Supplement 1

detailed descriptions of the photonic band structure diagrams of the photonic crystal lattices, the dispersion curves of the sandwich valley-topological edge waveguides, the design and fabrication methods of the valley-topological photonic crystal TE mode multiplexer, the design of the scatter suppression coupler, the loss of the connection waveguides, the TE mode detection method, the multiplexing communication setup, an analysis of MDM-WDM communication and captured constellation diagrams as well as the comparison with reported (de)multiplexer