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Wave Electronics and its Application in Information and Telecommunication Systems (WECONF)

Quantum Key Distribution Through a Multi-Core Optical Fiber

Alexander I. Zaitcev, O. V. Kolesnikov, T. V. Kazieva, L. N. Isaeva, К. Ерохин

Published May 29, 2023• 6 citations
Publisher

Abstract

The prospects of using multi-core fiber for constructing quantum networks have been analyzed. It has been shown that multi-core fiber has several advantages in implementing the technology of quantum key distribution among multiple groups of subscribers. Test experiments were conducted using scientific and educational complexes to simultaneously implement two quantum and real classical communication channels at speeds of 100 Mbps, 1 Gbps, and 10 Gbps through a single multi-core fiber. The possibility of simultaneous transmission of classical and quantum data through multi-core fiber using phase encoding has been demonstrated.

DOI
10.1109/weconf57201.2023.10147948

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The prospects of using multi-core fiber for constructing quantum networks have been analyzed. It has been shown that multi-core fiber has several advantages in implementing the technology of quantum key distribution among multiple groups of subscribers. Test experiments were conducted using scientific and educational complexes to simultaneously implement two quantum and real classical communication channels at speeds of 100 Mbps, 1 Gbps, and 10 Gbps through a single multi-core fiber. The possibility of simultaneous transmission of classical and quantum data through multi-core fiber using phase encoding has been demonstrated.
Today, it is not possible to abandon modern sources of information; with such rapid development of technology, we need to analyze large amounts of data. To a greater extent, applications that require speed and volume of transported information are responsible for the increase in transmitted data, such as streaming and cloud data processing services, as well as traffic transfer between data centers. The experimental part of the research involves several schemes for distributing a quantum channel inside a multi-core fiber, as well as different models for placing classical channels. To transmit the quantum channel, scientific and educational complexes developed by the Qrate company were used; the transmission of the quantum channel was implemented based on the BB84 protocol. The article analyzes experimental studies on the parallel transmission of three quantum channels in a multi-core optical fiber with satisfaction of the quantum bit error rate and key length, as well as a study of the influence of classical power on the transmission of a quantum channel along the adjacent core of the fiber under study. Such research provides a new direction for the development of microstructured fibers specifically for the needs of quantum communications.
Abstract In the contemporary era of information technology, cybersecurity has emerged as a pivotal subject. Quantum key distribution (QKD) networks have been implemented in various regions worldwide, demonstrating their superior secure communication capabilities in practice. The integration of QKD with traditional fiber optic networks will facilitate the deployment of upcoming quantum technologies. The recently proposed mode-pairing quantum key distribution (MP-QKD) protocol can drastically improve the transmission distance of QKD, thereby obviating the necessity for complex optical field setups. This paper focuses on the co-transmission of MP-QKD with classical signals in three types of optical fibers (single-mode fiber, few-mode fiber, and multi-core fiber). The Raman noise power in the co-transmission system is calculated, and the performance of MP-QKD is analyzed. The analytical results demonstrate the superiority of MP-QKD compared to other MDI-types in co-fiber transmission scenarios.
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.
There is an increasing demand for multiplexing of quantum key distribution with optical communications in a 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 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 center. The quantum key distribution system is stable and practical which is insensitive to the polarization disturbance of channels by using phase coding system based on Faraday-Michelson interferometer. We also discuss the fundamental limit for quantum key distribution performance in the multiplexing environment.
Quantum key distribution (QKD) coexisting with ultra-high-capacity classical optical signals over the same fiber is widely regarded as a cornerstone of future quantum-safe networks. This approach eliminates the need for dedicated fibers for QKD, significantly reducing infrastructure costs and facilitating large-scale deployment. As a promising foundation for next-generation high-capacity optical networks, multi-core fiber (MCF) opens new possibilities for such coexistence, offering an elegant and spectrum-efficient solution for the integration of quantum and classical channels. Here, we report the first field trial of QKD securely coexisting with bidirectional 106.7 Tb/s full-C-band dense wavelength-division-multiplexed coherent classical transmission over 25.2 km of installed standard-cladding diameter (125 μm) uncoupled-core four-core fiber in L'Aquila, Italy. Despite a classical launch power of 20 dBm per core, a secure key rate of 1.7 kb/s was achieved, using a commercial QKD system. We used the secure keys to achieve real-time encryption of up to 132 Gb/s live traffic within a 400 Gb/s channel, with key refresh intervals as short as 15 seconds. We used hardware encryption, introducing only 52 μs end-to-end latency and jitter below 4 μs compared to the unencrypted case. These results represent a major milestone toward practical, secure, and scalable integration of quantum and classical communication over deployed metropolitan multi-core fiber infrastructure.
We report a model to use to evaluate the performance of multiple quantum key distribution (QKD) channel transmission using spatial division multiplexing (SDM) in multicore (MCF) and few-mode fibers (FMF). This model is then used to analyze the feasibility of QKD transmission in 7-core MCFs in two practical scenarios involving the (1) transmission of only QKD channels and (2) simultaneous transmission of QKD and classical channels. In the first case, standard homogeneous MCFs enable transmission distances per core compatible with transmission parameters (distance and net key rate) very close to those of single-core single-mode fibers. For the second case, heterogeneous MCFs must be employed to make this option feasible.