Photometrical scrambling gain and focal ratio degradation in fibers for astronomical instruments

摘要

Optical fibres with extreme optical scrambling gains are required when used to link telescopes to spectrographs for the measurement of very high accuracy radial velocities. We started to study systematically the scrambling properties of optical fibres and in particular, the new FBP fibres from Polymicro and the high numerical aperture fibres from Crystal Fibre. The gam in photometrical scrambling by mechanical fibre scramblers is shown. The degradation of the focal ratio by these fibres is also reported. Finally, we present the first evaluation of a slit light pipe to homogenize the flux of several fibres arranged on a line in order to get a uniform slit aperture.