Glass-based optical On-Board-Transceiver for >25Gb/s/ch
The world’s first hybrid integrated on-board transceiver using a glass interposer
Within the project HyPOT, Fraunhofer IZM, together with its industrial and academic partners, is developing a hybrid integrated glass-silicon based interposer for data communication at a wavelength of 850 nm
A glass interposer with through glass vias (TGVs) is used as a carrier for the silicon components e.g. 12 channel VCSEL-, photodiode array and driver ICs. The glass interposer is processed at wafer level using state-of-the-art technology. The high frequency routing on the glass interposer is optimized for data rates up to 28Gbit/s/channel. The glass substrate with TGVs enables a low
signal loss transmission in the electrical and optical domain. The electro-optical components like photodiodes and VCSELs are
assembled on the glass carrier with flip-chip contacts where the optical path is trans-mitted through the glass interposer.
Fresnel-lenses are individually designed and monolithically integrated in the glass interposer for optical beam shaping. Alternatively, polymer lenses can be applied after flip-chip assembly. Advantageously for cooling is the bottom emitted optical signal and the flip-chip approach which allow an improved cooling of the components from the top. This approach excels cooling possibilities of commercial products.
The optical design reduces losses by coupling unit substitution with a standardized MT Prizm® ferrule down to <0.5 dB for RX or <2 dB for TX. Free space propagation with a collimated beam between these lenses and an electro-optical circuit board can be up to 2 mm.
These high coupling tolerances and low losses arise by a lens shape tailored to the demands of this setup. The customized polymer lenses are produced and characterized at Fraunhofer IZM.