Research On Equalization And Spectral Shaping Of Polarization Multiplexing Signals In WDM System

The existing commercial 100 G Ethernet will gradually be eliminated as the explosive growth of data traffic on the communication system and the 400 G Ethernet considering as the next generation backbone transmission technology is proposed in this context.Currently,the 112 Gbps Polarization Division Multiplexing-Quadrature Phase Shift Keying(PDM-QPSK)transmission system combined with polarization multiplexing and high-order modulation technology is characterized by high integration and high spectrum resource utilization.According to this situation,the study of 400 G Ethernet network technology in this context adopted a networking mode with four-carrier 4×112G Wavelength Division Multiplexing(WDM)system which inherited the advantages of 100 G network.In this way,400 G network can absorb a large number of mature technologies and may also form a 100 G to 400 G network transition smoothly.With the increase of transmission rate and distance,dispersion and non-linear effect will be accumulated gradually.Without corroding compensation technical the dispersion and non-linear effect will greatly limit the transmission capacity of optical fiber communication systems.Firstly the dispersion compensation algorithm in optical fiber communication system is analyzed in this context.At present,a method of compensating dispersion is usually compensated by using adaptive time-domain equalizer with digital signal processing technology.However,the ultra-high signal rate is beyond the ability of the current Digital Signal Processing(DSP)technology.Under this situation the structure of the pipeline equalizer in high-speed optical fiber communication system is widely used,although this approach can solve the problem,unfortunately instead of add delay in the adaptive equalizer and the delay affects the performance of the equalizer absolutely.In order to study the effect of feedback delay on the adaptive time-domain equalizer this context build a mathematical modeling for the weight of the equalizer which is a new method analyzing this problem.And then the performance of the equalizer could be analyzed numerically after the model is substituted into the iterative updating equation of the equalizer.This thesis analyze and compare two commonly used adaptive time-domain equalization algorithms,Least Mean Square(LMS)and Constant Modulus Algorithm(CMA).And the studies include the stability of the equalizer and also the convergence speed of various equalizers under different feedback delays.Moreover,in order to compensate the non-linear effect in the optical channel this thesis combine the spectrum shaping technology studying the tolerance of nonlinear effect with the high-speed Digital-to-Analog Converter(DAC)and the Analog-to-Digital Converter(ADC)technology in transmitter.In this thesis four different spectral shaping technology including Nyquist,Root Raised Cosine(RRC),Root M-Shaped Pulse(RMP)and Root Polynomial Pulse(RPP)which generated by the time-domain Finite Impulse Response(FIR)filter are studied and compared in a uniform 400 G optical fiber communication system for their tolerance of non-linear effect.Moreover the performance of four different spectral shaping in DAC bandwidth,DAC quantization resolution and ADC sampling rate are also studied.