Integration Of Quantum Key Distribution And Classical Optical Communications

Quantum communication,based on the principles of quantum mechanics to deliver information,is absolute security.Quantum key distribution(QKD),is one of its research priorities,offering numerous experimental demonstrations and practical applications,gradually entering people’s daily lives.Nonlinear Raman scattering noise generated by the strong classical telecommunication channels can interfere with weak quantum signals,and thus affect the performance of QKD.Therefore,current experimental and test networks use dark fibers to transmit quantum signals.This increase the number of fibers needed as the number of users expand in future quantum networks.The costs of installing or leasing extra dark fibers is high and fiber resources are lacking in some regions,which is an obstacle to future construction of a quantum communication network.Classical optical communications may be the main communications technology for the forseeable future,so integration of the quantum communication network with the existing classical optical communication network is essential.This means multiplexing QKD with strong classical data signals to deliver quantum signals and classic signals in one fiber.This thesis focuses on the researches in the integration of QKD and classical optical conmunications,including the integration of QKD and gigabit-capable passive optical network(GPON),and the integration of QKD and high rates of classical optical backbone network.On the integration of QKD and GPON side,we propose a new integration program of QKD and GPON based on wavelength division multiplexing(WDM).At the optical splitting point,we use filters to separate the quantum signals and make the quantum signals bypass the optical splitter,avoiding the losses produced by the optical splitters.This prevents the optical splitters from restricting the transmission distance and performance of QKD.On the integration of QKD and high rates of classical optical backbone network side,we realize the multiplexing and long distance co-propagation of QKD with Terabit classical coherent optical communication system for up to 80km.The data capacity is two orders of magnitude larger than the previous results.Our demonstration verifies the feasibility of QKD and classical communication to share the resources of backbone fibre links,and progress the utility of QKD a great step forward.