We report the observation of Zeno switching through an inverse Raman scattering (IRS) process in an optical fiber. In IRS, light at the anti-Stokes frequency is strongly attenuated in the presence of a pump field, allowing it to be used for all-optical switching and modulation. Our observed level of induced absorption via IRS in the optical fiber is > 20 dB in a time scale of less than 5 ps. The full Raman response spectrum was extracted experimentally and excellent agreement was found between the experimental data and theoretical modeling of IRS.