Experimental demonstration of simultaneous mode and polarization-division multiplexing based on silicon densely packed waveguide array.

A silicon mode and polarization-division multiplexing scheme based on a densely packed waveguide array structured as a bus waveguide is introduced. A short adiabatic taper is adopted for (de)multiplexing. Such a structure shows theoretical insertion losses that are <0.05 dB and crosstalk that is <-20 dB over a wide wavelength band for all five supported modes. The structures for (de)multiplexing are fabricated and characterized experimentally. A device, which consists of a multiplexer, a 50-µm-long straight-bus waveguide, and a demultiplexer, exhibits insertion losses that are <0.6 dB and crosstalk that is <-15 dB over an 80 nm wavelength band. The demonstrated (de)multiplexer has a total length of 60 µm, and the bus waveguide has an effective width of 1.58 µm.