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SPIRou / Infrared SpectroPolarimeter

2016 May: Fiber-link tests ongoing at IRAP/OMP

SPIRou fibers were delivered at IRAP/OMP and are currently under test

Fiber test bench

Fiber test bench at IRAP/OMP

All SPIRou fibers were delivered at IRAP / OMP and are currently being testing to verify that they meet specifications.

The SPIRou fiber link includes 4 separate sections.  The first section of the fiber link consists of a box mounted at the output of the polarimetric unit (installed at the Cassegrain focus of CFHT).  This box allows the two orthogonally polarized beams exiting the polarimeter to be injected into two separate fibers, with easy-to-handle connections. Two 35 m fibers are then used to transmit the stellar flux from the Cassegrain unit to the cryogenic spectrograph in the CFHT Coudé room, in a thermally stable environment at the 3rd floor of the telescope building.  Fiber feedthroughs will then ensure hermetic connections between the science fibers and the inside of the cryostat.  The last section of the fiber link consists of octagonal fibers, connecting the feedthrough to the pupil slicer. Their octogonal shape allows us to reach a high-enough level of scrambling and thus to meet our drastic specifications in terms of RV precision. 


Science fiber tests

Testing one of the 35m SPIRou science fiber

Fiber link section

The Cassegrain section of the fiber link, featuring three fibers in their aluminum box

Octagonal fibers

Octagonal fibers allowing high-enough scrambling performances at the entrance of the pupil slicer

All SPIRou fibers are fluoride fibers manufactured by Le Verre Fluoré in western France, and feature a 90µm core diameter. Meeting the goal performances, regarding in particular throughput and scrambling, required implementing several specific / innovative steps in the fabrication processes which took one and a half year to be completed. 


Final acceptance tests are currently ongoing at IRAP/OMP, under the supervision of our fiber engineer Yoan Micheau, to check that the throughput, focal ratio degradation, and scrambling performances of the overall fiber link are nominal.