Fibre optic cables can transmit large amounts of data at high speed and are therefore becoming increasingly important in the course of digitalization. In order to monitor the performance of data lines, the optical fibres are split and the branches linked to sensors. However, splitting causes performance loss that has to be minimized. This can be achieved, for instance, by asymmetric splitting: Instead of dividing the fibre in equal halves, only a smaller part is branched off. The production of asymmetrical branches is a technical challenge, however, as these structures, with a thickness of 50 micrometres, are even thinner than a human hair.

Coburg University has addressed this problem in the AsyMode project, receiving expert support from the Technology Campus Teisnach Sensor Technology (at Deggendorf Institute of Technology). The project aimed to develop an industrial production method for asymmetric branching of multimode fibres. This fibre type is designed for data transmission over short distances and is therefore mainly used to cable networks inside buildings. Singlemode fibres, on the other hand, are better suited for long-distance data transmission.

Technologies for asymmetric splitting already exist for singlemode fibres but cannot be transferred to multimode fibres. The AsyMode project team therefore simulated and tested various new methods to achieve a splitting ratio of at least 70 to 30 percent in a fibre splitter. And they succeeded: By using ion exchange, the team was even able to realise a ratio of 75 to 25, thus covering the relevant range for datacom applications.

Close collaboration with a local fibre optics company, LEONI Fiber Optics GmbH, enabled the scientists from Coburg and Deggendorf to produce the asymmetric splitters in the company’s facilities. Thus, the results were transferred directly to industrial production. In addition, a guideline was created that describes the required process parameters and can be easily transferred to other applications. Since both the arrangement of the fibres and their splitting ratio as well as the housings and connections can be flexibly adapted to customer requirements on request, international markets are also open to the asymmetrical splitters.