Optical Fiber Bundles Could Power the Future of Laser-Based Communications

Free-space optical communications (FSOC), which rely on laser-based data transmission, offer a compelling solution for high-speed links between aircraft, spacecraft, and ground stations. Achieving uninterrupted 360-degree coverage, however, typically requires multiple steerable optical terminals mounted on an aircraft’s fuselage—an approach that quickly exceeds size, weight, and power constraints.

To overcome this limitation, a research team led by Mr. Francesco Nardo of the Karlsruhe Institute of Technology (KIT), Germany, has explored an alternative architecture based on optical fiber bundles. In this concept, several compact external collectors guide incoming optical signals through fiber bundles to a single laser communication terminal (LCT) located inside the aircraft, significantly reducing system redundancy. The team’s findings were published on September 8, 2025, in the IEEE Journal of Selected Topics in Quantum Electronics, where they report the experimental validation of FBs in FSOC receivers.

The researchers characterized a commercially available fiber bundle operating at the standard FSOC wavelength of 1550 nm. Their study included measurements of loss mechanisms and signal distortion, as well as experiments emulating a turbulent air-to-air optical link to assess the impact of the fiber bundle on various performance metrics.

The results demonstrate that fiber bundles are a viable option for FSOC, although the tested commercial bundle—originally designed for visible-light wavelengths—came with some drawbacks. "Despite substantial link penalties, we expect improvements in fiber materials and fabrication techniques to enhance the performance of fiber bundles, further increasing their viability for FSOC applications," remarks Mr. Nardo, optimistic about the potential of this technology.

The team emphasizes that fiber bundles made from C-band-specific materials will be essential for implementing a distributed FSOC system. Further research will be needed to develop full LCT system designs, including transmission and multiplexing solutions capable of handling multiple signal streams. “Our work lays the foundation for future investigations into fiber bundles optimized for short-wavelength infrared operation in FSOC," concludes Mr. Nardo.

Source: IEEE Photonics Society

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