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 of (a) stabilized first span (black line) and stabilized second span (red line) where phase locking bandwidth of each span is shown, (b) unstablized 500-km link (black line), stabilized 500-km cascaded link (purple line), stabilized 500-km single-span link (red line), theoretical stabilized 500-km cascaded link (yellow line), and theoretical stabilized 500-km single-span link (blue line).