Coexistence of continuous variable QKD with intense DWDM classical channels

TL;DR

This paper experimentally demonstrates that continuous variable QKD can coexist with intense classical channels in DWDM networks, maintaining secure key rates over significant distances and power levels.

Contribution

It provides the first experimental validation of CV-QKD coexistence with high-power classical channels in DWDM networks, including channel optimization strategies.

Findings

CV-QKD tolerates classical channel power up to 11.5dBm over 25km

Positive key rate achieved at 75km with classical power of -3dBm and -9dBm

Simulation shows coexistence with 5 channel pairs in access networks

Abstract

We demonstrate experimentally the feasibility of continuous variable quantum key distribution (CV-QKD) in dense-wavelength-division multiplexing networks (DWDM), where QKD will typically have to coexist with several co- propagating (forward or backward) C-band classical channels whose launch power is around 0dBm. We have conducted experimental tests of the coexistence of CV-QKD multiplexed with an intense classical channel, for different input powers and different DWDM wavelengths. Over a 25km fiber, a CV-QKD operated over the 1530.12nm channel can tolerate the noise arising from up to 11.5dBm classical channel at 1550.12nm in forward direction (9.7dBm in backward). A positive key rate (0.49kb/s) can be obtained at 75km with classical channel power of respectively -3dBm and -9dBm in forward and backward. Based on these measurements, we have also simulated the excess noise and optimized channel allocation for the integration of CV-QKD in some access networks. We have, for example, shown that CV-QKD could coexist with 5 pairs of channels (with nominal input powers: 2dBm forward and 1dBm backward) over a 25km WDM-PON network. The obtained results demonstrate the outstanding capacity of CV-QKD to coexist with classical signals of realistic intensity in optical networks.