Design and implementation of adaptive coupling system for making space light into single-mode fiber

The adaptive coupling of making laser beam into single-mode fiber(SMF) plays an important role in free space optical communication. It’s the key point to the coupling of spatial light and single-mode fiber that finding the best position in the transverse plane of fiber precisely. An adaptive coupling system is proposed, which mainly comprises two-dimensional piezoelectric nanopositioning stage, driver, controller, photoelectric detector, coupling lens which is a closed loop control system. The adaptive coupling system uses optimized raster scanning algorithm to confirm the best position accurately. Theories of optimized raster scanning algorithm are expounded. Analysis results of experiment show that the adaptive coupling system proposed can search the best position automatically based on the power of the light which is coupled into the single-mode fiber. At the same time, it can correct the numerical deviation which is caused by atmospheric turbulence, and maintain high coupling efficiency which can improve the performance of the receiver.