GHz pulse train generation in fiber lasers by cavity induced modulation instability

We report on the experimental generation of highly stable pulse trains with GHz level repetition rate in a ring cavity fiber laser. We show both theoretically and experimentally that the generation mechanism of the pulse trains was due to the cavity induced modulation instability (CIMI) lasing of the fiber laser. Coexistence of the conventional modulation instability (MI) and the CIMI in the same fiber laser were also experimentally observed. It shows that the two effects are independent of each other.