Experimental Study On The Co-propagation Of Quantum Key Distribution And Classical Optical Communication Over The Same Fiber

With the increasing computing power of classical computers and the rapid development of quantum computers,the secure network infrastructure is urgent to be established.The security of quantum cryptography comes from the principles of quantum mechanics.One of the most mature applications is quantum key distribution(QKD),which can provide an information-theoretical secure way to distribute keys to two remote users.However,the quantum state used to carry the information is very fragile and requires additional dark fiber for separate transmission.Considering the shortage of optical fiber resources,the larger-scale deployment of QKD can be further promoted by the integration of QKD and classical optical communication based on the existing optical fiber network architecture.This thesis focuses on the topic of the transmission of QKD and classical optical communication over the same fiber,including:Firstly,we propose a mode-wavelength dual multiplexing scheme based on the few-mode fiber(FMF),which is one of the space division multiplexing fibers,as the quantum channel.The FMF has an advantage in suppressing spontaneous Raman scattering noise,because of its large effective core area of mode and additional modal isolation due to the mode-division multiplexing.With the FMF,we present for the first time a mode-wavelength dual multiplexing QKD implementation over weakly-coupled FMF coexisting with classical optical communication.The secure transmission distance reaches 86 km,which is the longest transmission distance based on space division multiplexing fiber.Secondly,we demonstrate a downstream quantum access network,as well as its coexistence with a 10 Gbit/s Ethernet passive optical network(10G-EPON).We show full coexistence based on the single feeder fiber structure,with a secure transmission distance of 21 km at a 9 dB attenuation of OLT downstream signals.We then optimize the coexistence performance by adopting the dual feeder fiber scheme and realizing two partial coexistence schemes,i.e.,dual feeder fiber coexistence and dual power splitter coexistence.In the dual feeder fiber coexistence scheme,the quantum access network is integrated with full-power 10G-EPON signals and provides secure keys for 64 users with a secure transmission distance of 11 km.In the dual power splitter coexistence scheme,we present a method to improve and flexibly distribute the secure key rate of each user by an independent quantum power splitter.Third,we prove that the impairment caused by classical data can be reduced by increasing the wavelength interval of quantum and classical optical signals,when the classical optical communication is the dense wavelength division multiplexing classical optical communication system with the optical supervisory channel and optical amplification modules.In the laboratory,we use the optical amplifier module to simulate the classical signal,and measure the noise of different wavelength windows in the O,E,and S bands.Moreover,we simulate the secure key rate of each wavelength to obtain the optimal quantum signal wavelength.In addition,I participate in the field experiment of the integration of QKD with the quantum signal wavelength of 1310 nm and Tbps data bandwidth dense wavelength division multiplexing communication network.