THIRRING SOLITONS IN THE PRESENCE OF DISPERSION

The effect of dispersion or diffraction on zero-velocity solitons in s tudied for the generalized massive Thirring model describing a nonline ar optical fiber with grating or parallel-coupled planar waveguides wi th misaligned axes. The Thirring solitons existing at zero dispersion/ diffraction are shown numerically to be separated by a finite gap from three isolated soliton branches. Inside the gap, there is an infinity of multisoliton branches. Thus, the Thirring solitons are structurall y unstable. In another parameter region (far from the Thirring limit), solitons exist everywhere.