Multi-fiber Coupling for Wide Field Fiber Interferometry

Adaptive Optics is now making it possible to efficiently use large telescopes in ground-based interferometers. Spatial filtering, especially with optical fibers, allows accurate interferometric measures to be done on these new interferometers (VLTI, Keck, OHANA). However, as telescope sizes increase and sensitivity improves, the problem of field of view of interferometers become more acute. In this paper, I focus on the observation of extended sources with fiber interferometers, and show that accurate visibility measurements are made difficult by the extent of the observed source. Out of the several solutions explored, one seems especially attractive: multi-fiber coupling. In this optical scheme, the pupil is subdivided in sub-pupils, each being coupled into a separate optical fiber. I show how this technique extends the field of view of fiber interferometers, reduces the errors in the interferometric measurements of extended sources, and provides flexibility which improves the sensitivity of fiber interferometers