Silicon Photonics for Mid-Board Optical Modules Marc Epitaux Chief Architect at Samtec, Inc
Outline Interconnect Solutions Mid-Board Optical Modules Silicon Photonics o Benefits o Challenges DragonFly Packaging Platform Conclusion
Interconnect Challenges Raw speed Distance Size Cooling and thermals Various environmental constraints
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
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
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)
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
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
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
DragonFly Electrical Signal Integrity Features Organic substrate 0.5mm edge connector BGA interconnect SiPho chip (200um) Modeling & Simulation Modeled the system in HFSS IL: -1.55 db Insertion loss @ 28 GHz RL: < -18 db up to 28 GHz Nyquist.
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
MBOM Implementation Example
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
Thank you Acknowledgments: Samtec Team IRT Nanoelec Partners