Binary Darboux transformation and multi-dark solitons for a higher-order nonlinear Schrödinger equation in the inhomogeneous optical fiber

Chong Yang,Xi-Yang Xie

Figure 3. Dark-two solitons via solutions (34) with the parameters: (a) n = 2, ς = 0, κ = 1, η = 0.5, λ1 = 0.125, λ2 = 0.5, ${\rho }_{1}=\tfrac{1}{2}\left(\tfrac{1}{2}-\tfrac{3\sqrt{7}}{4}{\rm{i}}\right)$, ${\rho }_{2}=\tfrac{1}{2}\left(\tfrac{1}{2}-\tfrac{\sqrt{15}}{2}{\rm{i}}\right)$, a(x) = 0.1, c(x) = 0.2 and f(x) = 0.1; (b) parameters are the same as (a) except for $a(x)=0.7x$.