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TNO achieves new heights in optical communication
TNO is a leading Dutch independent research and technology organization, dedicated to translating scientific knowledge into practical innovations that strengthen industry and society. TNO played a central role in the UltraAir project which led in December 2025 to the demonstration of a secure laser communication link between an aircraft and a satellite in geostationary orbit (36,000 kilometers above Earth), using Exail optical modulation and inertial navigation solutions.
Conducted in partnership with Airbus and supported by European Space Agency, the UltraAir project successfully established a stable optical link delivering data rates in the gigabit-per-second range from a moving airplane to space. By leveraging laser technology, UltraAir enables significantly higher bandwidth compared to traditional radio-frequency systems, while also offering enhanced security thanks to the narrow, hard-to-intercept optical beam.
TNO developed and validated advanced laser communication technologies, including high-precision optical terminals and tracking systems capable of maintaining a stable link between fast-moving platforms and satellites. Its expertise in photonics and secure communications was instrumental in pushing the limits of high-capacity, resilient connectivity.
Pictures from TNO/Airbus during the UltraAir demonstration: Exail optical modulation (ModBox) and inertial navigation system (INS) were hosted on the system (top-left picture) onboard a Dassault Falcon 20 aircraft, operated by French AVdef
Pushing the boundaries of aircraft-to-satellite links
“The UltraAir campaign delivered 31 successful links with closed loop tracking, each lasting 6 to 14 minutes and generating hours of telemetry. Seven tests transmitted data at 1.8 Gbps for several minutes with zero-bit errors. It highlights both the robustness and performance of the system.”
Thomas Liebig, Systems Engineer at TNO
Establishing a laser communication link between an aircraft and a geostationary satellite 36,000 kilometers away presents a formidable technological challenge. The system must maintain an extremely precise beam pointing between two constantly moving platforms, while compensating for aircraft vibrations, atmospheric turbulence and long-distance signal distortion. To overcome these constraints, TNO developed advanced optical, mechanical and control technologies capable of stabilizing the link and ensuring the accuracy required for high-speed data transmission.
“More than 100 experts in optics, opto-mechatronics, electronics and space and scientific instrumentation came together in the project.”
Sjoerd van Kuijk, Manufacturing, Assembly, Integration, and Testing (MAIT) Manager at TNO
Exail optical modulation and inertial navigation solutions were instrumental in this demonstration, that consisted in:
- Emitting a laser source and pointing it accurately towards the satellite,
- Locking the signal to establish a stable laser link,
- Optical modulation of the laser light in order to transfer data, as smoothly as in a Fiber-To-The-Home connection.
Schematic overview of the UltraAir demonstration between an aircraft and a GEO satellite
Delivering cutting-edge technology in optical modulation and inertial navigation systems (INS)
Within the UltraAir demonstration, Exail’s ModBox Optical Reference Transmitter played a critical role by converting electrical data signals onboard the aircraft into stable, modulated optical signals, enabling the transmission of secure, high-bandwidth information through the optical terminal toward the satellite.
The ModBox 1064 nm-NRZ-BPSK, used by TNO for these tests, integrates a high-speed phase modulation system operating at 2.8 Gb/s, together with analog modulation based on an AOM — acousto-optic modulator. More broadly, Exail’s ModBox platform is a versatile, high-performance electrical-to-optical conversion solution, capable of supporting a wide range of advanced telecom modulation formats at data rates of up to 56 Gb/s across multiple wavelength bands.
Exail's INS was also critical for the demonstration as it provided the absolute orientation and positioning of the dynamically moving aircraft, enabling the perfect stabilization of the laser beam to the exact direction, to establish and maintain the optical link over the 36000 km separating the aircraft and the satellite.
Featuring an inertial measurement unit based on fiber-optic-gyroscope technology, Exail's INS does not require maintenance, providing high accuracy and long lifetime with a compact form factor, ideal for extended operations in airplanes.
“We needed to know the perfect and absolute orientation of the system installed onboard the aircraft while it was pointing toward the satellite. This was only possible with a system such as Exail’s INS, which performed even better than we expected. When the acquisition sequence starts, it is essentially flying blind: the optical terminal must first be pointed very accurately toward the satellite. The aircraft and satellite then begin an initialization sequence, progressively aligning their laser beams. Once this alignment is achieved, they can lock onto each other and start exchanging data. However, there are periods when the laser link may be interrupted for various reasons. This is where the INS becomes crucial, as it helps maintain the right pointing direction during these gaps. We required a heading accuracy of 0.02°. Exail delivered a solution with a heading accuracy of 0.01°, and during the experiment the system ultimately achieved 0.006°, which was significantly better than expected.”
Geerten Kramer, Mechatronics Engineer at TNO
Exail's INS (left) and ModBox 1064 nm-NRZ-BPSK (right) were used in the aircraft that successfully established a high-speed laser link with a geostationary orbit.
Paving the way for Europe’s next-generation airborne connectivity
Exail is proud to have taken part in this technical achievement. UltraAir represents a major step forward for European technological sovereignty. By mastering high-speed, secure optical communication links for both civil and defense applications, Europe strengthens its autonomy in strategic connectivity infrastructures. This capability opens the door to resilient airborne communication networks, secure data exchange for governmental and military operations, and next-generation in-flight connectivity services—positioning Europe at the forefront of laser-based space communications.
Building on the success of UltraAir, efforts are now underway to further miniaturize the optical terminal for wider deployment. Beyond aircraft-to-satellite communications, this breakthrough paves the way for secure, high-speed laser links for ships, land vehicles, and next-generation airborne connectivity services.
