Research On Signal Processing Technology Of Modulation Anddemultiplexing Based On Stokes Space

Mode-division multiplexing is an important technology to improve the optical fiber transmission capacity.As the mode is extended,the damaging effect is more obvious,and the digital signal processing for mode division multiplexing is more complicated.Methods such as channel equalization based on Stokes space have been extensively studied in the polarization multiplexing,but the Stokes polarization signal processing technology of the mode division multiplexing needs to be further studied.In particular,for the system with different modulation schemes,the multiplexing system that uses different modulation formats for signal transmission to improve the transmission efficiency lacks the related research on the mixed transmission of the modulated signal,especially the different modulation formats.Because of the problem of mode coupling in mode impairments,the communication's system needs channel equalization at the receiving end through digital signal processing techniques.In this paper,the vector distribution characteristics of mixed transmission signals in different modulation formats in Stokes space are studied.Before the channel equalization,the machine learning algorithm is adapted to analyze the vector clustering numbers in Stokes space to realize the modulation format identification.An improved Stokes equalization method is proposed.Finally,the improved Stokes hierarchical fitting method is verified in the simulation system.The specific work of this article includes the following three points:First,the characteristics of Stokes vectors that are multiplexed with different modulation signals in Stokes space are analyzed.The theory of fiber mode and mode coupling is studied.The modal dispersion detection in the Stokes space and the Stokes space algorithm combined with LMS are theoretically described.Second,proposed a different modulation format hybrid transmission modulation format.Combined with the characteristics of the number of clusters and the expectation maximization of variant Bayesian,the modulation schemes are identified according to the difference of clustering numbers of the multiplexed signals in different modulation formats.This paper simulates the QPSK&16QAM system and verifies that before the DSP demultiplexing step,the cost function of the Stokes vector and the standard clustering number of the signal can be determined by the algorithm to determine the modulation format of the transmitted signal.Third,in order to solve the problem that the MMA algorithm cannot be equalized by different modulation formats of multiplexed signals(N-PSK&M-QAM),the distribution characteristic of N-PSK&M-QAM multiplexed signals in Stokes space is analyzed.Layer Fitting Stokes Spatial Decomposition Method.In the receiver DSP of QPSK&16QAM simulation system,the improved Stokes space algorithm is used for signal demultiplexing.Compared with the bit error rate of the back-to-back system,the algorithm is verified to be effective.