Design And Analysis Of OAM Generation And Multiplexing Device Based On Silicon Waveguide

With the rapid development of the Internet,various types of mobile communication services such as artificial intelligence,cloud computing,5G,and autonomous driving are emerging,and society has increasingly demanded for communication capacity.In the field of optical communications,the existing multiplexing technologies are approaching Shannon's limits in terms of spectrum utilization and system capacity,and cannot meet the ever-increasing communication capacity requirements.Space-Division Multiplexing?SDM?provides a solution to improve the capacity of communication system.OAM as a carrier for optical multiplexing is an important way of SDM.Therefore,as key components of OAM optical communication,the research of OAM generation and multiplexer is of great significance.A type of OAM generation and multiplexing device based on silicon waveguide is designed,which is mainly composed of an asymmetric directional coupler and a phase shifter.The mode coupling theory in the waveguide and the principle of generating OAM in the optical fiber are analyzed.The fundamental mode TE₀₀ is coupled into a first-order mode TE₁₀ through the asymmetric directional coupler.The air trench excites the first-order mode TE₁₀ to be two mutually orthogonal eigenmodes,so that the TE₁₀ is converted into an OAM mode after passing through a phase shifter.The structure of the OAM multiplexer is designed according to the phase difference relationship that generates OAM₊₁and OAM_-1.The Finite Difference Time Domain?FDTD?is used to optimize the device parameters.By adjusting the height,width and coupling length of the waveguide,and changing the length and position of the trench,the effects of different structural parameters on the performance of the device are analyzed.The simulation results show that the device can realize the generation and multiplexing of OAM modes with topological charges of+1,0,and-1.The device has a compact structure with a size of less than 80?m×5.3?m.At the communication wavelength of 1550 nm,the insertion loss of the device is less than 0.24 d B,and the crosstalk is less than-20.05 d B.The device has a simple manufacturing process and is easy to be integrated.It has important application value for improving the capacity of the optical communication system,and can be applied to the optical fiber communication system and other fields.