Research On MZI Interleaver Based On Fiber Resonant Cavity

Interleaver is one of the important devices in the dense wavelength division multiplexing system.It can evenly divide a group of channels into two groups of parity channels to achieve double the communication channel spacing and achieve the purpose of improving communication capacity.The Mach-Zehnder interferometer type(MZI)interleaver has the advantages of simple structure,easy integration,good channel uniformity,small insertion loss,low production cost,etc.,and has become the most widely used scheme for making Interleaver.The fiber microring resonator provides a new idea and method for designing a compact all-fiber wavelength interleaving filter.Interleaver based on fiber resonator will play a more important role in the future dense wavelength division multiplexing system.In order to improve the output spectrum characteristics of all-fiber MZI-Interleaver,based on the research of the output characteristics of micro-ring resonator and MZI-type wavelength interleaving filter,an improved Mach-Zehnder interference with self-feedback structure is proposed.The main research contents and results are as follows:1.Firstly,the research status of wavelength interleaving filters and the development of micro-ring resonators are summarized.The theoretical analysis methods of several micro-ring resonators are briefly introduced.The coupling mode theory and transfer matrix method are used to analyze the devices..By analyzing the working principle of the micro-ring resonator and using MATLAB software to simulate and analyze the influence of device performance parameters on the output spectrum characteristics of the device,it lays a theoretical foundation for the analysis and design of the following.2.For the traditional all-fiber MZI-Interleaver can' t meet the "cosine" output spectrum characteristics of the actual use,two improved methods are proposed,one for the cascaded MZI-Interleaver method for multiple couplers,and the other for the micro-ring resonator-assisted MZI-Interleaver,this paper not only analyzes its working principle,but also carries out numerical simulation analysis.The analysis results show that the cascaded MZI-Interleaver has a 25 dB cutoff bandwidth of about 31 GHz,while the micro-ring-assisted type The 25 dB cutoff bandwidth of MZI-Interleaver is about 34 GHz.Compared with the traditional all-fiber MZI-Interleaver,the channel-to-channel isolation of the output spectrum of the micro-ring-assisted MZI-Interleaver is significantly improved,and the edge of the steeper output spectrum is closer to the square wave.3.An improved MZI-Interleaver consisting of a 2×2 fiber coupler and a fiber coupler with a self-feedback fiber cavity is proposed.According to the structure of the device,the output normalized light intensity is derived by the coupled mode theory and the optical fiber transfer matrix theory,and the numerical simulation analysis is carried out.The analysisresults show that the phase adjustment caused by the length difference of the interference arm is adjusted with the self-feedback resonant cavity,which makes the output spectral form approximate to square wave.The calculated 25 dB cutoff bandwidth of 46.1GHz is significantly improved compared to the traditional all-fiber MZI-Interleaver.At the same time,the effects of the length of the micro-ring resonator-assisted MZI-Interleaver and the micro-ring resonator in the MZI-Interleaver with self-feedback structure,the transmission loss and the coupling ratio of the micro-ring resonator on the output spectrum characteristics are also analyzed and compared.It can be seen that MZI-Interleaver with self-feedback structure overcomes the defect that the micro-ring assisted MZI-Interleaver brings wavelength drift when the length of the micro-ring changes,and reduce the control requirements and transmission loss of the coupler coupling coefficient error.The number of required fiber couplers is reduced,the actual fabrication difficulty is reduced,and the practicality is improved,so that it can play an important role in the future dense wavelength division multiplexing system.