Time-Interleaved C-band Co-Propagation of Quantum and Classical Channels

Kavli Affiliate: Jing Wang

| First 5 Authors: , , , ,

| Summary:

A successful commercial deployment of quantum key distribution (QKD)
technologies requires integrating QKD links into existing fibers and sharing
the same fiber networks with classical data traffic. To mitigate the
spontaneous Raman scattering (SpRS) noise from classical data channels, several
quantum/classical coexistence strategies have been developed. O-band solutions
place the QKD channel in the O-band for lower SpRS noise but with the penalty
of higher fiber loss and can rarely reach beyond 80 km of fiber; another method
is C-band coexistence with attenuated classical channels, which sacrifices the
performance of classical channels for lower SpRS noise. In this work, a
time-interleaving technique is demonstrated 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,
the quantum channel is isolated from SpRS noise in both wavelength and time
domains. C-band co-propagation of a polarization-encoding decoy-state BB84 QKD
channel with a 100 Gb/s QPSK channel is experimentally demonstrated with
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 over 20, 50, and 100 km fibers,
respectively. These results were achieved with the presence of classical launch
power up to 10 dBm, which is at least one order of magnitude higher than
reported works. We also demonstrated the co-propagation of a QKD channel with
eight classical channels with total launch power up to 18-dBm (9-dBm per
channel), which is the highest power of classical channels reported in C-band
coexistence works.

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