the system has been evaluated in terms of quantum bit error rate (QBER) and key rate with respect to transmission range and propagation loss respectively considering the effect of Eve and quantum efficiency. QBER of received signal has been analyzed considering positive intrinsic negative (PIN), Avalanche photodiode (APD) and single photon detector (SPD) photodiodes. Higher transmission range of the order of 1000 m has been achieved using SPD as compared to other photodetectors. Lower QBER values have been observed with increase in DCR from 150 to 250 Hz as function of dead time in case of SPD photo detector.