Source-linked AI summary
Ultra-high bandwidth quantum secured data transmission
James F. Dynes, Winci W-S. Tam, Alan Plews, Bernd Fröhlich, Andrew W. Sharpe, Marco Lucamarini, Zhiliang Yuan, Christian Radig, Andrew Straw, Tim Edwards, Andrew J. Shields
TL;DR
QKD has largely required dedicated dark fibres, and its coexistence with conventional data has lagged common network bandwidths. This paper multiplexes QKD with high-speed data on shared fibre, demonstrating 200 Gb/s encrypted transport and feasibility of 10 Tb/s data with QKD over links up to 50 km.
Problem
QKD deployment has often relied on dedicated dark fibres, while demonstrated coexistence with conventional data remained far below common fibre-network bandwidths.
Source: p. 2Method
The system uses wavelength-division multiplexing to combine QKD and DP-QPSK data channels on shared fibre, with forward traffic carried on one fibre.
Source: pp. 2, 4Results
10 Tb/s of data with QKD is feasible over fibre lengths up to 50 km, with a QKD key rate of 139 kb/s at 10 Tb/s.
Source: pp. 2, 10Takeaways & Limitations
The approach suits point-to-point links such as off-site backup or data-center interconnections, where homogenous traffic can share transmission hardware and launch power can be controlled.
Source: p. 10The experiment kept total optical power below 0 dBm so that nonlinear fibre effects were negligible.
Source: p. 9
Abstract
from arXiv · showhide
Quantum key distribution (QKD) provides an attractive means for securing communications in optical fibre networks. However, deployment of the technology has been hampered by the frequent need for dedicated dark fibres to segregate the very weak quantum signals from conventional traffic. Up until now the coexistence of QKD with data has been limited to bandwidths that are orders of magnitude below those commonly employed in fibre optic communication networks. Using an optimised wavelength divisional multiplexing scheme, we transport QKD and the prevalent 100 Gb/s data format in the forward direction over the same fibre for the first time. We show a full quantum encryption system operating with a bandwidth of 200 Gb/s over a 100 km fibre. Exploring the ultimate limits of the technology by experimental measurements of the Raman noise, we demonstrate it is feasible to combine QKD with 10 Tb/s of data over a 50 km link. These results suggest it will be possible to integrate QKD and other quantum photonic technologies into high bandwidth data communication infrastructures, thereby allowing their widespread deployment.
Methods
The system combines a phase-encoded BB84 QKD setup with 100G DP-QPSK AES encryptors, multiplexing quantum and classical traffic over shared fibre. QKD-generated keys replace the encryptors’ usual publically exchanged AES keys, while the 101 km data link maintained stable pre-FEC error rates below threshold.
Methods
- The QKD system uses phase-encoded BB84 with efficient basis selection and decoy states, transmitting 0.4-photon signal pulses and two decoy intensities.Asymmetric Mach-Zehnder interferometers perform phase encoding and decoding; an optical MHz clock signal provides synchronization over the same fibre.Source: Methods · p. 11
- Two 100G AES encryptor line cards use DP-QPSK transceivers, with a multiplexer combining their wavelengths before they are mixed with quantum traffic.The line cards include forward error correction.Source: Methods · p. 11
- At 101 km, the pre-FEC BER averaged 2.2 × 10-3 over two hours, nearly tenfold below the 1.9 × 10-2 FEC threshold.The QKD-generated keys were pushed to the high-speed encryptors and used for a symmetrically enabled AES link.Source: Methods · p. 12
- CWDM combines quantum and classical signals on a single forward-direction fibre, using 1530 nm and 1550 nm bands to accommodate DWDM channels.The experiments used 100 GHz and 25 GHz filters with insertion losses of 0.9 dB and 2 dB, respectively.Source: Methods · p. 12