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arXiv:1709.10046 · Optics Express

Integrating quantum key distribution with classical communications in backbone fiber network

Yingqiu Mao, Bi-Xiao Wang, Chunxu Zhao, Guangquan Wang, Ruichun Wang, Honghai Wang, Fei Zhou, Jimin Nie, Qing Chen, Yong Zhao, Qiang Zhang, Jun Zhang, Teng-Yun Chen, Jian-Wei Pan

Published Feb 27, 2018• 266 citations
arXivHTMLPDF

Abstract

Quantum key distribution (QKD) provides information-theoretic security based on the laws of quantum mechanics. The desire to reduce costs and increase robustness in real-world applications has motivated the study of coexistence between QKD and intense classical data traffic in a single fiber. Previous works on coexistence in metropolitan areas have used wavelength-division multiplexing, however, coexistence in backbone fiber networks remains a great experimental challenge, as Tbps data of up to 20 dBm optical power is transferred, and much more noise is generated for QKD. Here we present for the first time, to the best of our knowledge, the integration of QKD with a commercial backbone network of 3.6 Tbps classical data at 21 dBm launch power over 66 km fiber. With 20 GHz pass-band filtering and large effective core area fibers, real-time secure key rates can reach 4.5 kbps and 5.1 kbps for co-propagation and counter-propagation at the maximum launch power, respectively. This demonstrates feasibility and represents an important step towards building a quantum network that coexists with the current backbone fiber infrastructure of classical communications.

DOI
10.1364/oe.26.006010

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Quantum key distribution (QKD) provides information-theoretic security based on the laws of quantum mechanics. The desire to reduce costs and increase robustness in real-world applications has motivated the study of coexistence between QKD and intense classical data traffic in a single fiber. Previous works on coexistence in metropolitan areas have used wavelength-division multiplexing, however, coexistence in backbone fiber networks remains a great experimental challenge, as Tbps data of up to 20 dBm optical power is transferred, and much more noise is generated for QKD. Here we present for the first time, to the best of our knowledge, the integration of QKD with a commercial backbone network of 3.6 Tbps classical data at 21 dBm launch power over 66 km fiber. With 20 GHz pass-band filtering and large effective core area fibers, real-time secure key rates can reach 4.5 kbps and 5.1 kbps for co-propagation and counter-propagation at the maximum launch power, respectively. This demonstrates feasibility and represents an important step towards building a quantum network that coexists with the current backbone fiber infrastructure of classical communications.
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There is an increasing demand for multiplexing of quantum key distribution with optical communications in single fiber in consideration of high costs and practical applications in the metropolitan optical network. Here, we realize the integration of quantum key distribution and an optical transport network of 80 Gbps classical data at 15 dBm launch power over 50 km of the widely used standard (G.652 Recommendation of the International Telecom Union Telecom Standardization Sector) telecom fiber. A secure key rate of 11 Kbps over 20 km is obtained. By tolerating a high classical optical power up to 18 dBm of 160 Gbps classical data on single-mode fiber, our result shows the potential and tolerance of quantum key distribution being used in future large capacity transmission systems, such as metropolitan area networks and data centers. The quantum key distribution system is stable, practical, and insensitive to the polarization disturbance of channels by using a phase coding system based on a Faraday-Michelson interferometer. We also discuss the fundamental limit for quantum key distribution performance in the multiplexing environment.
The integration of quantum key distribution (QKD) with classical optical networks has emerged as a pivotal strategy for building secure communication infrastructures. However, achieving their coexistence in silica-core fibers faces inherent limitations due to nonlinear interference, particularly under high classical signal power. In this paper, we experimentally demonstrate the coexistence of classical optical transport networks and QKD over 101.6 km of hollow-core fiber (HCF) with classical power exceeding 20 dBm for the first time to the best of our knowledge. Through systematic theoretical analysis, we characterize HCF’s transmission loss and nonlinear noise generation mechanisms, revealing its unique compatibility with high-power classical–quantum coexistence compared to conventional fibers. To address spectral interference from HCF’s absorption peaks and nonlinear effects, we propose a spectrally optimized multi-stage allocation (SOMA) scheme that coordinates low-loss channel selection and noise suppression. Experimental validation shows that, under the SOMA scheme, coexisting classical signals achieve 19 dBm in single-wavelength configuration and 21 dBm in multi-wavelength configuration, while maintaining a secure key rate above 10 kbps. This breakthrough establishes HCF as a viable platform for simultaneous high-capacity classical communication and quantum-secured data transmission, overcoming critical power limitations of existing fiber-based coexistence systems.