A test bed for simultaneous measurement of fiber near and far-field for the evaluation of fiber scrambling properties

Tobias Feger, Anna Brucalassi, Frank Grupp*, Florian Lang-Bardl, Ronald Holzwarth, Ulrich Hopp, Ralf Bender

*Corresponding author for this work

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

16 Citations (Scopus)


To improve our understanding of fiber scrambling properties a test bed where fiber near-field and far-field can be measured simultaneously is described. A variety of measurements has been conducted with a selection of fibers from different vendors, including state-of-the-art octagonal and hexagonal fibers. After characterization of the test bench with respect to stability and resolution, scrambling measurements have been conducted using LEDs with central wavelengths ranging between 465-635 nm. The dependence on wavelength regarding to photometrical scrambling has been initially demonstrated. Moreover, two mechanical combined fiber cables have been analyzed that were made from octagonal-circular and hexagonal-octagonal fiber sections. In this context an apparatus for focal ratio degradation (FRD) measurements was assembled to compare different shaped fibers and fiber combinations. Finally, all these preliminary investigations will help in choosing a fiber with good radial scrambling performance for the next generation fiber-link of the fiber optic coupled Cassegrain echelle spectrograph FOCES intended to be operated at the 2.0m Fraunhofer Telescope at the Wendelstein Observatory.

Original languageEnglish
Title of host publicationGround-Based and Airborne Instrumentation for Astronomy IV
Place of PublicationBellingham, Washington
Number of pages14
ISBN (Print)9780819491473
Publication statusPublished - 2012
Externally publishedYes
EventGround-Based and Airborne Instrumentation for Astronomy IV - Amsterdam, Netherlands
Duration: 1 Jul 20126 Jul 2012

Publication series

NameProceedings of SPIE
ISSN (Print)0277-786X


OtherGround-Based and Airborne Instrumentation for Astronomy IV


  • Fiber coupling
  • Fiber scrambling
  • Fraunhofer Telescope Wendelstein
  • Instrument stability
  • Non-circular fiber
  • Planet finding
  • Spectrographs

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