In this Letter, a bidirectional amplifier configuration suppressing the relative intensity noise in a 1950-nm linearly polarized single-frequency fiber laser (SFFL) is proposed. The scheme to amplify the signal in a nonlinear saturated amplification regime with low gain distribution for suppressing the RIN is theoretically analyzed. By optimizing the input power level and reflectivity of the bidirectional power-amplifier, the RIN is decreased maximally by $\gt\! 24 \;{\rm dB}$ within the frequency range of 200 kHz. A stable output power of over 5.16 W with a polarization extinction ratio of 21.2 dB is obtained. Additionally, the amplified signal maintains a linewidth of 7.1 kHz nearly identical with that of the seed, both with a signal-to-noise ratio of more than 60 dB. This all-optical technique on noise suppression applied to the fiber amplifier paves the way to realize low-noise SFFL with power improvement.

中文翻译：

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通过双向放大器配置抑制1950 nm单频光纤激光器中的强度噪声

在这封信中，提出了一种双向放大器配置，该配置可抑制1950 nm线性偏振单频光纤激光器（SFFL）中的相对强度噪声。从理论上分析了在非线性饱和放大方案中以低增益分布放大信号以抑制RIN的方案。通过优化双向功率放大器的输入功率水平和反射率，可将RIN最大降低$ \ gt \!。24 \; {\ rm dB} $在200 kHz的频率范围内。获得了超过5.16 W的稳定输出功率，偏振消光比为21.2 dB。此外，放大后的信号保持7.1 kHz的线宽，几乎与种子的线宽相同，两者的信噪比均大于60 dB。应用于光纤放大器的这种用于抑制噪声的全光学技术为通过功率改善实现低噪声SFFL铺平了道路。