Long‑term stable 850‑Hz linewidth single‑longitudinal‑mode ring cavity fber laser using polarization‑maintaining fber

A long-term stable single-longitudinal-mode (SLM) all polarization-maintaining (PM) compound-ring cavity fber laser is reported. The results show that the PM fber’s strong ability to resist the environment disturbance allows fnely designing the length of each secondary cavity in real time according to the main cavity under the laboratory environment, and then the efective longitudinal mode spacing can be sufciently increased by accurately using the Vernier efect, so that the mode-hopping can be efectively suppressed. Furthermore, the temperature compensation is used for asynchronously fneadjusting each cavity length to follow the Vernier efect requirement more strictly. The mode-hopping-free SLM operation time of the packaged laser reaches 11nbsp;h. As far as we know, this is the longest SLM free running time of ring cavity fber laser to date. The optical signal to noise ratio of the laser reaches 77nbsp;dB and the linewidth is less than 850nbsp;Hz with up to 50 mW maximum output power