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Proceedings Paper

Focal ratio degradation and transmission in VIRUS-P optical fibers
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Paper Abstract

We have conducted extensive tests of both transmission and focal ratio degradation (FRD) on two integral field units currently in use on the VIRUS-P integral field spectrograph. VIRUS-P is a prototype for the VIRUS instrument proposed for the Hobby-Eberly Telescope at McDonald Observatory. All tests have been conducted at an input f-ratio of F/3.65 and with an 18% central obscuration in order to simulate optical conditions on the HET. Transmission measurements were conducted with narrow-band interference filters (FWHM: 10 nm) at 10 discrete wavelengths (337 to 600 nm), while FRD tests were made at 365 nm, 400 nm and 600 nm. The influence of wavelength, end immersion, fiber type and length on both FRD and transmission is explored. Most notably, we find no wavelength dependence on FRD down to 365 nm. All fibers tested are within the VIRUS instrument specifications for both FRD and transmission. We present the details of our differential FRD testing method and explain a simple and robust technique of aligning the test bench and optical fiber axes to within ±0.1 degrees.

Paper Details

Date Published: 23 July 2008
PDF: 12 pages
Proc. SPIE 7018, Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation, 70182T (23 July 2008); doi: 10.1117/12.788411
Show Author Affiliations
Jeremy D. Murphy, The Univ. of Texas at Austin (United States)
Phillip J. MacQueen, The Univ. of Texas at Austin, McDonald Observatory (United States)
Gary J. Hill, The Univ. of Texas at Austin, McDonald Observatory (United States)
Frank Grupp, Univ.-Sternwarte, München (Germany)
Andreas Kelz, Astrophysikalisches Institut Potsdam (Germany)
Povilas Palunas, The Univ. of Texas at Austin, McDonald Observatory (United States)
Las Campanas Observatory (Chile)
Martin Roth, Univ.-Sternwarte, München (Germany)
Alexander Fry, The Univ. of Texas at Austin (United States)


Published in SPIE Proceedings Vol. 7018:
Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation
Eli Atad-Ettedgui; Dietrich Lemke, Editor(s)

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