Periodic-intensity self-oscillation caused by modulational instability is observed for the first time in a nonlinear dispersive fiber ring cavity. The oscillation stops immediately when the phase coherence is disturbed by cavity detuning. It is found that a noninstantaneous response of the nonlinear index competes with the modulational instability gain and produces asymmetrical Stokes sidebands.

• Received 16 May 1988

DOI:https://doi.org/10.1103/PhysRevA.38.5193