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• A highly stable narrow linewidth erbium-doped fiber laser was proposed. • The self-injection locked mechanism was utilized in the ring-cavity fiber laser. • The cascaded Type Ⅱ fiber rings cavity filter was used to keep single-longitudinal-mode output. • The maximum wavelength drift was 0.0041 nm and the maximum peak power fluctuation was kept at a low level of 0.16 dB. • The minimum linewidth at a 0.002 s was 1.82 kHz. Narrow linewidth erbium-doped fiber lasers (EDFLs) hold in significant potential optical fiber sensing, wavelength multiplexing transmission, and optical fiber communication. However, many EDFLs produced outputs with linewidth in several kHz level. Therefore, a high optical signal-to-noise ratio (OSNR), narrow linewidth single-longitudinal-mode (SLM) EDFL was proposed and investigated in this work. The EDFL utilized a combination of compound-ring cavity filter and a self-injection locked mechanism to generate a stable SLM output with an OSNR greater than 72 dB. The maximum wavelength drift and maximum peak power fluctuation over 60 min were maintained at low values of 0.0041 nm and 0.16 dB. Moreover, a narrow linewidth of 1.82 kHz at a measuring time of 0.002 s was realized. Furthermore, the research also investigated output power variations with different pump powers, relaxation oscillation, and the dependence of output central wavelength on the axial strain. [ABSTRACT FROM AUTHOR]

• A highly stable single-longitudinal-mode erbium-doped fiber laser was proposed. • A novel mode-selection filter, composed of two Type-Ⅱ fiber rings and a 1.5 m SA was used to realize SLM output. • The maximum wavelength drift was not observed and the maximum peak power fluctuation was kept at a low level of 0.16 dB. • The minimum linewidth at an integration time of 0.005 s was 2.8809 kHz. Single-longitudinal-mode (SLM) fiber lasers have the advantages of stable output, long coherence length, and low noise. However, several fiber lasers still maintain multiple longitudinal mode outputs. Thus, a highly stable SLM erbium-doped fiber laser (EDFL) was proposed and investigated. The dual-ring compound cavity (DRCC) filter, composed of two Type-Ⅱ fiber rings, and a 1.5 m unpumped erbium-doped fiber (EDF) was used as a mode-selection filter. The mode-selection capability of the DRCC filter and unpumped EDF was investigated and discussed theoretically and experimentally. The proposed EDFL could generate stable SLM output with an optical signal-to-noise ratio of ∼ 64 dB over 60 min. The maximum wavelength drift was not observed on an optical spectrum analyzer and the maximum peak power fluctuation was kept at a low level of 0.16 dB. The output power variations with different pump powers, the relative intensity noise, the relaxation oscillation, and the linewidth at different integration times were investigated. Furthermore, the performance of the proposed EDFL acted as a strain sensor and temperature sensor with sensitivities of 1.0 pm/με and 11.4 pm/℃ were also discussed. [ABSTRACT FROM AUTHOR]

• 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]