Abstract
It is demonstrated that the dynamics of small-amplitude dark solitons in optical fibers may be described by the well-known Korteweg–de Vries equation. This approach allows us to explain analytically the temporal self-shift of dark solitons due to the Raman contribution to the nonlinear refractive index, which has been observed experimentally by Weiner et al. [Opt. Lett. 14, 868 (1989)].