Modal noise in high-resolution, fiber-fed spectra: A study and simple cure

Citation
J. Baudrand et Gah. Walker, Modal noise in high-resolution, fiber-fed spectra: A study and simple cure, PUB AST S P, 113(785), 2001, pp. 851-858
Citations number
7
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC
ISSN journal
0004-6280 → ACNP
Volume
113
Issue
785
Year of publication
2001
Pages
851 - 858
Database
ISI
SICI code
0004-6280(200107)113:785<851:MNIHFS>2.0.ZU;2-#
Abstract
The transmission modes of a fiber introduce an unstable intensity distribut ion in high-resolution spectra which cannot be eliminated by flat-fielding because the pattern is sensitive to any small changes in fiber position or illumination. These instabilities, rather than photon shot noise, limit the achievable signal-to-noise ratio (S/N). In controlled laboratory experimen ts at a resolution of similar to 150,000, we found S/N limited to less than or equal to 500 for a range of fiber perturbations and illumination geomet ries from simple displacement to simulated seeing variations. We find an em pirical relation between the number of monochromatic modes and the level of modal noise for which we offer no rigorous explanation. More important, we demonstrate that continuous, low-amplitude agitation of the fiber close to its output completely eliminates the problem.