Silver halide and Chalcogenide fibers are tow major mid-IR fibers that are used in gas sensing and light transmission. For both purposes, especially for power transmission, it is important to increase the launching efficiency from the mid- IR source (Globar) to fiber so that the signal-to-noise ratio of the while system will be improved. However, due to the shape of the Globar, it is often difficult to get a uniform and small spot image with ordinary lens or mirror. In this paper, a 'mid-IR cavity' has been designed to increase the collecting ratio of IR radiation from a Globar. Comparing with direct forward collection method, the cavity offers not only higher power, more important, but also the uniform Gaussian and smaller spot. As result, higher signal to noise ratio has been obtained in the fiber ends. This can be used to improve the spectral resolution, signal processing time for FT-IR based real-time Chemical Vapor Deposition processing and other type of applications.