Periodically Poled Lithium-niobate-based Wavelength Converters for Waveband Extension to U-Band and Beyond

We developed periodically poled lithium niobate (PPLN)-based wavelength converters for U-band expansion, achieving 3-dB converted gain flatness and 6-dB noise figure for full U-band expansion. The expanded waveband is covered from 1624.23 to 1675.99 nm. A converted 1.2-Tbps/ch. wavelength-division-multiplexing signal was successfully transmitted over 100-km G.654.E fiber. By changing the PPLN temperature parameters of the same converters, the conversion bandwidth can be shifted to longer wavelengths beyond the U-band, which corresponds to 1675.99–1719.24 nm. In this situation, we demonstrated the extensibility beyond the U-band up to 1719 nm.