Boris Nasedkin

We have studied the spectral characteristics of fiber-optical components in the ranges of 400-800 nm and 1500-2100 nm: different types of attenuators, isolators, circulators and wavelength-division multiplexing (WDM) filters were considered for both ranges. Our work has demonstrated that the spectral characteristics of isolators under test significantly depend on temperature, and their changes may result in vulnerabilities.

We have considered various approaches to measuring insertion losses by fiber-optic elements. As a result, we have demonstrated that WDM-filter losses do not add up when using a laser source for measurements. We also demonstrated that using a supercontinuum source leads to an underestimation of the insertion losses.

The security of quantum key distribution (QKD) systems is constantly being tested, and attacks that utilize probing pulses are have been widely developed recently. One of the most challenging methods is the Trojan-horse attack, which has been successfully demonstrated at 1924 nm. Moreover, the induced-photorefraction attack (IPA) represent attacks that will do better in the visible spectral range. We experimentally investigate the spectral properties of several conventional QKD components. We show that transmission of various fiber optical elements beyond telecommunication range should be taken into account during QKD system design and development due to the possibility for attacks realization.