We compare the performance of spectral inversion through four-wave mixing in a long (13.5 km) and a short (1.5 km) dispersion-shifted optical fiber, respectively. While the effectiveness of the long fiber is limited by nonlinear phenomena such as stimulated Brillouin scattering and cross-phase modulation, the effectiveness of the short fiber is limited only by the available power, since the critical power levels where the deleterious nonlinear phenomena occur increase when the fiber length decreases. With the requirement of negligible spectral deformation of the inverted signal, the shorter fiber gives 60% higher conversion efficiency and four times more converted optical power. Measured with 12-nm wavelength conversion from the signal to the inverted replica. >