Optical Inter-Board Interconnects for high Throughput on-Board processors

Status date

The project objective was to design, manufacture and test a breadboard with very high density optical interconnects suitable for application in the next generation high throughput onboard digital processors.

  • Main issues were related to the manufacturing of the optoelectronic modules. In particular, realizing an hermetic feed through was  challenging and led to poor yield and higher prices if produced as is.
  • Another issue was also the assembly of the optoelectronic modules to the board without degrading the electrical performances and using a mounting process which is standard in surface mounting technology.
  • Test benches were also challenging as electrical interfaces could degrade the accuracy of the measurements  especially working at high speed data rate.
  • The optical flex supply chain was found to be important as a sole European source exists and wasn’t at the state of the art. 
Optoelectronic and passive modules are considered as a critical technology enabling the emergence of high demanding and high data rate processors.
In this context, developing the building blocks for implementing optical interconnects is a key point for the future processor.
These building blocks are well identified and some of them have proven mechanical reliable behavior and high data link performances:
  • Optoelectronic and passive modules
  • Optical flexes
  • Optical adaptor connectors
  • Electrical interposer used to interconnect the modules on PCB
Recommended future activities are finding a way to propose more mature optoelectronic modules by improving the production process.

Optical inter-board interconnects are key building block for digital transparent processor to be embedded in future flexible payload. This activity provided the opportunity to assess all mandatory building blocks to realize optical interconnects inside an optical interconnect breadboard mimicking an high-end processor. 

The project was divided in 7 work packages :
At the beginning of the study,  an exhaustive survey of the market was carried out in order to identify all the building blocks mandatory to build an optical breadboard (optical connectors, optical flex, optoelectronic at high data rate and passive modules).
Then the two following tasks were mainly dedicated to the optoelectronic and passive modules design and manufacturing which was realized by two different sub-contractors for the optoelectronic modules and testing according to the following test plan. 
Click for larger image.
The testing campaign shows that it was possible to reach a data rate of 1 Gbps at room temperature as illustrated in the following eye diagram
The testing have shown also that the performances were not degraded after radiation exposure
The others remaining work packages were then related to the detailed design, manufacturing and testing of the optical breadboard.
The breadboard was manufactured embedding an optical flex as seen in the picture here below and submitted to thermal testing and functional testing after vibrations withy levels equivalent to EQM ones

Click for larger image

Current status

 The study is completed