Free-space optical communication (FSOC) has always promised high-capacity, secure data links between aircraft, spacecraft, and ground stations.
Now, a new experimental study led by Francesco Nardo at the Karlsruhe Institute of Technology explores a novel way to make FSOC systems more flexible and efficient for high-altitude platforms. The team uses optical fiber bundles to route light from multiple collection points into a single laser terminal.
Rethinking Free-Space Optical Communication Architectures
FSOC relies on tightly collimated laser beams to transmit information through the atmosphere or space. This approach offers data rates far beyond what conventional radio-frequency links can do.
But getting reliable connectivity with 360-degree coverage on aircraft or high-altitude platforms usually means installing multiple articulated laser communication terminals (LCTs) across the fuselage.
Each terminal adds a lot of size, weight, power consumption, and system complexity. As platforms get more capable and missions get tougher, the need for lighter, more robust communication setups grows fast.
Routing Light Instead of Replicating Hardware
The Karlsruhe team suggests a different approach. Instead of mounting several full LCTs, they use small external optical collectors to capture incoming laser signals.
These signals travel through optical fiber bundles (FBs) to a single internal LCT that handles detection, processing, and transmission. It’s a simple idea that could really shake up FSOC system design.
Experimental Validation at 1550 nm
To see if this could actually work, the researchers did a detailed experimental study of a commercially available optical fiber bundle. They ran the tests at 1550 nm, which is the standard wavelength in FSOC because it transmits well through the atmosphere and is safer for eyes.
The team measured optical losses, modal distortion, and beam quality degradation caused by the bundle. These factors matter a lot since FSOC performance drops quickly if the signal gets distorted.
Simulating Turbulent Air-to-Air Links
They didn’t stop at lab measurements. The researchers also simulated a realistic air-to-air FSOC link with atmospheric turbulence.
This let them see how the fiber bundle changed key metrics like signal-to-noise ratio and link margin compared to a direct free-space path.
Performance Penalties and Material Limitations
The concept worked, but the tested fiber bundle caused substantial performance penalties. The main problem wasn’t the design, but that the commercial bundle was made for visible wavelengths, not the short-wavelength infrared C-band that FSOC uses.
This mismatch brought higher attenuation and more mode distortion, which cut down the link’s efficiency.
Why C-Band Optimization Is Essential
The authors point out that real-world distributed FSOC systems will need fiber bundles made from materials optimized for C-band transmission. Better fiber materials, improved polishing, and smarter bundle designs could cut current losses a lot.
With the right engineering, these penalties aren’t dealbreakers—they’re just challenges waiting for solutions.
Implications for Future High-Altitude Platforms
Looking ahead, this research points to a real need for more system-level studies. The team suggests that we should dig deeper into full LCT architectures that can handle multiple signal streams at once.
Fiber technology keeps advancing, and honestly, distributed FSOC architectures using optical fiber bundles might end up driving the next generation of airborne and spaceborne communication networks.
The study, “Experimental Characterization of Optical Fiber Bundles for Free-Space Optical Communication in High-Altitude Platforms,” appears in the IEEE Journal of Selected Topics in Quantum Electronics (DOI: 10.1109/JSTQE.2025.3607094). It lays out a pretty interesting roadmap for cutting down size, weight, and power in the optical communication systems of tomorrow.
Here is the source article for this story: IEEE Study Demonstrates Optical Fiber Bundles as a Promising Solution for High-Altitude Laser Communication Systems