FSO Communication System with Multi Actuator Adaptive Lens

The Coupling Efficiency (CE) of a beam propagating through the free space to a Single Mode Fiber (SMF) by a lens with focal length f and D aperture size is defined by the ratio of the power coupled to the fiber C > to the average power A > at the aperture plane [1]. In the presence of turbulence, the average CE depends also on the root mean square (RMS) of the wavefront phase (σ ϕ ) distortions as $\overline{CE}={8 \over {\pi^{2} D^2 w^2_a}} \left \vert \int \int_s \exp \left[- {x^2 +y^2 \over w^{2}_a} \right] ds \right\vert^{2} \ \exp [-\sigma^{2}_\phi]$ , where $w_{\alpha} = {\lambda f \over \pi w_{o}}$ is the projected mode field radius of the fiber on the aperture plane, w 0 is the radius of the optical fiber mode with integral is performed over the effective area of the receiving aperture [2].