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Journal of the Optical Society of America B

Multicore-fiber-based quantum-classical access network architecture with quantum signal wavelength-time division multiplexing

Chun Cai, Yongmei Sun, Jianing Niu, Peng Zhang, Yongrui Zhang, Yuefeng Ji

Published Feb 12, 2020• 8 citations
Publisher

Abstract

We propose a quantum-classical access network architecture based on multicore fiber to scale up the number of quantum key distribution (QKD) users. Quantum signals are integrated with classical signals in both feeder and drop fibers to save deployment cost since access networks are cost-sensitive. To increase the secure key rate (SKR) of QKD, we show that wavelength-time division multiplexing is suitable for quantum signals, which are required to support a large number of quantum users. Also, we propose a core and wavelength assignment scheme to alleviate spontaneous Raman scattering and intercore cross talk noise, which are the main impairment sources to QKD in this quantum-classical network. Finally, we experimentally show the performance of QKD in the proposed quantum-classical access network in terms of noise and channel loss. The experiment results are consistent with our analysis. The characteristics of the SKRs prove the superiority of wavelength-time division multiplexing. The properties of spontaneous Raman scattering in the feeder and drop fibers are shown in the experiments through the quantum bit error rates in different experimental conditions, which verifies the effectiveness of the proposed core and wavelength assignment scheme.

DOI
10.1364/josab.384344

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We propose a quantum-classical access network architecture based on multicore fiber to scale up the number of quantum key distribution (QKD) users. Quantum signals are integrated with classical signals in both feeder and drop fibers to save deployment cost since access networks are cost-sensitive. To increase the secure key rate (SKR) of QKD, we show that wavelength-time division multiplexing is suitable for quantum signals, which are required to support a large number of quantum users. Also, we propose a core and wavelength assignment scheme to alleviate spontaneous Raman scattering and intercore cross talk noise, which are the main impairment sources to QKD in this quantum-classical network. Finally, we experimentally show the performance of QKD in the proposed quantum-classical access network in terms of noise and channel loss. The experiment results are consistent with our analysis. The characteristics of the SKRs prove the superiority of wavelength-time division multiplexing. The properties of spontaneous Raman scattering in the feeder and drop fibers are shown in the experiments through the quantum bit error rates in different experimental conditions, which verifies the effectiveness of the proposed core and wavelength assignment scheme.
We propose a quantum access network based on multicore fiber (MCF) to scale up the number of users in quantum key distribution (QKD) networks. The MCF is used as feeder fiber and single core single mode fibers (SSMFs) are used as drop fibers. Quantum signals (QSs) are integrated with classical signals (CSs) in both MCF and SSMFs to save deployment cost since access networks are cost sensitive. Due to the integration, spontaneous Raman scattering (SRS) and intercore crosstalk (ICXT) are the main impairment sources to QKD. To alleviate the noise, we propose a core and wavelength assignment scheme (CWAS) that a dedicated core of MCF is used to transmit QSs and the wavelengths of QSs are set lower than those of upstream signals. Also, we demonstrate that wavelength time division multiplexing (WTDM) is suitable for QSs which are required to support large number of quantum users, since WTDM can realize higher secure key rate (SKR) than time division multiplexing (TDM) and require lower cost than wavelength division multiplexing (WDM). Finally, the proposed quantum access network is verified experimentally. The experiment results are consistent with our analysis. The properties of SRS in the proposed architecture are shown in the experiments through the quantum bit error rates (QBERs) in different experimental case, which verifies the superiority of the proposed CWAS. Also, the characteristics of the SKRs prove that the number of receivers has a great impact on the performance of QSs using WTDM.
We demonstrate quantum key distribution (QKD) with classical signals in a seven-core fiber using dense wavelength division multiplexing. Quantum signals are transmitted in an outer core separately and intercore crosstalk (IC-XT) is the main impairment of them. In order to alleviate IC-XT, we propose a quantum-classical interleave scheme. Then the properties of IC-XT are analyzed based on the measurement results, which indicate counter-propagation is a better co-existence method than co-propagation. Finally, we perform QKD experiments in the presence of two classical channels with a channel spacing of 100 GHz between quantum channel and the nearest classical channels. The experiment results prove counter-propagation almost immune to IC-XT, which is consistent with our analysis. Also, the feasibility of the transmission over the range of metropolitan area networks is validated with our scheme.
In this paper, we investigate measures to simultaneously improve the performance of classical and quantum key distribution systems in quantum access networks. First, we construct a multicore-fiber-based quantum access network architecture that supports simultaneous access to classical and quantum signals, and establish theoretical models of noise on classical and quantum channels. Secondly, a jointly optimized core wavelength allocation (JOCWA) scheme is proposed, which is applicable to multi-core fibers with any number of cores. Finally, simulation results show that the JOCWA scheme can improve the optical signal-to-noise ratio of the classical system by at least 20 dB, and can extend the secure transmission distance by about 35% compared with the benchmark scheme.
We demonstrate the realization of quantum key distribution (QKD) when combined with classical optical communication, and synchronous signals within a single optical fiber. In the experiment, the classical communication sources use Fabry-Pérot (FP) lasers, which are implemented extensively in optical access networks. To perform QKD, multistage band-stop filtering techniques are developed, and a wavelength-division multiplexing scheme is designed for the multi-longitudinal-mode FP lasers. We have managed to maintain sufficient isolation among the quantum channel, the synchronous channel and the classical channels to guarantee good QKD performance. Finally, the quantum bit error rate remains below a level of 2% across the entire practical application range. The proposed multiplexing scheme can ensure low classical light loss, and enables QKD over fiber lengths of up to 45 km simultaneously when the fibers are populated with bidirectional FP laser communications. Our demonstration paves the way for application of QKD to current optical access networks, where FP lasers are widely used by the end users.
To ensure the security of optical networks in the future, integrating quantum key distribution (QKD) with optical networks is one of the solutions. Moreover, the optical network based on multi-core fiber (MCF) is also one of the ways to improve the transmission capacity. Therefore, we study the integration of QKD into MCF-enabled optical networks. Aiming at the resource allocation problem of MCF-enabled wavelength division multiplexing optical networks, this paper proposes a resource allocation scheme which is suitable for independent-core-transmission of classical signals and quantum signals. For core resource, we propose the alternate core allocation algorithm. For wavelength resource, we propose the iteration-based wavelength allocation algorithm. The overall scheme uses the proposed two algorithms to first allocate the core and then allocate the wavelength. The simulation results show that the proposed scheme has a great improvement in secret key rate (SKR) compared with the benchmark scheme on the regular hexagonal 7-core fiber and 19-core fiber. And the proposed scheme still has good performance under long transmission distance and high classical signal power.
With 5G networks enabling high-speed, low-latency communication, future 6G and quantum communications will require even higher data rates and enhanced security. Integrating quantum-safe technologies with classical systems through cofiber transmission enables the reuse of existing fiber infrastructure via multiplexing—reducing deployment costs and avoiding redundant construction. This approach offers a sustainable and environmentally friendly pathway for network evolution, positioning it as a key breakthrough in the development of secure 6G architecture.By leveraging Dense Wavelength Division Multiplexing (DWDM) over Optical Transport Networks (OTN), the system establishes an efficient bidirectional coordination framework between quantum and classical channels. The architecture incorporates multi-stage amplification, dispersion compensation, and an advanced optical-domain processing mechanism based on a "split-amplifycombine" scheme for quantum pulses. These features preserve signal integrity for both quantum and classical data while mitigating nonlinear effects. Additionally, the design includes a dual-mode key management system that meets the stringent requirements of 6G for high-speed responsiveness and large-scale concurrent quantum key distribution (QKD) through the dynamic coordination of real-time key generation and pre-stored keys. Crucially, the study analyzes Raman scattering noise in co-fiber transmission and reveals the distinct impacts of forward and backward Raman scattering on communication performance. Simulation results demonstrate that backward Raman scattering causes significantly greater degradation in secure key rate (SKR) and quantum bit error rate (QBER) than forward Raman scattering as transmission distance increases. Notably, forward Raman scattering yields better quantum communication performance metrics under ultra-long-distance transmission conditions.