Can someone explain to me what it means by nonlinear mode? I heard people saying that soliton is a nonlinear mode of the nonlinear schrondinger equation and therefore perturbed pulses tend to reshape to the soliton shape. In the reshaping proces, the energy dispersed is known as continuous radiation. I am confused about the energy dispersion process. I can accept that when there is energy disspation, a system can tend to a mode. But if the energy is just dispersed but not dissipated, can the sytem be really go to the nonlinear mode? Or it will tend to it anyway? I am kind of confused. I need to hear some more on this. Please say something on this. Thanks.