Broadband On-Chip Mode-Division Multiplexer Based on Adiabatic Couplers and Symmetric Y-Junction

The mode-division multiplexer/demultiplexer (MMUX/DeMMUX) is the crucial component for the implementation of mode-division multiplexing (MDM) transmission. We propose an on-chip two-mode MMUX/DeMMUX based on adiabatic couplers. Thanks to the principle of mode evolution, the proposed MMUX possesses advantages of broadband operation and high tolerance of fabrication error. The performance is experimentally evaluated by integrating the proposed MMUX and DeMMUX into an on-chip MDM link, with a low crosstalk of <;-19 dB and insertion loss of <;1.5 dB over a wavelength range of 90 nm. Furthermore, reasonable performance degradation can be observed for deviations of gap and etch depth from -50 to 50 nm.