International Telecommunication Networks and Applications Conference (ITNAC)
From Strings to Streams: A Multi-Period Analysis of QKD over EONs, Showcasing Multi-Band vs. Multi-Fiber Solutions
Mohammadreza Dibaj, Pouya Mehdizadeh, Mohammad Sadegh Ghasrizadeh, Hamzeh Beyranvand, Juan Carlos Hernandez-Hernandez, José Alberto Hernández, David Larrabeiti, Farhad Arpanaei
Quantum key distribution over optical networks has been noted as a state-of-the-art approach to next-generation secure communication. We propose two approaches to manage the signal for quantum key exchange between two trusted nodes; in the first approach, the quantum channel (QCh) uses distinct fiber whereas the classic channel (CCh) and public interaction channel (PICh) use another fiber to be transmitted on C-band (C+L band), and in the second approach CCh and PICh are transmitted over C+L band and QCh only uses O-band, both routed on the same fiber. In this context, two variations of the initial approach have been put forth, namely scenario 1 and scenario 2. In scenario 1, the CChs are positioned within the extended C-band, while in scenario 2, they find their place within the extended C+L-band. Concerning the secondary approach, denoted as scenario 3, the CChs+PIChs and QChs are situated in the extended C+L-band and low-loss O-band with consideration of noises over QChs, respectively. We propose a heuristic resource allocation with a time-division multiplexing technique in quan-tum resource allocation to compare the resource utilization of the mentioned approaches. The simulation outcomes demonstrate the advantages of adopting scenario 3 in relation to fiber deployment. This is highlighted by an 86 % (34 %) enhancement in fiber efficiency when compared to scenario 1 (2), all while employing an equal count of quantum transmitters and receivers over the initial eight years. As per the specifications of scenario 3, during the concluding year, there has been a notable 44 % surge in quantum transmitter and receiver utilization for both scenarios 1 and 2. This upsurge is accompanied by a substantial reduction in fiber utilization, amounting to a 117 % (34 %) reduction concerning scenario 1 (2).
Quantum key distribution over optical networks has been noted as a state-of-the-art approach to next-generation secure communication. We propose two approaches to manage the signal for quantum key exchange between two trusted nodes; in the first approach, the quantum channel (QCh) uses distinct fiber whereas the classic channel (CCh) and public interaction channel (PICh) use another fiber to be transmitted on C-band (C+L band), and in the second approach CCh and PICh are transmitted over C+L band and QCh only uses O-band, both routed on the same fiber. In this context, two variations of the initial approach have been put forth, namely scenario 1 and scenario 2. In scenario 1, the CChs are positioned within the extended C-band, while in scenario 2, they find their place within the extended C+L-band. Concerning the secondary approach, denoted as scenario 3, the CChs+PIChs and QChs are situated in the extended C+L-band and low-loss O-band with consideration of noises over QChs, respectively. We propose a heuristic resource allocation with a time-division multiplexing technique in quan-tum resource allocation to compare the resource utilization of the mentioned approaches. The simulation outcomes demonstrate the advantages of adopting scenario 3 in relation to fiber deployment. This is highlighted by an 86 % (34 %) enhancement in fiber efficiency when compared to scenario 1 (2), all while employing an equal count of quantum transmitters and receivers over the initial eight years. As per the specifications of scenario 3, during the concluding year, there has been a notable 44 % surge in quantum transmitter and receiver utilization for both scenarios 1 and 2. This upsurge is accompanied by a substantial reduction in fiber utilization, amounting to a 117 % (34 %) reduction concerning scenario 1 (2).
In this letter, we propose to implement quantum key distribution (QKD) by using a multi-band strategy. We present a thorough noise analysis of quantum-classical coexistence while incorporating all relevant and precise noise parameters. Our research demonstrates that utilizing the entire extended C-band for quantum and transmitting classical channels (CChs) over the extended L-band with bandwidth of 75 GHz and power of 0 dBm yields no quantum communication beyond 13 km. To address the problem, we utilize the C+L-band to serve CChs and other bands (e.g., O, E, S) for quantum channels (QChs), while taking into account impairments over the quantum one. Results indicate that, while C+L-band is fully loaded, wavelengths of 1381 nm and below (1260-1381 nm) are appropriate for quantum signals, with 1381 nm offering the highest key rate (3.08 Mbit/sec) over a fiber length of 70 km. Finally, to explore an additional operational scenario when the network is not fully loaded, we focused on determining the optimal policy for assigning CChs. The results reveal the importance of prioritizing the maximization of the gap between the CChs and QChs. In addition, the channel assignment pattern of CChs affects the performance of QChs transmitted at other bands (O, E, and S).
Quantum key distribution (QKD) is considered as a promising solution for secure communications. Nevertheless, challenges such as the elevated cost of dark-fibers used for QKD, quantum transceivers (Q-TRx), and security issues with QKD trusted nodes impede its widespread deployment. This paper explores a multi-band elastic optical network (MB-EON) for implementing QKD on the existing fiber infrastructure, augmenting network capacity without the need for new fiber installations. The careful transmission of classical and quantum channels in MB-EON necessitates impairment-aware algorithms to shield quantum channels from potential disruptions caused by classical channels. To tackle this, we conduct an in-depth analysis of various noise sources to pinpoint the optimal key transfer scenario. Our study further includes calculations for the upper bound of the public interaction channel (PICh) bit rate in the BB84-Decoy protocol and the secret key rate (SKR). Furthermore, a time division multiplexing technique is proposed to allocate bit-rate of each Q-TRx and PICh-TRx among received demands and grooming them as a one connection. Furthermore, we delve into the QKD trusted node placement method as a robust solution for long-distance QKD, effectively minimizing Q-TRx usage and selecting less QKD trusted nodes to bolster network security by proposing the hot-links algorithm (HLA). Finally, three routing, modulation format, spectrum, and time slot assignment (RMSTA) algorithms are proposed and compared. The simulation results reveal that the proposed HLA trusted node placement method with flexible routing of classical channels and QKD channels demonstrates significant improvements in key transfer efficiency, network security, and blocking probability compared to the fixed-distance trusted node placement with joint routing of CChs and QKD channels.
Quantum key distribution (QKD) revolutionizes secure communication, offering unbreakable cryptography against quantum computers’ rising computational power. This paper explores the placement of trusted nodes to enhance the efficiency of quantum communication networks. Two practical scenarios are investigated: the multi-band (MB) setting, utilizing different wavelength bands for QKD and classical systems, and the multifiber (MF) solution, employing separate fibers for QKD and classical communication. The study optimizes secret key rate (SKR) per quantum transmitter and receiver (Q-TRx) in metro quantum-optical networks. A heuristic algorithm, considering noise sources and fiber attenuation, is proposed for routing, modulation, spectrum, and time assignment. The simulations conducted on various network topologies reveal optimal QKD trusted node distances (QTND) and wavelengths place. The simulation results indicate that the optimal QTND value for the MB-scenario and MF-scenario is 20 and 25 km, respectively. Compared to scenarios without QKD trusted node placement along the 40 km link, both the MB-scenario and MF-scenario exhibit 40% and 15% improvements, respectively, in SKR/QTRx relative to their optimal QTND values.
Elastic Optical Network (EON) is a promising solution to address the high capacity, low latency, and flexibility requirements of the upcoming 5th-generation (5G) networks. Furthermore, Multi-Core Fibers (MCFs) and Space Division Multiplexing (SDM) technique can be utilized to overcome the capacity limitation of the conventional Single Mode Fibers (SMFs). On the other hand, Quantum Key Distribution (QKD) is an effective solution to address the security issues in 5G transport networks. In this paper, we investigate the performance of QKD over elastic optical networks with multi-core fibers and address the resource allocation problem for quantum and classical channels of QKD (QChs and CChs) and conventional data channels (DChs). To do so, we calculate the background noise caused by different noise sources and accordingly calculate the Secret Key Rate (SKR) in quantum channels. Then, we propose an Integer Linear Programming formulation and a heuristic algorithm to allocate network resources (spectrum, core, and links) to QChs, CChs, and DChs, with the objective of maximizing the secret key rate and minimizing the number of utilized frequency slots (FSs). Finally, we evaluate the proposed ILP and heuristic algorithm in terms of SKR and the number of utilized FSs. In our simulations, we consider core and metro topologies, fixed and distance adaptive launch power for classical signals, different fiber specifications, and different assumptions regarding the relative locations of quantum and classical channels in a multi-core fiber.
In this paper, we investigate the impact of classical optical communications in quantum key distribution (QKD) over hollow-core fiber (HCF), multi-core fiber (MCF) and single-core fiber (SCF) and propose wavelength allocation schemes to enhance QKD performance. Firstly, we theoretically analyze noise interference in QKD over HCF, MCF and SCF, such as spontaneous Raman scattering (SpRS) and four-wave mixing (FWM). To mitigate these noise types and optimize QKD performance, we propose a joint noise suppression wavelength allocation (JSWA) scheme. FWM noise suppression wavelength allocation and Raman noise suppression wavelength allocation are also proposed for comparison. The JSWA scheme indicates a significant enhancement in extending the simultaneous transmission distance of classical signals and QKD, reaching approximately 100 km in HCF and 165 km in MCF under a classical power per channel of 10 dBm. Therefore, MCF offers a longer secure transmission distance compared with HCF when classical signals and QKD coexist in the C-band. However, when classical signals are in the C-band and QKD operates in the O-band, the performance of QKD in HCF surpasses that in MCF. This research establishes technical foundations for the design and deployment of QKD optical networks.
Optical network security is attracting increasing research attention, as loss of confidentiality of data transferred through an optical network could impact a huge number of users and services. Data encryption is an effective way to enhance optical network security. In particular, QKD is being investigated as a secure mechanism to provide keys for data encryption at the endpoints of an optical network. In a QKD-enabled optical network, apart from TDChs, two additional channels, called QSChs and PIChs, are required to support secure key synchronization. How to allocate network resources to QSChs, PIChs, and TDChs is emerging as a novel problem for the design of a security-guaranteed optical network. This article addresses the resource allocation problem in optical networks secured by QKD. We first discuss a possible architecture for a QKD-enabled optical network, where an SDN controller is in charge of allocating the three types of channels (TDCh, QSCh, and PICh) over different wavelengths exploiting WDM. To save wavelength resources, we propose to adopt OTDM to allocate multiple QSChs and PIChs over the same wavelength. An RWTA algorithm is designed to allocate wavelength and time slot resources for the three types of channels. Different security levels are included in the RWTA algorithm by considering different key updating periods (i.e., the period after which the secure key between two endpoints has to be updated). Illustrative simulation results show the effects of different security-level configuration schemes on resource allocation.