In this article, we report a method of free-radical photopolymerization on the top end of a single-mode optical fiber. The process is very simple to carry out and uses the visible light guided in the fiber. It permits one to produce, on the fiber end, a micronic polymer tip which may be viewed as an extension of the fiber core and whose optical properties improve the intrinsic capability of the fiber, particularly in terms of efficiency of coupling with a laser source. Formation of the tip is explained by self-guiding of the light within the material and photophysical response of the material.