Silicon Multi-Band On-Chip Mode-Division (De)Multiplexing for High-Speed Optical Interconnect in Both EDFA and TDFA Wavebands

We propose and demonstrate a four-mode division (de)multiplexer capable of operating in two distinct wavebands centered at 1550 nm and 1970 nm. The phase matching condition can be established across multiple wavebands in the asymmetric directional couplers. The 2 μm light can be coupled back and forth multiple times with a total coupling length that equals the minimum coupling length of the 1.55 μm light, and the structure could be scaled to more mode channels. As a proof of concept, the fabricated dual-band four-mode (TE₀-TE₃) device exhibits low insertion losses and crosstalk <2.2 dB and <−13.0 dB from 1510 to 1590 nm, <3.1 dB and <−10.6 dB from 1950 to 2000 nm, respectively. Moreover, we further demonstrate 4 × 114 Gbps optical transmission at 1.55 μm waveband and record-high 4 × 84 Gbps optical transmission at 2 μm waveband with PAM8 signals in the fabricated devices, respectively. The results indicate that the demonstrated multi-band mode division (de)multiplexer is promising for future chip-scale high-speed optical interconnects across multi-wavebands.