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IEEE Photonics Technology Letters

Crosstalk Impact on Continuous Variable Quantum Key Distribution in Multicore Fiber Transmission

Tobias A. Eriksson, Benjamin James Puttnam, Georg Rademacher, Ruben Soares Luis, Mikio Fujiwara, Masahiro Takeoka, Yoshinari Awaji, Masahide Sasaki, Naoya Wada

Published Feb 11, 2019• 33 citations
Publisher

Abstract

We investigate the excess noise induced by crosstalk in a trench-assisted homogeneous 19-core fiber for a continuous variable quantum key distribution (CV-QKD) receiver. Crosstalk is studied for both 30 wavelength division multiplexing channels of 24.5-Gbaud PM-16QAM with 100-GHz channel spacing and for an amplified spontaneous emission signal with 37.5-GHz bandwidth. We show that in-band crosstalk from neighboring cores prohibits secret key generation. However, it is possible to place CV-QKD channels at wavelengths not used by the classical channels even though wideband amplified spontaneous emission noise is present. The excess noise induced by crosstalk from a neighboring core is shown to be time-dependent.

DOI
10.1109/lpt.2019.2898458

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We investigate the excess noise induced by crosstalk in a trench-assisted homogeneous 19-core fiber for a continuous variable quantum key distribution (CV-QKD) receiver. Crosstalk is studied for both 30 wavelength division multiplexing channels of 24.5-Gbaud PM-16QAM with 100-GHz channel spacing and for an amplified spontaneous emission signal with 37.5-GHz bandwidth. We show that in-band crosstalk from neighboring cores prohibits secret key generation. However, it is possible to place CV-QKD channels at wavelengths not used by the classical channels even though wideband amplified spontaneous emission noise is present. The excess noise induced by crosstalk from a neighboring core is shown to be time-dependent.
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Joint Propagation of Continuous Variable Quantum Key Distribution and 18×24.518 \times 24.518×24.5 Gbaud PM-16QAM Channels
Continuous-variable quantum key distribution (CV-QKD) is a promising protocol that can be easily integrated with classical optical communication systems. However, in the case of quantum-classical co-transmissions, such as dense wavelength division multiplexing with classical channels and time division multiplexing with large-power classical signal, a quantum signal is more susceptible to crosstalk caused by a classical signal, leading to signal distortion and key distribution performance reduction. To address this issue, we propose a noise-suppression scheme based on carrier frequency switching (CFS) that can effectively mitigate the influence of large-power random noise on the weak coherent state. In this noise-suppression scheme, a minimum-value window of the channel's noise power spectrum is searched for and the transmission signal frequency spectrum shifts to the corresponding frequency to avoid large-power channel noise. A digital filter is also utilized to filter out most of the channel noise. Simulation results show that compared to the traditional fixed carrier frequency scheme, the proposed noise-suppression scheme can reduce the excess noise to 1.8%, and the secret key rate can be increased by 1.43 to 2.86 times at different distances. This noise-suppression scheme is expected to be applied in scenarios like quantum-classical co-transmission and multi-QKD co-transmission to provide noise-suppression solutions.