Temperature dependence of the optical fiber cable parameters in subcarrier wave quantum communication systems

A common approach to establishing long-distance synchronization links in quantum communication (QC) systems is based on using optical signals transmitted in cables, where they decay and are distorted. It is necessary to evaluate the transformation of the signal parameters during propagation and their influence on the QC systems. We investigate the temperature dependence of the synchronization signal phase of a subcarrier wave quantum communication system (SCWQC) in optical fiber cables. A temperature model was created in order to determine the signal phase delay in the cable. We estimate the influence of daily temperature fluctuations on the phase delay in ground- and air-based cables. For systems operating with ground-based cables, they do not have any significant impact on the synchronization of the signal phase. However, for systems operating through air-based cables, phase adjustment is required every 158 ms for stable operation. This allowed us to optimize the parameters for a calibration procedure of a previously-developed SCWQC system, increasing the overall sifted key generation rate.