Bilinear Forms and Dark-Dark Solitons for the Coupled Cubic-Quintic Nonlinear SchrÕdinger Equations with Variable Coefficients in a Twin-Core Optical Fiber or Non-Kerr Medium*

Mei-Xia Chu,Bo Tian,Yu-Qiang Yuan,Ze Zhang,and He-Yuan Tian

Fig. 1 (Color online) Linear-shaped dark-dark soliton via Solutions (11) with the parameters as $p_1={1}/{2}+{i}/{2},$ $c_1=0, c_2={1}/{2},$ $\mu_1=1,$ $\mu_2={3}/{2},$ $v=-{2}/{11}$, $R=1$, $\xi_1^{(0)}=0$ and $b(z)={1}/{7}$.