Modal Noise in High‐Resolution, Fiber‐fed Spectra: A Study and Simple Cure
Open Access
- 1 July 2001
- journal article
- research article
- Published by IOP Publishing in Publications of the Astronomical Society of the Pacific
- Vol. 113 (785) , 851-858
- https://doi.org/10.1086/322143
Abstract
The transmission modes of a fiber introduce an unstable intensity distribution 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 experiments at a resolution of ~150,000, we found S/N limited to ≤500 for a range of fiber perturbations and illumination geometries from simple displacement to simulated seeing variations. We find an empirical 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.Keywords
This publication has 4 references indexed in Scilit:
- Detection of C3in Diffuse Interstellar CloudsThe Astrophysical Journal, 2001
- Fiber feed for the CFHT Gecko spectrographPublished by SPIE-Intl Soc Optical Eng ,2000
- Speckle and Modal Noise in Optical Fibres Theory and ExperimentOptica Acta: International Journal of Optics, 1980
- Frequency dependence of modal noise in multimode optical fibersJournal of the Optical Society of America, 1980