Near field modal noise reduction using annealed optical fiber

Abstract

Incomplete and unstable mode population has long complicated the application of optical fiber for transferring star and calibration light to high precision spectrographs. The need for improved precision calibrators in support of radial velocity planet surveys has led to the introduction of coherent wavelengths sources using single mode fibers that are then coupled into multi-mode fibers, further exacerbating this problem. We explore mode scrambling in annealed optical fiber with and without agitation, as compared to that obtained using octagonal fiber and using an integrating sphere. We observe improved scrambling with annealed fibers compared to conventional and octagonal fibers.