Visible interferometric coupling of two telescopes through single mode optical fibers

Abstract

The diameter of large conventional astronomical telescopes is currently restricted to the range of eight to ten meters. With this limitation in mind, there is an emerging interest in various applications of optical interferometry which would allow the synthesis of apertures larger than can be realized using current mirror fabrication technologies. Interferometry allows the substitution of the separation between telescopes to determine the limiting resolution rather than the diffraction limited resolving power of the individual telescope aperture(s). The implementation of this process, however, requires solutions to a number of difficult problems in the transport and recombination of optical wavefronts. The use of single mode (SM) optical fibers to transport and recombine optical wavefronts in interferometers offers a number of advantages as compared to other, more established techniques, yet suffers from an inefficient coupling of the wavefront energy into the very narrow fiber cores. We present preliminary results of an experiment in which interferometric recombination of wavefronts from two telescopes using SM fibers was used to obtain white light fringes on the bright star Arcturus (α Bootis). Our experience leads us to believe that for many imaging applications the continued development of fiber based interferometry will yield significant resolution gains over the diffraction limited performance associated with conventional monolithic aperture systems.