This article reports an original technique for measuring the flexural resonance response of optical fibers of around 1 mm in length considered as atomic force microscope cantilevers. This technique was found particularly suitable for precisely investigating the effect of aging of optical fibers due to external factors such as temperature, action of hydrogen, or ionic aggressive solutions. Compared to the corresponding atomic force microscopy images, the measurement of the resonance frequency shift leads to the determination of two factors characteristic of the surface reactivity of the fiber: first, the decrease in frequency that can be considered in terms of mass loading, and second both the frequency increase and the loss in Q factor resulting from the variation of the Young modulus and the internal friction of the fiber.