Noise Suppression Wavelength Allocation Scheme For Co-Fiber Transmission Of Quantum And Classical Optical Signals

Quantum Key Distribution(QKD)technology based on the three laws of quantum mechanics can greatly improve the security of the communication process.Integrating QKD with existing optical networks has become a key step in promoting large-scale applications of QKD.The co-fiber transmission method in which quantum and classical signals are transmitted through one fiber has the advantages of increasing transmission capacity and reducing costs.However,in the process of co-fiber transmission,due to the strong power of classical signals,the noise will have a serious impact on quantum signals.Therefore,how to reduce the noise of the quantum signals during the transmission of the co-fiber is a critical issue to be solved.In this thesis,we will study the noise suppression wavelength allocation scheme for co-fiber transmission of quantum and classical signals.The specific contributions and innovations are as follows:Firstly,we propose segmented or interleaved wavelength allocation schemes for quantum and classical signals.For existing wavelength allocation schemes,the algorithms are complex and not convenient for practical applications.Based on the study of the noise during the co-fiber transmission,we analyze the noise characteristics mainly based on four-wave mixing(FWM)and Raman scattering,and propose two more practical shcemes based on segmented or interleaved quantum and classical signals.The segmented scheme puts the quantum signals in the high frequency band and the classical signals in the low band.The interleaved scheme uses the frequency interleaving method of the two kinds of signals.By carefully designing the quantum-quantum,classical-classical,and quantum-classical channel spacing,the noise of the two schemes is greatly reduced.The simulation analysis and experimental measurement in standard single-mode fiber show that both schemes can basically eliminate the influence of four-wave mixing.And under the simulation conditions in this thesis,with reasonable channel spacing settings,the segmented and interleaved scheme can reduce the Raman scattering noise by up to 30%and 5.3%,respectively.Further,we compare the two schemes under the same bandwidth,and the results show that the interleaved scheme can improve the secure key rate by 14%compared with the segmented scheme.It shows that the interleaved scheme is more suitable for standard single-mode fiber.In addition,the performances of the two schemes under the same bandwidth when quantum and classical signals are placed in different cores of a multi-core fiber are experimentally measured.The results show that the segmented scheme is more suitable under this condition.Secondly,we propose a selective noise avoiding scheme.In the existing wavelength allocation schemes,completely avoiding the four-wave mixing noise will cause problems such as the degradation of Raman scattering suppression performance and low channel resource utilization.Therefore,we propose a selective noise avoiding scheme.By selectively avoiding degenerate or non-degenerate four-wave mixing noise,the scheme reduces the frequency limitation on the quantum channel.Therefore,the suppression of Raman scattering and the channel utilization have been enhanced.Through simulation analysis and experimental measurements,under the simulation conditions in this thesis,we find that the selective noise avoiding scheme can reduce noise by up to about 18.6%compared with other common schemes.In addition,we also measure the performance of co-core and non-co-core transmission of quantum and classical signals in multi-core fibers.Compared with the traditional scheme,the selective noise avoiding scheme can reduce the noise of 24%?79.6%when co-core transmission,and reduce the noise of 11%?24%when the no-co-core transmission.It shows that the selective noise avoiding scheme also has advantages in multi-core fiber.