High OSNR single-longitudinal-mode thulium-doped fiber laser based on a cascaded dual-ring cavity filter.

• A high OSNR single-longitudinal-mode thulium-doped fiber laser based on a cascaded dual-ring cavity filter was proposed and demonstrated. • A CDRC filter was used as the mode-selection mechanism. • The proposed TDFL has highly stability and SLM laser output over 60 min, and the linewidth was 11.82 kHz with an integration time of 0.001 s. A high optical-signal-to-noise ratio (OSNR) single-longitudinal-mode (SLM) thulium-doped fiber laser (TDFL) is proposed and has been investigated. SLM lasing was realized by utilizing a uniform fiber Bragg grating (UFBG) and a cascaded dual-ring cavity (CDRC) filter. The design, simulation, and characteristic analysis of three compound-cavity filters based on the Vernier effect are presented in detail, and provided the basis for experiments. The single-wavelength SLM lasing with a high OSNR of ∼75.10 dB, operating at 2048.44 nm was pumped by a 793 nm laser diode, and the SLM lasing was continuously monitored for 60 minutes. The peak power fluctuation and wavelength drift were less than 0.685 dB and 0.01 nm, respectively, over this time span. During the test, the relative intensity noise was below −128.49 dB/Hz above 1 MHz and the linewidth was 11.82 kHz with an integration time of 0.001 s. [ABSTRACT FROM AUTHOR]