Experimental study on adaptive optical wavefront correction with dual mirrors in Free Space Optical Communication

Abstract The wavefront of light wave contains a tilt component after atmospheric turbulence, which increases the wavefront distortion and reduce the quality of laser communication. A fast steering mirror (FSM) must be introduced to correct the wavefront tilt. The adaptive optical closed-loop control algorithm based on Zernike mode decomposition is used to correct the wavefront distortion of light wave after indoor (0.5 m), 600 m, 1 km, 5 km, 10 km, and 100 km transmission. The experimental results show that, under the above-mentioned six different distances, the wavefront phase decreased from 9.5 μm, 15 μm, 12.5 μm, 22 μm, 35 μm, and 450 μm to 5 μm, 10 μm, 7.5 μm, 8 μm, 20 μm, and 300 μm, respectively, only after the closed-loop of the FSM; only after the closed-loop of the deformable mirror (DM), the wavefront phase decreased to 8 μm, 9 μm, 9 μm, 20 μm, 15 μm, and 300 μm, respectively. Further, when the FSM and DM are closed simultaneously, the wavefront phase decreases to 0.2 μm, 2.1 μm, 0.4 μm, 3.1 μm, 5 μm, and 200 μm. The correction effect of closed-loop of FSM and DM at the same time is better than that of either FSM or DM only.