Free space to few-mode fiber coupling efficiency improvement with adaptive optics under atmospheric turbulence

In this paper, coupling efficiency between free-space-optical beam and few-mode fibers under atmosphere turbulence is investigated when adaptive optics (AO) is used for compensating wave-front aberrations. The experimental results show that, the coupling efficiency of SMF, two mode fiber and four mode fiber is improved by 16 dB, 11 dB and 10 dB with AO under moderate turbulence.