Hexabundles: imaging fibre arrays for low-light astronomical applications

Joss Bland-Hawthorn, Julie Bryant, Gordon Robertson, Peter Gillingham, John O'Byrne, Gerald Cecil, Roger Haynes, Scott Groom, Simon Ellis, Martin Maack, Peter M. W. Skovgaard, Danny Noordegraaf

Research output: Contribution to journalConference articlepeer-review


We demonstrate for the first time an imaging fibre bundle (“hexabundle”) that is suitable for low-light applications in astronomy. The most successful survey instruments at optical-infrared wavelengths today have obtained data on up to a million celestial sources using hundreds of multimode fibres at a time fed to multiple spectrographs. But a large fraction of these sources are spatially extended on the celestial sphere such that a hexabundle would be able to provide spectroscopic information at many distinct locations across the source. Our goal is to upgrade single-fibre survey instruments with multimode hexabundles in place of the multimode fibres. We discuss two varieties of hexabundles: (i) closely packed circular cores allowing the covering fraction to approach the theoretical maximum of 91%; (ii) fused noncircular cores where the interstitial holes have been removed and the covering fraction approaches 100%. In both cases, we find that the cladding can be reduced to ~2μm over the short fuse length, well below the conventional ~10λ thickness employed more generally. We discuss the relative merits of fused/unfused hexabundles in terms of manufacture and deployment, and present our first on-sky observations.
Original languageEnglish
JournalProceedings of SPIE, the International Society for Optical Engineering
Publication statusPublished - 2010
EventGround-based and Airborne Instrumentation for Astronomy III - San Diego, CA, USA
Duration: 1 Jan 2010 → …


ConferenceGround-based and Airborne Instrumentation for Astronomy III
CitySan Diego, CA, USA
Period01/01/2010 → …


  • astronomical instrumentation
  • multimode fibre
  • integral field spectrograph
  • galaxy surveys


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