Reconfigurable Three-Mode Converter for Flexible Mode Division Multiplexing Optical Networks

Mode converters with reconfigurable functionality are essential for enabling flexible operation in modern mode division multiplexing (MDM) technology-based optical networks. In this paper, we propose a novel reconfigurable three-mode converter capable of converting the TE
₀
, TE
₁
, and TE
₂
modes to any desired output mode, such as TE
₀
, TE
₁
, or TE
₂
, for use in MDM optical communication system. Our device utilizes thermo-optic (TO) effects and consists of cascaded Y-junctions and Mach-Zehnder interferometers (MZIs), comprising two three-arm mode converters and one two-arm mode converter. The analytical and numerical verification of our device demonstrates its efficient operation, and the measurement results align favorably with the simulated performance. Our photonic integrated circuit (PIC) compatible fabricated device exhibits the mode conversion efficiency (MCE) of higher than 92.5% with maximum insertion loss (IL) of 8.3 dB and crosstalks (XTs) lower than -18.9 dB in the entire C band (1.530-1.565 μm). Our three-mode energy efficient and polarization-insensitive converter offers promising potential in enhancing the flexibility of MDM optical networks, making it a viable candidate for future development and deployment.