Efficient and Broadband All-Optical Wavelength Conversion Between C and O Bands in Nanophotonic Lithium Niobate Waveguides

With the emergence of 5G communication, the traditional wavelength division multiplexing (WDM) technology within the C-band faces challenges in meeting the increasing data traffic demands in optical transmission networks. To increase the transmission capacity, using extended wavebands beyond the C-band, such as S, L, and O bands, is a promising solution. An efficient approach to utilizing multiple optical wavebands is all-optical wavelength conversion (AOWC), which is fully transparent to symbol rate and modulation format. In this paper, we experimentally demonstrated broadband AOWC of a 56Gbaud on-off keying (OOK) signal between C and O bands in a single thin-film periodically poled lithium niobate (PPLN) waveguide. For both C-to-O and O-to-C AOWCs, a marginal 0.2 dB received optical power (ROP) penalty was successfully achieved between the idler and back-to-back (B2B) signal waves. Additionally, for more detailed performance evaluations, we measured the 3-dB signal bandwidths and on-chip conversion efficiencies (CEs) in 5 mm and 1 cm long PPLN waveguides for both C-to-O and O-to-C AOWCs. As a result, the maximum 3-dB signal bandwidth of 85 nm (from 1500 to 1585 nm) was obtained in the 5-mm-long PPLN waveguide and the maximum on-chip CE of −7.2 dB was obtained in the 1-cm-long PPLN waveguide.