Utilizing the second Stokes line of the stimulated Raman scattering in a multimode, graded‐index optical fiber pumped by a 1.32‐&mgr;m Nd:YAG laser, we have first demonstrated an optical time domain reflectometry at a wavelength of 1.5 &mgr;m for a multimode fiber. As a result, the maximum detectable fault location length of 28 km was successfully obtained. The present technique is applicable to the fault location in ultralong length.