Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1610.04475 · Physical Review A

Long-distance copropagation of quantum key distribution and terabit classical optical data channels

Liujun Wang, Kaiheng Zou, Wei Sun, Yingqiu Mao, Yixiao Zhu, Hua‐Lei Yin, Qing Chen, Yong Zhao, Fan Zhang, Teng‐Yun Chen, Jian-Wei Pan

Published Jan 3, 2017• 140 citations
arXivHTMLPDF

Abstract

Quantum key distribution (QKD) generates symmetric keys between two remote parties and guarantees the keys are not accessible to any third party. Wavelength-division multiplexing between QKD and classical optical communications by sharing the existing fiber-optics infrastructure is highly desired in order to reduce the cost of QKD applications. However, comparing to the light for classical transmission, quantum signals are very weak and easily affected by impairments from classical light, such as the spontaneous Raman-scattering effect. Here, by selecting an optimal wavelength of quantum signals, we significantly reduce the influence of the Raman-scattering effect. In addition, through coherent optical communication technology, we achieve high-speed classical data transmission with relatively low launch powers, thereby further reducing the impairments from classical light. As a result, we realize the multiplexing and long-distance copropagation of QKD and terabit classical data transmission up to 80 km. The data capacity is two orders of magnitude larger than the existing results. Our demonstration verifies the feasibility of QKD and classical communication to share the resources of backbone fiber links and thus taking the utility of QKD a great step forward.

DOI
10.1103/physreva.95.012301

Related papers

Long-distance transmission of quantum key distribution coexisting with classical optical communication over a weakly-coupled few-mode fiber

Bi-Xiao Wang, Yingqiu Mao, Lei Shen +10 more

Quantum key distribution (QKD) is one of the most practical applications in quantum information processing, which can generate information-theoretical secure keys between remote parties. With the help of the wavelength-division multiplexing technique, QKD has been integrated with the classical optical communication networks. The wavelength-division multiplexing can be further improved by the mode-wavelength dual multiplexing technique with few-mode fiber (FMF), which has additional modal isolation and large effective core area of mode, and particularly is practical in fabrication and splicing technology compared with the multi-core fiber. Here, we present for the first time a QKD implementation coexisting with classical optical communication over weakly-coupled FMF using all-fiber mode-selective couplers. The co-propagation of QKD with one 100 Gbps classical data channel at -2.60 dBm launched power is achieved over 86 km FMF with 1.3 kbps real-time secure key generation. Compared with single-mode fiber using wavelength-division multiplexing, given the same fiber-input power, the Raman noise in FMF using the mode-wavelength dual multiplexing is reduced by 86% in average. Our work implements an important approach to the integration between QKD and classical optical communication and previews the compatibility of quantum communications with the next-generation mode division multiplexing networks.

arXiv:2002.00420•Optics Express•Apr 6, 2020•54 citations

Integrating quantum key distribution with classical communications in backbone fiber network

Yingqiu Mao, Bi-Xiao Wang, Chunxu Zhao +11 more

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.

arXiv:1709.10046•Optics Express•Feb 27, 2018•266 citations

QUANTUM KEY DISTRIBUTION IN OPTICAL COMMUNICATION NETWORKS

Akabarsaheb Babulal Nadaf, RajeshKumar Rameshbhai Savaliya, Vinay Kumar Nassa +1 more

Background: Quantum Key Distribution (QKD( is a promising technology for secure communication, leveraging the principles of quantum mechanics to provide theoretically unbreakable encryption. With the exponential growth in data traffic and the increasing need for secure communication in backbone fiber networks, integrating high-bit-rate multiplexing techniques into QKD systems can enhance their efficiency and scalability. Problem: Traditional QKD systems face limitations in terms of data rate and network scalability, particularly in high-capacity optical communication networks. As data demands increase, there is a critical need for methods that can support high-bit-rate multiplexing while maintaining the security and performance of QKD. Method: This study proposes a novel QKD approach using high-bit-rate multiplexing in backbone fiber networks. The method involves encoding quantum keys using multiple optical channels simultaneously to increase the data throughput of the QKD system. We employ a combination of time-division multiplexing (TDM( and wavelength-division multiplexing (WDM( to optimize the use of fiber resources and enhance key distribution rates. Results: Simulation results demonstrate that the proposed method achieves a key distribution rate of 10 Mbps over a 200 km fiber link with a quantum bit error rate (QBER( of 1.5%. This represents a 50% improvement in key rate compared to conventional QKD systems without multiplexing. Additionally, the method shows enhanced scalability and network utilization, supporting up to 16 multiplexed channels with minimal impact on security.

ICTACT Journal on Communication Technology•Sep 1, 2024•0 citations

Quantum communications over optical fiber networks

Thomas E. Chapuran, Robert J. Runser, P. Toliver +13 more

Quantum communications is an emerging field with many promising applications. Its usefulness and range of applicability in optical fiber will depend strongly on the extent to which quantum channels can be reliably transported over transparent reconfigurable optical networks, rather than being limited to dedicated point-to-point links. This presents a number of challenges, particularly when single-photon quantum and much higher power classical optical signals are combined onto a single physical infrastructure to take advantage of telecom networks built to carry conventional traffic. In this paper, we report on experimental demonstrations of successful quantum key distribution (QKD) in this complex environment, and on measurements of physical-layer impairments, including Raman scattering from classical optical channels, which can limit QKD performance. We then extend the analysis using analytical models incorporating impairments, to investigate QKD performance while multiplexed with conventional data channels at other wavelengths. Finally, we discuss the implications of these results for evaluating the most promising domains of use for QKD in real-world optical networks.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Sep 11, 2007•3 citations

Coexistence of Continuous-Variable Quantum Key Distribution and Classical Data over 120 km Fiber

Adnan A. E. Hajomer, Ivan D. Derkach, Vladyslav C. Usenko +2 more

Integrating quantum key distribution (QKD) with classical data transmission over the same fiber is crucial for scalable quantum-secured communication. However, noise from classical channels limits QKD distance. We demonstrate the longest-distance continuous-variable QKD (CV-QKD) over 120 km (20 dB loss) in the asymptotic regime, and over 100 km (17 dB loss) in the finite-size regime, both coexisting with a fully populated coarse wavelength division multiplexing system. Natural mode filtering of the local oscillator and phase noise mitigation enabled this without additional filtering or wavelength reallocation. Benchmarking against a commercial discrete-variable QKD system and considering finite-size effects confirms the feasibility of CV-QKD as a plug-and-play solution for typical 80-100 km long-haul optical networks. Our results set a record fiber distance for CV-QKD, showing its potential for cost-effective, large-scale deployment in existing network infrastructure.

arXiv:2502.17388•Physical Review Letters•Sep 5, 2025•22 citations

Quantum and classical communications on shared infrastructure

Sima Bahrani, Osama Elmabrok, Guillermo Currás-Lorenzo +2 more

Future communications networks not only should enable massive exchange of classical bits, but also the transmission of quantum bits on which many quantum applications rely. This will be the key to offering quantum technologies in a cost-efficient way, and it should encompass the integration of quantum and classical networks at the core of existing optical communications networks, as well as at the access end of such networks. In this work, we cover a range of proposals that enable such an integration for one of the imminent applications of quantum technologies, i.e., quantum key distribution (QKD), by which users can securely exchange a secret key for their cryptographic needs. This will include using wavelength division multiplexing techniques to send quantum and classical data on the same fiber as well as wireless access for QKD users to passive optical networks. In each case, we explore optimal arrangements to find the best way forward for an amicable coexistence.

International Conference on Transparent Optical Networks•Jul 1, 2019•3 citations
Quantum key distribution (QKD) generates symmetric keys between two remote parties and guarantees the keys are not accessible to any third party. Wavelength-division multiplexing between QKD and classical optical communications by sharing the existing fiber-optics infrastructure is highly desired in order to reduce the cost of QKD applications. However, comparing to the light for classical transmission, quantum signals are very weak and easily affected by impairments from classical light, such as the spontaneous Raman-scattering effect. Here, by selecting an optimal wavelength of quantum signals, we significantly reduce the influence of the Raman-scattering effect. In addition, through coherent optical communication technology, we achieve high-speed classical data transmission with relatively low launch powers, thereby further reducing the impairments from classical light. As a result, we realize the multiplexing and long-distance copropagation of QKD and terabit classical data transmission up to 80 km. The data capacity is two orders of magnitude larger than the existing results. Our demonstration verifies the feasibility of QKD and classical communication to share the resources of backbone fiber links and thus taking the utility of QKD a great step forward.
Quantum key distribution (QKD) is one of the most practical applications in quantum information processing, which can generate information-theoretical secure keys between remote parties. With the help of the wavelength-division multiplexing technique, QKD has been integrated with the classical optical communication networks. The wavelength-division multiplexing can be further improved by the mode-wavelength dual multiplexing technique with few-mode fiber (FMF), which has additional modal isolation and large effective core area of mode, and particularly is practical in fabrication and splicing technology compared with the multi-core fiber. Here, we present for the first time a QKD implementation coexisting with classical optical communication over weakly-coupled FMF using all-fiber mode-selective couplers. The co-propagation of QKD with one 100 Gbps classical data channel at -2.60 dBm launched power is achieved over 86 km FMF with 1.3 kbps real-time secure key generation. Compared with single-mode fiber using wavelength-division multiplexing, given the same fiber-input power, the Raman noise in FMF using the mode-wavelength dual multiplexing is reduced by 86% in average. Our work implements an important approach to the integration between QKD and classical optical communication and previews the compatibility of quantum communications with the next-generation mode division multiplexing networks.
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.
Background: Quantum Key Distribution (QKD( is a promising technology for secure communication, leveraging the principles of quantum mechanics to provide theoretically unbreakable encryption. With the exponential growth in data traffic and the increasing need for secure communication in backbone fiber networks, integrating high-bit-rate multiplexing techniques into QKD systems can enhance their efficiency and scalability. Problem: Traditional QKD systems face limitations in terms of data rate and network scalability, particularly in high-capacity optical communication networks. As data demands increase, there is a critical need for methods that can support high-bit-rate multiplexing while maintaining the security and performance of QKD. Method: This study proposes a novel QKD approach using high-bit-rate multiplexing in backbone fiber networks. The method involves encoding quantum keys using multiple optical channels simultaneously to increase the data throughput of the QKD system. We employ a combination of time-division multiplexing (TDM( and wavelength-division multiplexing (WDM( to optimize the use of fiber resources and enhance key distribution rates. Results: Simulation results demonstrate that the proposed method achieves a key distribution rate of 10 Mbps over a 200 km fiber link with a quantum bit error rate (QBER( of 1.5%. This represents a 50% improvement in key rate compared to conventional QKD systems without multiplexing. Additionally, the method shows enhanced scalability and network utilization, supporting up to 16 multiplexed channels with minimal impact on security.
Quantum communications is an emerging field with many promising applications. Its usefulness and range of applicability in optical fiber will depend strongly on the extent to which quantum channels can be reliably transported over transparent reconfigurable optical networks, rather than being limited to dedicated point-to-point links. This presents a number of challenges, particularly when single-photon quantum and much higher power classical optical signals are combined onto a single physical infrastructure to take advantage of telecom networks built to carry conventional traffic. In this paper, we report on experimental demonstrations of successful quantum key distribution (QKD) in this complex environment, and on measurements of physical-layer impairments, including Raman scattering from classical optical channels, which can limit QKD performance. We then extend the analysis using analytical models incorporating impairments, to investigate QKD performance while multiplexed with conventional data channels at other wavelengths. Finally, we discuss the implications of these results for evaluating the most promising domains of use for QKD in real-world optical networks.
Integrating quantum key distribution (QKD) with classical data transmission over the same fiber is crucial for scalable quantum-secured communication. However, noise from classical channels limits QKD distance. We demonstrate the longest-distance continuous-variable QKD (CV-QKD) over 120 km (20 dB loss) in the asymptotic regime, and over 100 km (17 dB loss) in the finite-size regime, both coexisting with a fully populated coarse wavelength division multiplexing system. Natural mode filtering of the local oscillator and phase noise mitigation enabled this without additional filtering or wavelength reallocation. Benchmarking against a commercial discrete-variable QKD system and considering finite-size effects confirms the feasibility of CV-QKD as a plug-and-play solution for typical 80-100 km long-haul optical networks. Our results set a record fiber distance for CV-QKD, showing its potential for cost-effective, large-scale deployment in existing network infrastructure.
Future communications networks not only should enable massive exchange of classical bits, but also the transmission of quantum bits on which many quantum applications rely. This will be the key to offering quantum technologies in a cost-efficient way, and it should encompass the integration of quantum and classical networks at the core of existing optical communications networks, as well as at the access end of such networks. In this work, we cover a range of proposals that enable such an integration for one of the imminent applications of quantum technologies, i.e., quantum key distribution (QKD), by which users can securely exchange a secret key for their cryptographic needs. This will include using wavelength division multiplexing techniques to send quantum and classical data on the same fiber as well as wireless access for QKD users to passive optical networks. In each case, we explore optimal arrangements to find the best way forward for an amicable coexistence.