Erbium-doped fiber dual-ring laser with stable single-longitudinal-mode and 55-nm tuning range

In the investigation, we propose and demonstrate a stabilized and wavelength-selectable erbium-doped fiber (EDF) compound-ring laser with single-longitudinal-mode (SLM) oscillation covering both C-band and L-band ranges. Here, the dual-ring-cavity (DRC) scheme with an unpumped EDF-based saturable absorber (SA) is proposed in the EDF laser to guarantee SLM output. The proposed DRC of EDF laser can produce the mode-filter and ultra-narrowband auto-tracking filter effects to suppress the densely multi-longitudinal-mode (MLM) and extend the effective gain of EDF in a wavelength range of 1525.0-1580.0 nm. In addition, the observed output stabilities of power and wavelength in the proposed EDF DRC laser are also experimented and discussed.