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Free-space optical communications (FSOC), which use lasers for data transmission, are a promising approach for achieving high-speed links between aircraft, spacecraft, and ground stations. However, achieving 360-degree coverage requires multiple articulated terminals installed on the fuselage of aircraft, exceeding size, weight, and power limits.
These systems use mechanical gimbals to redirect the optical components as needed to maintain a link with another stationary or moving transceiver. However, aircraft would need multiple of them to achieve 360-degree coverage. Optical fibers could help minimize the need for fully capable communications systems installed at each gimbal by relaying incoming and outgoing signals to and from a centralized unit.
These systems use mechanical gimbals to redirect the optical components as needed to maintain a link with another stationary or moving transceiver. However, aircraft would need multiple of them to achieve 360-degree coverage. Optical fibers could help minimize the need for fully capable communications systems installed at each gimbal by relaying incoming and outgoing signals to and from a centralized unit.
To address this technical challenge, a research team led by Mr. Francesco Nardo from the Karlsruhe Institute of Technology, Germany, investigated a novel solution: using optical fiber bundles (FBs). Multiple FBs could route light from small, external collectors to a single laser communication terminal (LCT) housed inside the aircraft, minimizing redundancy. Their paper, published on September 8, 2025, in the IEEE Journal of Selected Topics in Quantum Electronics, experimentally validated the viability of FBs in FSOC receivers.
To test the proposed architecture, the team characterized a commercially available FB at the standard FSOC wavelength of 1550 nm. They measured different types of losses and distortion, simulated a turbulent air-to-air link, and quantified the impact of the FB on various performance metrics.
The overall results showed that while FBs are feasible for FSOC, the tested commercial bundle, which was optimized 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 research team highlights that FBs made from C-band-specific materials will be required to realize a distributed FSOC system. Thus, further research will be needed to develop full LCT system architectures, including transmission and multiplexing components to manage multiple signal streams. "Our work lays the foundation for future investigations into FBs optimized for short-wavelength infrared operation in FSOC," concludes Mr. Nardo.
