Development of Low Microbend Loss Radiation Resistant Fiber

Lupine Materials and Technology, Inc. (LMT) proposes the development of a novel microstructured optical fiber designed for high radiation tolerance and low microbend loss, addressing critical challenges in applications such as fusion reactors and high-radiation environments. Microbend losses have been identified as a limiting factor in the integration of long-length optical fibers into high-temperature superconductor (HTS) cables, leading to a loss of sensing signal and, consequently, sensor functionality. This issue is largely independent of the sensing technique employed and presents a challenge for both fiber Bragg grating (FBG) sensors and Rayleigh backscattering-based distributed sensors. Current radiationtolerant optical fibers suffer from significant microbend losses, limiting their effectiveness fibers are embedded in HTS magnets, while current low microbend loss fibers are not radiation tolerant at all. This project aims to overcome these limitations by employing a microstructural design to tune the fiber’s refractive index difference (delta) through air holes, rather than relying solely on chemical dopants. This approach allows the core and cladding to be made from potentially the same material, and to be optimized for radiation tolerance, while optimizing the fiber's optical performance. The Phase I project will involve the development, design, and modeling of at least two fiber designs. Existing commercial radiation-tolerant fibers will be characterized as benchmarks, with particular attention to their performance under microbend conditions at both room and cryogenic temperatures. Additionally, a comprehensive plan for manufacturing these novel fiber designs will be developed to facilitate manufacturing to occur in Phase II of the project. This project leverages nearly a decade of experience in optical fiber sensing for superconducting magnets from LMT’s team, as well as its established collaboration with LUNA Innovations, a leader in optical fiber sensing technologies. By integrating low microbend loss with high radiation tolerance, this project has the potential to significantly improve the performance of optical fibers in harsh environments, contributing to more reliable and robust sensor systems in superconducting magnets and other components of fusion power plants.