Automatic alignment between two optical fiber collimators

Optical fiber collimators are widely used in many parts of optical apparatus such as optical isolators, optical switch, etc, and the automatic alignment between two optical fiber collimators becomes an important part of the manufacture. Since the automatic alignment process is the multi-degree-of- freedom motion control, the traditional hill-climbing algorithm takes much time and always fails. Based on the optical field formed by the collimator's end, a fast multiple freedom search algorithm is proposed for automatic alignment between two optical fiber collimators. The blind search method is used in coarse alignment process. In this method, the collimator will move in a symmetrical square spiral trace to catch the first light. In fine alignment, the collimator will move in a circle trace to find such two points in which the optical powers are equal, and then the algorithm will forecast the direction of the power increasing. This search method in fine alignment process can adjust misalignments on multiple axial directions simultaneously. Due to this advantage, this fine alignment process is shortened time with little effects of noises and inter-coupling among axes on alignment automation. Experimental results show that the alignment speed of the proposed search method is better than that of traditional hill-climbing algorithm. The cycle time for six-degree freedom, x, y, z and θ x, θ y, θ z, alignment automation is about 120-140s.