Influence of the fiber displacement on coupling light beam into single-mode fiber

The sticking point of coupling space light into single-mode fiber is how to find the optimal position of fiber precisely.Based on the field-matching theory,the influence of the fiber position error on coupling efficiency of light from free space to single-mode fiber is numerically evaluated.The results show that the fiber-coupling efficiency degrades rapidly with the increasing of the fiber position error.We designed a fiber adjusting mechanism to position the fiber precisely,which improve the fiber-coupling efficiency greatly.To ensure a certain degree of coupling efficiency,micro-lenses fiber is also introduced into the coupling system.These results are helpful for optimization designs of coupling space light into single-mode fiber.