Fig. 4: High-speed single-λ MDM on-chip interconnect.
a Schematic of the single-λ MDM transmission based on the packaged five-mode chip. Input continuous-wave light is divided by a splitter into five paths, each modulated by a modulator (MOD) and then coupled to a packaged chip via a fiber array (FA). Each path corresponds to an orthogonal mode in the MDM chip. At the receiver end, the mixed signal is demultiplexed by a mode deMUX and then coupled into photodiodes (PD) through another fiber array, where different mode channels are received and demodulated individually. b Macroscope image of the packaged MDM chip with a pair of fiber arrays. c False-color SEM image of the five-mode MUX. It confirms the successful transfer of the expected digital pattern onto the chip. Etched holes with well-defined square shapes and point-like contacts along diagonals indicate a high-quality fabrication result that accurately replicates the target design. This fabrication robustness stems from our digitally designed pattern and its relatively large MFS. d BER measurements for the MDM and single-port transmission for all five-mode channels under different ROPs. An indicative FEC threshold is given at 0.02, corresponding to a pre-FEC BER for the OFEC threshold. BER, bit-error rate; ROP, received optical power. e BER measurements for MDM transmission for all five channels under different data rates. At the data rate of 324 Gb s−1, all five channels exhibit BER values below the OFEC threshold. f Corresponding eye diagrams for the 108 GBaud PAM-8 signals at different channels.
