Compound pulse solitons in a fiber ring laser

We report on the existence of a different form of solitary waves in a passively mode-locked fiber ring laser. Studying the interaction between bound solitons observed in a passively mode-locked fiber laser revealed that the bound-soliton pair behaves as a unit, and the properties of their interaction have exactly the same features as those of the single-pulse soliton in the laser, which suggests that the observed bound solitons are in fact another form of solitary waves in the laser. Numerical simulation confirmed the existence of a different form of solitons in the laser.