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• A five wavelength-switchable single-longitudinal-mode erbium-doped fiber laser was proposed. • A cascaded PS-FBG was designed and analyzed. To the best of our knowledge, this is the first time that the PS-FBG is used as a multi-channel filter to realize stable multiple SLM single-wavelength outputs. • Five single-wavelength switchable SLM outputs were generated in stable condition over 60 min. • The minimum linewidth at an integration time of 0.001 s was 1.3102 kHz. Wavelength-switchable fiber lasers play an important role in optical fiber communication systems. Although phase-shifted fiber Bragg grating (PS-FBG) has a narrow 3 dB bandwidth, it has rarely been reported as a multi-channel optical filter. Therefore, a five wavelength-switchable single-longitudinal-mode (SLM) erbium-doped fiber laser (EDFL) was implemented and analyzed, where the cascaded PS-FBG with a 3 dB bandwidth of each channel narrower than 0.024 nm was used as a five-channel filter. The design, fabrication, and characterization of cascaded PS-FBG were implemented and analyzed in detail. By tuning the micro-displacement platform, five-single wavelength switchable SLM outputs with a high optical signal-to-noise ratio (OSNR) were generated and the outputs were monitored over 60 min. The measured maximum wavelength drift and the peak power fluctuation were 0.02 nm and 1.73 dB. The relaxation oscillation peaks were lower than −100 dB/Hz and the minimum linewidth at an integration time of 0.001 s was 1.3102 kHz. To the best of our knowledge, this is the first time that the PS-FBG is used as a multi-channel filter to realize multiple SLM single-wavelength outputs. [ABSTRACT FROM AUTHOR]

• 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]