The analysis of the efficiency of protecting methods against active optical probing attacks on the fiber quantum key distribution systems in the spectral range of 1260 – 1650 nm

In this paper, the results of research of spectral features of several passive fiber optic components are presented. There are spectra of isolators, circulators, spectral filters, and WDM, that are used in quantum key distribution (QKD) systems, and contribute to the protection of these systems against active optical probing attacks. We also provide an estimate of the degree of isolation required to protect the QKD system from Trojan-horse attacks. Based on the isolation requirements and measurement data we analyzed the efficiency of the QKD system protection through the use passive isolating components. As an example, we have shown the achievement of the required isolation level (150 dB) in the considered spectral range in the system presented in the article.