Research On Algorithm And Equipment Of Fiber Polarization Mode Dispersion Measurement

Optical fiber communication is a communication method in which optical waves are used as carriers and optical fibers are used as transmission media to transmit information from one place to another.At present,optical fiber communication has become the most important means of transmission of information and an important infrastructure of the information society due to its ultra-high speed,low error rate,high reliability and low price.Among them,optical fiber,as the most important part of optical fiber communication technology,plays a decisive role in the performance of the entire optical fiber communication system.So far,theoretical studies on the formation of fiber polarization mode dispersion,vector representation,and main state model have been basically improved.However,there are still many unsolved problems in the application of fiber polarization mode dispersion measurement methods in practical scenarios.The existing commercial polarization mode dispersion measuring instruments have the disadvantages of large volume,high cost,high requirements on the measurement environment,and cannot perfectly meet the current market demand.In this paper,the principle of polarization mode dispersion generation,classical polarization mode dispersion measurement method and common signal processing methods were deeply studied.The theory and method of using polarization denoising algorithm to improve the accuracy of polarization mode dispersion measurement were analyzed.This paper had completed the following innovative research results:1.Measuring the polarization mode dispersion of a fiber using a fixed analyzer method is susceptible to noise.In response to this research topic,this paper proposed two experimental optimization schemes.i.An experimental scheme(FA-WD)based on the wavelet threshold denoising algorithm to improve the accuracy of the polarization mode dispersion of the fiber measured by the fixed analyzer method was proposed.The principle of wavelet threshold denoising algorithm and the characteristics of different types of wavelet basis functions were introduced in this paper.Several rules were drawn for the selection of threshold function,decomposition layer and basis function.An experimental platform was set up to cormpare FA-WD with other measurement methods.The experimental results showed that the maximum error of FA-WD measurement in single-mode fiber was 2.27%,which was much better than the maximum error of 17.25%obtained by the fixed analyzer method.In addition,FA-WD measured a standard deviation of 0.02 for single mode fiber,which was much better than 0.41 for the fixed analyzer method.Therefore,this paper proved that the test stability of the FA-WD measurement scheme is greatly improved.ii.An experimental scheme(FA-FFT)using Fourier analysis to improve the measurement of the polarization mode dispersion of a fiber by a fixed analyzer method was proposed.FA-FFT used the probability distribution characteristics of the spectral signal itself and denoised and reconstructed the transformed results by Fourier analysis,which effectively reduced the influence of noise on the results.By building an experimental platform,we tested different types and lengths of fiber.The measurement results showed that the maximum error of single-mode fiber was 2.66%,which indicates that FA-FFT can obtain the polarization mode dispersion value of the fiber quickly,accurately and stably under the limited computing resources.2.Aiming at the problems existing in the existing fiber polarization mode dispersion measuring instrument on the market,this paper proposed a development plan of a polarization mode dispersion measurement prototype with low cost,small volume and high measurement accuracy.The FA-FFT scheme was engineered with the help of characteristics of FA-FFT measurement method including small calculation,simple experimental procedure and high modularity of experimental equipment.The test results verified that the experimental prototype developed had a manufacturing cost of only 30%of the existing polarization mode dispersion measuring instrument when the measurement indexes such as accuracy and accuracy were basically the same.In summary,the proposed FA-WD and FA-FFT fiber polarization mode dispersion measurement scheme effectively overcomes the error introduced by the noise when using the fixed analyzer method to measure the polarization mode dispersion of the fiber,and improves the measurement accuracy,which provides a new idea for the study of the polarization mode dispersion measurement method.In addition,the polarization mode dispersion measurement prototype developed in this paper fills the gaps in related fields in China and provides a basis for the development of related instruments.