A watts-level single-longitudinal-mode kHz-linewidth fiber laser based on a gain-controlled active compound cavity

We proposed a fiber laser based on a gain-controlled active compound cavity. Through the gain control of the main cavity and the seeding of the sub-cavity, a single-longitudinal-mode, mode-hopping-free continuous-wave lasing at 1550 nm was achieved. The stabilized output power was 36 dBm, with a signal-to-noise ratio of 40 dB. The 3 dB linewidth of the RF spectrum under the single-frequency lasing was 7.1 kHz. Furthermore, the laser's wavelength shift was less than 0.01 nm for over 2 h of lasing time.