A 40 GHz, 770 fs regeneratively mode-locked erbium fiber laser operating at 1.6 µm

We report a 40-GHz harmonically and regeneratively FM mode-locked erbium fiber laser with a phase-locked loop (PLL) circuit operating in the 1.6 µm region. The oscillation wavelength was extended to the L-band by using a 15 m erbium-doped fiber with an Er3+ concentration of 3500 ppm as a gain medium. As a result, a 770 fs transform-limited Gaussian pulse with a 14 mW output power was successfully generated with a timing jitter as low as 88 fs. The wavelength is tunable over 20 nm between 1583 and 1603 nm.