Fig. 1. Schematic of a silicon-based micro-ring optical engine co-packaged with an XPU

Fig. 2. Research progress of multi-wavelength lasers. (a) 16-channel laser SuperNova by Ayar Labs^[25]; (b) 4×4 200 GHz DFB array laser by Intel^[26]; (c) dark-pulse optical frequency comb laser and array MZM transmitter^[27]; (d) Kerr optical frequency comb and micro-ring array transmitter^[28]; (e) quantum dot FP cavity mode-locked laser by Innolume^[29]; (f) quantum dot mode-locked laser by Institute of Physics, Chinese Academy of Sciences^[30]

Fig. 3. Research progress of MRMs. (a) Carrier-injection-type MRM by Cornell University^[34]; (b) carrier-depletion-type MRM by University of Surrey^[35]; (c) carrier-depletion-type MRM by Oracle Corporation^[36]; (d) lateral-junction 100% doped MRM by XIOPM^[37]; (e) L-shaped-junction MRM by Intel Corporation^[38]; (f) dual-segment MRM by HPE^[39]; (g) vertical-junction spoke MRM by Ayar Labs^[40]; (h) vertical-junction MRM by AMD^[41]; (i) interdigitated-electrode vertical-junction MDM by Columbia University^[42]; (j) vertical-junction MDM by Beijing Institute of Technology^[43]

Fig. 4. Research progress of micro-ring thermal control. (a) Multi-metric thermal tuning by University of Toronto^[49]; (b) independent optical power level tracking thermal tuning by University of California, Berkeley^[50]; (c) dual-mode calibrated thermal tuning by Yonsei University^[51]; (d) high-precision closed-loop feedback thermal tuning by ETH Zurich^[52]

Fig. 5. Research progress of silicon-based germanium detectors. (a) Inductive-peaking vertical-PIN silicon-based germanium detector by HUST^[57]; (b) U-shaped-electrode vertical-PIN silicon-based germanium detector by HUST^[58]; (c) fin-shaped PIN silicon-based germanium detector by IHP^[59]

Fig. 6. Three types of DWDM receivers capable of receiving arbitrary polarization. (a) Polarization-insensitive micro-ring DWDM receiver structure; (b) polarization-diverse micro-ring DWDM receiver structure; (c) active polarization-tracking micro-ring DWDM receiver structure

Fig. 7. Research progress of CMOS drivers for MRM. (a) 45 nm SOI micro-ring driver by University of California, Berkeley^[67]; (b) Intel nonlinear equalization micro-ring driver^[53]; (c) Intel 8-channel micro-ring driver^[68]; (d) ISCAS dual-segment micro-ring driver^[69]

Fig. 8. Research progress of CMOS TIA. (a) Regulated shunt-feedback TIA by Intel^[70]; (b) low-noise TIA by ISCAS^[71]; (c) 16 nm three-stage TIA by University of Toronto^[72]; (d) 7 nm FinFET three-stage TIA by AMD^[73]

Fig. 9. Side view of the integrated packaging forms of the micro-ring optical engine. (a) 2.5D integrated packaging; (b) FOWLP integrated packaging; (c) 3D integrated packaging; (d) monolithic integration

Fig. 10. Research progress of optical engine substrate. (a) Low-temperature co-fired ceramic interposer by Acacia^[82]; (b) glass interposer packaging by The Georgia Institute of Technology^[83]; (c) silicon interposer technology by IMEC^[84]; (d) cavity-embedded organic substrate by NCAP^[85]

Fig. 11. Research progress of optical engine fiber connectors. (a) Reflow-compatible silicon optical engine package by IBM^[86]; (b) pluggable optical connector by Intel^[88]; (c) glass optical connector by Corning^[90]; (d) vertical optical coupling connector by US Conec^[91]