Long-Term Stabilization of an Actively Mode-Locked Er-Doped Fiber-Ring Laser via Dynamic Intracavity Loss Feedback

We demonstrate a long-term stabilized all-fiber actively mode-locked laser (AMLL) by locking the optical pulse train to a mode locker. By dynamically controlling the bias voltage of the intracavity electrooptical modulator, we established an optoelectronic phase-locked loop and achieved long-term phase stabilization of the AMLL. With the help of an optical-microwave phase detector, sensitive phase error signal is obtained and used for the phase stabilization. With this approach, the AMLL achieved long-term stable operation, and the residual fractional frequency stability is significantly improved from 1.8 × 10 ^-13 to 2.8 × 10 ^-15 at 1 s and from 2.1 × 10 ^-16 to 6.8 × 10 ^-19 at 4000 s.