A Wide-Range Narrow-Linewidth Tunable Fiber Laser

This paper presents a wide-range narrow-linewidth tunable fiber laser based on a double-ring cascaded composite resonator and a ring resonator for cyclic narrowing of the linewidth, achieving single longitudinal mode output with wide wavelength tunability and effective narrowing of the linewidth. The proposed wide-range narrow-linewidth tunable fiber laser has a moderate and stable output power level within a 40 nm wavelength tuning range. Additionally, the proposed tunable laser successfully suppresses multi-longitudinal mode competition, obtaining stable single longitudinal mode output, a 20 kHz narrow linewidth characteristic, and a high signal-to-noise ratio better than 70 dB in the 1530–1570 nm range.