Low-Loss Silica Waveguide Dual-Mode Switch Based on Parallel-Modal-Processing

The arbitrary MDM signal routing scheme incorporating the parallel-modal-processing on a silica planar lightwave circuit is proposed. Specifically, a low-loss thermo-optic E₁₁/E₂₁ mode demultiplexing switch that offers the function of mode separation and routing is theoretically proposed and experimentally demonstrated. This dual-mode switch is composed of a 1 × 2 directional coupler-based selective mode switch unit and a cascaded 2 × 2 multimode interference coupler-based mode-insensitive switch unit. The CMOS-compatible processing is employed in device fabrication. For all mode routing states, the measured fiber-to-fiber insertion loss of both E₁₁ and E₂₁ modes is less than 6 dB within the entire C-band. The demonstrated work highlights the feasibility of direct parallel-processing of high-order modes without the introduction of (de)multiplexers. The proposed scheme promises MDM networks a simple framework with low optical loss.