Peter Demmer

Waveguide and packaging technology for optical backplanes and hybrid electrical-optical circuit boards

Due to ever-faster processor clock speeds, there is a rising need for increased bandwidth to transfer large amounts of data, noise-free, within computer and telecommunications systems. A related requirement is the demand for high bit-rate, short-haul links. Here, optical transmission paths are a viable alternative to high-frequency electrical interconnections, whereby layers with integrated waveguides are particularly suitable. The reasons for this include that a higher connection density can be achieved and the power dissipation, as well as interference from electromagnetic radiation, are significantly lower. The article presents general considerations and the results of research conducted by the German BMBF Project NeGIT, into the manufacture of circuit boards with embedded polymer optical waveguides. The electrical-optical boards were fabricated using precise photolithographic processes and standard lamination methods. They possess the thermal stability necessary for manufacturing processes and operational conditions, in terms of both bond strength and the stability of the optical properties. As part of this project, a design of an optical coupling in the daughter card and board backplane interfaces was developed and is presented as the centerpiece of this study.

New generation interconnection technology: printed circuit boards with integrated optical layers

The need for high data rate interconnects within computing and telecommunication equipment is continuously rising. As the performance of electrical interconnects is physically limited through the skin effect, optical interconnects can be used to overcome this problem. Within this paper some results achieved in the frame of the German research and development project NeGIT (new generation interconnection technology), focusing on printed circuit boards with integrated optical waveguides are introduced. The waveguides are part of an optical layer which is manufactured by a photolithographic process. Using standard lamination processes the optical layer is combined with electrical FR4-layers and the result is an electrical-optical printed circuit board which shows a sufficiently high thermal resistivity taking into account the manufacturing processes like lamination and soldering. The compound strength as well as the stability of the optical layer properties are good. Apart from the waveguide technology the concept for optical module-to-board coupling is presented.

New-generation interconnect

A new-generation interconnect for optical backplane systems based on printed circuits board is presented for transmitting data via integrated multimode polymer optical waveguides both on electro-optical transmitter/receiver processing boards and on optical backplane board. Different developments concerning this system such as optical waveguide technology, transmitter/receiver module activities, and optical interconnect/coupling concepts are discussed.