Real-time observation of invisible dual-soliton pulsation in fiber laser

It is found that the two pulsating solitons exhibit the same evolving process with identical period. However, the soliton characteristics including spectral profile, spectral bandwidth and sideband intensity are asynchronized integrally. The time difference between the evolving trajectories of two pulsating solitons is four roundtrip period. To best of our knowledge, it is the first unambiguous observation of multi-soliton pulsation with overall asynchronous evolution.