Low-Penalty Band-Switchable Multi-Band Optical Cross-Connect Using PPLN-Based Inter-Band Wavelength Converters

In multi-band optical networks, a band-switchable multi-band optical cross-connect (MB-OXC), which enables not only the output port but also the output wavelength band of the input signals to be switched, can significantly increase the accommodated traffic volume. An all-optical inter-band wavelength converter (AO-WC) is a key device to achieve the band-switchable MB-OXC and is required to have little signal degradation even when optical signals pass through it many times. In this article, we propose a low-penalty band-switchable MB-OXC using AO-WCs with periodically poled lithium niobate (PPLN) waveguides. The PPLN-based AO-WC enables high conversion efficiency (∼10 dB) and low noise figure (∼5 dB) for the wavelength-band conversion between the entire C-band and L-band over 4.8 THz. In addition, we experimentally evaluate the signal quality of a 96-channel 32-Gbaud DP-16QAM WDM signal with wavelength-band conversion by the PPLN-based AO-WCs. By optimizing the input power to the PPLN-based AO-WC, it is shown that the signal quality required to improve accommodated traffic volume can be achieved even after >20 wavelength-band conversions. These results confirm physical-layer feasibility of a band-switchable MB-OXC using the PPLN-based AO-WCs.