In this paper, we demonstrate a simple structure, ultra-narrow linewidth, extremely high stability and high optical signal to noise ratio single-longitudinal-mode (SLM) erbium-doped fiber laser (EDFL). Nested Fiber Ring (NFR), nested in the ring cavity of EDFL, is employed to serve as a high quality mode filter to eliminate the dense longitudinal mode of the EDFL. The mode-selection capability of the RIR is investigated and discussed theoretically and experimentally. Saturable absorber, which composes of a section of unpumped polarization maintaining erbium-doped fiber and a Fabry–Perot fiber Bragg grating (FP-FBG), is employed to produce a dynamic narrowband grating to ensure the SLM laser output. Saturable absorber, consisted of a section of unpumped polarization maintaining erbium-doped fiber, produces a dynamic narrowband grating to ensure the SLM laser output. We achieve a ultra-narrow linewidth SLM laser output of 550 Hz. The laser has an optical signal-to-noise ratio (OSNR) of more than 59 dB. In addition, the stability of the wavelength and power fluctuations below 0.03 nm and 0.02 dB, respectively. The single-longitudinal-mode fiber laser has a compact structure, ultra-narrow linewidth, and excellent performance, and is expected to be used in the fields of coherent communications, precision metrology, and so on.

中文翻译：

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使用嵌套光纤环和可饱和吸收体的超窄线宽单纵模光纤激光器

在本文中，我们展示了一种结构简单、超窄线宽、极高稳定性和高光信噪比的单纵模（SLM）掺铒光纤激光器（EDFL）。嵌套光纤环（NFR）嵌套在EDFL的环形腔中，用作高质量模式滤波器，以消除EDFL的密集纵模。从理论上和实验上研究和讨论了 RIR 的模式选择能力。可饱和吸收体由一段非泵浦保偏掺铒光纤和法布里-珀罗光纤布拉格光栅（FP-FBG）组成，用于产生动态窄带光栅以保证SLM激光输出。可饱和吸收器由一段非泵浦保偏掺铒光纤组成，产生动态窄带光栅以确保SLM激光输出。我们实现了 550 Hz 的超窄线宽 SLM 激光输出。该激光器的光信噪比 (OSNR) 超过 59 dB。此外，波长和功率波动分别稳定在0.03 nm和0.02 dB以下。单纵模光纤激光器结构紧凑、超窄线宽、性能优良，有望应用于相干通信、精密计量等领域。