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Paper: Focal ratio degradation in optical fibers of astronomical interest
Volume: 3, Fiber Optics in Astronomy
Page: 26
Authors: Ramsey, Lawrence W.
Abstract: This paper discusses the sources of the focal ratio degradation (FRD) of step index fused silica core optical fibers, and describes the measurements of FRD properties. It is concluded that, although the FRD does not appear to be sensitive to the large scale bending of the fiber, this bending might induce stress which causes microbends. It was found that larger core fibers appear to have better FRD characteristics than smaller core fibers of identical construction, and that soft buffered fibers have better FRD features than hard buffered fibers. The best f-ratios to feed typical glass-clad fibers appears to be from about f/3.0 to about f/7.0, depending on the fiber diameter. Finally, it was found that good FRD characteristics are not compatible with the good radial image scrambling needed for high-precision radial velocity observations.
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