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Proceedings Paper

The influence of motion and stress on optical fibers
Author(s): Jeremy D. Murphy; Gary J. Hill; Phillip J. MacQueen; Trey Taylor; Ian Soukup; Walter Moreira; Mark E. Cornell; John Good; Seth Anderson; Lindsay Fuller; Hanshin Lee; Andreas Kelz; Marc Rafal; Tom Rafferty; Sarah Tuttle; Brian Vattiat
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Paper Abstract

We report on extensive testing carried out on the optical fibers for the VIRUS instrument. The primary result of this work explores how 10+ years of simulated wear on a VIRUS fiber bundle affects both transmission and focal ratio degradation (FRD) of the optical fibers. During the accelerated lifetime tests we continuously monitored the fibers for signs of FRD. We find that transient FRD events were common during the portions of the tests when motion was at telescope slew rates, but dropped to negligible levels during rates of motion typical for science observation. Tests of fiber transmission and FRD conducted both before and after the lifetime tests reveal that while transmission values do not change over the 10+ years of simulated wear, a clear increase in FRD is seen in all 18 fibers tested. This increase in FRD is likely due to microfractures that develop over time from repeated flexure of the fiber bundle, and stands in contrast to the transient FRD events that stem from localized stress and subsequent modal diffusion of light within the fibers. There was no measurable wavelength dependence on the increase in FRD over 350 nm to 600 nm. We also report on bend radius tests conducted on individual fibers and find the 266 μm VIRUS fibers to be immune to bending-induced FRD at bend radii of R 10 cm. Below this bend radius FRD increases slightly with decreasing radius. Lastly, we give details of a degradation seen in the fiber bundle currently deployed on the Mitchell Spectrograph (formally VIRUS-P) at McDonald Observatory. The degradation is shown to be caused by a localized shear in a select number of optical fibers that leads to an explosive form of FRD. In a few fibers, the overall transmission loss through the instrument can exceed 80%. These results are important for the VIRUS instrument, and for both current and proposed instruments that make use of optical fibers, particularly when the fibers are in continual motion during an observation, or experience repeated mechanical stress during their deployment.≥

Paper Details

Date Published: 24 September 2012
PDF: 24 pages
Proc. SPIE 8446, Ground-based and Airborne Instrumentation for Astronomy IV, 84465F (24 September 2012); doi: 10.1117/12.925496
Show Author Affiliations
Jeremy D. Murphy, The Univ. of Texas at Austin (United States)
Gary J. Hill, McDonald Observatory, The Univ. of Texas at Austin (United States)
Phillip J. MacQueen, McDonald Observatory, The Univ. of Texas at Austin (United States)
Trey Taylor, McDonald Observatory, The Univ. of Texas at Austin (United States)
Ian Soukup, The Univ. of Texas at Austin (United States)
Walter Moreira, McDonald Observatory, The Univ. of Texas at Austin (United States)
Mark E. Cornell, McDonald Observatory, The Univ. of Texas at Austin (United States)
John Good, McDonald Observatory, The Univ. of Texas at Austin (United States)
Seth Anderson, The Univ. of Texas at Austin (United States)
Lindsay Fuller, The Univ. of Texas at Austin (United States)
Hanshin Lee, McDonald Observatory, The Univ. of Texas at Austin (United States)
Andreas Kelz, Leibniz-Institut für Astrophysik Potsdam (Germany)
Marc Rafal, McDonald Observatory, The Univ. of Texas at Austin (United States)
Tom Rafferty, McDonald Observatory, The Univ. of Texas at Austin (United States)
Sarah Tuttle, McDonald Observatory, The Univ. of Texas at Austin (United States)
Brian Vattiat, McDonald Observatory, The Univ. of Texas at Austin (United States)


Published in SPIE Proceedings Vol. 8446:
Ground-based and Airborne Instrumentation for Astronomy IV
Ian S. McLean; Suzanne K. Ramsay; Hideki Takami, Editor(s)

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