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Journal of Lightwave Technology

Availability-Aware Key Service With Dedicated Path Protection in Quantum Key Distribution Optical Networks

Bowen Chen, Bing He, Nianying Zheng, Hong Chen, Weidong Shao, Limei Peng, Pin‐Han Ho, Vimal Bhatia

Published Sep 5, 2025• 2 citations
Publisher

Abstract

Quantum key distribution (QKD)-based optical networks utilize quantum mechanics to secure communications by establishing secure, albeit expensive, quantum channels. A critical criterion for these QKD networks is to ensure network availability, which requires each service to adhere to a minimum unavailability constraint to maintain maximum network availability. This paper tackles the challenge of providing dedicated path protection for a select set of key services within QKD optical networks, adhering to specific unavailability constraints to ensure the gap between working and protection paths' unavailability remains within the allowable limit for each services. Considering the constraints of the limited timeslot resources and unavailability for the dedicated-path protection, we develop integer linear programming (ILP) models, to minimize the overall timeslot consumption in QKD optical networks. Additionally, we propose two novel algorithms for timeslot and availability management as minimum timeslot consumption (MTC) algorithm, and maximum availability (MA) algorithm to reduce the timeslot consumption. Simulations indicate that the ILP model based solution achieves the lowest timeslot consumption, however, it requires considerably more processing time compared to the proposed MTC and MA algorithms. Moreover, the MTC and MA algorithms outperform conventional dedicated-path protection (CDP) and fixed routing (FR) algorithms in reducing total timeslot consumption and improving average unavailability.

DOI
10.1109/jlt.2025.3606640

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Quantum key distribution (QKD)-based optical networks utilize quantum mechanics to secure communications by establishing secure, albeit expensive, quantum channels. A critical criterion for these QKD networks is to ensure network availability, which requires each service to adhere to a minimum unavailability constraint to maintain maximum network availability. This paper tackles the challenge of providing dedicated path protection for a select set of key services within QKD optical networks, adhering to specific unavailability constraints to ensure the gap between working and protection paths' unavailability remains within the allowable limit for each services. Considering the constraints of the limited timeslot resources and unavailability for the dedicated-path protection, we develop integer linear programming (ILP) models, to minimize the overall timeslot consumption in QKD optical networks. Additionally, we propose two novel algorithms for timeslot and availability management as minimum timeslot consumption (MTC) algorithm, and maximum availability (MA) algorithm to reduce the timeslot consumption. Simulations indicate that the ILP model based solution achieves the lowest timeslot consumption, however, it requires considerably more processing time compared to the proposed MTC and MA algorithms. Moreover, the MTC and MA algorithms outperform conventional dedicated-path protection (CDP) and fixed routing (FR) algorithms in reducing total timeslot consumption and improving average unavailability.
Quantum key distribution (QKD)-enabled optical networks utilize quantum mechanics to secure communications by establishing secure quantum channels. A critical criterion for QKD-enabled optical networks is ensuring network availability, which requires each quantum key service to adhere to a maximum unavailability constraint to maintain the network availability. This paper addresses the challenge of offering dedicated path protection for quantum key services in QKD-enabled optical networks. It ensures that the unavailability gap between the working and protection paths remains within the allowable limit for each quantum key service, adhering to specific unavailability constraints. Considering the constraints of the limited timeslot resources and network availability, we proposed quantum key service approach named a maximum availability (MA) algorithm. Simulation results indicate that the MA algorithm surpasses both the traditional dedicated-path protection (TDP) and fixed dedicated-path routing (FDR) algorithms in reducing total timeslot consumption and enhancing average availability.
Quantum key distribution (QKD) is considered a secure solution for key distribution and applied in optical networks to overcome security issues by providing key services in different lightpaths. In optical networks, lightpaths in fibers can be used for the delivery of QKD due to their good transmission performance. Accordingly, optical networks secured by QKD have been regarded as an important paradigm, and survivability in this paradigm is an issue worthy of study. In this paper, we focus on the protection schemes for key services in optical networks secured by QKD. Specifically, in consistency with two characteristics of key services (i.e., the key-updating process and key-volume adaptive routing), two key-volume adaptive protection schemes (i.e., dedicated protection and shared protection) are proposed for the networks against link failures. In such scenarios, the designed key-protection threshold can alleviate the tight network resources caused by the key-updating process. Simulation work has been conducted to evaluate the performance of the proposed schemes in terms of blocking probability, resource utilization, and proportion of secret-key consumption with different key-protection thresholds and update periods. Numerical results show that the two proposed schemes are effective in providing protection. Furthermore, evaluating the impact of protection on network security verifies a trade-off that exists between how much protection can be provided for key services versus the overall security of the network, given a certain resource budget.
In quantum key distribution (QKD) networks, the quantum service channel (QSCh) is highly sensitive to link failures, as any interruption in the quantum channel can immediately halt key generation, and hence the transmission of secured data across optical networks. Hence, robust protection mechanisms are essential to ensure continuous secure key distribution. However, conventional protection approaches, such as dedicated protection and fixed-path routing, often suffer from low resource efficiency and poor adaptability to heterogeneous relay environments. To ensure both survivability and efficient resource allocation in QKD based optical networks, we propose a shared path protection scheme based on hybrid relays. In the proposed approach, K-candidate paths are computed for both the traditional data channel (TDCh) and QSCh, and the working path is selected using a weighted metric that considers both the hop-count and the security degree. To enhance resilience, the shared protection paths are established, allowing multiple backup paths to reuse network resources for connection requests. A connection request is accepted only if both the working and the protection paths are successfully reserved, thereby ensuring strong protection. The system incorporates joint allocation of wavelength and time-slot, and introduces a protection threshold to support shared use of backup resources. Simulation results show that the proposed method achieves lower blocking probability, while maintaining high wavelength and time-slot efficiency compared to the baseline methods in different networks.
Growing practicality and deployment of optical quantum key distribution (QKD) has renewed interest in information-theoretic secure (ITS) key exchange for future communication networks. Providing ITS keys as a service over existing optical network infrastructures is feasible, however it poses significant challenges, particularly due to limited access to large-scale QKD testbeds and the need to ensure reliability under network failures. To address this gap, this work presents a discrete-event QKD optical network simulator designed to study ITS key-as-a-service provisioning under fiber link failure conditions. The simulator integrates survivability and resource management concepts inspired by wavelength-division multiplexed optical networks. Using this framework, the performance of a time-slot key-rate-aware shared path protection (TSKRA-SPP) scheduling algorithm is evaluated in terms of throughput, failure tolerance, and quality of service (QoS). TSKRA-SPP provides high failure tolerance while keeping resource consumption significantly low compared to baseline Shared Path Protection (SPP) algoirthm. The results validates the proposed simulation framework to be an effective tool for analyzing resilient ITS key provisioning in QKD-enabled optical networks.