Light scrambling and focal ratio degradation of thin multimode fibers with different core geometries

Man-Yin Leo Lee; Zhiheng Lin; Chit-Ho Hui; Renbin Yan; YiuHung Cheung; Horace Tsz-Hong Hung; Matthew A. Bershady; Sabyasachi Chattopadhyay; Michael P. Smith

doi:10.1117/12.3016312

18 July 2024 Light scrambling and focal ratio degradation of thin multimode fibers with different core geometries

Man-Yin Leo Lee, Zhiheng Lin, Chit-Ho Hui, Renbin Yan, YiuHung Cheung, Horace Tsz-Hong Hung, Matthew A. Bershady, Sabyasachi Chattopadhyay, Michael P. Smith

Author Affiliations +

Proceedings Volume 13096, Ground-based and Airborne Instrumentation for Astronomy X; 1309668 (2024) https://doi.org/10.1117/12.3016312
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Conference Poster

Abstract

The performance of fiber-fed astronomical spectrographs is highly influenced by the properties of fibers. The near-field and far-field scrambling characteristics have a profound impact on the line spread function (LSF) of the spectra. Focal ratio degradation (FRD) influences the output beam size, thereby affecting the throughput, as well as the size of the collimator and dispersion elements. While previous research has indicated that these properties depend on the shape of the fiber core and showed that non-circular core fibers can yield uniform near-field scrambling, the result remains inconclusive for far-field. In this study, we investigate the near-field and far-field scrambling properties, along with the FRD, of 50-micron core fibers with different core geometries. We find that in addition to excellent near-field scrambling, octagonal-core fibers can also produce more uniform far-field output when compared to circular-core fibers. They also have less FRD effect when being fed with a f/3 beam.

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Man-Yin Leo Lee, Zhiheng Lin, Chit-Ho Hui, Renbin Yan, YiuHung Cheung, Horace Tsz-Hong Hung, Matthew A. Bershady, Sabyasachi Chattopadhyay, and Michael P. Smith "Light scrambling and focal ratio degradation of thin multimode fibers with different core geometries", Proc. SPIE 13096, Ground-based and Airborne Instrumentation for Astronomy X, 1309668 (18 July 2024); https://doi.org/10.1117/12.3016312

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