Investigation of focal ratio degradation caused by stress in large-core astronomical fibers

The focal ratio degradation (FRD) properties of optical fibers in the Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) caused by different stress were investigated by employing an Energy Distribution Method (EDM). We analyzed the FRD in two conditions with uniform stress and non-uniform stress. The qualitative and quantitative analyses on the output light spot from the optical fibers show that the output focal ratio is stable with uniformly compressed while FRD becomes more serious with the increasing non-uniform stress.