On-Chip Silicon Two-Mode (De)Multiplexer for OFDM/OQAM Data Transmission Based on Grating-Assisted Coupler

We fabricate and demonstrate on-chip two-mode (de)multiplexing using a tapered asymmetrical grating-assisted contradirectional coupler-based TE0 and TE2 mode multiplexer and demultiplexer on the silicon-on-insulator platform. The designed silicon photonic device is composed of apodized grating couplers, a narrow waveguide, a bus waveguide, and an asymmetrical multimode grating-assisted contradirectional coupler. The operation principle of such a mode (de)multiplexer is analyzed according to the coupled mode theory. System experiments of orthogonal-frequency-division-multiplexing-based offset quadrature amplitude modulation (OFDM/OQAM) 256-ary QAM data transmission have been carried out for two-mode (de)multiplexing application at 23.89 Gbit/s. The bit error rate (BER) performance for the signal transmission through the fabricated two-mode (de)multiplexer is evaluated. The optical signal-to-noise ratio (OSNR) penalties of data transmission through the fabricated two-mode (de)multiplexer are less than 2 dB at a BER of 2e^-2 (20% forward error correction threshold).