Optimization of space laser coupling with few-mode fiber in the presence of random angular jitter

In a space laser communication system with a few-mode fiber as the receiving terminal, the influence of random angular jitter on the communication performance cannot be ignored. Therefore, it is necessary to research the coupling characteristics of the space laser–FMF system with random angular jitter. A space laser–FMF coupling model with random angular jitter is proposed based on the Laguerre–Gaussian mode. The coupling efficiency and bit error rate (BER) of the communication system are optimized by the relative aperture of the coupling lens. When the relative aperture is 0.15, the standard deviation of random jitter is 3, the signal-to-noise ratio is 5, the coupling efficiency after optimization is improved by 29%, and the BER is reduced by 46%. In this case, the maximum BER reduction after optimization is 55%. The research shows that in the presence of random angular jitter, adjusting the relative aperture can significantly optimize the coupling efficiency and the BER of the space laser–FMF coupling system. The ability of the relative aperture to optimize the coupling efficiency increases with random jitter standard deviation, which exhibits an upper limit for the optimization of the BER.