Study of focal ratio degradation for fibers

Along with the development of spectroscopy, the focal ratio degradation of fibers is the most important for instrumental applications in astronomy. Fibers are very susceptible to the effects of focal ratio degradation, especially the shape and stress of fibers. The focal ratio degradation of fibers caused through bending (including C-shape, S-shape and circle of the fiber) and stress is analyzed and studied in this paper. Finally, we get a conclusion that stress and bending of fibers have serious influences on the focal ratio degradation. The analyses of focal ratio degradation have great significance for the construction and application of fibers in astronomy. (paper)