Subject of study. This study investigates a method of finding a sequence of nodes in a metropolitan optical transport network to connect a sender and receiver through a quantum channel propagating in the same optical fiber as the information channels to maximize the secret key generation rate. Aim of the work. The purpose of this work is to route the subcarrier wave quantum key distribution in a metropolitan optical transport network to maximize the secret key generation rate. Method. A metropolitan optical transport network is represented as a graph, where the vertices are the network nodes and the edges are the fiber optic lines connecting them. The weight of an edge corresponds to the secret key generation rate on the respective segment of the fiber optic line. The final key generation rate is limited by the slowest section of the path. The desired optimal route can be found by solving the graph bottleneck problem. A brute force algorithm is used. Main results. The optimal paths connecting two given nodes via a quantum channel for different network topologies are found. The results demonstrate the need for a more efficient algorithm when considering a larger number of nodes. Practical significance. The findings of this study could be used in the integration of quantum communications in existing metropolitan optical transport networks.
Subject of study. This study investigates a method of finding a sequence of nodes in a metropolitan optical transport network to connect a sender and receiver through a quantum channel propagating in the same optical fiber as the information channels to maximize the secret key generation rate. Aim of the work. The purpose of this work is to route the subcarrier wave quantum key distribution in a metropolitan optical transport network to maximize the secret key generation rate. Method. A metropolitan optical transport network is represented as a graph, where the vertices are the network nodes and the edges are the fiber optic lines connecting them. The weight of an edge corresponds to the secret key generation rate on the respective segment of the fiber optic line. The final key generation rate is limited by the slowest section of the path. The desired optimal route can be found by solving the graph bottleneck problem. A brute force algorithm is used. Main results. The optimal paths connecting two given nodes via a quantum channel for different network topologies are found. The results demonstrate the need for a more efficient algorithm when considering a larger number of nodes. Practical significance. The findings of this study could be used in the integration of quantum communications in existing metropolitan optical transport networks.
Quantum key distribution (QKD) systems have already reached a reasonable level of maturity. However, a smooth integration of commercial QKD systems in metropolitan area networks has still remained challenging because of technical and economical obstacles. Mainly the need for dedicated fibers and the strong dependence of the secret key rate on both loss budget and background noise in the quantum channel hinder a practical, flexible and robust implementation of QKD in current and next-generation optical metro networks. In this paper, we discuss these obstacles and present approaches to share existing fiber infrastructures among quantum and classical channels. Particularly, a proposal for a smooth integration of QKD in optical metro networks, which implies removing spurious background photons caused by lasers, amplifiers and nonlinear effects in optical fibers, is presented and discussed.
A version of an erbium doped fiber amplifier (EDFA) application scheme designed to increase the efficiency of the simultaneous quantum key distribution session and transmission of information by classical channels in a single optical fiber is explored.A theoretical study of the possibility to use EDFA in the explored way was conducted by numerical simulation methods.The mathematical model is based on the EDFA dynamics equations and the equations that determine the secure key generation rate in case of the subcarrier-wave quantum key distribution.A method for determining the optimal parameters of the scheme under study is described and the evaluation of the feasibility of using EDFA in the explored way is performed.A comparative analysis of the subcarrier-wave quantum key distribution system performance when integrated into an optical network is made in terms of the secure key generation rate for the cases when EDFA is either used or not.The results obtained demonstrate high efficiency of the scheme under study, i.e., the maximum achievable distance of the secure key distribution is increased while maintaining the efficiency of the information transmission.
Quantum key distribution (QKD) systems have already reached a reasonable level of maturity. However, a smooth integration and a wide adoption of commercial QKD systems in metropolitan area networks has still remained challenging because of technical and economical obstacles. Mainly the need for dedicated fibers and the strong dependence of the secret key rate on both loss budget and background noise in the quantum channel hinder a practical, flexible and robust implementation of QKD in current and next-generation optical metro networks. In this paper, we discuss these obstacles and present approaches to share existing fiber infrastructures among quantum and classical channels. Particularly, a proposal for a smooth integration of QKD in optical metro networks, which implies removing spurious background photons caused by optical transmitters, amplifiers and nonlinear effects in fibers, is presented and discussed. We determine and characterize impairments on quantum channels caused by many classical telecom channels at practically used power levels coexisting within the same fiber. Extensive experimental results are presented and indicate that a practical integration of QKD in conventional optical metro networks is possible.
A quantum key distribution system based on the subcarrier wave modulation method has been demonstrated which employs the BB84 protocol with a strong reference to generate secure bits at a rate of 16.5 kbit/s with an error of 0.5% over an optical channel of 10 dB loss, and 18 bits/s with an error of 0.75% over 25 dB of channel loss. To the best of our knowledge, these results represent the highest channel loss reported for secure quantum key distribution using the subcarrier wave approach. A passive unidirectional scheme has been used to compensate for the polarization dependence of the phase modulators in the receiver module, which resulted in a high visibility of 98.8%. The system is thus fully insensitive to polarization fluctuations and robust to environmental changes, making the approach promising for use in optical telecommunication networks. Further improvements in secure key rate and transmission distance can be achieved by implementing the decoy states protocol or by optimizing the mean photon number used in line with experimental parameters.
Nowadays, critical sectors in government, finance, and military are facing increasingly high security challenges. However, traditional public-key crypto-systems based on computational complexity are likely to suffer from upgrade computational power. Quantum key distribution (QKD) is a promising technology to effectively address the challenge by providing secret keys due to the laws of quantum physics. Limited by the transmission distance of quantum communications, remote parties have to share secret keys by exchanging keys through the trusted relay nodes hop by hop. However, if relaying hop by hop is still used in metro quantum-optical networks (MQON), a large amount of key resources will be wasted since the distance between any two nodes is short. Therefore, the problem of how to distribute quantum keys with lower waste of key resources over MQON is urgent. In order to solve this problem, we design a novel quantum node structure that is able to bypass itself. Also, by extending the connectivity graph, auxiliary graphs are constructed to describe the adjacency of quantum nodes in different levels influenced by the physical distance. Based on the novel node, two routing, wavelength and time-slot assignment algorithms are proposed, in which some middle nodes can be bypassed to reduce the resource consumption as long as the distance between the two parties meets the requirement of quantum key distribution. Simulations have been conducted to verify the performance of the proposed algorithms in terms of blocking probability, resource utilization, number of bypassed nodes, and security rate per service. Numerical results illustrate that our algorithms perform better on resource utilization than a traditional scheme without bypass. Furthermore, a tradeoff between the keys saved and blocking probability is analyzed and discussed in our paper.
In this paper we study the performance of subcarrier-wave quantum key distribution (SCW QKD) in the presence of classical channels of optical transport network utilizing dense wavelength division multiplexing (DWDM). We consider the impact of spontaneous Raman scattering noise as well as the four-wave mixing and channel isolation efficiency. We calculate quantum bit error rate as well as the secure key generation rate of SCW-QKD protocol for different parameters of DWDM system and quantum channel allocations. Our calculations show, that quantum channel allocation at the wavelength of 1310 nm is preferable to allocation at C-band due to lower nonlinear noise, despite fiber's larger attenuation at this wavelength.