Fiber Array Attach for Co-Packaged Optics: High Volume Production Process Control and Performance

Optical loopbacks are used for decades to monitor optical fibers coupling on photonic integrated circuit dies providing the insertion loss values. So far, they are the standard monitoring and reporting measurements used for fiber array attach process. However, removing the loopbacks in the next generation of photonic modules (such as in co-packaged optics) could lead to significant wafer die footprint reduction, assuming an alternate performance monitoring is available. In response to this global market trend, we developed two innovative technics to monitor the optical coupling process even if no loopbacks are present into the fiber attach site. Using an optical backscattering reflection and an in-line glass lid parallelism measurements, we can now predict the equivalent insertion loss values obtained through a predictive model. Thanks to these two techniques compatible with the high-volume manufacturing of co-packaged optics, we are now able to guarantee the quality of an optical fiber to die coupling on fully functional fiber attach sites.