The Design And Performance Analysis Of Wavelength-mode Division Multi/demulti-plexer

In recent years,with the rapid growth of cloud computing and big data,our society has completely entered the information age.However,the requirements for bandwidth in this era is far beyond our current level.The optical transmission technology,such as wavelength division multiplexing,polarization division multiplexing and mode division multiplexing,can improve the bandwidth,but a single multiplexing system is limited to improve the capacity of communication system.In order to further improve the communication capacity,wavelength-mode division multi/demultiplexing technology has been proposed recently.In the wavelength-mode division multi/demultiplexing system,wavelength division multi/demulti-plexer is the key device for wavelength selection and wavelength multiplexing.On the other hand,mode division multi/demulti-plexer is the key device to complete mode conversion and mode multiplexing.Wavelength-mode division multi/demulti-plexer based on photonic crystal not only combines the technical advantages of WDM and MDM,but also has various advantages of photonic crystals,which is an important research direction of future optical networks.Firstly,the coupled mode theory is analyzed,and the mode coupling of the normal type transverse coupling structure is studied in particular.Then the band gap of the two-dimensional square lattice photonic crystal is calculated by the plane wave expansion method.The photonic crystal combination resonator is consist of five point defects.We use finite difference time domain method?FDTD?to analyze the relationship between the resonant wavelength of the combination resonator with the radius of the defect medium column and their refractive index.Based on those work,we designed a wavelength division multi/demulti-plexer.We also using the the plane wave expansion method?PWM?to study the waveguide dispersion characteristics of two-dimensional square lattice photonic crystal and verifying its coupling characteristics by the finite difference time domain method.According to the phase matching theory,a mode division multi/demulti-plexer is designed.Finally,combine two kinds of multiplexing techniques together,a kind of wavelength-mode division multi/demulti-plexer based on photonic crystal is designed.In this paper,we also designed two wavelength-mode division multi/demulti-plexers.The simulation results show that the first one?four channels?can realize TE₀ mode and TE₁ mode of1530 nm,1550 nm wavelength-mode division multiplexing/demultiplexing of four channels with a low insertion loss?<0.11 dB?and a low mode crosstalk?<-16 dB?.At the same time,the size of the device is only 41.47×20.57?m,and it also has the characteristics of process tolerance.The other one?six channels?can realize TE₀ mode,TE₁ mode and TE₂ mode of 1530 nm,1550 nm wavelength-mode division multiplexing/demultiplexing of six channels with a low insertion loss?<0.419 dB?and a low mode crosstalk?<-10 dB?,while the size of the device is only 74.8×28.6?m.These two devices have important value in high speed and large capacity wavelength-mode division multiplexing optical communication system.