Stabilized single-longitudinal-mode fiber laser with broadband and flat wavelength output

In this study, we present and experimentally demonstrate an erbium-doped fiber (EDF) quad-fiber-ring (QFR) laser with selectable and flat single-longitudinal-mode (SLM) wavelength output. The designed QFR scheme not only can suppress dense multi-mode oscillation, but also can broaden and flatten the output wavelength covering C- and part of L-bands over a bandwidth from 1519.0 to 1579.0 nm when using a C-band EDF as gain medium. Additionally, the output power, optical signal to signal ratio (OSNR), linewidth, stability and tunability of the proposed EDF laser are also discussed.