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

To increase the transmission capacity in optical transport networks, multi-band (MB) wavelength-division multiplexing transmission technology is an attractive solution. A band-switchable MB optical cross-connect (BS-OXC) enables not only the output port but also the output wavelength band of the input signals to be switched. This feature contributes to flexible upgrading to MB networks and effective use of expanded wavelength resources. A key device of the BS-OXC is an all-optical inter-band wavelength converter (AO-WC) based on nonlinear optical effects. To fully bring out the benefits of the BS-OXC, the low penalty with the passage of the AO-WCs, i.e., cascadability, is important. This paper introduces our works on a BS-OXC with AO-WCs based on periodically poled lithium niobate (PPLN) waveguides that provide wideband and high-efficiency wavelength conversion. We also review a recent experimental demonstration for the high cascadability of PPLN-based AO-WCs. Furthermore, we report a feasibility demonstration of the BS-OXC in a C-band and C+L-band hybrid network as an early stage of upgrading to the MB network.