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Proceedings Paper

APOGEE fiber development and FRD testing
Author(s): Sophia Brunner; Adam Burton; Jeff Crane; Bo Zhao; Fred R. Hearty; John C. Wilson; Larry Carey; French Leger; Mike Skrutskie; Ricardo Schiavon; Steven R. Majewski
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Paper Abstract

Development of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) near-infrared spectrograph has motivated thorough investigation into the properties and performance of optical fibers. The fiber selected for APOGEE is a step index, multi-mode fiber, developed by PolyMicro, with a 120μm low OH, fused silica core, 25μm cladding, and 10μm buffer. The instrument design includes a 40 meter fiber run, connecting the spectrograph to the 2.5m Sloan Digital Sky Survey (SDSS) telescope, and an additional 2.5 meter fiber segment located within the instrument dewar, a vacuum-sealed, cryogenic environment. This light path is convoluted and includes many transitions and connections where the beam is susceptible irrevocable loss. To optimize the spectrograph performance it is necessary to minimize the losses incurred in the fiber system, especially those resulting in focal ratio degradation (FRD). The focus of this research has been to identify potential sources of loss and where applicable, select material components to minimize this effect. There is little previous documented work concerning the performance of optical fibers within this wavelength band (1.5-1.7μm). Consequently, the following includes comprehensive explanations of the APOGEE fiber system components, our experimental design and optical test bed set-up, beam alignment procedures, fiber terminating and polishing techniques, and results from our examination of FRD as correlated with source wavelength, fiber length and termination, and environmental conditions.

Paper Details

Date Published: 20 July 2010
PDF: 15 pages
Proc. SPIE 7735, Ground-based and Airborne Instrumentation for Astronomy III, 77356A (20 July 2010); doi: 10.1117/12.857223
Show Author Affiliations
Sophia Brunner, Univ. of Virginia (United States)
Adam Burton, Univ. of Virginia (United States)
Jeff Crane, Carnegie Observatories (United States)
Bo Zhao, Univ. of Florida (United States)
Fred R. Hearty, Univ. of Virginia (United States)
John C. Wilson, Univ. of Virginia (United States)
Larry Carey, Univ. of Washington (United States)
French Leger, Univ. of Washington (United States)
Mike Skrutskie, Univ. of Virginia (United States)
Ricardo Schiavon, Gemini Observatory (United States)
Steven R. Majewski, Univ. of Virginia (United States)

Published in SPIE Proceedings Vol. 7735:
Ground-based and Airborne Instrumentation for Astronomy III
Ian S. McLean; Suzanne K. Ramsay; Hideki Takami, Editor(s)

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