Quantum Key Distribution has become a mature quantum technology that has outgrown dedicated links and is ready to be incorporated into the classical infrastructure. In this scenario with multiple potential nodes, it is crucial having efficient ways to allocate the network resources between all the potential users. We propose a simple method for routing and wavelength assignment in wavelength multiplexed networks in which classical and quantum channels coexist. The proposed heuristics take into account the specific requirements of quantum key distribution and focus on keeping at bay the contamination of the quantum channels by photons coming from the classical signals from non-linear processes, among others. These heuristics reduce the shared path between classical and quantum channels and improve the signal-to-noise ratio in the quantum channels, improving their quantum key rate. We compare the results to the usual classical RWA approach.
Quantum Key Distribution has become a mature quantum technology that has outgrown dedicated links and is ready to be incorporated into the classical infrastructure. In this scenario with multiple potential nodes, it is crucial having efficient ways to allocate the network resources between all the potential users. We propose a simple method for routing and wavelength assignment in wavelength multiplexed networks in which classical and quantum channels coexist. The proposed heuristics take into account the specific requirements of quantum key distribution and focus on keeping at bay the contamination of the quantum channels by photons coming from the classical signals from non-linear processes, among others. These heuristics reduce the shared path between classical and quantum channels and improve the signal-to-noise ratio in the quantum channels, improving their quantum key rate. We compare the results to the usual classical RWA approach.
As quantum key distribution networks grow in size and complexity, resource assignment has become increasingly important. In passive optical networks without wavelength conversion, we need to assign a full route between origin and destination with the same wavelength from a finite set. This problem is computationally intensive and the common solution in classical optical networks is using heuristics. We adapt these heuristics to hybrid quantum networks where the quantum channel can share some of the optical links with classical channels. In this quantum–classical multiplexing, nonlinear effects can become the limiting factor in the range of the network. The signal in the classical channels can be subject to Raman Scattering or Four-Wave-Mixing and produce light in the quantum channels. While these processes are not efficient, even a single photon can ruin the quantum channel. We propose heuristics for the routing and wavelength assignment problem for hybrid quantum–classical networks with power control for the classical channels. By keeping the transmitted power to its bare functional minimum, we can reduce the interference to the quantum channels. We study their efficiency under different scenarios.
We propose a low-complexity near-optimal wavelength allocation technique for quantum key distribution access networks that rely on wavelength division multiple access. Such networks would allow users to send quantum and classical signals simultaneously on the same optical fiber infrastructure. Users can be connected to the access network via optical wireless or wired links. We account for the background noise present in the environment, as well as the Raman noise generated by classical channels, and calculate the secret key generation rate for quantum channels in the finite-key setting. This allows us to examine the feasibility of such systems in realistic scenarios when the secret key exchange needs to be achieved in a limited time scale. Our numerical results show that, by proper choice of system parameters for this noisy system, it is possible to exchange a secret key in tens of seconds. Moreover, our proposed algorithm can enhance the key rate of quantum channels, especially in high noise and/or high loss regimes of operation.
In quantum key distribution (QKD) metropolitan area networks (MANs), the tidal effect of traffic, which is caused by the imbalanced distribution of users, decreases network resource utilization and leads to an imbalanced distribution of quantum keys. Additionally, there is noise interference when both classical and quantum signals are transmitted together within the same optical fiber. To solve these problems while considering the specific requirements of the services, we propose heuristic routing and wavelength allocation algorithm. Firstly, the routing scheme based on Minimization of Network Load Standard Deviation (MNLSD) is applied to balance traffic, reduce blocking rate, and achieve the goal of balancing secure key rate of QKD system. Based on this, we design a wavelength allocation scheme by Priority Based on Noise Influence (PBNI), which is applied to the scenarios where quantum channels are fixed but classical services dynamically arrive. It achieves noise suppression by flexibly scheduling classical services. Simulation results shows that MNLSD can reduce the standard deviation of link load up to 83.9% and the blocking rate up to 20% compared to benchmark scheme. Additionally, when compared to benchmark scheme, PBNI can improve the secure key rate of QKD system up to 127.3%.
Optimal wavelength assignment in dense-wavelength-division-multiplexing (DWDM) systems that integrate both quantum and classical channels is studied. In such systems, weak quantum key distribution (QKD) signals travel alongside intense classical signals on the same fiber, where the former can be masked by the background noise induced by the latter. Here, we investigate how optimal wavelength assignment can mitigate this problem. We consider different DWDM structures and various sources of crosstalk and propose several near-optimal wavelength assignment methods that maximize the total secret key rate of the QKD channels. Our numerical results show that the optimum wavelength assignment pattern is commonly consisted of several interspersed quantum and classical bands. Using our proposed techniques, the total secret key rate of quantum channels can substantially be improved, as compared to conventional assignment methods, in the noise dominated regimes. Alternatively, we can maximize the number of QKD users supported under certain key rate constraints.
Currently, with the continuous advancement of network and communication technology, the amount of data carried by the optical network is very huge. The security of high-speed and large-capacity information in optical networks has attracted more and more attention. Quantum key distribution (QKD) provides information-theoretic security based on the laws of quantum mechanics. Introducing QKD into an optical network can greatly improve the security of the optical network. In order to reduce the cost of deployment on QKD infrastructure, quantum signals in QKD and classical signals in optical networks are multiplexed in the same fiber by wavelength-division manner. Moreover, due to the limited wavelength resources in an optical fiber, time-division technology is adopted to construct different kinds of channels in QKD system for efficient utilization of wavelength resources. Under such situation, how to satisfy the security requirements of service requests and complete the efficient scheduling of multi-dimensional resources, i.e., wavelengths and timeslots, is a challenging problem. This paper addresses this problem by considering multi-dimensional routing, wavelength, and timeslot allocation (RWTA) in short-distance quantum key distribution optical networks (QKD-ON), in which any two nodes can directly establish a quantum channel, and the maximum distance between any two nodes is less than the distance that can carry out point-to-point quantum key distribution process. While accommodating services with security requirements in QKD optical networks, to avoid the wavelength time-slot fragmentation caused by the constraints of wavelength consistency and time-slot continuity, we propose a time-window-based security orchestration strategy as well as relative-loss of time continuous compactness based RWTA strategy. We conducted the simulations under various scenarios, e.g., different key updating periods and different distributions on wavelength resources, etc., and the results show that the proposed strategy can achieve better performance compared with the baselines in terms of key success rate, key-updating delay, and blocking probability.
In this paper, low-complexity channel allocation methods are proposed for quantum access networks. We consider dense-wavelength-division-multiplexing passive optical network (DWDM-PON) structures that enable users to exchange secret keys, in addition to data transmission. We consider two main sources of noise in such systems, Raman scattering and four-wave mixing, and examine optimal channel allocation in different scenarios. We also take into account finite-key effects in the quantum key distribution (QKD) channels. Our numerical results show that the proposed wavelength assignment methods can significantly enhance the secret key generation rate of users.