Best connections: New connecting technologies for optical components
Also private users are to benefit from the fast data transfer through fibre optic networks. So that the data can reach every household, these networks must branch. Yet it’s not so easy to weld fibre optics or connect them to optical components like filters or lasers. The light conducting core of the fibre is about one tenth the diameter of a human hair, and the efficient, interference free transmission of light waves depends greatly on the precision of the junctions.
“Fibre to the home – that’s the keyword,” explained Christian Kutza, Managing Director of FOC-Fibre Optics Components in Adlershof. Together with the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute and other companies in Berlin, FOC has developed a new connecting technology. “We intend to offer large piece numbers at prices fit for the world market,” emphasised Kutza. The foundation is provided by a tiny rectangular plastic board of one by three millimetres containing integrated waveguides functioning as couplers between the component and the fibre. The perfect vertical alignment of the fibre’s severed edge to the waveguide is obtained with a receiving U groove that is precision etched into the board. “Simple, but highly effective,” concluded Kutza with satisfaction. “We avoid adhesive in the optical path and save complex adjustments and subsequent control based on measurements.” FOC has already set up assembly areas and sold its first components to pilot projects.
At the Fraunhofer Institute for Reliability and Microintegration (IZM), researchers headed by Stefan Schmitz have modified the established and low cost technology of wire bonding. This uses short polymer fibres to link optical components to each other and to a PCB of plastic coated glass. First, the bonding tool presses on one end of the fibre parallel to the board. The two plastics are then literally welded together under the action of heat and friction generated by ultrasound. The fibre is then formed into a small loop to the next contact, there bonded, and then severed. “We have adapted the process parameters like temperature and fibre routing to the new highly sensitive materials. The qualities achieved with our automatic bonder are comparable with those of previous procedures,” concluded Schmitz. The next step will be to demonstrate applications in sensor installations and data transfer and to initiate series production.
by Uta Deffke