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Proceedings Paper

Investigation of focal ratio degradation in optical fibres for astronomical instrumentation
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Paper Abstract

A differential method was used to investigate the focal ratio degradation (FRD) exhibited by, and throughput of, a selection of current-generation optical fibres. These fibres were tested to establish which would be best suited to feed the High Resolution Spectrograph being built for the Southern African Large Telescope (SALT), as well as for future instruments on WIYN and SALT. The double re-imaging system of Bershady et al. (2004) was substantially modified to improve image quality and measurement efficiency, and to permit a direct FRD-measurement in the far-field. The re-imaging method compares the beam profile produced by light which passes through a fibre to that which does not. Broad and intermediate band-pass filters were used between 400-800 nm to test for wavelength dependence in the observed FRD over a wide range in beam-speeds. Our results continue to be at odds with a mico-bend model for FRD. We conclude that the new Polymicro FBP fibre is the most suitable product for broadband applications.

Paper Details

Date Published: 9 July 2008
PDF: 11 pages
Proc. SPIE 7014, Ground-based and Airborne Instrumentation for Astronomy II, 70146C (9 July 2008);
Show Author Affiliations
Lisa Crause, South African Astronomical Observatory (South Africa)
Matthew Bershady, Univ. of Wisconsin, Madison (United States)
David Buckley, South African Astronomical Observatory (South Africa)

Published in SPIE Proceedings Vol. 7014:
Ground-based and Airborne Instrumentation for Astronomy II
Ian S. McLean; Mark M. Casali, Editor(s)

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