Cascaded optical frequency transfer over 500-km fiber link using regenerative amplifier

Deng Xue^{1, 2, 3}, Jiao Dong-Dong^{1, 2, 3}, Liu Jie^{1, 3}, Zang Qi^{1, 2, 3}, Zhang Xiang^{1, 2, 3}, Wang Dan^{1, 3}, Gao Jing^{1, 2, 3}, Dong Rui-Fang^{1, 2, 3}, Liu Tao^{1, 3, †}, Zhang Shou-Gang^{1, 2, 3}

Plots of phase noise PSD versus Fourier frequency for phase noise of the free-running local oscillator (black line), input laser (red line), and regenerative amplifier (blue line).