Figure 1

The figures represent the bright and the dark solitary wave solutions ( 25 ), where bright is used to describe solitary waves whose peak intensity is larger than background (reflecting applications in optics) and the descriptor dark is used to describe solitary waves with lower intensity than the background, with ${\mathit{c}}_{\mathbf{1}}\mathbf{=}\mathbf{-}\mathbf{2}$ , ${\mathit{c}}_{\mathbf{2}}\mathbf{=}\mathbf{-}\mathbf{1}$ , ${\mathit{e}}_{\mathbf{1}}\mathbf{=}\mathbf{3}$ , ${\mathit{e}}_{\mathbf{2}}\mathbf{=}\mathbf{4}$ and ${\mathit{e}}_{\mathbf{3}}\mathbf{=}\mathbf{1}$ .