This paper reports the network operator point of view about the introduction of quantum key distribution (QKD) in optical networks to secure the data plane and/or specific applications, focusing on the design aspects that go beyond pure transmission. The functional architecture of a quantum key distribution network is depicted focusing on the integration in the existing telecommunications infrastructure. Some use cases of the utilization of the QKD layer, presenting results from in-field demonstrations, are reported together with a technology agnostic numerical model about resource sharing in a metropolitan area network environment.
This paper reports the network operator point of view about the introduction of quantum key distribution (QKD) in optical networks to secure the data plane and/or specific applications, focusing on the design aspects that go beyond pure transmission. The functional architecture of a quantum key distribution network is depicted focusing on the integration in the existing telecommunications infrastructure. Some use cases of the utilization of the QKD layer, presenting results from in-field demonstrations, are reported together with a technology agnostic numerical model about resource sharing in a metropolitan area network environment.
Increasing incidents of cyber attacks and evolution of quantum computing poses challenges to secure existing information and communication technologies infrastructure. In recent years, quantum key distribution (QKD) is being extensively researched, and is widely accepted as a promising technology to realize secure networks. Optical fiber networks carry a huge amount of information, and are widely deployed around the world in the backbone terrestrial, submarine, metro, and access networks. Thus, instead of using separate dark fibers for quantum communication, integration of QKD with the existing classical optical networks has been proposed as a cost-efficient solution, however, this integration introduces new research challenges. In this paper, we do a comprehensive survey of the state-of-the-art QKD secured optical networks, which is going to shape communication networks in the coming decades. We elucidate the methods and protocols used in QKD secured optical networks, and describe the process of key establishment. Various methods proposed in the literature to address the networking challenges in QKD secured optical networks, specifically, routing, wavelength and time-slot allocation (RWTA), resiliency, trusted repeater node (TRN) placement, QKD for multicast service, and quantum key recycling are described and compared in detail. This survey begins with the introduction to QKD and its advantages over conventional encryption methods. Thereafter, an overview of QKD is given including quantum bits, basic QKD system, QKD schemes and protocol families along with the detailed description of QKD process based on the Bennett and Brassard-84 (BB84) protocol as it is the most widely used QKD protocol in the literature. QKD system are also prone to some specific types of attacks, hence, we describe the types of quantum hacking attacks on the QKD system along with the methods used to prevent them. Subsequently, the process of point-to-point mechanism of QKD over an optical fiber link is described in detail using the BB84 protocol. Different architectures of QKD secured optical networks are described next. Finally, major findings from this comprehensive survey are summarized with highlighting open issues and challenges in QKD secured optical networks.
As a promising quantum application, Quantum Key Distribution (QKD) technology has been rapidly developed from point-to-point communication to a large-scale commercial network. However, considering the cost of QKD components and network infrastructure, building a QKD network is challenged by its expensive capital expenditure, which significantly hinders its future popularization. In this article, we envision an evolution roadmap consisting of three stages for the future development of QKD networks, aiming at achieving a fully integrated network architecture that combines QKD and telecommunications networks. Powered by several critical technologies, such as link multiplexing, miniaturized QKD, and transmission optimization, QKD is foreseen to be integrated into telecommunications networks as an add-on module that can be flexibly deployed. After that, we introduce the integrated network architecture design in detail, and respectively provide four QKD-related function implementations. At last, key technologies that should be concerned and further investigated are also discussed with performance evaluation, which can provide theoretical guidance for both industries and academia. Based on the proposed roadmap and integrated architecture, we believe a scalable, easy-to-use, and affordable QKD service can be brought to current telecommunication networks, and extensively applied by ordinary people while using daily applications.
Secure networks composed of optical networks and quantum key distribution (QKD) are considered in this paper. A network layer structure is defined to focus on issues important with respect to the QKD network layer that controls QKD links and supplies a secure key for message transmission. A multiple-user QKD network layer can be constructed with timing synchronization, secure key sharing between indirectly connected nodes with switched QKD systems and key relays, and key management to control the volume of key generation and supply in response to the demand from optical network nodes.
Quantum Key Distribution (QKD) has progressed from a theoretical cryptographic concept to an emerging secure communication infrastructure technology. While early work focused on protocol security and physical-layer feasibility, current research increasingly addresses scalable network deployment, hardware acceleration, and integration with classical communication systems. As QKD expands from point-to-point links to metropolitan, backbone, and hybrid satellite–terrestrial networks, new engineering challenges arise in topology design, entropy generation, real-time key distillation, and multi-vendor interoperability. This survey provides an infrastructure-oriented review of QKD networks, examining architectural models, quantum randomness as a root of trust, FPGA and system-on-chip (SoC) based acceleration techniques, and programmable control-plane integration. Key management system architectures and standardized interfaces are analyzed to highlight their roles in enabling scalable, interoperable deployments. The paper also synthesizes major standardization efforts and deployment initiatives shaping carrier-grade QKD infrastructures. Finally, open engineering challenges, including scalability, control-plane integration, certification harmonization, and hybridization with post-quantum cryptography, are identified, positioning QKD as a foundational component of next-generation secure communication systems.