Simulation Design And Optical Properties Prediction Of Multichannel Orbital Angular Momentum Fiber Coupler

Under the background of "Internet +",the amount of information transmission is increasing rapidly,and orbital angular momentum(OAM)mode has become a research hotspot of new space division multiplexing technology in the field of spatial light and optical fiber communication.Due to the unique optical properties of OAM modes,the generation conversion of fiber OAM modes has become a difficult problem in this field.In addition,the excellent data fitting ability of neural networks in recent years has established a bridge between fiber structure and optical properties.With the help of neural networks,researchers can quickly predict the optical properties of optical fibers to aid in the design and optimization of structures.The main research contents of this paper are as follows:(1)A multi-channel orbital angular momentum fiber coupler is proposed and designed.In this paper,a simple and compact all-fiber multi-channel OAM mode coupler is proposed for the generation conversion of different types of optical fiber OAM modes,using traditional computer simulation technology and based on the "phase-shifted coupling" theoretical model,and the fiber structure is simulated and optimized.The mode field,phase,coupling wavelength and purity of the generated OAM modes under different propagation lengths of each supermode are studied.The final fiber coupler can output four different OAM modes from four channels respectively.(2)A method for predicting optical properties based on neural network is proposed.In the design process of optical fiber coupler,although traditional computer simulation technology can solve the high-intensity mathematical and physical simulation calculation to a certain extent,the calculation speed is slow and the efficiency is low.At the same time,researchers still need to spend a lot of time to adjust the structure of the optical fiber,and repeat trial based on intuitive experience.A lot of repetitive work is inevitable in scientific research work,and the efficiency needs to be improved.In this paper,by establishing an artificial neural network,the prediction of optical properties such as coupling wavelength in the fiber coupler can be realized.Taking the excitation of four modes of OAM fiber as an example,prediction networks are established and designed respectively,and the test results show that the prediction accuracy is good.Compared with the traditional simulation technology,this work is faster and more efficient,which provides a certain reference value for the design of optical components.