Analysis of the chromatic dispersion effect on the subcarrier wave QKD system

Abstract

In this paper we investigate the chromatic dispersion impact on the quantum key distribution system based on multi-mode weak coherent phase-coded states. We provide an asymptotic secure key rate estimation, taking into account error detection probability due to chromatic dispersion. We demonstrate numerically and experimentally that the effect of chromatic dispersion in an optical fiber without any compensation hinders the secret key distribution at a distance more than 53 km. Finally, we propose a modification to the considered quantum communication system in order to mitigate the influence of chromatic dispersion on its performance.

Heterodyne-based subcarrier wave quantum cryptography under the chromatic dispersion impact

“…The influence of chromatic dispersion on the DV-SCW system was investigated in [25]. There was shown that SCW QKD systems are prone to the influence of the chromatic dispersion.…”

“…One of the methods of mitigating the dispersion influence, proposed in [25], is to send only one half of the spectrum to the channel. In the case of QKD with coherent detection, one have to carry out classical heterodyning via spectral filter and beam splitter.…”

“…For the SMF-28e fiber that was also used in [25], β 1 = 4.8964 • 10 −6 s/km and β 2 = −2.0407 • 10 −23 s 2 /km. While such model is an analytical simplification, taking into account only two sidebands, in [25] it was extensively investigated in the context of its application to SCW QKD; the results were also compared with the results obtained by numeric solution of the nonlinear Schrodinger equation. Now let us write the simplified expressions for the electric fields considering the dispersion phase shifts:…”

“…However, this method is extremely prone to the chromatic dispersion, since in this case each sideband in the channel undergoes a different phase shift depending on the frequency. Its influence on SCW DV-QKD and possible ways to reduce the negative impact were examined in [25].…”

Plug&Play subcarrier wave quantum key distribution with deep modulation

“…It is a valid approximation if dispersion compensator is used on Alice's side. Otherwise the dispersion should be included into analysis at distances longer than 25 km [17].…”