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Focal Ratio Degradation for Fiber Positioner Operation in Astronomical Spectrographs

Author(s): Belland, B; Gunn, James E; Reiley, D; Cohen, J; Kirby, E; et al

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Abstract: © 2019 The Author(s). Focal ratio degradation (FRD), the decrease of light's focal ratio between the input into an optical fiber and the output, is important to characterize for astronomical spectrographs due to its effects on throughput and the point spread function. However, while FRD is a function of many fiber properties such as stresses, microbending, and surface imperfections, angular misalignments between the incoming light and the face of the fiber also affect the light profile and complicate this measurement. A compact experimental setup and a model separating FRD from angular misalignment was applied to a fiber subjected to varying stresses or angular misalignments to determine the magnitude of these effects. The FRD was then determined for a fiber in a fiber positioner that will be used in the Subaru Prime Focus Spectrograph (PFS). The analysis we carried out for the PFS positioner suggests that effects of angular misalignment dominate and no significant FRD increase due to stress should occur.
Publication Date: Sep-2019
Electronic Publication Date: 21-Feb-2019
Citation: Belland, B, Gunn, J, Reiley, D, Cohen, J, Kirby, E, De Oliveira, AC, De Oliveira, LS, Roberts, M, Seiffert, M. (2019). Focal Ratio Degradation for Fiber Positioner Operation in Astronomical Spectrographs. Journal of Astronomical Instrumentation, 8 (3), 10.1142/S2251171719500077
DOI: doi:10.1142/S2251171719500077
ISSN: 2251-1717
EISSN: 2251-1725
Type of Material: Journal Article
Journal/Proceeding Title: Journal of Astronomical Instrumentation
Version: Final published version. This is an open access article.

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