Silicon Photonics for Mid-Board Optical Modules Marc Epitaux

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1 Silicon Photonics for Mid-Board Optical Modules Marc Epitaux Chief Architect at Samtec, Inc

2 Outline Interconnect Solutions Mid-Board Optical Modules Silicon Photonics o Benefits o Challenges DragonFly Packaging Platform Conclusion

3 Interconnect Challenges Raw speed Distance Size Cooling and thermals Various environmental constraints

4 Why Miniature Mid-Board Optical Modules? Bring optics on board, closer to the chipset (opposed to the front-pluggable approach) Optical flies over to backplane or front panel Highest density Novel cooling options Qualified to Telcordia, sometimes MIL standards Form factor comparison between MBOM & Front Pluggables FireFly Optical Modules in array. Densest interconnect in the industry

5 Mid-Board Optics Standardization Consortium for On-Board Optics Effort to standardize on-board optics Has adopted a two connectors mounting concept Two lane width proposed: 8x and 16x Three module length proposed 0.6mm pitch highspeed connector Full specification expected by mid-year with first sample Q1 18

6 Why Silicon Photonics? Direct modulated laser diode is challenged with next generation data rates (>28Gbps) Optical function integration: photodetection, WDM filter, modulation, splitter Higher channel counts (8x, 16x) Enable advanced modulation: PAM, WDM, QAM, DPSK Single mode operation allows longer reach (up to 2km) Volume manufacturing (wafer processing)

7 Silicon Photonics Challenges Circuit integration o Platform and CAD tool homogenization o Limited generic component offering o Test infrastructure Light coupling o Laser integration o Single mode fiber coupling and alignment Packaging integration o High speed signaling and interconnect o Thermal management Example: Laser integration Platform/PDK? Fabrication/foundry? Coupling approach? Test and Reliability? Courtesy UCSB

8 DragonFly Packaging Platform Development carried out in the IRT Nanoelec program Architectural Features MBOM packaging Semiconductor manufacturing SiPho Engine (BGA ed) Single mode optics Flip-chipped PMDs Backside illumination 4x 56G bandwidth

9 FIBER COUPLING EFFICIENCY (%) DragonFly Optical Layout Optical Features Single mode fiber Free space optical layout Grating Coupler o 1D output (3dB IL) o 2D input (6dB IL) o Mode converter Alignment Strategy o Passive o Active 100% 90% 80% 70% 60% 50% 40% 30% 20% FIBER COUPLING EFFICIENCY FROM 10K MONTE CARLO With same tolerances Design D would be better for Active Alignment 10% Design A Design B Design C Design D Design E 0% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % OF POPULATION Design C: better for Passive Alignment

10 DragonFly Electrical Signal Integrity Features Organic substrate 0.5mm edge connector BGA interconnect SiPho chip (200um) Modeling & Simulation Modeled the system in HFSS IL: db Insertion 28 GHz RL: < -18 db up to 28 GHz Nyquist.

11 DragonFly Thermal Management Power Density Multi-Gbps interconnect requires signal processing and electronic compensation (CDR, CTLE, FFE, DFE, PAM4, ) Smaller, integrated device increases drastically the power density (1.7W/cm 2 at the MBOM level) 200G DragonFly Driver + CDR TIA + CDR Laser Driver Phase Shifter Micro-Controller + IO Ctrl Total Est. Power 1 300mW 1 400mW 400mW 100mW 150mW 3 350mW Heatsink Alternatives Convection cooling (not sufficient) Conduction cooling Immersion Autodesk CFD 360 Simulation

12 MBOM Implementation Example

13 Conclusion The combination of Mid-Board Optics packaging platform and Silicon Photonics is offering new high performance horizon for optical interconnect: o Bring the fibers closer to the signal processor (ASIC, FPGA, switch) o o o Increase the interconnect density Offer a path to 100Gbps and much beyond Extend optical link reach However the promises of photonics integration is still facing challenges: o o o Circuit integration Light coupling Packaging integration o A novel Mid-Board Silicon Photonics packaging platform has been presented which address most of those challenges

14 Thank you Acknowledgments: Samtec Team IRT Nanoelec Partners