Focal-ratio degradation (FRD) mitigation in a multimode fibre link using mode-selective photonic lanterns

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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
38 Downloads (Pure)


We present a new way to mitigate focal-ratio degradation (FRD) when using optical fibres to transport multimode light. Our approach exploits a custom multicore fibre (MCF) with six dissimilar cores that are single-mode at ∼1550 nm wavelength and minimally coupled over 7 m. We fabricated adiabatic mode-selective photonic lanterns (PLs) at each end of the MCF to create a fibre link with multimode ports, the PLs coupling each spatial mode of the multimode ports to a specific core of the MCF and vice versa. The PL-MCF-PL link exhibits superior FRD behaviour compared to a conventional multimode fibre that also supports six modes, because it inhibits the transfer of light from lower order modes to higher order modes. These results open up a potential powerful new approach to mitigate FRD in multimode fibre links, with particular applications in astronomical instruments.

Original languageEnglish
Pages (from-to)2381-2388
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date30 Jan 2021
Publication statusPublished - Apr 2021


  • instrumentation: miscellaneous
  • instrumentation: spectrograph
  • methods: data analysis
  • techniques: miscellaneous
  • techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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