Dark solitary waves in optical fibers.

It is argued that the form of dark solitary wave solution [~tanh p(z - u(g)t)] previously predicted is highly questionable because the radial dependence of the field was not properly treated. In this Letter a previously developed method for exactly treating the radial dependence of the field is extended to dark-pulse wave solutions, and a new class of solutions is presented that exists in the anomalous dispersion region of the fiber. The average intensity for these solutions exhibits a double hump, in contrast to the single hump associated with the bright-pulse wave.