Quintuple-ring based erbium fiber laser with tunable single-frequency output in L-band bandwidth

Abstract In this article, we propose an erbium-doped fiber (EDF) laser with a quintuple-ring design to achieve single-longitudinal-mode (SLM) operation and stable and wide wavelength selectable over the L-band range. The mode-filtering effect produced by the quintuple-ring scheme can mitigate side-mode oscillations, enabling stable SLM output and extending the wavelength-tunable bandwidth from 1558.0 nm to 1620.0 nm (62 nm). The matching optical signal-to-noise ratio (OSNR), output power, optical and maximum output fluctuations in both power and wavelength are verified and discussed across the accessible wavelength output bandwidth. Furthermore, the proposed quintuple-ring configuration effectively narrows the laser linewidth to the sub-kHz target.