Coupling elements for optical printed circuit boards with precision molded alignment structures

In this paper we present a board level optical interconnect based on embedded standard multimode glass fibers and novel surface mounted coupling elements for passive alignment. The coupling elements are placed onto fiber stubs extending into milled openings in the optical PCB and provide a low loss butt coupling without the need for focusing optics or mirrors. Now we present for the first time temperature resistant, molded coupling elements, which withstand soldering temperatures and are transferred from highly accurate LIGA structures. Measurements on a complete optical link with passively aligned coupling elements, VCSEL drivers and receiver electronics show a clearly open eye and an error free transmission of a 2.5 Gbit PRBS signal over several hours of test. For an extension of the technology to higher transmission rates we developed coupling elements for multiple parallel optical interconnects.