All-optical wavelength conversion for hybrid WDM–MDM signals using segmented thin-film PPLN waveguides

The hybrid multiplexing technique is an essential way to satisfy the rapid growth of optical communication capacity. All-optical wavelength conversion (AOWC), a fundamental function to support the all-optical networks, becomes challenging for hybrid multiplexed signals involving wavelength-division multiplexing (WDM) and mode-division multiplexing (MDM). An AOWC method is presented for hybrid WDM-MDM signals based on a segmented thin-film periodically poled lithium niobate (STFPPLN) waveguide, which has the ability to deal with each mode in a separate segment. By considering three modes (<i>T</i><i>E</i>₀, <i>T</i><i>E</i>₁, and <i>T</i><i>E</i>₂), the STFPPLN waveguide is designed and a difference-frequency generation (DFG) conversion efficiency of -9.67<i>d</i><i>B</i> with a uniformity variation of 0.37 dB throughout the C band is achieved using a 100 mW pump in an 11 mm long waveguide. The conversion bandwidth is predicted as 87.5 nm, which enables 330 WDM-MDM channels (110 wavelengths × 3 modes), with the crosstalk suppressed below -50<i>d</i><i>B</i>.