iNEMI-IPSR Board-Level Optical Interconnect Project

iNEMI and IPSR (Integrated Photonic Systems Roadmap) are working together to assess the system-level benefits of, and issues associated with, single-mode (SM) expanded beam coupling for on-board interconnect. With this information, the industry will be able to properly prioritize the component development required to accelerate silicon-photonics implementation.




The IPSR, along with other industry roadmaps, predicts that silicon-photonics-based transceiver modules will provide the most cost-effective solutions for on-board interconnections in the future. However, before the anticipated cost benefits of silicon photonics can be realized, new high- performance and cost-effective solutions to optical packaging and connectorization must be developed. Obtaining optimum performance and functionality from silicon photonics devices requires single mode operation which, to date, has meant high-cost components. Costs associated with packaging and connectorization currently dominate the manufacturing cost of short-distance interconnects, and are inhibiting commercial implementation of such systems. 
To address the need for lower-cost SM connections, manufacturers have begun developing expanded-beam optical connectors in which the optical mode of the SM fiber (~ 10 microns diameter) is expanded to a larger collimated beam (e.g. 80 microns in diameter). This expansion relaxes the alignment tolerance between connector elements from submicron to a few microns, making the use of injection molded parts feasible. Furthermore, the use of expanded-beam connectors offers the added benefit of improved tolerance to contamination of the optical interface with dust. However, to date, expanded-beam versions of SM connectors have shown higher losses than desired by system designers, and thus have not been commercialized. 

Scope of Work

This iNEMI-IPSR project plans to design, assemble and test a prototype on-board fiber optic interconnection system based on silicon photonic transceiver modules, single-mode fiber cables, and expanded-beam optical connectors for the package, backplane, and front-plane interfaces.  The prototype will be based on 12-fiber ribbon fiber cables and 12-channel optical connectors, and will operate at 25 Gbps channel rate.  Existing technologies will be leveraged wherever possible to allow a system demonstration to be performed in the shortest possible timeframe.

Phase 1

This first project assessed the performance of prototypes of board-level interconnect systems based on single-mode (SM) fiber, expanded-beam optical coupling, and silicon photonics transceivers. The objective was to evaluate existing and developing components, and identify gaps in the board-level technologies needed for practical implementation.  Additional information.

Phase 2 (Expanded-Beam Module Interface)

This follow-on project, currently in formation, plans to specify, design, model, build and demonstrate a board-level optical interconnect system with an expanded-beam optical connector developed for the chip module. Additional information

Papers & Presentations


On-Board Optical InterconnectionA Joint Development Project Consortium, Terry Smith (3M) and John MacWilliams (U.S. Competitors), presentation from AIM Photonics 2015 Fall Meeting (October 31-November 2; Cambridge, Massachussetts)