Single-Longitudinal Mode Ytterbium-Doped Fiber Laser Using Four 2 × 2 Fiber Couplers for Multiple Subring Ring Cavities

In this paper, we present a single-longitudinal mode (SLM) Ytterbium-doped fiber laser (YDFL) featuring a six-subring cavity (SSRC) structure. The YDFL achieves SLM output through use of the SSRC architecture. We evaluated the stability of both wavelength and power during the experimental measurements. The results show that the wavelength and power fluctuations over one hour were less than 0.01 nm and 0.03 dB, respectively. Measurements confirmed that the YDFL, with the SSRC structure, operates stably in a SLM state. Finally, by applying Lorentzian fitting to the measured data, a linewidth of 2.4 kHz was obtained.