Experimental Astronomy

, Volume 24, Issue 1, pp 1–7

Air-clad fibres for astronomical instrumentation: focal-ratio degradation


DOI: 10.1007/s10686-008-9132-7

Cite this article as:
Åslund, M.L. & Canning, J. Exp Astron (2009) 24: 1. doi:10.1007/s10686-008-9132-7


Focal-ratio degradation (FRD) of light launched into high-numerical aperture (NA) single-annulus all-silica undoped air-clad fibres at an NA of 0.54 is reported. The measured annular light distribution remained Gaussian after 30 m of propagation, but the angular FWHM of the output annulus doubled from 4° after 1 m propagation to 8.5° after 30 m, which is significantly larger than that reported of standard doped-silica fibres (NA < 0.22). No significant diffractive effects were observed. The design of air-clad fibres for broad-band, high-NA astrophotonics applications is discussed.


Focal-ratio degradationHigh-numerical apertureAir-clad fibres

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© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  1. 1.Interdisciplinary Photonics Laboratories, School of ChemistryUniversity of SydneySydneyAustralia