An optical coupling system consisting of a laser diode (LD), aspherical lens, and Graded-index (GRIN) fiber is experimentally constructed in butterfly packaging and theoretically simulated. The effects of incident wave-length, laser beam waist radius, lens thickness, GRIN radius, and positioning errors of optical components on coupling efficiency (CE) are systematically investigated. To achieve a large CE value in the GRIN fiber coupling system, the optical structures with appropriate parameters and positions are carefully adjusted in the experiment and simulation. The model coupling efficiency reached 85.5 when the lens and fiber endface losses are neglected, in line with an actual situation. The CE trends under misalignment and tolerance adjustments can be explained by the beam propagation theory and the light-gathering ability of the GRIN fiber. The study is useful in optimum launch optics for designing and fabricating GRIN fiber on coupled packaging of optoelectronic devices.
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