Realization Of Quantum Switching Node Supporting Variable Bandwidth Switching

As a theoretically unconditional safe and efficient communication method,quantum communication has drawn more and more attention in recent years.Its security is determined by the Heisenberg uncertainty and the quantum uncodability of quantum mechanics.As a relatively mature technology,Quantum Key Distribution(QKD)has also come out of the laboratory in recent years and has taken a big stride forward to practicality.However,in the practical process,the problem that must be considered is multi-user network.Due to the particularity of the quantum signal,in the actual networking,the requirements for the switching nodes are different from those in the normal optical network.This paper is mainly for the scene of quantum communication and classical communication convergence network.Considering on the dynamic bandwidth requirements of quantum services and classical services,this paper focuses on how to realize the flexible signal exchange in frequency spectrum.The specific research contents are as follows.Firstly,considering the particularity of quantum signal in optical transmission and switching,we design a switching node with variable bandwidth that supports both quantum signal and classical signal.The dynamic selection characteristics of Wavelength Selective Switch(WSS)are mainly applied in this switching node.We design the node respectively from physical layer structure,management server,communication signaling,control layer software and node routing strategy,and set up a quantum switch node prototype that meets the above requirements.The prototype supports 2 × 2 ports in the wavelength range from 1528.733 nm to 1566.723 nm with 12.5 GHz minimum frequency spacing.A pair of quantum key distribution(QKD)system based on BB84 protocol in the laboratory is used to study the impact of the point-to-point key distribution when the system is connected to the switching node.And the switching node is proved to be feasible.Secondly,a pair of existing QKD system based on BB84 protocol in the laboratory was used to experimentally study the changes of its key generation number,loss and so on,when the system passes through such a switching node,which illustrate the practicality of this switching node.Due to the limitations of experimental conditions,it is impossible to carry out large-scale experimental studies.Finally,the paper discusses the problems that should be considered when using this switching node in the networking under large-scale and multi-user network environment.At the same time,we consider the problems when the switch node designed in this paper is applied to the trusted relay quantum network,and use the first-fit routing spectrum allocation strategy to study the use of mutil-user situations.It shows that the switching node designed in this paper can be used in the future large-scale networks that transport the quantum signal and classic signal.