Design And Research Of All-optical Decoder And Encoder Based On PPLN Waveguides

With the continuous development of internet applications,the network data flow is rising rapidly,and the existing optical network exchange ability is weak,which can not match with the high-speed transmission technology,and brings great loss to the communication system.The realization of all-optical network is an effective way to solve this problem.All-optical logic signal processing is one of the core technologies of constructing all-optical network.PPLN waveguide is a kind of optical crystal with high non-linear coefficient,which has the advantages of fast response,strong transmission and low loss,making it an indispensable part in the field of all-optical logic signal processing.In this thesis,how to use PPLN waveguide to realize optical devices with complex logic functions is studied in depth.The final research results are as follows:(1)According to the simple optical logic operation that can be realized by a single PPLN waveguide,under the condition of quasi-phase matching,an all-optical 2-4 line decoder waveguides cascade structure with sum frequency residual light wave as the final output signal light is designed.Through the calculation and simulation with Matlab software,the waveforms and eye diagrams of the all-optical decoder are obtained,the parameters such as full width half maximum,extinction ratio,peak power and delay time are analyzed.The results show that the scheme not only realizes the logic function of the all-optical decoder,but also ensures the signal transmission quality.(2)Based on the analysis of the logic function of 8-3 line encoder,two kinds of all-optical8-3 line encoder PPLN waveguides cascade structure are designed,the distributed fourier algorithm and the finite difference method are used to calculate and simulate the coupled wave equations of the PPLN waveguide,the waveforms and eye diagrams of the all-optical encoder signals are analyzed.The results show that the two schemes can achieve the logic function of all-optical 8-3 line encoder,which provides a new device type for all-optical logic signal processing.(3)On the basis of constant parameter setting of all-optical 2-4 line decoder and all-optical 8-3 line encoder except the waveguide length,the all-optical decoder and encoder with the waveguide length ranging from 20 mm to 60 mm are calculated and simulated,and the variation of extinction ratio of each signal light in the two all-optical logic devices with the waveguide length is analyzed.