The Study On Characterisce Of Multi-wavegength Phtonic Crsytal Wavelength Division Multiplexers Based Multimode Interference Thoery

Nowadays, in the times of information explosion, the demand for bandwidth in datacommunication is growing rapidly. Using WDM (wavelength division multiplexing) technology toexpand the capacity of optical fiber communication system is feasible and widely applied.Wavelength Division Multiplexer is a key device in WDM system, whose performance has made agreat impact on communication system transmission quality. Photonic crystal wavelength divisionmultiplexers based on MMI(multimode interference) theory not only combine the advantages ofphotonic crystals and WDM system, but also contain many features of MMI devices, which providea new way in the field of miniaturized and integrated WDM devices.In this paper, firstly, the self-imaging theory is analyzed using MPA(Mode PropagationAnalysis) with the case of general self-imaging theory, and the mathematical conditions about thedirect and mirror replicas of the input field are obtained in this kind of system. ThroughPWM(plane wave method) and FDTD(finite difference time domain) simulations, self-imagingtheory and coupling characteristics are analyzed in the two parallel photonic crystal waveguidescoupling system when the input is asymmetric. Simulation results show that decoupling propertyexists in the square lattice dielectric photonic crystal waveguide coupling system, and can adjust thestructural parameters of this MMI system to change the length of the coupling beat .By comparingand analyzing , through regulating the radius of dielectric rods between two waveguides, thecoupling beat length changes most obviously. It would be beneficial to design smaller photoniccrystal devices. Secondly, a novel two-dimensional photonic crystal three WDM device and a noveltwo-dimensional photonic crystal four WDM device based on MMI effect are designed. Theperformance parameters have been obtained by using FDTD. The simulation results show that theinsertion loss of each wavelength is less than 0.2dB; the channel isolation is about 15dB.Themaximum size of the device is 37.5μm. Finally, based on the features of MMI Photonic crystalwavelength division multiplexers, their applications and prospects in integrated optics and fiber tothe home technology are briefly discussed.