  We experimentally study a fiber-based optical ring cavity integrated with a
mechanical resonator mirror and an optical amplifier. The device exhibits a
variety of intriguing nonlinear effects including synchronization and
self-excited oscillation. Passively generated optical pulses are observed when
the frequency of the optical ring cavity is tuned very close to the mechanical
frequency of the suspended mirror. The optical power at the threshold of this
process of mechanical mode locking is found to be related to quantum noise of
the optical amplifier.
