Characterization of a single-photon detector at 1.55 μm operated with an active hold-off technique for quantum key distribution

To better understand how the active hold-off technique in single-photon detectors (SPDs) based on InGaAs/InP avalanche photodiodes (APDs) enhances the performance of a quantum key distribution (QKD) system based on the BB84 protocol, we have evaluated the dependence of the raw key creation rate (Rraw) as well as the quantum bit error rate (QBER) on the number of active hold-off gates. The results of our analysis reveal that at 10 MHz repetition rate of the gate, by holding-off 200 gate pulses immediately following an avalanche event, the afterpulse contribution to the QBER drops down to 2.35% without noticeable decrease in the Rraw.