Long distance co-propagation of quantum key distribution and terabit classical optical data channels

TL;DR

This paper demonstrates the successful long-distance co-propagation of quantum key distribution and terabit classical optical data channels over 80km using wavelength filtering techniques, significantly increasing data capacity and reducing infrastructure costs.

Contribution

It introduces a spectral and temporal filtering method enabling long-distance multiplexing of QKD with high-capacity classical channels, surpassing previous data capacity limits.

Findings

Co-propagation achieved over 80km distance.

Data capacity increased by two orders of magnitude.

Feasibility of sharing backbone fibre links for QKD and classical data.

Abstract

Quantum key distribution (QKD) generates symmetric keys between two remote parties, and guarantees the keys not accessible to any third party. Wavelength division multiplexing (WDM) between QKD and classical optical communications by sharing the existing fibre optics infrastructure is highly desired in order to reduce the cost of QKD applications. However, quantum signals are extremely weak and thus easily affected by the spontaneous Raman scattering effect from intensive classical light. Here, by means of wavelength selecting and spectral and temporal filtering, we realize the multiplexing and long distance co-propagation of QKD and Terabit classical coherent optical communication system up to 80km. The data capacity is two orders of magnitude larger than the previous results. Our demonstration verifies the feasibility of QKD and classical communication to share the resources of backbone fibre links, and thus taking the utility of QKD a great step forward.