Coupling Method for Making Space Light into Single-Mode Fiber Based on Laser Nutation

Based on the theory of mode-field matching, the relationship between coupling efficiency and jitter amplitude, radius ratio of Airy disk and single-mode fiber mode field is analyzed. In order to reduce the effect of random angle jitter on coupling efficiency, an automatic coupling scheme for making space light into single-mode fiber based on laser nutation is designed. The miss distance is calculated by data acquisition card and the offset voltage is output. The influence factors of algrithm precision and the relationship between laser nutation signal frequency and jitter frequency are analyzed. The feasibility of the algorithm is verified by Matlab simulation and experiments. Accuracy of miss distance angle is about 3 μrad obtained by experiment. The system feasibility is verified by space laser communication system. The coupling efficiency of the system is 67% when there is no disturbance, and it is improved by 6.5% when the disturbance is introduced and the control system is used to compensate the disturbance. The system response speed reaches 40 Hz. The coupling system is simple in structure and accurate in control algorithm. The controller signal processing speed is fast, and it has a great significance on the coupling of space light to single mode optical fiber. © 2016, Chinese Lasers Press. All right reserved.