The integration of Quantum Key Distribution (QKD) into optical networks has emerged as a promising solution for securing sensitive data transmission in mobile fronthaul applications. However, implementing QKD typically requires dedicated dark fibers, which increases network complexity and deployment costs. This paper explores an approach that leverages Multi-Core Fibers (MCF) to integrate both classical and quantum channels within the same optical fiber, utilizing Space Division Multiplexing (SDM). By dedicating separate cores for quantum and classical channels, the proposed system minimizes the need for additional infrastructure while ensuring secure and efficient communication. Crosstalk between cores, a critical factor in MCF design, is analyzed through simulations, considering parameters such as core pitch and operating spectrum. Results demonstrate the feasibility of achieving minimal inter-core crosstalk for reliable quantum and classical channel coexistence. This study underscores the potential of MCF-based SDM as a cost-effective and scalable solution for future quantum-secured mobile networks.
The integration of Quantum Key Distribution (QKD) into optical networks has emerged as a promising solution for securing sensitive data transmission in mobile fronthaul applications. However, implementing QKD typically requires dedicated dark fibers, which increases network complexity and deployment costs. This paper explores an approach that leverages Multi-Core Fibers (MCF) to integrate both classical and quantum channels within the same optical fiber, utilizing Space Division Multiplexing (SDM). By dedicating separate cores for quantum and classical channels, the proposed system minimizes the need for additional infrastructure while ensuring secure and efficient communication. Crosstalk between cores, a critical factor in MCF design, is analyzed through simulations, considering parameters such as core pitch and operating spectrum. Results demonstrate the feasibility of achieving minimal inter-core crosstalk for reliable quantum and classical channel coexistence. This study underscores the potential of MCF-based SDM as a cost-effective and scalable solution for future quantum-secured mobile networks.
On the one hand, Quantum key distribution (QKD) offers unparalleled security relying on the principles of quantum mechanics. On the other hand, space division multiplexing (SDM) is recognized as the route toward a capacity upgrade for current core optical communication networks and will progressively permeate into shorter-reach networks. Incorporating QKD into classical networks, with SDM being one of its components, will enhance data communication security. Understanding the security implications of implementing QKD over SDM is crucial for the practical deployment of quantum-secure communication technologies, especially in scenarios where high data capacity and multiplexing techniques are essential. In this paper, we study a QKD eavesdropping use case where connectivity is provided via SDM fibers. Specifically, we discuss the detector blinding attack (DBA) concerning inter-core crosstalk in an entanglement based QKD system. Additionally, we analyze the blinding power of DBA over quasi-homogeneous and heterogeneous seven-core fiber scenarios. Furthermore, the potential countermeasures to mitigate the impact of such attacks are discussed.
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.
Quantum key distribution (QKD) is regarded as an alternative to traditional cryptography methods for securing data communication by quantum mechanics rather than computational complexity. Towards the massive deployment of QKD, embedding it with the telecommunication system is crucially important. Homogenous optical multi-core fibers (MCFs) compatible with spatial division multiplexing (SDM) are essential components for the next-generation optical communication infrastructure, which provides a big potential for co-existence of optical telecommunication systems and QKD. However, the QKD channel is extremely vulnerable due to the fact that the quantum states can be annihilated by noise during signal propagation. Thus, investigation of telecom compatibility for QKD co-existing with high-speed classical communication in SDM transmission media is needed. In this paper, we present analytical models of the noise sources in QKD links over heterogeneous MCFs. Spontaneous Raman scattering and inter-core crosstalk are experimentally characterized over spans of MCFs with different refractive index profiles, emulating shared telecom traffic conditions. Lower bounds for the secret key rates and quantum bit error rate (QBER) due to different core/wavelength allocation are obtained to validate intra- and inter-core co-existence of QKD and classical telecommunication.
The rapid evolution of mobile communication technology is propelling us from the era of 5G to the cusp of 6G, which promises ultra-high speeds, ultra-low latency, and seamless global connectivity. However, these ambitious goals require not only significant advancements in traditional communication technologies but also the integration of novel approaches to address emerging security and efficiency challenges. Quantum communication, particularly Quantum Key Distribution (QKD), offers a groundbreaking solution due to its inherent security based on the principles of quantum mechanics. This paper proposes an innovative architecture that combines QKD with Passive Wavelength Division Multiplexing (WDM) for 6G fronthaul networks. The architecture, which includes components for signal transmission, processing, and monitoring, uses WDM to transmit both quantum signals and classical signals over a single fiber, optimizing resource utilization, ensuring security, and enhancing reliability. The quantum signals are detected by single-photon detectors to generate secure keys, while the classical signals carry regular communication data. The passive WDM system efficiently uses fiber resources, is cost-effective, and is easy to upgrade, making it highly compatible with classical optical communication. Extensive simulation experiments are conducted to evaluate the impact of key parameters such as transmission distance, attenuation coefficient, photon count per pulse, dark count rate, and detection efficiency on the secure key rate and quantum error rate. The results indicate that careful optimization of these parameters can substantially enhance system performance, making the architecture highly suitable for high-security transmission scenarios in 6G networks. This research provides new insights into the integration of quantum and classical communications in 6G fronthaul networks, demonstrating the potential of quantum-enhanced 6G networks.
Broadband access in optical domain usually focuses in providing a pervasive cost-effective high bitrate communication in a given area. Nowadays, it is of utmost interest also to be able to provide a secure communication to the costumers in the area. Wireless access networks rely on optical domain for both fronthaul and backhaul of the radio access network (C-RAN). Multicore fiber (MCF) has been proposed as a promising candidate for the optical media of choice in nextgeneration wireless. The capacity demand of next-generation 5G networks makes interesting the use of high-capacity optical solutions as space-division multiplexing of different signals over MCF media. This work addresses secure MCF communication supporting C-RAN architectures. The paper proposes the use of one core in the MCF to transport securely an optical quantum key encoding altogether with end-to-end wireless signal transmitted in the remaining cores in radio-over-fiber (RoF). The RoF wireless signals are suitable for radio access fronthaul and backhaul. The theoretical principle and simulation analysis of quantum key distribution (QKD) are presented in this paper. The potential impact of optical RoF transmission crosstalk impairments is assessed experimentally considering different cellular signals on the remaining optical cores in the MCF. The experimental results report fronthaul performance over a four-core optical fiber with RoF transmission of full-standard CDMA signals providing 3.5G services in one core, HSPA+ signals providing 3.9G services in the second core and 3GPP LTEAdvanced signals providing 4G services in the third core, considering that the QKD signal is allocated in the fourth core.
The advancement of 6G networks demands high-capacity, ultra-low latency, and secure communication infrastructure. Traditional fronthaul solutions face significant challenges in meeting these demands due to increasing data traffic, network densification, and security vulnerabilities. To address these issues, this paper proposes an innovative 6G passive Wavelength Division Multiplexing (WDM) fronthaul architecture integrated with Quantum Key Distribution (QKD). By leveraging quantum cryptographic principles, our approach ensures unbreakable security and protects network transmissions from potential cyber threats and eavesdropping attacks. The proposed architecture effectively combines high-speed optical transmission with quantum-secured key exchange, optimizing network reliability and reducing security risks. Through comprehensive simulations, we evaluate key performance factors, including secure key rate (SKR), quantum bit error rate (QBER), detector efficiency, and quantum transmission loss. Results indicate that our architecture maintains high SKR with minimal QBER, even under challenging transmission conditions, ensuring robust quantum-secured communication. Additionally, the passive nature of WDM significantly reduces power consumption and maintenance costs, improving network sustainability. This research establishes a practical pathway for integrating quantum security into next-generation optical fronthaul networks, enabling highly secure, scalable, and efficient data transmission for future 6G applications, including autonomous vehicles, smart cities, and industrial IoT.