Optical transmission characteristics of Large-tolerance Fiber Collimator

A Large-tolerance Fiber Collimator (LTFC) consisting of a Thermally Expanded Core Fiber (TECF) and an aspherical lens is designed to solve the problems of low beam coupling efficiency and small coupling tolerance of conventional collimators. According to the Gaussian beam coupling theory, the beam deviation coupling model of the LTFC is established to analyze the effects of coupling deviation and fiber Mode Field Diameter (MFD) on the collimator coupling efficiency. Beam coupling simulations are carried out by ZEMAX, which analyzes the influence of the interaction of the three coupling deviations on the beam coupling efficiency. And the final experimental platform is built to test the performance of the designed LTFC in combination with simulation. The results show that the LTFC can achieve a beam coupling efficiency more than 80% with an angular deviation less than 0.06°, a radial deviation less than 0.06 mm, and an axial deviation less than 2 mm. The coupling efficiency can reach 97.24% when the collimator fiber MFD is 28μm and all the deviations are extremely small(close to 0). The LTFC has a large coupling tolerance while obtaining a high coupling efficiency, which reduces the difficulty of beam coupling.