| The advent of the"Internet+"era has promoted the development of AI artificial intelligence,cloud computing,Internet of things,big data and other technologies,which puts higher requirements on the transmission rate,transmission capacity,transmission quality and stability of communication system.Optical communication system is an excellent solution.In this context,the future optical network must move toward high-capacity and high-speed.At present,the bandwidth of the metropolitan area network and the backbone core network has reached several tens of Gb/s,and the length is several hundred or even thousands of kilometers.The effects of chromatic dispersion(CD)and polarization mode dispersion(PMD)cannot be ignored.Accurate measurement of CD and PMD values can help to study ways to reduce the influence of dispersion,and then scientifically and effectively design and build optical communication systems;in the access network,the distributed base station of the 4G network enlarges the distance between the base-band processing unit(BBU)and the remote radio unit(RRU),so that the influence of dispersion is increased.In addition,new optical fibers such as ultra-low loss optical fibers are emerging in recent years,it's very important to measure their dispersion value accurately in the manufacturing process of the optical fiber cable.Therefore,it is of great significance to study and analyze the measurement methods of chromatic dispersion and polarization mode dispersion on the basis of which more optimized schemes are proposed.In order to optimize the problems of CD and PMD measurement system,this paper studies the traditional measurement methods recommended by the International Telecommunication Union.By comparing the advantages and disadvantages of each method,the optimized modulation phase shift method is used to measure the dispersion;combine the singular value decomposition(SVD)denoising and the fixed analyzer to mesure the polarization mode dispersion.The main work and innovative achievements of the thesis are as follows:1.Optimize the conventional modulation phase shift method to measure the CD coefficient.The dual phase detector structure is used to solve the phase ambiguity problem of a single phase detector with one voltage corresponding to two phases in the traditional method,and combined with the phase tracking and compensation technology to optimize the measurement scheme.2.The CD measurement experiment platform was built by selecting the appropriate module.The measurement data was processed by related algorithms,and the results were compared with commercial measurement instruments to verify the effectiveness of the scheme.3.This paper studies and analyzes the singular value decomposition(SVD)denoising algorithm,and proposes a new method to determine the effective order,which solves the disadvantages of relying on engineering experience to determine the order in the singular value decomposition denoising algorithm.Using SVD to process the experimental data of the fixed analyzer method(FA),the noise in the system is effectively eliminated,the extreme value counting is more accurate,and the accuracy of the measurement result is improved.4.The measurement platform of the PMD measurement scheme is built,and the measurement results are compared with the measurement results of the FTB-5500 instrument and the denoised by the Butterworth filter.It is proved that the measurement scheme can effectively eliminate noise and improve measurement accuracy.5.Optical fiber CD/PMD measurement prototype was manufactured.The CD measurement wavelength range from 1520nm to 1660nm,minimum step wavelength is 0.1 nm,uncertainty is 0.2 ps;The PMD measurement wavelength range from 1520nm to 1660nm,uncertainty is O.Olps.It has an important practical significance for breaking the monopoly of foreign manufacturers on fiber dispersion measuring instruments. |
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