Stress-Induced Group Delay Variation in Hole-Assisted Fibers

In this paper, we have studied stress-induced group delay variations in hole-assisted fibers (HAFs), experimentally and theoretically for parallel transmission systems. Recently, HAFs having low bending losses have been developed. A fiber ribbon that uses HAFs will be suitable for parallel transmission systems when used in a small space. Additional skew occurs when a fiber ribbon is used under nonuniform stress environment. It is important to know the difference between single-mode fibers (SMFs) and HAFs with respect to stress-induced group delay variations. First, we find out the difference experimentally. Then, we propose a theory to explain the difference. The results calculated by the proposed theory are in good agreement with experimental data. Finally, we discuss the group delay variations, such as the difference between SMFs and HAFs, and the wavelength dependence. We also try to explain the measured group delay variations of five HAFs in a unified way in order to estimate group delay variations of HAFs with various cross-sectional structures.