Experimental Research On Automatic Alignment And Control Algorithm Of Spatial Light-fiber Coupling

Compared with radio communication,Free Space Optical Communication(FSO)has many advantages,such as,good confidentiality,large communication capacity,and strong anti-electromagnetic interference ability.Therefore,FSO communication has been widely used in recent years.Some optical components are often used in FSO systems,such as,Erbium Doped Fiber Amplifier(EDFA),Wavelength Division Multiplexer(WDM),etc.Most of these components use single-mode fiber input optical signal,thus,the coupling technology of space light and single-mode fiber is one of the key technologies facing the FSO system.Because the core diameter of a single-mode fiber is very small,it is particularly difficult to manually realize the coupling and alignment when using its input optical signal.Therefore,an automatic alignment method can be considered to reduce the difficulty of coupling and alignment.Aiming at this problem,this thesis studies the space-light-single-mode fiber coupling automatic alignment technology.The main work is as follows:1.Based on the principle of mode field matching,the coupling efficiency of coupling a spaceplane wave into a single-mode fiber through a lens under ideal conditions was analyzed,and the coupling efficiency of the three alignment deviations of axial,radial,and angle on the single-mode fiber was simulated and analyzed impact.2.Using piezoelectric ceramics with three different displacement modes,a five-degree-of-freedom spatial light-single-mode fiber coupler was designed,and the corresponding constant voltage DC power supply and voltage amplifier circuits were designed according to the working conditions of the three piezoelectric ceramics.The structure of connecting three kinds of piezoelectric ceramics and the design of fixing the structure and single-mode fiber was introduced.3.According to the working principle of the automatic alignment system,the driver program of the AN9767 module used to drive and control piezoelectric ceramics and the host computer command serial port receiving program and command packet analysis program architecture based on the FPGA development platform was designed.4.A space light-single-mode fiber coupling automatic alignment experiment platform based on a single-mode fiber coupler was built,and a Stochastic Parallel Descent Algorithm(SPGD)was written,and the optical power coupled into the single-mode fiber was calculated as system performance evaluation function to realize automatic alignment of space light and single-mode fiber coupling.The experimental results show that the designed coupler combined with the stochastic parallel gradient descent algorithm can realize the automatic alignment of the spatial light-single-mode fiber coupling,and the coupling efficiency of the coupling system after the closed loop can reach about 53.2%.The design scheme was of great significance to the research of space light-single mode fiber coupling automatic alignment system.At the same time,the coupling automatic alignment device has the advantages of small structure,high precision,and easy construction.