REFLOW Project is developing extremely stable signal technology for the Einstein Telescope
As part of the development of the Einstein Telescope (ET), the German company Microwave Photonics GmbH and the Dutch company Sabratha are collaborating on the REFLOW project to develop technology for transmitting extremely precise signals over long distances via fiber optics. REFLOW is a project within the German-Dutch Interreg program COMET (CoMaking the Einstein Telescope). The project is receiving a grant of 75,000 euros from COMET to further develop and test the joint technology.
The Einstein Telescope will be an underground observatory for gravitational waves: minuscule ripples in spacetime that arise from extreme events in the universe, such as colliding black holes. To measure such small signals, various components of the detector must function with exceptional precision and in perfect synchronization. This places high demands on the distribution of timing and reference signals. Even very minor disturbances during transport can affect accuracy.
Photo: Kickoff on July 9 for the REFLOW project (Ultra-Low-Noise RF-over-Fiber System for LO Reference Distribution in the Einstein Telescope).
Project REFLOW
REFLOW is a collaboration between Microwave Photonics GmbH in Duisburg and Sabratha in Enschede. Microwave Photonics possesses specialized expertise in RF-over-Fiber: a technology that transmits high-frequency electrical signals via light through optical fiber. Sabratha develops photonic chips that can efficiently convert electrical signals into optical signals.
Within REFLOW, the companies are combining these technologies into a single integrated system. The goal is to develop and test a prototype capable of transmitting synchronized signals over long fiber-optic links, while keeping their phase—the exact position of the signal in time—as stable as possible.
It is precisely this stability that is important for the Einstein Telescope. The future detector consists of multiple measurement systems that must be very precisely synchronized with one another. REFLOW is investigating how high-performance fiber-optic technology and integrated photonics can together provide a compact and reliable solution.
“The project enables us to validate our technology in a highly demanding use case while simultaneously strengthening our collaboration with European partners,” says Steven Ye, co-founder and CTO of Sabratha.
REFLOW officially launched on July 9, 2026. The project is supported by COMET, which brings together Dutch and German companies and research institutions to jointly tackle technological challenges for the Einstein Telescope.
Photo: Photonic chip from Sabratha.
Spin-off potential — photonics, telecommunications, and precision technology
The technology being developed within REFLOW can also be valuable outside the Einstein Telescope. Highly stable signal distribution via fiber optics is relevant for applications in which timing, synchronization, and reliability are crucial. Examples include advanced telecom networks, scientific research infrastructures, measurement and control systems, and other forms of precision technology.
For Dutch and German high-tech companies, this development also offers opportunities to build new knowledge and products centered on integrated photonics and high-performance fiber-optic systems. In this way, the project contributes to European expertise in technological fields that are becoming increasingly important for digital and scientific infrastructures.
REFLOW demonstrates how the Einstein Telescope can serve as a catalyst for cross-border innovation. By combining specialized knowledge from the Netherlands and Germany, the project creates technology that is essential for fundamental scientific research and also offers prospects for new applications. In doing so, the Einstein Telescope not only strengthens Europe’s position in gravitational-wave astronomy but also bolsters the high-tech ecosystem in which innovative companies and research institutions collaborate to develop technology for the future.
Foto onder: RF-over-Fiber (RFoF) van Microwave Photonics
Test your idea
REFLOW is the first project to receive funding from the COMET programme, but the programme is looking for more Dutch and German SMEs and research institutions that wish to work together on technological solutions. In the Netherlands, the programme area covers the provinces of Groningen, Drenthe, Overijssel, Gelderland, North Brabant and Limburg, and in Germany, the federal states of Lower Saxony and North Rhine-Westphalia.
Would you like to find out more or submit a project idea yourself? Companies and research institutions from the programme area can test their idea without obligation via the COMET website or contact us via info@comet-interreg.eu.