Fig. 1. Structure of the all-PM compound ring cavity fiber laser

Fig. 2. Single-longitudinal-mode characteristics monitored by the designed laser. (a) Single-longitudinal-mode characteristics measured by the F-P scanning interferometer; (b) beat frequency signals between a long-term stable single-longitudinal-mode adjustable diode laser and the designed laser with a frequency counter

Fig. 3. Output characteristics of the designed laser. (a) Laser output optical spectrum measured by the OSA, the insert shows the laser output power varying with pump power; (b) measured results of the output laser linewidth using a standard self-heterodyne system

Fig. 4. Measured RIN power spectrum density of the ring cavity fiber laser in the wide frequency range of 1mHz--50MHz and the measurement results of intensity noise of DBR fiber laser^[23]

Fig. 5. Measured frequency noise of the ring cavity fiber laser in the wide frequency range of 1mHz--1MHz and frequency noise of DBR fiber laser^[23]