EDP Sciences
Free access
Volume 418, Number 3, May II 2004
Page(s) 1179 - 1186
Section Instruments, observational techniques, and data processing
DOI http://dx.doi.org/10.1051/0004-6361:20034090

A&A 418, 1179-1186 (2004)
DOI: 10.1051/0004-6361:20034090

Single-mode versus multimode interferometry: A performance study

E. Tatulli, P. Mège and A. Chelli

Laboratoire d'Astrophysique, Observatoire de Grenoble, 38041 Grenoble Cedex, France
(Received 17 July 2003 / Accepted 6 December 2003)

We compare performances of ground-based single-mode and multimode (speckle) interferometers in the presence of partial Adaptive Optics correction of atmospheric turbulence. It is first shown that for compact sources (i.e. sources smaller than the Airy disk of a single telescope) not entirely resolved by the interferometer, the remarkable property of spatial filtering of single-mode waveguides coupled with AO correction significantly reduces the speckle noise which arises from residual wavefront corrugations. Focusing on those sources, and in the light of the AMBER experiment (the near infrared instrument of the VLTI), we show that single-mode interferometry produces a better Signal-to-Noise Ratio on the visibility than speckle interferometry. This is true for bright sources ( K < 5), and in any case as soon as Strehl ratio of 0.2 is achieved. Finally, the fiber estimator is much more robust - by two orders of magnitude - than the speckle estimator with respect to Strehl ratio variations during the calibration procedure. The present analysis theoretically explains why interferometry with fibers can produce visibility measurements with a very high precision, $1\%$ or less.

Key words: techniques: interferometric -- techniques: adaptive optics -- methods: analytical

Offprint request: E. Tatulli, Eric.Tatulli@obs.ujf-grenoble.fr

© ESO 2004