Abstract
We propose and demonstrate a single-longitudinal-mode (SLM) grating-based erbium fiber laser with a passive multiple-ring cavity structure in S-band operation. The laser is fundamentally structured by adding three different short ring cavities, which serve as the mode filters, into a major ring cavity. When an S-band mode-restricting intracavity fiber Bragg grating is combined, the proposed resonator can guarantee a SLM laser oscillation. Proposed fiber laser effectively suppresses the side-mode frequencies of 1 GHz and provides an output power of 0.1 dBm with a side-mode suppression ratio (SMSR) of 48.6 dB at 1513.35 nm.