Quasi-Soliton Within a Distributed Bistable Optical System

In an arbitrary bistable distributed system -e.g. passive ring resonator with nonlinear medium and stationary input signal - spatially limited solitary initial perturbation (seed pulse) of a sufficiently large amplitude and arbitrary form turns into an asymtotically rectangular pulse with exponentially small instability increment (quasisoliton). The properties of the quasisoliton are analized within the frames of a different dispersion models. Such a quasisoliton regime was realized experimentally in acousto-electronic model system and in the system with bicompound injection laser and external cavity.