Compact Mode Division (de)Multiplexer Based on Collaterally Coupled SOI Waveguides

We present the design of a compact 5-mode division (de)multiplexer based on silicon-on-insulator waveguides for on-chip optical interconnects. The configuration consists of two coupled sections where each section comprises of two collocated asymmetric directional couplers to couple light from two input waveguides carrying independent signals into two TE modes (TE
₁
, TE
₂
or TE
₃
, TE
₄
) of an interconnect trunk waveguide. For coupling into the TE
₀
mode of the trunk waveguide, an adiabatic taper is used to connect a fifth input waveguide. The proposed design with collocated directional couplers offers an advantage of a small footprint compared to sequential designs. The total coupling length of the device for multiplexing TE
₁
to TE
₄
modes is only 38.89 μm. In addition, the device exhibits low insertion loss ~0.24 dB and crosstalk better than -33 dB at the design wavelength of 1550 nm.