In this paper, an erbium-doped fiber (EDF) octa-ring laser system with continuous-wave (CW) tunability and stable single-longitudinal-mode (SLM) output is presented and investigated. The octa-ring configuration can cause a mode-filter operation based on the Vernier effect for dense side-mode suppression and gain extension. Therefore, the available wavelength-tuning bandwidth of the laser can be achieved from 1519.0 to 1575.0 nm by utilizing conventional C-band EDF based gain-medium. Moreover, the output power, output stability, optical signal to noise ratio (OSNR) and laser linewidth of the demonstrated EDF laser are also executed and discussed.
