Focal ratio degradation: a new perspective

Dionne M. Haynes, Michael J. Withford, Judith M. Dawes, Roger Haynes, Joss Bland-Hawthorn

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review

11 Citations (Scopus)


We have developed an alternative FRD empirical model for the parallel laser beam technique which can accommodate contributions from both scattering and modal diffusion. It is consistent with scattering inducing a Lorentzian contribution and modal diffusion inducing a Gaussian contribution. The convolution of these two functions produces a Voigt function which is shown to better simulate the observed behavior of the FRD distribution and provides a greatly improved fit over the standard Gaussian fitting approach. The Voigt model can also be used to quantify the amount of energy displaced by FRD, therefore allowing astronomical instrument scientists to identify, quantify and potentially minimize the various sources of FRD, and optimise the fiber and instrument performance.

Original languageEnglish
Title of host publicationAdvanced optical and mechanical technologies in telescopes and instrumentation
EditorsEli Atad-Ettedgui, Dietrich Lemke
Place of PublicationBellingham, Washington
Number of pages8
ISBN (Print)9780819472281
Publication statusPublished - 2008
EventAdvanced Optical and Mechanical Technologies in Telescopes and Instrumentation - Marseille, France
Duration: 23 Jun 200828 Jun 2008

Publication series

NameProceedings of SPIE
ISSN (Print)0277-786X


OtherAdvanced Optical and Mechanical Technologies in Telescopes and Instrumentation


  • Astronomical instrumentation
  • Focal ratio degradation
  • FRD
  • Optical fiber
  • Scattering
  • Surface roughness

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