Time-Interleaving Enabled Co-propagation of QKD and Classical Channels over 100-km Fiber with 10-dBm Classical Launch Power

Abstract

The commercial success and wide deployment of quantum key distribution (QKD) technology depend on the integration of QKD links into existing fiber networks and sharing of the same fibers with classical data traffic. To mitigate the spontaneous Raman scattering (SpRS) noise from classical data channels, several strategies have been developed with their pros and cons, e.g., the placement of QKD in the O-band sacrifices the fiber loss and can rarely reach beyond 80 km; the attenuation of classical channels sacrifices the performance of classical channels. In this work, we developed a time-interleaving technique to enable the co-propagation of quantum and classical channels in the C-band without sacrificing either performance. By embedding QKD pulses in the gaps between classical data frames, we can isolate the quantum channel from Raman noise in both wavelength and time domains. We experimentally demonstrated the co-propagation of a polarization-encoding decoy-state BB84 QKD channel with a 100 Gb/s QPSK channel with 10-dBm launch power in the C-band over 100 km of fiber. Quantum bit error rate (QBER) of 1.12%, 2.04%, and 3.81% and secure key rates (SKR) of 39.5 kb/s, 6.35 kb/s, and 128 b/s are achieved after 20, 50, and 100 km fibers with the presence of 10-dBm classical launch power. The dispersion walk-off effect of SpRS noise is also experimentally investigated