Experimental Study On Measurement Scheme Of Chromatic Dispersion And Polarization Mode Dispersion

In order to meet the demands of data services such as big data,cloud computing and artificial intelligence in the Internet era,optical communication systems are moving towards high-speed,more flexible modulation formats,high spectrum utilization and dynamic reconfiguration.However,as the transmission rate continues to increase,the structure of the optical communication system becomes more and more complicated and the bandwidth resources become more and more tense.In order to ensure reliable and effective operation of the system under multi-channel and high efficiency and guide the optical fiber manufacturers to manufacture Market-compatible products and help operators to maintain and revamp their systems,related parameters such as chromatic dispersion(CD)and polarization mode dispersion(PMD)of each optical channel signal must be monitored in the key locations in the optical network.Therefore,it is necessary to study the cause,mechanism and influence of chromatic dispersion and polarization mode dispersion,and to explore experimental measurement schemes to realize the measurement of CD and PMD in optical fiber link,which is important for the development of optical fiber communication system significance.At present,many well-known foreign manufacturers have produced related testing equipment,but the prices are relatively expensive.The domestic manufacturers of such equipment are scarce and need to increase the research and manufacture of CD and PMD testing equipment.In this paper,the commonly used methods for measuring chromatic dispersion and polarization mode dispersion are explored,and the comparative analysis of each measurement method in the aspects of the difficulty of experimental operation,the main instruments used and the measurement accuracy are carried out.In the end,the experimental scheme of measuring the chromatic dispersion by the modulation phase shift method and measuring the polarization mode dispersion by the fixed analyzer method is mainly studied,which mainly includes the following two aspects:(1)Based on the principle of chromatic dispersion measurement by modulation phase shift method,an experimental system was set up by using laboratory equipment to verify the reliability and accuracy of the scheme.In order to make the experimental measurement scheme more practical,through the market research,the alternative module of the relevant instrument was selected,the system was modularized and the related algorithm was used to collect and process the measured data of the modular experimental system.The measured results were compared with those of the CD400 based on the experimental system and the commercial instrument.The feasibility of measuring the chromatic dispersion based on the modular experimental system was also verified.(2)In order to eliminate the influence of noise on the experimental measurement scheme,several commonly used filtering methods are analyzed and compared.Empirical mode decomposition adaptive filtering(EMD)is finally selected to measure the signal processing.The principle and process of EMD filtering to eliminate the noise in the PMD experimental scheme of FA measurement are described in detail.The experiments compare results based on the empirical mode decomposition adaptive filtering,wiener filtering method and commercial instruments.The results show that the use of EMD filter for different types and lengths of fiber can improve the accuracy of the fixed analyzer method for measuring polarization mode dispersion.