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Proceedings Paper

An optimal method for producing low-stress fibre optic cables for astronomy
Author(s): Graham Murray; Naoyuki Tamura; Naruhisa Takato; Paul Ekpenyong; Daniel Jenkins; Kim Leeson; Shaun Trezise; Timothy Butterley; James Gunn; Decio Ferreira; Ligia Oliveira; Laerte Sodre
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Paper Abstract

An increasing number of astronomical spectrographs employ optical fibres to collect and deliver light. For integral-field and high multiplex multi-object survey instruments, fibres offer unique flexibility in instrument design by enabling spectrographs to be located remotely from the telescope focal plane where the fibre inputs are deployed. Photon-starved astronomical observations demand optimum efficiency from the fibre system. In addition to intrinsic absorption loss in optical fibres, another loss mechanism, so-called focal ratio degradation (FRD) must be considered. A fundamental cause of FRD is stress, therefore low stress fibre cables that impart minimum FRD are essential. The FMOS fibre instrument for Subaru Telescope employed a highly effective cable solution developed at Durham University. The method has been applied again for the PFS project, this time in collaboration with a company, PPC Broadband Ltd. The process, planetary stranding, is adapted from the manufacture of large fibre-count, large diameter marine telecommunications cables. Fibre bundles describe helical paths through the cable, incorporating additional fibre per unit length. As a consequence fibre stress from tension and bend-induced ‘race-tracking’ is minimised. In this paper stranding principles are explained, covering the fundamentals of stranded cable design. The authors describe the evolution of the stranding production line and the numerous steps in the manufacture of the PFS prototype cable. The results of optical verification tests are presented for each stage of cable production, confirming that the PFS prototype performs exceptionally well. The paper concludes with an outline of future on-telescope test plans.

Paper Details

Date Published: 30 October 2017
PDF: 16 pages
Proc. SPIE 10401, Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems, 104011R (30 October 2017); doi: 10.1117/12.2289829
Show Author Affiliations
Graham Murray, Durham Univ. (United Kingdom)
Naoyuki Tamura, Kavli Institute for the Physics and Mathematics of the Universe (Japan)
Naruhisa Takato, Subaru Telescope, National Astronomical Observatory of Japan (United States)
Paul Ekpenyong, PPC Broadband Fiber Ltd. (United Kingdom)
Daniel Jenkins, PPC Broadband Fiber Ltd. (United Kingdom)
Kim Leeson, PPC Broadband Fiber Ltd. (United Kingdom)
Shaun Trezise, PPC Broadband Fiber Ltd. (United Kingdom)
Timothy Butterley, Durham Univ. (United Kingdom)
James Gunn, Princeton Univ. (United States)
Decio Ferreira, Lab. Nacional de Astrofísica (Brazil)
Ligia Oliveira, Lab. Nacional de Astrofísica (Brazil)
Laerte Sodre, Univ. de São Paulo (Brazil)

Published in SPIE Proceedings Vol. 10401:
Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems
Tony B. Hull; Dae Wook Kim; Pascal Hallibert, Editor(s)

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