A focal-ratio-degradation resistant multimode fiber link using mode-selective photonic lantern

Aurelien Benoit, Stephanos Yerolatsitis, Kerrianne Harrington, Tim A. Birks, Robert R. Thomson

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)
25 Downloads (Pure)


We report a new route to mitigate focal-ratio degradation (FRD) in multimode optical fiber links. Our approach uses a custom multicore fiber (MCF) with dissimilar cores, which is then tapered at both ends to form multimode cores and create mode-selective photonic lantern (PL) transitions. The cores of the MCF are single-moded at 1550 nm and sufficiently spaced such that there is no observable core-To-core cross talk after a 7 m fiber length. The mode-selective PLs at each end of the MCF, in combinations with the low core-To-core cross talk of the MCF at 1550 nm, ensure that the relative amount of power in each spatial mode is preserved throughout the fibre link. As such, a PL-MCF-PL link using this approach has the potential to be resistant to FRD by inhibiting the coupling of light from lower-order to higher-order modes. We show that the full PL-MCF-PL link exhibits lower FRD than a custom multimode fiber that guides the same number of modes. A study of how the FRD behavior of the PL-MCF-PL link varies as a function of wavelength indicates some bandwidth limitations due to the wavelength-dependent properties of the PLs and the cross coupling in the MCF.

Original languageEnglish
Title of host publicationAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV
EditorsRamon Navarro, Roland Geyl
ISBN (Electronic)9781510636903
ISBN (Print)9781510636897
Publication statusPublished - 13 Dec 2020
EventSPIE Astronomical Telescopes + Instrumentation 2020 - Virtual, Online, United States
Duration: 14 Dec 202022 Dec 2020

Publication series

NameProceedings of SPIE
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceSPIE Astronomical Telescopes + Instrumentation 2020
Country/TerritoryUnited States
CityVirtual, Online


  • Focal ratio degradation
  • integral fiber-fed spectrograph
  • photonic lantern

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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