A Wavelength-Tunable Single-Longitudinal-Mode Fiber Ring Laser With a Large Sidemode Suppression and Improved Stability

A high-performance single-longitudinal-mode (SLM) fiber ring laser incorporating a high finesse ring filter that contains a section of weakly pumped erbium-doped fiber is proposed and experimentally demonstrated. The incorporation of the high finesse ring filter can suppress multimode oscillation, improve power stability, and increase sidemode suppression ratio (SMSR). A stable SLM oscillation with a tunable range from 1522 to 1573 nm and an SMSR as high as 68 dB is experimentally demonstrated.