Abstract
In mode division multiplexing (MDM) optical system, the mode filter has become an inseparable part to reduce modal crosstalk and transmit the desired modes unabatedly. As filtering out lower-order mode is difficult, here we propose a reconfigurable structure of a higher-order mode pass filter consisting of two tunable mode converters and a directional coupler (DC) in a three-mode planar waveguide platform. By switching the working states of the mode converters, the structure can also be used as a fundamental mode (TE0) pass filter and hence dynamic output signals can be achieved. For the second-order mode (TE2) transmission, the simulated excess loss is ∼0.61 dB at 1.550 μm and the extinction ratio remains ≥24 dB (power ratio of TE0 & TE2 Launch) and ≥25 dB (power ratio of TE1 & TE2 Launch) at the entire C-band (1.530-1.565 μm). The device has negligible polarization dependence and hence the TM polarization exhibits similar results.