Investigation of focal ratio degradation in optical fibres for astronomical instrumentation

Lisa Crause; Matthew Bershady; David Buckley

doi:10.1117/12.791041

9 July 2008 Investigation of focal ratio degradation in optical fibres for astronomical instrumentation

Lisa Crause, Matthew Bershady, David Buckley

Proceedings Volume 7014, Ground-based and Airborne Instrumentation for Astronomy II; 70146C (2008) https://doi.org/10.1117/12.791041
Event: SPIE Astronomical Telescopes + Instrumentation, 2008, Marseille, France

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.

Citation Download Citation

Lisa Crause, Matthew Bershady, and David Buckley "Investigation of focal ratio degradation in optical fibres for astronomical instrumentation", Proc. SPIE 7014, Ground-based and Airborne Instrumentation for Astronomy II, 70146C (9 July 2008); https://doi.org/10.1117/12.791041

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